SURGICAL ANATOMY OF THE HAND AND UPPER EXTREMITY part 04

 

432 Regional Anatomy

FIGURE 8.20. Median nerve in the antecubital fossa and forearm. Note that most of the median

nerve branches in the antecubital fossa are medial. In the distal forearm, the median nerve

almost always exits from beneath the radial side of the muscle belly of the middle finger flexor

digitorum superficialis.

8.1 Flexor Forearm 433

FIGURE 8.21. The course and muscle innervation of the anterior interosseous nerve.

434 Regional Anatomy

FIGURE 8.22. Arteries of the forearm and the ulnar nerve.

SURGICAL EXPOSURES

Antecubital Fossa

Anteromedial Approach

Indications

The contents of the antecubital fossa may be exposed

through an anterior approach, which provides excellent

exposure of the biceps tendon, median and ulnar nerves,

the brachial, radial, and ulnar arteries, and the radial nerve.

Landmarks

Landmarks include the biceps, mobile wad of three and PT

muscles, biceps tendon, and elbow flexion creases.

Patient Position/Incision

With the patient supine, the forearm in supination, and the

elbow extended, an incision is made 5 to 6 cm proximal to

the flexion crease along the medial edge of the biceps muscle, which continues obliquely across the elbow flexion

crease to the lateral and flexor side of the forearm, where it

turns distally along the inner or medial edge of the mobile

wad of three (Fig. 8.23).

Technique

After dividing the superficial fascia and ligating the superficial

veins as required, the deep fascia is opened to enter the triangular antecubital fossa. The guiding landmarks are the biceps

tendon and the lacertus fibrosus centrally and the brachioradialis as part of the mobile wad of three laterally, along with

the PT and flexors medially (1). The lacertus fibrosus is

incised along the exposed edge of the PT and reflected proximally. The biceps tendon divides the antecubital fossa into

medial and lateral compartments, with the medial compartment’s major components being the vascular tree and the

8.1 Flexor Forearm 435

FIGURE 8.23. Anteromedial approach to the antecubital fossa: patient position (A) and incision (B).

A

B

median nerve. The brachial artery lies close to the medial side

of the biceps tendon and divides into the radial and ulnar

arteries at the distal edge of the lacertus fibrosus. The vessels

may be gently mobilized by blunt dissection with scissors.

The ulnar artery is deeper than the radial and sometimes is

hidden by the more superficial radial artery. Similarly, the

common interosseous artery and its anterior interosseous

branch lie behind and somewhat deep to the parent ulnar

artery. These vessels may be mobilized as needed by ligating

their muscular branches. Multiple branches arise on the lateral side of the radial artery, the largest of which is the radial

recurrent artery. Most of these multiple branches arise distal

to the radial recurrent and, along with the radial recurrent,

supply the adjacent mobile wad muscles. The radial recurrent

branch of the radial artery continues proximally, where it

joins the anterior branch of the profunda brachii artery in the

region of the lateral epicondyle. Soon after its origin from the

radial artery, the radial recurrent sends a branch that enters

the arcade of Frohse adjacent to the PIN. It may be necessary

to ligate some of these vessels to mobilize the adjacent mobile

wad of muscles and thus expose deeper structures, including

the radial nerve and supinator, or to allow retraction of the

vascular bundle to the medial side, which aids in identification of the ulnar artery and its branches. Henry has characterized these branches arising from the radial side of the radial

artery as a fanlike leash that spreads from a common stem (the

radial recurrent artery) and thus can be dealt with as a single

structure (1). Although Henry is correct in his observation

that the vessels comprising this fanlike vascular leash seldom

lie in a single plane, but rather diverge in a set of layers two or

three deep, these vessels do not always arise from a common

single stem and thus must be dealt with as individual vessels.

These vessels may arise as two to three individual branches

from the radial artery or as multiple branches arising from a

common stem distal to the radial recurrent artery. These vessels are separate and distinct from the radial recurrent artery,

436 Regional Anatomy

FIGURE 8.24. Anteromedial approach to the antecubital fossa: technique and deep dissection.

Passing the surgeon’s index finger down the lateral side of the biceps tendon is a useful technique to find the radial recurrent vessel(s). Tying these vessels allows medial retraction of the

radial artery and lateral retraction of the mobile wad muscles.

and although the radial recurrent artery also may send

branches to the mobile wad muscles, the arrangement of this

vascular leash is different from that portrayed by Henry (1).

These branches, including the radial recurrent, may be identified by running a finger down the lateral side of the biceps

tendon (Fig. 8.24). In contrast to the more superficial radial

artery, which is easily identified in the interval between the

brachioradialis and the FCR and on top of the PT, the ulnar

artery descends deep into the medial side of the antecubital

fossa, which it exits beneath the deep head of the PT to enter

the interval between the FDS and FDP. Mobilization of the

radial artery by this means allows it to be moved toward the

ulna, which may aid in uncovering the ulnar artery.

Anterolateral Approach

Indications

The anterolateral approach, although somewhat similar to

the approach described previously for exposure of the antecubital fossa, probably is better suited to expose the lateral

half of the antecubital fossa and may be used to expose

radial nerve entrapment syndromes and biceps tendon rupture.

Landmarks

Useful landmarks are the biceps and mobile wad of three

muscles, biceps tendon, and the elbow flexion crease.

Patient Position/Incision

With the patient supine and the forearm supinated, the skin

incision begins 4 to 5 cm proximal to the elbow flexion

crease in the interval between the brachialis and the brachioradialis, curves into the elbow flexion crease, and then

continues distally into the forearm along the inner or

medial margin of the mobile wad of three (Fig. 8.25A and

B). The biceps tendon medially and the brachioradialis laterally are landmarks.

8.1 Flexor Forearm 437

FIGURE 8.25. Anterolateral approach to the antecubital fossa. Patient position (A) and incision

(B). Identification of the radial nerve usually is performed successfully by blunt separation of the

interval between the brachioradialis and brachialis.

A

B

Technique

The lateral antebrachial cutaneous nerve of the forearm is

identified as it exits from beneath the lateral margin of the

biceps muscle and may be located as it becomes more

superficial near the lateral aspect of the biceps tendon.

Care must be taken not to mistake this nerve for the radial

nerve, which is deeper and lies between the brachialis and

brachioradialis. The radial nerve is located by blunt separation of these two muscle bellies, beginning 1 to 2 cm

proximal to the elbow joint space. This interval is developed further by blunt dissection, and retraction of the

brachioradialis laterally and the brachialis medially provides additional exposure (see Fig. 8.25C and D). The

radial nerve is traced distally, where it divides into the PIN

and sensory branches. The PIN enters the supinator muscle beneath the leading edge of the ECRB and the arcade

of Frohse accompanied by a branch of the radial recurrent

artery, whereas the sensory branch continues distally

under cover of the brachioradialis. The radial recurrent

artery and other branches may require ligation to mobilize

the mobile wad of three or the main trunk of the radial

artery, and it is found by running a finger down the radial

or lateral side of the biceps tendon as described for the

anteromedial approach to the antecubital fossa.

Shaft of the Radius

Indications

This approach may be used for fractures, tumors, or infections of the radius.

Landmarks

These include the biceps and the mobile wad of three muscles, the elbow flexion crease, and the radial styloid.

Patient Position/Incision

With the patient supine and the forearm in supination, an

incision is begun in the interval between the distal and lateral aspect of the biceps and the proximal origins of the

mobile wad of three. The incision continues obliquely

across the elbow flexion crease and then curves distally to

parallel the medial edge of the mobile wad of three, to end

near the radial styloid (Fig. 8.26A and B).

Technique

After opening the deep fascia and identifying the major

structures in the antecubital fossa, the radial recurrent

artery is ligated. Next, the supinator muscle is identified

along with its motor branch, which enters the muscle

belly proximally and anterolaterally. The motor branch of

the radial nerve, the PIN at this level, travels between the

deep and superficial portions of the supinator. Using the

biceps tendon as a guide, the proximal portion of the

obliquely oriented insertional edge of the supinator is

identified. The insertional edge of the muscle is detached

with a scalpel or sharp periosteal elevator as desired (see

Fig. 8.26C). Exposure of this region is facilitated by flexion of the elbow and gentle retraction of the mobile wad

muscles. After the supinator is released, the forearm is

pronated to reveal an extensive expanse of radius. Additional exposure of the distal aspect of the radius is

obtained by reflection of the insertion of the brachioradialis (see Fig. 8.26D). Caution: The AIN and its branches

may be at risk during this approach, and this is especially

true of the branches to the FPL.

Median and Ulnar Nerves

Volar Approach

Indications

Exposure of the median and ulnar nerves through a volar

approach is an extension of the approach to the radius

described previously. The median and ulnar nerves may

require exposure in the forearm for nerve suture or grafting

or nerve tumors. The volar approach is designed to expose

the nerves in the middle and distal thirds of the forearm.

Exposure of the median nerve in the proximal third of the

forearm is described under the antecubital fossa approach,

and exposure of the ulnar nerve in the proximal forearm is

described in the section on ulnar nerve transposition

(Chapter 7, Cubital Tunnel Syndrome).

Landmarks

Landmarks include the elbow flexion crease and the interval between the PT and the FCR.

Patient Position/Incision

With the patient supine and the forearm in supination, an

incision is begun at the elbow flexion crease along the lateral side of the PT and continued distally in the midline of

the forearm to the wrist flexion crease (Fig. 8.27).

Technique

Dissection to expose the median nerve begins by finding

the cleavage interval between the PT and the FCR (the

interval between the thumb and index finger in Henry’s

manual mnemonic) (1). The interval of separation is best

begun in the region of their respective tendons and then

carried proximally. The median nerve is identified in this

region beneath the distal edge of the PT and just before its

entrance between the deep and superficial portions of the

438 Regional Anatomy

8.1 Flexor Forearm 439

FIGURE 8.26. Exposure of the shaft of the radius. Incision (A) and proximal dissection (B).

(continued on next page)

A

B

FDS. If no interval exists between the PT and FDS (as

sometimes occurs), then the FDS muscle fibers must be

separated by blunt dissection to reveal the median nerve.

An alternative and more distal approach may be achieved at

the level of the myotendinous junction and in the interval

between the ring and little finger superficialis. The median

nerve lies beneath the muscle belly of the middle finger

superficialis, and by separation and retraction of the ring

and little finger superficialis muscle bellies, it may be

viewed in this region. After the median nerve exits from

beneath the oblique edge of the muscle belly of the middle

finger superficialis, it is not difficult to identify or locate.

This constant relationship between the median nerve and

the middle finger superficialis muscle belly is an important

identification landmark, especially in trauma cases. The

ulnar nerve is located in the interval between the superficialis and the underlying profundus. Retraction of the finger flexors is aided by flexing the wrist and fingers. Once

again, identification of the interval is easier at the

myotendinous junction followed by proximal dissection.

The interval between the FCU tendon and the FDS of the

little finger reveals the ulnar neurovascular bundle lying on

the FDP.

Medial Approach (McConnell Approach)

Indications

A more direct approach to the ulnar nerve that also allows

exposure of the median nerve in the middle and distal

thirds is obtained through the medial side of the forearm.

This approach, originally described by McConnell (25), is

440 Regional Anatomy

FIGURE 8.26. (continued) C: Using the biceps tendon as a guide, the insertional edge of the

supinator is incised and elevated along with the posterior interosseous nerve in this muscle envelope.

C

recounted here with some modifications based on the

description by Henry (1).

Landmarks

The landmarks are the pisiform bone and the medial epicondyle.

Patient Position/Incision

With the patient supine and the forearm in supination, an

incision is made from the radial side of the pisiform to the

medial epicondyle (Fig. 8.28).

Technique

Beginning distally and opening the fascia along the radial

side of the FCU tendon, the ulnar neurovascular bundle is

found just radial to this tendon and traced proximally to the

junction of the proximal and middle thirds of the forearm.

At this location, the ulnar artery angles away laterally

toward its parent vessel, the brachial artery, whereas the

ulnar nerve continues proximally in a straight course

toward the medial epicondyle. If the median nerve also

must be exposed, the cleavage plane between the FDS and

the FDP is developed, which leads to the median nerve

closely applied in a shallow groove to the underside of the

FDS (1). The median nerve in this region, as noted by

Henry (1), lies first to the radial side of the proximal muscle belly of the deep portion of the FDS and then to the

radial side of the fibrous tissue linkage between the proximal and distal bellies. Below this level, fascia binds the

median nerve in a lateral groove between the middle and

index finger muscle bellies and tendons.

Median Nerve in the Distal Forearm

Indications

The median nerve is relatively superficial in the distal aspect

of the forearm and may be subject to laceration because of

its exposed position. This incision also may be useful for

removal of median nerve tumors in this area.

Landmarks

Useful landmarks are the long axis of the middle finger and

the PL tendon, if present.

Patient Position/Incision

With the patient supine and the forearm in supination, a

longitudinal or gently curved incision is made at the wrist

flexion crease and continued proximally in line with the

middle finger axis for a distance of 10 to 12 cm, as needed

(Fig. 8.29).

8.1 Flexor Forearm 441

FIGURE 8.26. (continued) D: Pronation of the forearm facilitates exposure of the remainder of the radial shaft.

D

442 Regional Anatomy

FIGURE 8.27. Approach to the median and ulnar nerves. A: Incision. B: Proximal exposure of the

median nerve is in the interval between the pronator teres and the flexor carpi radialis. This

interval may be most easily identified at their distal zone of separation. The ulnar nerve is found

in the interval between flexor digitorum superficialis (FDS) of the little finger and the flexor carpi

ulnaris. C: The distal aspect of the median nerve may be identified beneath FDS to the middle

finger and in the interval between the FDS of the middle and ring fingers.

A

B

C

8.1 Flexor Forearm 443

FIGURE 8.28. The McConnell approach to the median nerve (see also Fig. 8.7). A: Incision. B, C:

The interval between the flexor digitorum superficialis (FDS) and flexor carpi ulnaris is used to

expose the median nerve, which travels as a 9satellite9 on the undersurface of the FDS. This

approach also provides excellent exposure of the ulnar nerve and artery.

A

B

C

Technique

The median nerve at this level is located between the middle and index finger components of the FDS and exits

from beneath the radial margin of the middle finger FDS

muscle belly. The palmar cutaneous branch leaves the

median nerve along its lateral aspect approximately 3 to 4

cm from the proximal margin of the transverse carpal ligament (26).

Lateral Antebrachial Cutaneous Nerve

Indications

This nerve is a useful autograft donor nerve for digital nerve

repair (14).

Landmarks

It may be located just to the lateral aspect of the biceps tendon at the intersection of the biceps tendon and the

interepicondylar line of the humerus (13).

Patient Position/Incision

With the patient supine and the forearm in supination, a

transverse incision is made in the elbow flexion crease centered over the biceps tendon (Fig. 8.30).

Technique

Staying to the lateral side of the tendon, the nerve is found

as it emerges from the anterior surface of the brachialis

muscle. The nerve is closely applied to the lateral aspect of

the biceps tendon, and in some instances appears to blend

with the lateral substance of the biceps tendon (13). The

nerve lies in the same coronal plane as the biceps tendon,

just deep to the antecubital veins and the antecubital fascia.

It is in this region that the posterior branch is given off. Distally, cutaneous branches ramify along the course of the

cephalic vein. Digital nerve grafts usually do not require

extensive amounts of graft, and this incision usually is adequate to harvest a sufficient length of graft, but it may be

extended as needed.

444 Regional Anatomy

FIGURE 8.29. Exposure of the median nerve in

the distal forearm. The relatively superficial

location and the consistent exit of this nerve

from beneath the muscle belly of the flexor digitorum superficialis to the middle finger facilitates this exposure.

CLINICAL CORRELATIONS

Pronator Syndrome

Sites of Compression

There are four potential sites of proximal median nerve

compression, one in the distal arm and three in the proximal forearm (27) (Fig. 8.31). The distal arm site has been

discussed under the section on Clinically Significant

Arcades in Chapter 6. In the forearm, the median nerve

may be compressed at one of three levels, in the following

order of frequency: the PT, the flexor superficialis arch, and

the lacertus fibrosus (27,28).

Pronator Teres

Dissections of the proximal forearm have revealed either a

fibrous band on the dorsum of the superficial head of the

pronator overlying the median nerve, or a fibrous band as a

component of the deep ulnar head of the pronator when

the latter was present, or, when the deep head was absent, a

separate fibrous band attached to the coronoid process of

the ulna proximally. In some instances fibrous bands were

noted on both heads, which formed a definite fibrous

arcade (28).

Flexor Superficialis Arch

A fibrous arcade was observed in approximately one-third

of the dissections at the proximal margin of the FDS to the

middle finger (28).

Lacertus Fibrosus

Entrapment of the median nerve beneath the lacertus fibrosus is the least common cause of median nerve entrapment

in the proximal forearm. It may be secondary to hypertrophy or enlargement of the lacertus (28).

Localizing Tests

Functional muscle testing may give some indication of the

site of compression (Fig. 8.32). If complaints are produced

by flexion of the elbow against resistance between 120 and

135 degrees of elbow flexion, compression may be in the

8.1 Flexor Forearm 445

FIGURE 8.30. Approach for the lateral antebrachial cutaneous nerve. The nerve most often is

found just lateral to the biceps tendon as it emerges from the interval between the biceps and

brachialis muscles.

distal arm beneath a ligament of Struthers (see Chapter 6).

Compression by the lacertus fibrosus may be aggravated by

active flexion of the elbow against resistance with the arm

in pronation. If symptoms are increased by resisted pronation of the forearm (usually combined with wrist flexion to

relax the FDS), the nerve may be compressed between the

pronator, and if the symptoms are aggravated by resisted

flexion of the FDS to the middle finger, compression may

be at the FDS proximal arch (27,28).

Treatment

Operative technique for treatment of pronator syndrome

includes complete exploration of the median nerve from the

distal arm to the proximal forearm. The median nerve is

explored from the region of a possible anomalous supracondylar process and associated ligament of Struthers to the

proximal edge of the FDS, with release of all potentially

constricting structures, including the ligament of Struthers

and the lacertus fibrosus (27). At the level of the PT, compression may be due to muscle hypertrophy or constricting

muscle fascial bands. Further decompression of the median

nerve is achieved by tracing the median nerve into the substance of the PT and releasing any areas of constriction. The

final site of possible constriction is in the proximal edge of

the FDS, which may be exposed by entering the interval

between the FCR and the PT. The median nerve may be

constricted here beneath a fibrous tissue arch along the

leading edge of the FDS. A persistent median artery also has

been observed as a cause of pronator syndrome. Reported

cases have demonstrated penetration of the median nerve

by the median artery and constriction of the nerve by vascular leashes from the median artery (29,30).

Anterior Interosseous Nerve Syndrome

Compression of the AIN characteristically results in complete or partial loss of function of the FPL and the FDP of

the index finger and long fingers, as well as the PQ, without any sensory deficits (31–33). These findings may be

associated with vague complaints of discomfort in the

proximal forearm. In the complete AIN syndrome

(AINS), the affected patient assumes an unusual pinch

posture with the distal joint of the index and thumb in

extension (32,33).

Anatomic Variations

Although the FPL and FDP of the index finger are innervated exclusively by the AIN, the FDP of the long finger

is exclusively innervated by the AIN only 50% of the time.

In the remaining 50%, the long finger FDP is at least partially innervated by the ulnar nerve (23). Variations from

the classic AINS include isolated paresis or paralysis in

either the index profundus or the FPL. In both the com446 Regional Anatomy

FIGURE 8.31. Sites of compression in the pronator syndrome. A:

The ligament of Struthers from an anomalous supracondylar

process to the medial epicondyle, which may compress the

median nerve. B: The pronator teres. C: The lacertus fibrosus

(the least common cause). D: A fibrous arch in the flexor digitorum superficialis of the middle finger.

A

B

C

D

plete and partial types, there often is an antecedent history

of unusual muscular exertion, blunt trauma, or edema in

the extremity (23).

Differential Diagnosis

AINS, especially the incomplete type, must be distinguished from flexor tendon rupture, flexor tendon adhesion, and stenosing tenosynovitis. If a Martin-Gruber

connection is present between the AIN and the ulnar

nerve, there may be intrinsic muscle paresis or atrophy

(34). The incomplete type of AINS may be distinguished

from rupture of the FPL by noting passive flexion of the

interphalangeal joint of the thumb with wrist and MCP

joint hyperextension in AINS, in contrast to absence of

thumb interphalangeal joint flexion in rupture of the

FPL (35).

Compression Sites

The nerve usually is compressed by fibrous bands that run

from the deep (most common) or superficial head of the

PT to the brachialis fascia (23) (Fig. 8.33). Other sites of

compression have been identified, including the fibrous

tissue arcade of the FDS, which the AIN passes beneath to

lie on the IOM (27). Other reported causes of compression include enlarged bursae or tumors, aberrant or

thrombosed vessels, a double lacertus fibrosus overlying

the nerve, compression of the nerve as it runs deep to both

heads of the PT, and fractures of the forearm and distal

humerus (23,27). Three aberrant muscles have been identified in association with AINS, including an accessory

head of the FPL called Gantzer’s muscle, the palmaris profundus, and the flexor carpi radialis brevis (27,36,37).

Although an accessory head of the FPL (Gantzer’s muscle)

8.1 Flexor Forearm 447

FIGURE 8.32. Localizing tests for the pronator syndrome. A: Test for presence of ligament of

Struthers. B: Test for lacertus fibrosus and pronator teres muscle compression. C: Test for

median nerve compression by a fibrous tissue arch in the flexor digitorum superficialis of the

middle finger.

A B

C

448 Regional Anatomy

FIGURE 8.33. Anterior interosseous nerve compression sites. A: Deep head of the pronator teres.

B: Fibrous arch of the middle finger flexor digitorum superficialis. C: Gantzer’s muscle. Presence of

abnormal muscles in the form of flexor carpi radialis brevis (D) and palmaris profundus (E).

A C B

D E

has been identified as an a cause of AINS (33,38), both

Dellon and Mackinnon (39) and Al-Qattan (40) have

noted that Gantzer’s muscle always is posterior to the

median nerve and AIN. However, in dissections of the

forearm in which Gantzer’s muscle was present, the

authors demonstrated the possibility of a pincer-like effect

between this abnormal posterior head and the adjacent

anterior FDS that could produce compression of the

median nerve as well as the AIN. The median nerve and

AIN passed through the interval between these two muscles, which share a common origin on the medial epicondyle (see discussion of Gantzer’s muscle under the section on Anatomic Variations, later).

Pathogenesis

The common denominators in this condition appear to be

localized edema superimposed on an anatomic abnormality

that is either congenital or acquired.

Treatment

Patients who present with paresis may be observed because

most improve spontaneously without surgery (23). This is

especially true in children with AINS associated with fractures of the forearm and elbow region. Exploration and

decompression is advised in patients who present with complete paralysis of either muscle tendon unit and who have

shown no improvement as determined by physical examination or repeat electromyography after 12 weeks of observation (23). The AIN is exposed through a curved incision

beginning at the antecubital flexion crease just medial to the

biceps tendon. The median nerve is traced distally to its

entrance between the two heads of the PT, and the superficial head of the PT is mobilized and retracted to reveal the

usual site of origin of the AIN from the posterior aspect of

the median nerve. The site of compression may be identified by noting a pale discoloration in the nerve with or

without a concomitant indentation of the nerve. All potential sites of compression are released; it is not necessary to

perform an internal neurolysis. It may be necessary to

divide the insertion of the PT to facilitate exposure of the

AIN at the superficialis fibrous arcade.

Compartment Syndrome

Compartment syndrome is a clinical complex that results

from increased pressure in a closed and limited space that

compromises the circulation and function in that space.

Although this condition may occur in any closed anatomic

space, it is most common and devastating in the volar

aspect of the forearm (41). The fact that the forearm muscles are encased in a semirigid fascial tube makes such a progression possible; even the skin may act as a restricting

membrane in some instances.

Associated Injuries/Etiology

The most common associated injuries are fractures of the

elbow or forearm, soft tissue injuries, arterial injury, burns

(thermal and electrical), and injection injuries (41,42). The

pathophysiology of compartment syndrome is best

explained by the arteriovenous (AV) gradient theory of

Matsen and Rorabeck (43). The relationship between local

blood flow and the AV gradient is expressed by LBF = Pa −

Pv/R, in which the local blood flow in a compartment

equals the local arterial pressure minus the local venous

pressure divided by the local vascular resistance. If the AV

gradient is significantly reduced, the local vascular resistance becomes relatively ineffective and for practical purposes can be ignored. Because veins are collapsible, the pressure inside them cannot be less than the surrounding local

tissue pressure; thus, when tissue pressure rises, so does the

pressure on the local veins, resulting in a decreased AV gradient. When this occurs, local blood flow is reduced to the

extent that it cannot meet the metabolic needs of the muscles and nerves. The AV gradient theory explains why with

increased tissue pressure and a reduction in local arterial

pressure, as in hypotension, hemorrhage, peripheral vascular disease, arterial occlusion, and limb elevation above the

heart, the net effect of any given increase in tissue pressure

is exaggerated by lowering the local AV gradient. Lowering

of the AV gradient results in decreased oxygen perfusion of

the muscles and nerves, with subsequent death of the muscles and replacement by fibrous tissue, which in turn causes

“strangulation neuropathy.” The final result is a forearm

fixed in pronation, with the wrist flexed, the MCP joints

hyperextended, and the PIP and distal interphalangeal

(DIP) joints flexed (41,44). If the ulnar nerve also is

involved, total sensory loss is noted on the flexor side of the

hand. This is a classic description of Volkmann’s ischemic

contracture. Mubarak and Carroll believe that Volkmann’s

contracture is caused by circulatory changes in a closed

osteofascial compartment due to buildup of tissue fluid

pressure in the compartments (41). Their studies suggest

that the normal range of compartmental pressures is 0 to 8

mm Hg. In a compartment syndrome, pressures may rise to

30 to 50 mm Hg or more. Failure to diagnose and treat a

compartment syndrome early and adequately may result in

irreversible changes.

Muscle Infarct

Seddon introduced the concept of the ellipsoid infarct, noting that circulation in the central aspect of the muscle belly

was most severely impaired, in contrast to the periphery of

the muscle, where collateral circulation was less likely to be

impaired (44). The muscle infarct is most prominent in the

middle third of the muscle and is more severe next to the

bone along the course of the anterior interosseous artery.

The most severely affected muscles are the FDP and the

8.1 Flexor Forearm 449

FPL (the deeper muscles), followed by the FDS and PT.

Involvement of the wrist flexors, extensors, and brachioradialis is less likely. Degeneration of the nerves that pass

through the area of muscle infarct is due not only to the initial ischemia but to the chronic compression, which results

in a nerve that is thin and cordlike (38). The muscle infarct

is replaced by dense fibrous tissue that contracts and produces the characteristic Volkmann’s deformity (41,44).

Most Important Facts

The most important facts to remember about compartment

syndrome are the clinical findings and the need for early

treatment. The clinical findings are based on muscle and

nerve ischemia and include pain that is persistent and progressive (45). Accentuation of the pain by passive muscle

stretching is a very reliable clinical test in making the diagnosis. Pain may be absent late in the course of the disorder

because of prolonged nerve ischemia, and pain also may be

absent when compartment syndrome is superimposed on a

central or peripheral sensory defect. Diminished sensation

is the second most important finding, and indicates nerve

ischemia as it passes through the involved compartment

(45). The third most important finding is muscle weakness,

which, when progressive, is very important in establishing

the diagnosis (45). The clinical assessment of elevated compartment pressure by palpation of the extremity may give

some indication of the presence or absence of compartment

syndrome, but this must be recognized as a qualitative factor in the decision-making process regarding fasciotomy.

Wick Catheter

Mubarak and associates have popularized the use of a

wick catheter to measure compartment tissue pressures

(41,42,46). The wick catheter is connected to a transducer and a recorder and can provide reliable objective

assessment of intracompartmental pressure. Based on

extensive clinical use and experience, the originators of

this technique have advised that fasciotomy is recommended when the intracompartmental pressure is >30

mm Hg in normotensive patients and >20 mm Hg in

hypotensive patients, when associated with the typical

clinical picture of compartment syndrome (42).

Although the need for fasciotomy may be based in part

on the duration and intensity of the compartment syndrome, it seldom if ever is possible to determine accurately the duration of the elevated pressure, and therefore

it must be assumed that the duration is equal to or has

exceeded the critical threshold of 8 hours (45).

Forearm Compartments

Cross-sectional anatomy of the forearm demonstrates three

major compartments, the volar, extensor, and mobile wad

(47) (Fig. 8.34). Pressure studies have revealed that these

three compartments are interconnected, unlike the compartments in the leg. Therefore, release of the volar compartment may be sufficient to release all three compartments. However, if there is any indication that elevated

pressure is present in the remaining two compartments,

then release of the extensor compartment should be performed, which almost always decompresses the mobile wad

compartment as well as the extensor compartment (47).

The PQ has been identified as a fourth forearm compartment based on the findings of a well defined fascial covering measuring 0.4 to 0.5 mm in thickness, a compartment

floor formed by the IOM, and dye injection studies showing its separation from the other forearm compartments

(48). A compartment syndrome involving this compartment was noted after a crush injury with an associated fracture of the distal radius (49).

450 Regional Anatomy

FIGURE 8.34. The three compartments of the forearm:

volar, dorsal, and mobile wad.

Treatment Techniques

The volar incision is designed to preserve superficial veins

and nerves while allowing decompression of the underlying

superficial and deep muscle groups and subsequent covering of the vital structures, including nerves. The fasciotomy

incision may include the carpal tunnel and the antecubital

fossa, as indicated (45) (Fig. 8.35). All muscle compartments and muscles are examined with the understanding

that the most severely involved muscles are deep and

include the FDP and FPL. The muscle fascia is split if the

muscle appears pale or ischemic. The skin incision is left

open, but the margins may be loosely reapproximated to

cover vital structures such as the median nerve. Delayed

skin closure or skin grafting is performed as indicated in 5

to 10 days.

Biceps Tendon Rupture at Distal

Insertion

This clinical entity is placed in this chapter on the forearm

rather than the elbow because the major points of anatomy

relate more to the forearm than to the elbow. Although rupture of the distal biceps insertion is much less common than

that of the proximal origin (long head of the biceps), the

functional loss is much greater (2). Distal ruptures treated

nonoperatively have been reported to result in a 60%

decrease in strength of both elbow flexion and supination

(26).

Diagnosis

This injury usually occurs in men and often is associated

with a history of forceful contraction of the biceps against a

heavy load or against unexpected resistance (50). Weak and

painful elbow flexion and forearm supination are noted.

The biceps tendon cannot be palpated in its normal course

in the antecubital fossa, and there may be ecchymosis in the

forearm, elbow, and arm.

Treatment

Most surgeons recommend reattachment of the biceps tendon using a two-incision approach originally described by

Boyd and Anderson (51).

Technique

The avulsed and retracted biceps tendon is identified through

a transverse incision in the antecubital fossa (Fig. 8.36). The

biceps tendon usually is retracted several centimeters proximal

to the antecubital flexion crease and may be located by incision of the deep fascia and retraction of the proximal margin

of the incision. The tendon is grasped and brought distally

into the operative site. A #1 Mersilene or similar suture is

passed through the biceps tendon using a Bunnell-type suture

technique, followed by identification of the bicipital tunnel

between the supinator and the flexor-pronator muscles. The

location of this tunnel is facilitated by supination of the forearm, which brings the radial tuberosity into the bottom of the

operative site. Palpation of the radial tuberosity helps to guide

the surgeon’s finger or blunt instrument into the tunnel,

which is medial to the tuberosity. A second incision is made

on the posterolateral aspect of the elbow, through which the

muscles on the lateral surface of the olecranon are reflected to

expose the head and neck of the radius. The forearm is then

pronated, which brings the radial tuberosity into view. An

osseous trap door is made in the tuberosity and two drill holes

are made beneath the hinge. The Mersilene suture is then

passed from front to back using a curved clamp and the biceps

tendon is brought into the posterolateral operative site, where

the two ends of the suture are passed through the drill holes

and the tendon end passed into the trap door defect. Flexion

of the elbow facilitates placement of the tendon stump into

the trap door defect and tying the suture.

Postoperative Care

The elbow is flexed to 110 degrees and the forearm is placed

in mid-supination. This position is maintained for 2 weeks,

followed by progressive range-of-motion and progressive

resistance exercises.

8.1 Flexor Forearm 451

FIGURE 8.35. Fasciotomy incision for forearm compartment syndrome.

452 Regional Anatomy

FIGURE 8.36. Distal biceps tendon rupture. Incision (A) and anterior exposure (B). Lateral incision (C) and reattachment of biceps tendon (D).

A

B

C

D

ANATOMIC VARIATIONS

Nerve

Martin-Gruber Connection

One of the most significant neural anomalies in the forearm

is the Martin-Gruber anastomosis or connection. Based on

a world literature review, Leibovic and Hastings identified

an overall incidence of 17% (34). Based on their review,

four types (I to IV) were identified (Fig. 8.37).

Type I

Type I was the most common (60%) and was represented

by motor branches from the median to the ulnar nerve to

innervate “median” muscles. Leibovic and Hastings further

subdivided type I into Ia and Ib (34). Type Ia is a branch

from the median nerve to the ulnar nerve in the forearm

that continues on into the hand to innervate the thenar

muscles (those ordinarily supplied by the median nerve).

These are median fibers traveling on the ulnar nerve to the

hand. In type Ia, these fibers innervate thenar muscles only,

and in type Ib they innervate ulnar intrinsic as well as

thenar muscles.

Type II

Type II (35%) sends motor branches from the median to

the ulnar nerve to innervate “ulnar” muscles.

Type III

Type III (3%) sends motor fibers from the ulnar to the

median to innervate “median” muscles.

8.1 Flexor Forearm 453

FIGURE 8.37. The Martin-Gruber connection. Normal pattern and types of median-to-ulnar and

ulnar-to-median nerve connections. (Redrawn from Leibovic SJ, Hastings H II. Martin-Gruber

revisited. J Hand Surg [Am] 17:47–53, 1992, with permission.)

Type IV

Type IV (1%) sends motor fibers from the ulnar to the

median to innervate ulnar muscles. Type IV is divided into

IVa and IVb. Type IV is a branch from the ulnar to the

median nerve in the forearm that continues into the hand

to innervate the ulnar intrinsic muscles. In IVa, these fibers

innervate ulnar intrinsic muscles only, whereas in IVb they

innervate ulnar intrinsic and thenar muscles.

Anatomy/Clinical Significance

The double lines in the median and ulnar nerves in Figure

8.38 indicate possible sites of nerve interruption that could

be partially or completely masked in the various types of

Martin-Gruber connections. In a type Ia connection, a low

median nerve lesion could be completely masked; a low

median or high ulnar lesion would be masked in a type Ib

connection. In type II connection, a high ulnar lesion could

be completely masked. In the rare type III, a high median

lesion may be missed, and in the even rarer type IV, a low

ulnar lesion (IVa) or a low ulnar and high median (type

IVb) lesion may be missed.

Evidence to date indicates that Martin-Gruber connections carry only motor fibers. Uchida and Sugioka found

that the entry point of the crossing fiber from the median

to the ulnar nerve was 3 to 10 cm distal to the medial

humeral condyle (52). They noted that there might be a significant risk of injury to this cross-over connection in ulnar

nerve transposition.

454 Regional Anatomy

FIGURE 8.38. The Martin-Gruber connection. Normal pattern; the double lines represent sites of

nerve interruption that could be partially or completely masked in the various types of MartinGruber connections. (Redrawn from Leibovic SJ, Hastings H II. Martin-Gruber revisited. J Hand

Surg [Am] 17:47–53, 1992, with permission.)

Radial Nerve

Sensory Branch

The sensory component of the radial nerve may be absent

in the forearm and only the motor component may be present. In such cases, the lateral antebrachial cutaneous nerve

innervates the area normally supplied by the radial sensory

branch (3).

Motor Branch (Posterior Interosseous Nerve)

The PIN may pass over instead of through the supinator

(3).

Median Nerve

Although the median nerve usually passes between the two

heads of the PT, it may pass superficial or deep to the two

heads or it may pierce the superficial head. It also may lie

on the superficial rather than deep surface of the FDS. The

median nerve also may split in the forearm and allow passage of the ulnar artery or one of its branches (53).

Ulnar Nerve

The ulnar nerve may pass in front of the medial epicondyle.

The Nerve of Henle

In a study of 40 cadaver upper extremities, McCabe and

Kleinert found this nerve to be present as a branch of the

ulnar nerve in 23 (57%) of the extremities (54). In 18

(78%) of the 23 nerves of Henle identified, the branch

arose 16 cm proximal to the ulnar styloid from the radial

side of the ulnar nerve, near the site where the ulnar nerve

and artery lie parallel in the proximal forearm. This configuration was the more common of the two patterns, and the

authors called this pattern the typical or proximal pattern.

The nerve of Henle traveled distally on the palmar ulnar

surface of the ulnar artery and could be traced in most cases

distal to the wrist flexion crease. At a point 6 cm proximal

to the ulnar styloid, a branch arose from the nerve of Henle

that coursed superficially to pierce the antebrachial fascia

just radial to the FCU musculotendinous junction, presumably to innervate an area of skin of the distal, ulnar,

flexor surface of the forearm. This branch to the skin was

present in 13 of the 18 nerves of Henle that arose proximally. In the remaining five cases, the nerve of Henle arose

approximately 8 cm proximal to the ulnar styloid, and the

authors called this configuration the atypical or distal pattern. This nerve traveled with the ulnar artery for 1 to 2 cm

before branching to the skin as previously described for the

typical or proximal nerve of Henle. The authors noted the

similarity between this distal variant and a prior description

of the palmar cutaneous branch of the ulnar nerve

(PCBUN). They noted that no separate PCBUNs were

found in their 40 dissections.

They concluded that the nerve of Henle provided sympathetic nerve fibers to the ulnar artery and sensory fibers

to the distal forearm and ulnar side of the palm. They

believed that the atypical or distal pattern of the nerve of

Henle and the PCBUN were the same structure, noting

that a previous description of the PCBUN showed it to be

similar in location and prevalence to the distal and atypical

pattern of the nerve of Henle (55).

The findings of McCabe and Kleinert are contrasted

to those of Martin et al., who studied the cutaneous

innervation of the palm in 25 hands and noted the

PCBUN to be present in 4 of 25 specimens and the nerve

of Henle as a sensory branch to be present in 10 of 25

specimens (56). See discussion on innervation of the

palm in Chapter 10A.

Muscle

Brachioradialis

Occasionally, the tendon of insertion at the radial styloid

may be represented by two or three slips.

Clinical Significance

The sensory branch of the radial nerve may pass between

these slips on its way to the dorsal aspect of the wrist, and

should be protected if the insertion of the brachioradialis is

to be detached for transfer or for purposes of exposure of

the distal radius (53).

Accessory Brachioradialis

An accessory brachioradialis, called the supinator longus

accessorius or brachioradialis brevis, arises adjacent to the

brachioradialis and inserts on the radial tuberosity to act as

a true supinator (53). It also may insert into the supinator

or the tendon of the PT, or onto the ulna (53).

Clinical Significance

Spinner described entrapment of the superficial branch of

the radial nerve by the brachioradialis brevis. The site of

compression is located 3 to 4 cm proximal to the arcade of

Frohse (33).

Supinator

The degree of separation of the superficial and deep layers

may vary from complete separation to fusion, and should

be appreciated when looking for the PIN in the supinator

(53). Accessory muscle fascicles may arise from the annular

ligament (53). A proximal fibrous band from the supinator

may be present that may cause PIN compression (27).

8.1 Flexor Forearm 455

Pronator Teres

A portion of the origin of the superficial head of the PT

may be extended proximally by direct extension of the muscle to the medial supracondylar ridge or by a ligament that

connects the muscle to a supracondylar process on the

humerus (53).

Clinical Significance

Either the brachial artery and median nerve or just the

median nerve may pass beneath this abnormally located

portion of the PT to reach the antecubital fossa. In addition, the deep or ulnar head of the PT may be absent.

Flexor Carpi Radialis

The FCR, in addition to its normal insertion on the base of

the index and middle finger metacarpals, may insert on the

trapezium and scaphoid bone (53).

Flexor Carpi Radialis Brevis

The flexor carpi radialis brevis is a small muscle arising from

the radius that inserts into the sheath of the FCR tendon

and may be a source of compression in AINS (27).

Palmaris Longus

This muscle may be digastric or fleshy throughout its

length. It may have a proximal tendon as well as a distal tendon, or it may be fleshy distally and have a tendon proximally (palmaris longus inversus). The tendon of insertion

may comprise one, two, or three slips.

Incidence

This muscle is absent approximately 11% of the time (53).

It is absent more often in women, and on the left side in

both sexes.

Clinical Significance

All of these factors must be considered when the PL is chosen for transfer, tendon graft, or other reconstructive purposes. In addition, median nerve compression may result

from a reversed PL (57,58).

Palmaris Profundus

The palmaris profundus is an anomalous muscle arising from

the middle third of the radius on the lateral aspect that is

superficial to the FDS and deep to the PT (36,53,59). Its

tendinous portion passes through the carpal canal and inserts

onto the deep surface of the palmar aponeurosis (36,59).

Clinical Significance

Because it lies beneath the transverse carpal ligament and

adjacent to the median nerve, it may be a source of compression of the median nerve (60). It also has been reported

to be a source of compression of the AIN proximally (27).

Flexor Carpi Ulnaris

An anomalous radial insertion of the FCU has been

reported in which a part of the ulnar nerve passed through

a split in the FCU tendon at the wrist (61).

Clinical Significance

This anomaly would be significant in surgical procedures

about the FCU tendon, such as opponens plasty, FCU

transfer, or excision of the pisiform, and the wary surgeon

identifies and protects the ulnar nerve when operating in

this area (61).

Anconeus Epitrochlearis

The anconeus epitrochlearis is a small anomalous muscle

near the origin of the FCU proximal to the aponeurosis

joining the humeral and ulnar heads of the FCU. It arises

from the medial border of the olecranon and inserts into

the medial epicondyle. This muscle is superficial to the

ulnar nerve and takes the place of the fibrous arch of the

deep fascia. It may vary in size and shape from small and

fusiform to a thick, rectangular structure that is palpable on

physical examination (62,63). It has been reported to have

a variable incidence as high as 25% (62). It has been

described as an auxiliary extension of the medial portion of

the triceps, but it is anatomically distinct from the triceps

and is innervated by the ulnar nerve. This muscle often is

seen in other species and presumably is an atavistic anomaly in humans. In humans, the muscle may be replaced by

a ligament called the epitrochleoanconeus ligament, and

because its course and attachments are similar to those of

the muscle, this ligament is believed to be a rudiment of the

muscle (64).

Clinical Significance

This muscle crosses over the ulnar nerve in the cubital tunnel and has been reported to be a source of compression of

the ulnar nerve in cubital tunnel syndrome (62,63). In cases

of ulnar neuropathy due to the anconeus epitrochlearis

muscle, treatment is complete or partial excision of the

muscle to relieve any pressure on the nerve (63).

Flexor Digitorum Superficialis

There may be muscular interconnections between the FDS

and the FPL. Occasionally, an accessory muscle is derived

from the FDS and arises from the coronoid process to

attach to one of the deep flexors (accessorius profundus digitorum of Gantzer) (53).

Clinical Significance

This muscle may be a source of compression of the AIN

(27).

456 Regional Anatomy

Flexor Digitorum Profundus

Intertendinous Connections

The degree of functional separation between the FDP of

the four fingers may vary, but if the profundus of the index

finger FDS is completely independent, it may be called the

flexor digitorum indicis. Intertendinous connections from

the FPL to the index FDP are comparatively common. Linburg and Comstock found an incidence of 31% in one

extremity and an incidence of 14% in both extremities on

clinical examination of 194 patients. In 43 cadavers, the

unilateral incidence was 25% and the bilateral incidence

was 6% (65). This finding is known as the Linburg-Comstock anomaly.

Clinical Significance

This intertendinous connection, usually at the wrist or distal forearm level, may interfere with certain specific functions, such as holding and simultaneously cocking the hammer of a pistol. Although the FPL and FDP of the index

finger usually are independent, phylogenetically both tendons are derived from a common mesodermal mass

(65,66).

Flexor Pollicis Longus

The FPL is said to be uniquely human because in primates

there is only one deep digital flexor muscle that provides a

tendon to the thumb as well as the four fingers, in contrast

to the anatomically distinct FDP and FPL musculotendinous units in the human (2,53). Although the primate configuration has been noted in humans, it is very rare compared with the more common abnormality, in which the

tendon of the FPL sends connections to the index FDP

(67).

Gantzer’s Muscle

A more common anomaly is the presence of an accessory

head of the FPL called Gantzer’s muscle. In a study of 25

limbs, an accessory head was found in 52% (13 of 25 limbs)

(40). This accessory head was supplied by the AIN, arose

from the medial humeral epicondyle in 85%, and had a

dual origin from the epicondyle and coronoid process of the

ulna in the remainder. Gantzer’s muscle is posterior to both

the AIN and median nerve (39,40). Its usual insertion is to

the ulnar part of the FPL and its tendon (40).

Clinical Significance

Although the usual insertion of Gantzer’s muscle is the

ulnar side of the FPL (40), it may send anomalous slips to

the index FDP, which may result in pain in the distal forearm as well as the inability to flex the interphalangeal joint

of the thumb without also flexing the DIP joint of the

index finger (40, 65). Although Gantzer’s muscle has not

been implicated as a cause of pronator syndrome

(27,33,38), both Lister and Spinner (33,38) have listed

Gantzer’s muscle as a cause of AINS. Al-Qattan (40) and

Dellon and MacKinnon (39) agree that Gantzer’s muscle is

posterior to both the AIN and median nerve. Al-Qattan

demonstrated that the median nerve was closely related to

Gantzer’s muscle in two situations: (a) when the median

nerve passed deep to the deep head of the pronator, and (b)

when the deep head of the pronator was absent (40).

Kaplan and Spinner noted that there were two other situations in which Gantzer’s muscle might contribute to

median nerve compression in the forearm: (a) a division of

Gantzer’s muscle distally into a slip inserting into the

undersurface of the FDS in the vicinity of the superficialis

arch, and (b) perforation of the median nerve in the proximal forearm by Gantzer’s muscle (68).

Summary

There is some controversy as to the association of Gantzer’s

muscle with AINS. However, Gantzer’s muscle may be

related to median nerve compression in the unique circumstances noted previously, in which the authors dissected a

forearm in which Gantzer’s muscle was present and

demonstrated the possibility of a pincer-like effect between

this abnormal posterior head and the adjacent anterior

FDS that could produce compression of the median nerve

as well as the AIN. The median nerve and AIN passed

through the interval between these two muscles, which

share a common origin on the medial epicondyle. Gantzer’s

muscle may be a cause of inability to flex the interphalangeal joint of the thumb without also flexing the DIP

joint of the index finger.

Vascular

Radial Artery

Many of the anomalies of the radial and ulnar artery in the

forearm have been identified in conjunction with the

development of the radial forearm flap, which requires

sacrifice of the radial artery (69–72). The greatest concern

in harvesting the radial forearm free flap is the integrity of

the ulnar arterial supply of the hand (73,74). The ulnar

artery supplies the hand through the superficial palmar

arch, which is either “complete” in the sense that it provides branches to the thumb and four fingers, or completed through branches from the deep palmar arch (62).

In 265 specimens, Coleman and Anson found a complete

superficial arch in 77.3% of cases (75). The ulnar artery

supply to the long, ring, and little fingers is rarely if ever

compromised by anomalous patterns (74). However, the

index finger and thumb potentially are compromised by

the combination of two concurrent arterial anomalies.

The first anomaly is an incomplete superficial arch that

does not send branches to the thumb and index. The second, which also must be present to produce digital

ischemia, is a complete lack of communication between

8.1 Flexor Forearm 457

the superficial and deep arches. The coexistence of these

two anomalies, which would put the thumb and index finger at risk for ischemia if the radial artery were sacrificed,

occurred in 12% of specimens (74,75). The fact that the

incidence of the predicted ischemia is much less may be

accounted for by the presence of the anterior interosseous

artery and a persistent median artery (73). The latter vessel, which usually joins the superficial palmar arch, may

provide protective circulation to the hand after sacrifice of

the radial artery (68,74).

Other Reported Variations of the Radial Artery

1. The brachial artery has been noted to divide into the

radial and ulnar arteries 8 cm distal to the antecubital

fossa (72). In this configuration, the radial artery passed

deep to the PT and did not have its normal connections

with the skin and subcutaneous tissues in the proximal

half of the forearm. In this configuration, the survival of

the flap is based on a perforating vessel from the radial

artery that is 7 cm proximal to the radial styloid (76). If

the flap is designed proximal to this perforating vessel in

the presence of a deep radial artery, the radial forearm

flap may be devoid of significant blood supply.

2. A small branch of the radial artery was found in its normal position, but the main component was superficial to

the thumb extensors and entered the hand several centimeters radial to its normal location (70).

3. An aberrant dorsal course of the artery has been reported

in which the radial artery passed around Lister’s tubercle

of the radius to enter the hand dorsal to the extensor

tendons (71).

Clinical Significance

Any of the aforementioned anomalies of the radial artery

may make it difficult if not impossible to use the radial

artery–based forearm flap as a viable source of composite

tissue for reconstructive purposes.

Ulnar Artery

The ulnar artery may arise proximal to the elbow and, if so,

it then passes superficially from the antecubital fossa over

the origins of the PT, FCR, and PL muscles. In this configuration, the brachial artery supplies the common

interosseous artery, which in turn supplies the recurrent

artery (2). In this superficial position, the ulnar artery is

commonly under the deep fascia, but rarely subcutaneous.

In some instances, the superficial ulnar artery, after passing

over the PT and FCR, passes beneath the proximal origin

of the PL muscle and then continue its superficial course

(77,78). In the mid-portion of the forearm, the superficial

ulnar artery comes into contact with the lateral or radial

margin of the FCU and then courses distally to assume its

normal course just before reaching the wrist (77,78).

Clinical Significance

The incidence of this anomaly is approximately 3%, and it

should be kept in mind when performing intravenous injections in the cubital fossa to avoid accidental intra-arterial

injection (77). In addition, recognition of such an anomaly

is essential to avoid catastrophic injury to the remaining

blood supply to the hand during harvest of the radial forearm flap (69). If the surgeon is unaware of this anomaly, the

ulnar artery is at risk because the radial forearm flap usually

is raised under tourniquet control and the ulnar artery may

be mistaken for one of the superficial veins of the forearm.

Median Artery

Developmental Anatomy

The median artery is normally a transitory vessel that develops from the axial artery of the upper extremity during early

embryonic life (30). It maintains the superficial palmar

arterial arch while the radial and ulnar arteries are developing (2). When the radial and ulnar arteries develop, the

median artery usually involutes and does not persist into

postfetal life (30). The incidence of a persistent median

artery in adult life has been reported to range from 1% to

17% (30). It usually is a long, thin vessel that arises from

the anterior interosseous artery and passes distally between

the FDP and FPL to the median nerve, which it supplies

throughout its course in the forearm (2). However, in

approximately 8% of individuals, the median artery is a

large vessel that continues into the palm to help form the

superficial palmar arterial arch (53). Although the median

artery may contribute to the superficial palmar arch, if the

arch is incomplete, the median artery becomes the dominant blood supply to the index and long fingers (30). The

median artery also has been shown to be the dominant

blood supply to the proximal median nerve in 30% of cases

(30).

Clinical Significance

The median artery has been associated with carpal tunnel

and pronator syndromes (27,29,30). In the pronator syndrome, the median artery has been noted to penetrate the

median nerve and also to form vascular leashes that constricted the nerve (29,30). The median artery also may represent a significant source of circulation to the hand in

those cases at risk owing to an anomaly of the radial artery,

or after its sacrifice (74).

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460 Regional Anatomy

CHAPTER

FOREARM

JAMES R. DOYLE

PART

EXTENSOR FOREARM

DESCRIPTIVE ANATOMY

Contents

n Nerves: The dorsal forearm contains cutaneous nerves,

the terminal sensory branches of the radial and ulnar

nerves, and the posterior interosseous nerve (PIN).

n Muscles: The dorsal forearm contains the primary extensors of the wrist, the extrinsic finger and thumb extensors, the long abductor of the thumb, and the supinator

and anconeus.

External Landmarks

Important landmarks in the dorsal forearm are the lateral

epicondyle and supracondylar ridge of the distal humerus,

the olecranon process of the ulna, the radial head, the

“mobile wad of three” [brachioradialis, extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis

(ECRB)], the outcropping thumb muscles, the radial and

ulnar styloid, and Lister’s tubercle (Fig. 8.39).

ANATOMIC RELATIONSHIPS

The “Mobile Wad of Three”

Understanding of the anatomic relationships on the extensor aspect of the forearm is best begun by reviewing the

mobile wad of three arising from the supracondylar ridge

and lateral epicondyle of the humerus (1). These three muscles, the brachioradialis, ECRL, and ECRB, are called the

mobile wad of three because they may be grasped between

the surgeon’s thumb and index finger and provide a useful

landmark for placement of incisions and the identification

of deeper structures.

2

Extensor Mnemonic

Henry used a manual mnemonic for identification of the

superficial extensors (1). Using the opposite hand and

beginning with the thumb, which is placed behind the

forearm on the lateral epicondyle, we note that the

obliquely oriented thumb parallels the muscle fibers of the

anconeus. The index marks the extensor carpi ulnaris

(ECU), the middle finger the extensor digiti minimi, and

the ring finger the common finger extensors. The little

finger is not used (Fig. 8.40). These four muscles arise

from a conjoined fibrous origin from the lateral epicondyle. The extensor digitorum communis (EDC) and

extensor digiti minimi attach to the extensor mechanism

in the fingers, and the ECU to the dorsal and ulnar base

of the little finger metacarpal. The apex of the triangular

anconeus arises from the inferior edge of the lateral epicondyle and the base attaches to the proximal edge of the

ulna.

Extensor Forearm Muscle Groups

There are two groups or layers of extensor forearm muscles:

superficial and deep. The muscular components of the

extensor forearm are:

Superficial (Fig. 8.41)

n Anconeus

n ECRL

n ECRB

n EDC

n Extensor digiti minimi (EDM)

n ECU

Deep (Fig. 8.42)

n Supinator

n Abductor pollicis longus (APL)

n Extensor pollicis brevis (EPB)

n Extensor pollicis longus (EPL)

n Extensor indicis proprius (EIP)

8

462 Regional Anatomy

FIGURE 8.39. A, B: Landmarks on the extensor surface of the forearm.

A B

8.2 Extensor Forearm 463

FIGURE 8.40. Henry’s mnemonic for the superficial extensors of the forearm.

464 Regional Anatomy

FIGURE 8.41. A–C: Anatomic relationship

of the superficial extensors to the deep and

“outcropping” muscles of the forearm.

A

B

C

Superficial Muscle Group

Anconeus

The anconeus is a small, triangular muscle that arises by a

tendon from the posterior surface of the lateral epicondyle.

Its fibers course toward the ulna and on the way cover the

posterior aspect of the annular ligament. The fibers insert

on the lateral aspect of the olecranon and proximal onefourth of the posterior surface of the ulna. The anconeus

assists the triceps in elbow extension.

Extensor Carpi Radialis Longus

The ECRL is partially covered by the brachioradialis and

arises distal to the origin of the brachioradialis from the

remaining or distal third of the lateral supracondylar

ridge, from the anterior aspect of the lateral intermuscular

septum, and from the common tendon of origin of the

forearm extensors. The muscle fibers end at the junction

of the middle and proximal thirds of the forearm in a substantial tendon that continues distally to insert on the

radial side of the dorsal base of the index metacarpal. Its

course is deep to the APL and EPB, and over the dorsal

aspect of the radius it lies in a shallow groove. It is an

extensor of the wrist, and because of its insertion on the

index metacarpal produces radial deviation of the hand in

extension when unopposed by the more centrally located

ECRB.

Extensor Carpi Radialis Brevis

The ECRB is shorter than the ECRL and is partially covered by it. It arises from the lateral epicondyle, from a tendon of origin that it shares with the other forearm extensors, and from the lateral collateral ligament of the elbow.

Its muscle fibers end at approximately the middle third of

the forearm and its substantial tendon continues distally,

similar to but ulnar to the ECRL. It also is an extensor of

the wrist, and because of its more central location produces

extension of the wrist without radial deviation. The insertion of the ECRB is at the dorsal surface of the middle finger metacarpal on its radial side but distal to its styloid

process. Over the distal radius, it lies in a shallow groove

separated from its companion radial wrist extensor, the

ECRL, by a low osseous ridge.

Extensor Digitorum Communis

The EDC arises from the lateral humeral condyle by a common extensor tendon, the adjacent intermuscular septa, and

the antebrachial fascia. It divides into four tendons that pass

beneath the extensor retinaculum to insert into the dorsal

extensor expansion over the fingers.

Extensor Digiti Minimi

The EDM is a small muscle ulnar to and usually connected

to the EDC. It arises from the common extensor tendon

8.2 Extensor Forearm 465

FIGURE 8.42. Deep extensor muscle of the forearm.

and from adjacent intermuscular septa. Its tendon, including variations, is described in Chapter 10.

Extensor Carpi Ulnaris

The ECU arises from the lateral epicondyle by the common

extensor tendon, and from the posterior border of the ulna

by an aponeurosis shared with the flexor carpi ulnaris

(FCU) and flexor digitorum profundus. It ends in a tendon

that courses through a groove between the head and styloid

process of the ulna. It attaches to the tubercle of the ulnar

side of the little finger metacarpal. It acts as a wrist extensor

with the ECRB and ECRL, and along with these extensors

acts synergistically with the finger flexors to stabilize the

wrist during forceful grip. The ECU also is an adductor of

the wrist.

Deep Extensor Group

The deep extensor group is unique, according to Henry, in

that all of its tendons (except perhaps the proprius) can be

seen in one’s own hand and that all go to the thumb or

index finger. Henry has further noted that except for the

APL, which arises from both radius and ulna, the tendons

all point to their bone of origin. The EPB points to the

radius and the EPL and EIP to the ulna (1).

Supinator

The supinator was included in the deep muscle group in the

first part of this chapter (Flexor Forearm). Although the

supinator is considered to be a deep extensor of the forearm,

it was included there because it often is encountered in surgical approaches to the flexor aspect of the forearm. The

supinator wraps around the proximal one-third of the

radius and has superficial and deep layers. The superficial

portion arises from the lateral epicondyle of the humerus,

the collateral ligament of the elbow joint, and the annular

ligament. The deep head arises from the “supinator crest” of

the ulna as well as portions of the annular ligament and collateral ligament. It attaches to the volar and lateral side of

the proximal third of the radius as far distally as the insertion of the pronator teres (PT). Its oblique insertion parallels the origin of the flexor pollicis longus. The PIN courses

between the two layers of the muscle at almost a right angle

to the muscle fibers. The supinator acts in slow, unopposed

supination of the forearm and together with the biceps in

fast or forceful supination.

Abductor Pollicis Longus

The APL arises from the posterior shaft of the ulna distal

to the anconeus, from the adjacent interosseous membrane (IOM), and from the posterior surface of the radius

distal but adjacent to the insertion of the supinator. It

curves over the radial aspect of the wrist to insert by multiple (two to four) tendons into the dorsal and palmar

base of the thumb metacarpal. It acts to abduct the

thumb along with the abductor pollicis brevis and, with

the EPL and EPB, extends the thumb at the carpometacarpal joint.

Extensor Pollicis Brevis

The EPB is ulnar to and closely applied to the APL. It

arises from the posterior surface of the radius and the IOM

distal to the origin of the APL. It inserts on the dorsal base

of the proximal phalanx of the thumb, where it extends the

proximal phalanx and the thumb metacarpal. Accompanied by the APL, it travels through a synovium-lined

fibroosseous canal over the radial styloid (the first dorsal

compartment), where it and the APL may be involved with

de Quervain’s stenosing tenosynovitis (2). In one-third of

wrists, the EPB may travel in a separate canal, and both

canals must be released in de Quervain’s tenosynovitis to

relieve the condition (3). The APL and EPB, the so-called

outcropping muscles of the thumb, emerge from between

the muscle bellies of the EDC and ECRB and obliquely

cross over both the ECRB and ECRL tendons and their

synovial sheaths.

Extensor Pollicis Longus

The EPL arises from the IOM and the adjacent dorsal

aspect of the ulna in the middle third of the forearm. Its origin is distal to the origin of the APL and proximal and ulnar

to the EPB origin. It passes to the ulnar side of Lister’s

tubercle, which acts as a fulcrum point or “turning pulley”

to enable the EPL to change its course and thus end on the

dorsal aspect of the distal phalanx of the thumb. The action

of the EPL includes extension of the interphalangeal and

metacarpophalangeal (MCP) joints, elevation of the thumb

into the plane of the palm, and adduction of the extended

thumb.

Extensor Indicis Proprius

The EIP arises from the dorsal surface of the ulna and the

adjacent surface of the IOM distal to the EPL and ulnar to

the EPB. It continues to the extensor hood of the MCP

joint of the index finger. It almost always is situated to the

ulnar side of the EDC tendon to the index. The details of

the normal arrangement and anatomic variations are discussed in Chapter 10.

Intersection Zones

The extensor surface of the forearm demonstrates two zones

of muscle–tendon “intersection” (see Fig. 8.41B and C), the

first of which is the crossing over of the EPB and APL over

the radial wrist extensors. The second zone of intersection is

between the EIP and EPL with the overlying finger extensors. Only the first zone has clinical relevance. This zone

and its clinical implications are discussed later, under the

section on Clinical Correlations.

466 Regional Anatomy

SURGICAL EXPOSURES

Posterior Interosseous Nerve

Four surgical approaches have been described for exposure of the PIN (4–9). The first is the anterolateral

approach in the antecubital fossa, the second is a transbrachioradialis, and the third and fourth are posterolateral approaches.

Anterolateral Approach

Indications

The anterolateral approach has been described as an excellent approach for exposure of all possible compressive structures in radial nerve compression syndromes and has been

advised as the approach of choice when the exact area of

compression is not clear from the preoperative evaluation

(4,6).

Landmarks

Useful landmarks are the “mobile wad of three,” the lateral

aspect of the biceps/brachialis muscles, the elbow flexion

crease and the biceps tendon.

Patient Position/Incision

With the patient supine and the forearm in supination the

incision begins 4-5 cm proximal to the elbow flexion crease

on the anterolateral aspect of the arm between the biceps/

brachialis and brachioradialis (Fig. 8.43). It crosses the

antecubital fossa to the inner or medial aspect of the

“mobile wad” where it continues distally. The biceps tendon

8.2 Extensor Forearm 467

FIGURE 8.43. Patient position (A) and incision (B) for the anterolateral approach to the posterior

interosseous nerve (PIN).

A

B

provides a useful and readily palpable landmark to identify

the inner margin of the “mobile wad.”

Technique

Staying to the lateral side of the biceps tendon the radial

recurrent branch of the radial artery is identified, ligated

and retracted laterally to expose the interval between the

brachioradialis and the brachialis muscle belly (Fig.

8.44). Beginning at or proximal to the elbow flexion

crease the radial nerve is traced distally while looking for

potential sites of compression. Identification of the

fibrous edge of the ECRB as an impingement factor is

facilitated by pronation of the forearm and flexion of the

wrist. During this maneuver the radial nerve is viewed to

note any possible impingement by the fibrous edge of the

ECRB. If any impingement is noted or suspected the

fibrous margin of the ECRB is excised (see Fig. 8.18).

The fibrous arcade of Frohse is identified and incised (6).

Care is taken to avoid injury to the branch of the radial

nerve to the superficial head of the supinator while dividing the arcade of Frohse. Complete division of the arcade

may also be accompanied by incision of the superficial

portion of the supinator from the arcade of Frohse to the

point of arborization and exit of the PIN from the distal

aspect of the supinator. Exposure of the distal course of

the nerve and its distal point of exit is facilitated by

pronation of the forearm and gentle retraction of the

“mobile wad.”

468 Regional Anatomy

FIGURE 8.44. Deep dissection in the anterolateral approach to the posterior interosseous nerve

(PIN). A: The biceps is a useful guide to the radial recurrent artery, which may be 9hooked9 with

the surgeon’s finger before ligation.

A

Transbrachioradialis Approach

Indications

This approach is said to be the most direct to the radial tunnel and with experience may be the most accessible (6–8).

Landmarks

The “mobile wad of three” and especially the brachioradialis and the radial head.

Patient Position/Incision

With the patient supine, the elbow flexed and the forearm

pronated a 6 cm long incision is made directly over the brachioradialis and centered over the neck of radius in the proximal forearm (Fig. 8.45). The incision may be associated

with a significant scar and the originator of the technique

has subsequently suggested a transverse incision (7,8).

Technique

Dissection is directly through the muscles fibers of the brachioradialis down to the PIN (7,8). The longitudinal, blunt

muscle splitting is carried deeper until fat is seen in the

depths of the dissection, which signals the location of the

superficial branch of the radial nerve. Beneath this branch

is the arcade of Frohse and the PIN. The dissection is carried proximally and distally to decompress the five potential

areas of compression (see section on Radial Tunnel Syndrome).

8.2 Extensor Forearm 469

FIGURE 8.44. (continued) B: Ligation of the radial recurrent vessels permits medial retraction

of the radial artery and lateral retraction of the brachioradialis and extensor carpi radialis longus

to expose the PIN and supinator muscle.

B

470 Regional Anatomy

FIGURE 8.45. Transbrachioradialis approach to the posterior interosseous nerve (PIN). A: A 6 cm

long incision is made directly over the brachioradialis and centered over the neck of radius. B:

Blunt muscle splitting is carried deep until fat is seen in the depths of the dissection, which signals the location of the superficial branch of the radial nerve. Beneath this branch is the arcade

of Frohse and the PIN.

A

B

Posterolateral Approaches

Indications

It has been said that posterolateral approaches to the PIN are

best suited for exposure of the distal portion of the nerve due

to the limited proximal exposure, and that if the lesion is not

localized to the area of the Arcade of Frohse, the posterolateral approach should not be used (4). This concept may not

be true if the fascial origin of the wrist and finger extensors is

carefully removed from the lateral epicondyle, which can provide a more comprehensive proximal exposure.

Landmarks

Useful landmarks are the lateral epicondyle, the “mobile

wad of three,” the EDC and the ECU.

Position/Incision

With the patient supine, the forearm in pronation and the

elbow slightly flexed a 7–8 cm long incision is made beginning just distal to the lateral epicondyle in the interval

between the ECRB and the EDC (Fig. 8.46).

8.2 Extensor Forearm 471

FIGURE 8.46. Posterolateral approach to the posterior interosseous nerve: incision and landmarks. The incision is located between the extensor carpi radialis brevis (ECRB) and the extensor

digitorum communis (EDC). The greater mobility of the 9mobile wad of three9 (brachioradialis,

extensor carpi radialis longus and brevis) compared with the relatively fixed EDC aids in placement of the incision.

Technique

Standard Posterolateral Approach. The standard posterolateral approach is begun by identifying the interval

between the ECRB and the EDC (Fig. 8.47). This is

done by grasping the “mobile wad” of muscles containing

the brachioradialis, ECRL and ECRB which move more

readily than the adjacent EDC. The comparative difference in mobility between the mobile wad and the EDC

indicate the interval of approach. After incision of the

fascia the interval is further verified by noting the muscle

separation distally between the ECRB and the EDC

which are separated by a long narrow “V” shaped interval. The proximal portion or apex of this narrow triangle

begins at approximately the junction of the proximal and

middle thirds of the forearm and the base, which is distal,

contains the origins of the “outcropping” muscles of the

thumb. Working from this distal interval (the “back

door”), the muscles are split proximally to reveal the

underlying supinator. Release of the ECRB and ECRL

from the epicondyle and the supracondylar ridge respectively will permit visualization of the radial nerve well

prior to its entrance into the supinator. Caution: If

release of these muscle origins is required, the radial collateral ligament complex, especially the lateral ulnar collateral ligament portion (see section on elbow ligaments

in Chapter 7), must not be released. The PIN is sandwiched between the two heads of the relatively thin

supinator and courses across the direction of its muscle

fibers. If required, identification of the PIN in the substance of the supinator may be made by making a small

incision in the direction of the muscle fibers at a spot

three fingerbreadths distal to the radial head on the back

of the radius (1). Further exposure is best achieved by

identification of the nerve proximally and releasing it

from its muscle envelope from proximal to distal. Great

care is taken at the distal end to avoid injury to the multiple branches as they exit the supinator to avoid postoperative paresis (5).

Modified Posterolateral Approach. A somewhat similar

approach between the muscles of the fifth and sixth extensor compartments (EDM and ECU) has been described

and is said to allow complete visualization of: the nerve

through the supinator, all potential compressing structures, and the lateral humeral epicondyle (5). This

approach allows simultaneous management of the radial

nerve problem as well as a possibly coexistent lateral epicondylitis (5). The incision begins at the lateral epicondyle and continues distally on the mid-posterior aspect

of the forearm to approximately the mid-portion of the

forearm. The correct fascial incision is in the interval

between the EDM and the ECU. Identification of this

interval is aided by noting small vessels that exit the fascia

between these muscle groups (5). There is a septum

between these two muscles that is contiguous proximally

with the lateral collateral ligament, and staying just anterior to this septum avoids injury to this structure (5).

Retraction of the EDM dorsally reveals the underlying

supinator. Identification of the PIN proximally as it enters

the supinator is aided by release of the conjoined tendon

of origin of the wrist and finger extensors from the lateral

epicondyle. This proximal release also allows identification of any proximal fibers that may compress the PIN. In

my experience, this approach is not as easy as the standard

posterolateral approach.

472 Regional Anatomy

FIGURE 8.47. Posterolateral approach to

the posterior interosseous nerve (PIN): deep

dissection. The interval between the extensor carpi radialis brevis (ECRB) and the

extensor digitorum communis (EDC) is

found distally and these muscles are separated proximally to reveal the underlying

supinator. Release of the ECRB and extensor

carpi radialis longus from the epicondyle

and the supracondylar ridge, respectively,

permits visualization of the radial nerve well

before its entrance into the supinator. The

PIN is sandwiched between the two heads

of the relatively thin supinator and courses

across the direction of its muscle fibers. If

required, identification of the PIN in the

substance of the supinator may be made by

making a small incision in the direction of

the muscle fibers at a spot three fingerbreadths distal to the radial head on the

back of the radius.

Approach to the Posterior Radius

Indications

Portions or all of this approach may be used for exposure of

the radius for fractures, fracture dislocations, tumors, or

infection.

Landmarks

Useful landmarks include the lateral epicondyle, the radial

head, Lister’s tubercle, and the radial styloid.

Position/Incision

With the patient supine, the elbow slightly flexed, and the

forearm in pronation, an incision is begun at the lateral epicondyle of the humerus and ending at Lister’s tubercle at

the distal radius (Fig. 8.48). The incision may be straight or

gently curved.

Technique

The interval between the ECRB and the EDC is used for

exposure of the radius, and this interval may be identified

8.2 Extensor Forearm 473

FIGURE 8.48. Posterior approach to the radius: patient position, landmarks, and incision. The

interval between the extensor carpi radialis brevis and the extensor digitorum communis (EDC) is

used for siting the incision and is identified by grasping the muscles of the 9mobile wad of three9

(brachioradialis, extensor carpi radialis longus and brevis), which move more readily than the

adjacent EDC.

by grasping the muscles of the mobile wad of three (the brachioradialis, ECRL, and ECRB), which move more readily

than the adjacent EDC (Fig. 8.49). The comparative difference in mobility between the mobile wad and the EDC

indicates the interval of approach. After incision of the fascia, the interval is further verified by noting the muscle separation distally between the ECRB and the EDC. Working

from this distal interval (the “back door”), the muscles are

split proximally to reveal the underlying supinator. The

supinator muscle encases the proximal third of the radius

and contains the PIN, which must be dealt with to complete this exposure successfully. The approach to the PIN

depends on the requirements or goals of the surgery. If complete exposure of the radius is required, the PIN is exposed

proximal to its entrance into the supinator; if a less than

complete exposure is required, the PIN may be identified at

its more distal exit point from the supinator (approximately

1 cm proximal to the distal edge of the supinator). If proximal identification is required, the ECRB and ECRL are

partially detached from the lateral epicondyle and supracondylar ridge to identify the PIN before its entrance into

the supinator. Detachment of these muscles is done with

care to avoid injury to the lateral elbow ligaments, especially

the lateral ulnar collateral ligament component (see discussion of elbow ligaments in Chapter 7). After identification

of the nerve proximally, the superficial half of the “supinator sandwich” is opened by incising the supinator muscle

across its fibers along the course of the PIN. Multiple motor

branches from the PIN to the supinator are encountered

and should be preserved. After dissection of the PIN, the

forearm may be supinated to reveal the attachment of the

supinator along the volar surface of the radius, where it may

be removed by subperiosteal dissection. A suitable alternative to dissecting the PIN from the supinator would be to

474 Regional Anatomy

FIGURE 8.49. Posterior approach to the radius: the interval between the extensor carpi radialis

brevis and the extensor digitorum communis (EDC) is identified distally, and the muscles are split

proximally to reveal the underlying supinator. After identification of the posterior interosseous

nerve (PIN), the superficial half of the 9supinator sandwich9 is opened by incising the supinator

muscle across its fibers along the course of the PIN. In the middle third of the radius, the insertion of the pronator teres (PT) as it crosses over from the volar compartment is found near the

distal insertion of the supinator. A short longitudinal incision here, which is a nerve- and vascular-free zone, allows for easy identification and removal of the insertion of the PT. The muscle

bellies of the abductor pollicis longus and extensor pollicis brevis may be mobilized for retraction

by releasing their margins proximally and distally as required to facilitate exposure of the radius.

The interval between the radial wrist extensors and the nearby extensor pollicis longus and EDC

is used to expose the distal third of the radius.

detach the insertion of the supinator as just described without dissecting the PIN from its “sandwich,” but only if the

PIN was clearly identified first both proximally and distally.

In the middle third of the radius, the insertion of the PT is

encountered as it crosses over from the volar compartment

and is found near the distal insertion of the supinator. The

point of insertion of the PT tendon is in a comparative bare

spot on the radius between the distal margin of the supinator and the adjacent outcropping muscles of the thumb.

With the forearm in mid-position, this bare spot can be palpated and coincides with the longitudinal midpoint of the

radius. A short longitudinal incision here, which is in a

nerve- and vascular-free zone, allows for easy identification

and removal of the insertion of the PT if needed for a tendon transfer. The muscle bellies of the APL and EPB also

are encountered in this region and may be mobilized for

retraction by releasing their margins proximally and distally

as required to facilitate exposure of the radius. The interval

between the radial wrist extensors and the nearby EPL and

EDC is used to expose the distal third of the radius.

Throughout this dissection, the branches of the PIN must

be handled gently if at all to avoid neurapraxia or permanent damage.

Approach to the Ulnar Shaft

Indications

Approaches to the ulna are used for management of fractures, tumors, or infection.

Landmarks

Useful landmarks are the olecranon process, the subcutaneous margin of the ulna, and the ulnar styloid.

Patient Position/Incision

With the forearm in pronation and the elbow flexed to 90

degrees and resting on a soft pad to elevate it above the

operating hand table, an incision is begun at the olecranon

and continued distally over the subcutaneous margin of the

ulna to end at the styloid process at the wrist (Fig. 8.50).

Portions or all of this incision may be used as required by

the surgical exposure.

Technique

The ulna represents the medial mid-axial line of the forearm and has no wraparound or cross-over muscles to contend with in surgical exposures. The subcutaneous margin

of the ulna distinctly separates the volar and dorsal surface

of the forearm and is easily palpable throughout its course,

making dissection and surgical approaches relatively easy.

The ECU and FCU, respectively, flank the dorsal and

volar aspects of the ulna (Fig. 8.51). Proximally, the exposure is safe as long as the dissection is subperiosteal.

Although the ulnar nerve may be at risk in very proximal

exposures as it passes through the two heads of the FCU,

injury to this nerve may be avoided by exposing the nerve

8.2 Extensor Forearm 475

FIGURE 8.50. Surgical approach to the ulna: patient position, landmarks, and incision.

before it enters the FCU. Injury to other structures, such

as the ulnar artery, is unlikely as long as the dissection

remains subperiosteal. However, the dorsal or posterior

cutaneous sensory branch of the ulnar nerve is at risk in

this exposure. The ulnar nerve gives off the important dorsal sensory branch an average of 6.4 cm from the distal

aspect of the head of the ulna and 8.3 cm from the proximal border of the pisiform. Its mean diameter at origin is

2.4 mm. The nerve passes dorsal to the FCU and pierces

the deep fascia to become subcutaneous on the medial

aspect of the forearm at a mean distance of 5 cm from the

proximal edge of the pisiform. The nerve gives an average

of five branches with diameters between 0.7 and 2.2 mm

distal to its exit from beneath the FCU. These 5 branches

pass over the dorsal medial aspect of the wrist, hand, ring,

and little fingers (10).

CLINICAL CORRELATIONS

De Quervain’s Tenosynovitis

Description and Findings

In 1895, de Quervain published his description of tenosynovitis involving the first dorsal extensor compartment containing the APL and EPB tendons (2). The well known

condition that bears his name is characterized by pain over

the region of the radial styloid and often is associated with

swelling, tenderness, or crepitation in the fibroosseous

canal.

Diagnosis

The most pathognomonic objective sign is Finkelstein’s test,

which is correctly performed by grasping the patient’s

476 Regional Anatomy

FIGURE 8.51. The extensor and flexor carpi ulnaris (FCU), respectively, flank the dorsal and volar

aspects of the ulna. Proximally, the exposure is safe as long as the dissection is subperiosteal. Distally, however, the dorsal or posterior cutaneous sensory branch of the ulnar nerve is at risk in

this exposure. This branch is on average 6.4 cm from the distal aspect of the head of the ulna and

8.3 cm from the proximal border of the pisiform. The nerve passes dorsal to the FCU and pierces

the deep fascia to become subcutaneous on the medial aspect of the forearm at a mean distance

of 5 cm from the proximal edge of the pisiform.

thumb and then ulnar deviating the hand (11) (Fig. 8.52).

A false-positive test may result if the thumb is flexed in the

palm and grasped by the patient’s fingers, followed by ulnar

deviation of the wrist (12). The reader may be convinced of

the validity of this concept when this maneuver is tried on

his or her own wrist (see discussion of Finkelstein’s test in

the Appendix).

Relevant Anatomy of de Quervain’s

Tenosynovitis

The APL and EPB ordinarily share a common fibroosseous

canal (the first dorsal compartment), which contains two to

four slips of the APL and a single slip of the EPB. Surgical

release of the fibrous tissue roof of this canal usually is associated with relief of the symptoms associated with this condition. However, a second canal that contains the EPB has

been identified in 34 of 100 cadaver wrists (3). This septum, which formed a separate narrow compartment for the

EPB, ranged in length from 0.5 to 2 cm. Failure to appreciate the relatively high incidence of a separate compartment for the EPB may lead to the false assumption that one

of the multiple tendon slips of the APL noted at the time of

surgery is the EPB (3). If traction on one of the unroofed

tendons does not result in extension of the MCP joint of

the thumb, a separate canal or compartment must be

searched for (usually dorsally) and released. The presence of

a second canal may, in some instances, explain the failure to

improve after a steroid injection into the first compartment.

In those cases, a second and more dorsal injection may be

tried. In addition to the need for complete release of the

involved tendons, the sensory branches of the radial nerve

must be identified and protected during release of the first

dorsal compartment (Fig. 8.53).

Radial Tunnel Syndrome

Anatomy

In the mid-portion of the arm, the radial nerve passes

through the spiral groove to enter the anterolateral aspect of

the distal third of the arm on its way to the forearm, where

it lies between the brachioradialis laterally and the brachialis

medially. The ECRL covers it anterolaterally, and the

capitellum of the humerus is posterior. The radial tunnel

begins at the level of the radiohumeral joint and extends

through the arcade of Frohse to end at the distal end of the

supinator (6). Division of the radial nerve into motor (posterior interosseous) and sensory (superficial radial) components may occur at any level within a 5.5-cm segment from

2.5 cm above to 3 cm below Hueter’s or interepitrochlear

line (a line drawn through the tips of the epicondyles of the

humerus) (13). The superficial radial nerve remains on the

underside of the brachioradialis until it reaches the midportion of the forearm and is not subject to compression in

the radial tunnel (6).

Symptoms

The radial tunnel syndrome (RTS) must be distinguished

from PIN syndrome (PINS): RTS is a subjective symptom

complex without motor deficit that involves a motor

8.2 Extensor Forearm 477

FIGURE 8.52. Finkelstein’s test: the correct (A) and incorrect (B) technique. Finkelstein’s test is

correctly performed by grasping the patient’s thumb and then ulnar deviating the hand. A falsepositive test may result if the thumb is flexed in the palm and grasped by the patient’s fingers,

followed by ulnar deviation of the wrist.

A B

nerve, in contrast to PINS, which is an objective complex

with motor deficit affecting a motor nerve (6). The symptoms in RTS are similar to lateral epicondylitis, with complaints of pain over the lateral aspect of the elbow that

sometimes radiates to the wrist (5,9). Because the pain is

believed to be due to compression of a motor nerve, the

description of the pain as a deep ache is not surprising. A

dynamic state may exist in which pronation, elbow extension, and wrist flexion are combined with contraction of

the wrist and finger extensors to produce compression of

the PIN (9).

Physical Findings/Provocative Tests

These may include point tenderness 5 cm distal to the lateral epicondyle. The absence of sensory or motor disturbances in RTS is characteristic. To a limited extent,

provocative tests may give some indication of the

anatomic location of the compression, but are not always

reliable. The so-called middle finger test involves extension of the middle finger with the elbow in extension and

the wrist in neutral. The test is considered to be positive if

pain is produced in the region of the proximal portion of

the ECRB (6). Sanders has modified this test as follows:

With the elbow in full extension, the forearm in full

pronation, and the wrist held in flexion by the examiner,

the patient is asked actively to extend the long and ring

fingers against resistance. According to Sanders, these

positional modifications produce maximum compression

on the PIN and represent a more reliable form of the test

(9). If symptoms are reproduced with the elbow in full

flexion, the forearm in supination, and the wrist in neutral, then fibrous bands are suspected (6). Reproduction of

symptoms by passive pronation of the forearm with the

elbow in 45 to 90 degrees of flexion and the wrist in full

flexion indicates entrapment by the ECRB. Compression

at the arcade of Frohse is suspected if the symptoms are

reproduced by isometric supination of the forearm in the

fully pronated position (6).

Diagnostic Tests

Electrodiagnostic studies to date have not been useful in the

diagnosis because there are no motor deficits, and conduction velocity studies through the radial tunnel are not reliable. However, the most reliable test is the injection of 2 to

3 mL of 1% lidocaine without epinephrine into the radial

tunnel (4,6). Relief of pain and a PIN palsy confirms the

diagnosis. A prior injection into the lateral epicondylar

region without relief of pain also supports the diagnosis (4).

Anatomic Sites of Compression

The five structures in the radial tunnel that represent potential sites of compression may be recalled by a useful

mnemonic (Fig. 8.54): FREAS (6). The structures from

proximal to distal are: Fibrous bands, Recurrent radial vessels (the leash of Henry), Extensor carpi radialis brevis,

Arcade of Frohse, and Supinator (the distal border). The

fibrous bands are anterior to the radial head at the beginning of the radial tunnel and are the least likely cause of

compression. The radial recurrent vessels cross the PIN to

supply the adjacent brachioradialis and ECR muscles, and

it is postulated that engorgement of these vessels with exercise may compress the nerve (6,9). The tendinous proximal

margin of the ECRB also may compress the PIN and may

be mistakenly identified as the arcade of Frohse, which lies

478 Regional Anatomy

FIGURE 8.53. Relevant anatomy of de Quervain’s tenosynovitis.

The abductor pollicis longus (APL) and extensor pollicis brevis

(EPB) ordinarily share a common fibroosseous canal (the first

dorsal compartment) that contains two to four slips of the APL

and a single slip of the EPB. A second canal may be present that

contains the EPB tendon. If traction on one of the unroofed tendons does not result in extension of the metacarpophalangeal

joint of the thumb, a separate canal or compartment must be

searched for and released. Note also the proximity of the dorsal

sensory branches of the radial nerve, which are at risk during

surgery.

FIGURE 8.54. A: Artist’s depiction of potential radial nerve compression sites at the elbow and

forearm in radial tunnel syndrome. F, fibrous tissue bands; R, radial recurrent artery; E, extensor

carpi radialis brevis (fibrous leading edge); A, arcade of Frohse ; S, supinator. These potential sites

of compression may be recalled by a useful mnemonic: FREAS. B: Fresh cadaver dissection of right

arm anterolateral view (proximal is to the left) showing the radial nerve between the brachialis

and extensor carpi radialis longus muscle bellies. The angled probe is tenting up the fibrous tissue bands that may compress the radial nerve in radial tunnel syndrome.

479

A

B

deep to the proximal margin of the ECRB muscle (4,6).

The arcade of Frohse is the fibrous proximal border of the

superficial portion of the supinator (6–13). It is the most

common site of compression of the PIN and is located from

3 to 5 cm below Hueter’s line (14). Eversmann has found

that sometimes the tendinous margin of the ECRB and the

arcade of Frohse may overlap and form a scissors-like pincer effect on the radial nerve in this area (4). It is appropriate to continue the exploration to the distal border of the

supinator, although it is a rare site of compression. More

often, a mass such as a ganglion may be found beneath the

superficial portion of the supinator (4,6).

Posterior Interosseous Nerve Syndrome

In contrast to RTS, PINS is characterized by objective

motor signs of entrapment of the PIN manifested by weakness or complete palsy of the finger and thumb extensors.

There usually is no history of antecedent trauma.

Physical Findings

In complete PINS, active extension of the wrist occurs with

radial deviation owing to loss of the ECRB, whereas the

more proximally innervated ECRL remains intact. There is

associated loss of finger and thumb extension. Partial loss of

function is more common, with lack of extension of one or

more fingers or isolated loss of thumb extension (4,6). Sensation always is intact.

Diagnostic Tests

In contrast to RTS, electromyography is positive in the

muscles innervated by the PIN. Computed tomography

scans or magnetic resonance imaging may show a mass in

the radial tunnel (6).

Surgical Exposures

Surgical exposure for RTS or PINS is described in the section on Surgical Exposures, earlier.

Radial Neuritis at the Wrist

Wartenberg in 1932 described an isolated neuritis of the

sensory branch of the radial nerve (15). Although a variety

of causes have been implicated, the most common causes

are iatrogenic or traumatic.

Anatomy

The sensory branch of the radial nerve (SBRN) begins in

the volar and proximal aspect of the forearm and continues

to the distal forearm under cover of the brachioradialis,

where it enters the subcutaneous layer of the dorsal-radial

aspect of the distal forearm between the tendons of the brachioradialis and the ECRB (Fig. 8.55). Its exit point is a

mean 9 cm proximal to the radial styloid and it usually

bifurcates into two branches a mean of 5.1 cm proximal to

the radial styloid. These two branches pass close to the first

dorsal compartment over the radial styloid. The dorsalmost

branch divides into multiple branches and continues to the

thumb–index finger web space and the index and middle

fingers, whereas the volar branch becomes the dorsoradial

digital branch of the thumb (16).

Surgical Risks to the Sensory Branch of the

Radial Nerve

A recognized risk in the application of external fixator pins

for distal radius fractures is injury to the SBRN. The mean

distance of the nearest branch from the center of the first

dorsal compartment is less than 0.5 cm, and in many

instances a branch runs directly over the center of the first

dorsal compartment. This places the branches of the SBRN

at risk during release of the first dorsal compartment for de

Quervain’s tenosynovitis or when a distal radial bone graft

is taken from the area between the first and second dorsal

compartments. During repair or reconstruction of radial or

ulnar collateral ligaments at the thumb MCP joint, dorsal

digital branches are nearby. Similarly, the course of the

SBRN should be kept in mind during placement of arthroscopic portals, limited wrist arthrodesis, open reduction

and internal fixation of distal radius or scaphoid fractures,

or procedures on the basilar joint of the thumb (16).

Intersection Syndrome

Intersection syndrome presents with localized pain and

sometimes swelling where the muscle bellies of the APL and

EPB intersect the ECRL and ECRB tendons in the dorsal

and distal forearm. This area, approximately 4 cm proximal

to the radial styloid, also may show redness and crepitation

in severe cases.

Pathology

The condition has been variously referred to as peritendinitis crepitans, APL bursitis, and cross-over tendinitis. Grundberg and Reagan concluded, however, that the condition

was in fact tenosynovitis of the second dorsal compartment

(ECRL and ECRB) (17). They noted that the zone of crossover or intersection of the APL and EPB muscle bellies over

the ECRL and ECRB tendons represented the site of complaint and physical findings, but not the site of the true

pathologic process (Fig. 8.56). They concluded that because

the ECRL and ECRB were encased in a tight compartment,

the symptoms and physical findings did not present at the

site of the true lesion, but rather proximal to it. Surgical

release of the second dorsal compartment revealed charac480 Regional Anatomy

8.2 Extensor Forearm 481

FIGURE 8.55. Sensory branch of the radial nerve. This

branch begins in the volar and proximal aspect of the

forearm and continues to the distal forearm under

cover of the brachioradialis to the dorsal-radial aspect

of the distal forearm, where it exits between the tendons of the brachioradialis and the extensor carpi radialis brevis at a mean of 9 cm proximal to the radial styloid. It usually bifurcates into two branches a mean of

5.1 cm proximal to the radial styloid. These two

branches pass close to the first dorsal compartment over

the radial styloid. The dorsalmost branch divides into

multiple branches and continues to the thumb–index

finger web space and the index and middle fingers, and

the volar branch becomes the dorsoradial digital branch

of the thumb.

482 Regional Anatomy

A

B

teristic synovitis and uniformly corrected the problem.

They noted two similar conditions in which the site of the

lesion was distal but manifested itself proximally: flexor

tenosynovitis of the finger and flexor tenosynovitis of the

wrist flexors (17).

Treatment

If conservative measures for relief of the tenosynovitis are

not successful, release of the second compartment is performed through a longitudinal incision centered over the

radial wrist extensors that starts over the wrist and continues proximally to the swollen area. The EPL crosses over the

ECRL and ECRB in this area through a separate sheath,

but may be at risk. Similar precautions are required for the

dorsal sensory branch of the radial nerve.

Extensor Indicis Proprius Syndrome

EIP syndrome usually manifests itself as dorsal wrist pain

that is localized to the musculotendinous junction of the

EIP. The pain is aggravated by use of the wrist and hand,

usually during strenuous activities. Symptoms are localized

to the dorsum of the wrist over the fourth dorsal compartment.

Physical Findings

Pertinent physical findings include swelling and tenderness

localized to the radial side of the fourth dorsal compartment. The swelling usually diminishes with wrist extension

and is most noticeable during wrist flexion. Crepitation

may be present with wrist and finger movement and localized tenderness usually is present over the radial side of the

fourth compartment.

Pertinent Anatomy

In a study of 263 specimens, Cauldwell et al. noted that

the EIP usually had a 1:1 ratio between muscle and tendon and that the musculotendinous junction was within

the confines of the fourth dorsal compartment in 75% of

the specimens. Four percent of the specimens had muscle

beyond the distal confines of the dorsal compartment

(18). Ritter and Inglis, who reported this syndrome in

1969, noted that the fourth extensor compartment was

small, measuring 8 to 10 mm wide. Their anatomic studies revealed that the four EDC and the EIP tendons were

loose inside the fourth compartment when the wrist and

fingers were extended, but with wrist and finger flexion,

the EIP musculotendinous junction would pass into the

fourth compartment so that a probe could not be passed

through the compartment. They concluded that any

increase in size of any of the contents of the fourth compartment, such as hypertrophy of the EIP in a training

athlete or synovitis of the surrounding tendon sheaths,

could produce pain and disability (19).

Diagnostic Test

In 1973, Spinner and Olshansky described a useful diagnostic test for this condition. With the wrist in complete

flexion, the patient is asked to perform extension of the

index finger MCP joint against resistance. Pain that is radial

and distal to Lister’s tubercle is considered to represent a

positive test for EIP syndrome (20).

Extensor Pollicis Longus Tenosynovitis

Etiology/Pathogenesis

Tenosynovitis of the EPL is a relatively uncommon condition and, excluding rheumatoid arthritis, the most common

associated condition is a fracture of the distal radius. Surprisingly, it is the anatomically reduced or initially undisplaced fractures that usually are associated with this condition. The tendency for EPL rupture may be due to

pressure-induced ischemia in an intact and unyielding

fibroosseous canal, in contrast to those canals that are

decompressed because of the comminuted and displaced

Colles fractures (21).

8.2 Extensor Forearm 483

FIGURE 8.56. Intersection syndrome. A: In intersection syndrome, the zone of cross-over or

intersection of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscle bellies

over the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons (4 cm proximal to the

radial styloid) represents the site of complaint and physical findings, but not the site of the

pathologic process. The pathologic process (stenosing tenosynovitis) is in the second dorsal extensor compartment, which contains the ECRL and ECRB and is distal to the intersection zone. These

tendons are encased in a tight fibrosynovial compartment. B: Fresh cadaver dissection of the

radiodorsal aspect of the right wrist showing the fibrosynovial sheath of the ECRL and ECRB,

which has been injected with a dilute solution of methylene blue. This compartment is the site

of the true lesion in intersection syndrome. Note that the APL and EPB to the right (proximal)

cross obliquely over the ECRL and ECRB tendons in a synovial-free zone; note also the extensor

pollicis longus (EPL) and sensory branch of the radial nerve to the right (proximal) and the EPL

tendon.

Diagnosis/Treatment

The condition is associated with pain, swelling, tenderness,

and sometimes crepitation over the course of the EPL at the

distal radius. These findings usually are noted during the

rehabilitation period after the fracture. Unlike other forms

of tenosynovitis, the EPL tendon is likely to rupture, and

therefore early release and transposition of the EPL from its

normal course around Lister’s tubercle is required. The tendon is transposed to the radial side of the tubercle, where it

lies in the subcutaneous tissue (21).

ANATOMIC VARIATIONS

Muscles

Several anomalous muscle tendon units encountered in the

forearm are presented, along with the clinical relevance of

these structures. The list, although not comprehensive, is

representative of those variations most commonly encountered on the extensor surface of the forearm and that in the

author’s opinion match the scope of this text.

Extensor Carpi Radialis Intermedius

This anomalous muscle was termed the extensor carpi radialis intermedius (ECRI) because of its origin between the

ECRL and ECRB (22). However, in a more recent study of

39 cases of this anomalous muscle, Wood found that in 19

the muscle belly arose on top of and toward the radial side

of the ECRL, in 17 the muscle arose between the ECRL

and ECRB (the intermedius position), and in 3 cases the

muscle arose on top of the ECRB (23) (see Fig. 10.104).

The incidence of this anomalous musculotendinous unit

was 12% in the 312 limbs. Thirty-two of the 39 anomalous

muscles had a good muscle belly, a strong tendon, and good

excursion and thus represented musculotendinous units

that would be suitable for tendon transfer (23). In a similar

study of 173 limbs, the ECRI was found in 24% of the

limbs, many of which were large enough to act as a tendon

transfer (24). In Wood’s series, the ECRI or the accessory

tendons mentioned later that originated with or near the

ECRL usually inserted on the middle finger metacarpal. If

the anomalous muscle originated nearest the ECRB, the

tendon usually inserted on the index finger metacarpal. In

addition to the ECRI musculotendinous unit, both Wood

(23) and Albright and Linburg (24) noted the presence of

accessory tendons from the radial wrist extensors. Wood

(23) noted 41 such tendons originating from the ECRB

and inserting with the ECRL on the index finger

metacarpal. Twenty-nine tendons originated from the

ECRL and inserted on the middle finger metacarpal with

the ECRB, and 24 tendons arose from the ECRL and

inserted alongside the normal tendon at the index finger

metacarpal. Only seven tendons originated from the ECRB

and inserted on the middle finger metacarpal. In two arms,

the ECRL and ECRB shared a common tendon that

inserted on both the index and middle finger metacarpal.

Clinical Relevance

These studies indicate that the ECRI or accessory tendons

are worth looking for, especially in patients with quadriplegia, because they can be used as transfers for thumb opposition, to motor the flexor pollicis longus or as a motor for

the EPL. Wood noted that there is a fairly high incidence of

bilateral variations of this type, and that 12% of individuals

have a good ECRI tendon and approximately 36% have at

least one and sometimes several accessory tendons that

might be available for transfer (23). Albright and Linburg

not only emphasized the usefulness of the ECRI and accessory tendons as transfers in tetraplegia, but also noted the

importance of and high incidence (35%) of cross-connections between the ECRB and ECRL. They noted that identification and release of these interconnections was important if either of these tendons were to be used as transfers

because failure to do so might result in loss of independent

excursion in the transfer and thus possible failure of the

transfer. These interconnections usually were found under

the outcropping muscles to the thumb and often were difficult to detect because they blended into the major tendons

except when traversing from one to another (24).

Extensor Medii Proprius

The extensor medii proprius (EMP) is a muscle analogous

to the EIP in that it has a similar origin but inserts into

the extensor aponeurosis of the middle finger. In a study

of 58 hands, von Schroeder and Botte noted the presence

of the EMP in 6 hands for an incidence of 10.3% (25).

The EMP usually is covered by the EDC and usually is

not seen until the EDC is retracted or removed. The EMP

was always distal and medial to the EIP on the IOM, and

in all cases the two muscles had a common origin. In 4 of

6 instances, the EMP was represented by a single tendon

(25). The insertion was palmar and ulnar to the EDC

insertion on the middle finger. The width of the tendon

ranged from 10 to 30 mm (25) (see Fig. 10.101).

Extensor Indicis et Medii Communis

The extensor indicis et medii communis (EIMC) is an anomalous EIP that splits and inserts into both the index and middle fingers. It was identified in the aforementioned study by

von Schroeder and Botte, who noted its presence in 2 of 58

hands for an incidence of 3.4% (25). The tendon split into its

index and middle finger components near the myotendinous

junction. In one specimen, the insertion into the index finger

was similar to the usual insertion of the EIP on the palmar

and ulnar aspect of the EDC. In the other specimen, a double tendon was present, with one tendon inserting into the

484 Regional Anatomy

usual EIP location and the second slip inserting into the deep

fascia near the MCP joint. In both specimens, the insertion

into the middle finger was not into the extensor hood but

into the joint capsule of the middle finger in one case and into

the deep fascia proximal to the MCP joint in the other. The

muscle belly of the EIMC was similar to the EIP, and like the

EIP had no juncturae tendinum (25) (see Fig. 10.102).

Clinical Relevance of the EMP and the EIMC

Awareness of the incidence of these two muscles and other

anomalous muscles may be helpful in extensor tendon identification as it relates to repair or reconstruction.

REFERENCES

1. Henry AK. Extensile exposure, 2nd ed. Edinburgh: E and S Livingstone, 1966.

2. de Quervain F. Ueber eine Form von chronischer Tendovaginitis.

Corresp Blatt F Schweizer Arz (Basel) 25:389–394, 1895.

3. Leslie BM, Ericson WB Jr, Morehead JR. Incidence of a septum

within the first dorsal compartment of the wrist. J Hand Surg

[Am] 15:88–91, 1990.

4. Eversmann WW Jr. Entrapment and compression neuropathies.

In: Green DP ed. Operative hand surgery, 3rd ed. New York:

Churchill Livingstone, 1993.

5. Foster RJ. Radial tunnel syndrome: decompression by a posterior

lateral approach. In: Blair WF, ed. Techniques in hand surgery.

Baltimore: Williams & Wilkins, 1996.

6. Gelberman RH, Eaton R, Urbaniak JR. Peripheral nerve compression. J Bone Joint Surg Am 75:1854–1878, 1993.

7. Lister GD. Radial tunnel syndrome. In: Gelberman RH, ed.

Operative nerve repair and reconstruction. Philadelphia: JB Lippincott, 1991.

8. Lister GD, Belsole RB, Kleinert HE. The radial tunnel syndrome. J Hand Surg [Am] 4:52–59, 1979.

9. Sanders WE. Letter. J Bone Joint Surg Am 74:309–310, 1992.

10. Botte MJ, Cohen MS, Lavernia C, et al. The dorsal branch of the

ulnar nerve: an anatomic study. J Hand Surg[Am] 15:603–607,

1990.

11. Finkelstein H. Stenosing tendovaginitis at the radial styloid

process. J Bone Joint Surg 12:509–540, 1930.

12. Elliott BG. Finkelstein’s test: a descriptive error that can produce

a false positive. J Hand Surg [Br] 17:481–482, 1992.

13. Frohse F, Frankel M. Die Muskeln des menschlichen Armes. In:

Bardelben’s Handbuch der Anatomie des Mensch. Jena, Germany:

Fisher, 1908.

14. Fuss FK, Wurzl GH. Radial nerve entrapment at the elbow: surgical anatomy. J Hand Surg [Am] 16:742–747, 1991.

15. Wartenberg R. Cheiralgia paraesthetica (Isolierte Neuritis des

Ramus superficialis Nervi radialis). Z Ges Neurol Psychiatr

141:145–155, 1932.

16. Abrams RA, Brown RA, Botte MJ. The superficial branch of the

radial nerve: an anatomic study with surgical implications. J

Hand Surg [Am] 17:1037–1041, 1992.

17. Grundberg AB, Reagan DS. Pathologic anatomy of the forearm:

intersection syndrome. J Hand Surg [Am] 10:299–302, 1985.

18. Cauldwell EW, Anson BJ, Wright RR. The extensor indicis proprius muscle: a study of 263 consecutive specimens. Q Bull

Northwest Univ Med School 17:267–279, 1943.

19. Ritter WA, Inglis AE. The extensor indicis proprius syndrome. J

Bone Joint Surg Am 51:1645–1648, 1969.

20. Spinner M, Olshansky K. The extensor indicis proprius syndrome: a clinical test. Plast Reconstr Surg 51:134–138, 1973.

21. Wolfe SW. Tenosynovitis. In: Green DP ed. Operative hand

surgery, 4th ed. New York: Churchill Livingstone, 1999.

22. Wood J. Variations in human myology. Proc R Soc Lond

15:229–244, 1866.

23. Wood VE. The extensor carpi radialis intermedius tendon. J

Hand Surg [Am] 13:242–245, 1988.

24. Albright JA, Linburg RM. Common variations of the radial wrist

extensors. J Hand Surg[Am] 3:134–138, 1978.

25. von Schroeder HP, Botte MJ. The extensor medii proprius and

anomalous extensor tendons to the long finger. J Hand Surg

[Am] 16:1141–1145, 1991.

8.2 Extensor Forearm 485

9

WRIST

RICHARD A. BERGER

JAMES R. DOYLE

MICHAEL J. BOTTE

The wrist is a unique joint interposed between the distal

aspect of the forearm and the proximal aspect of the hand.

There are common or shared elements to all three regions,

which integrate form and function to maximize the

mechanical effectiveness of the upper extremity. The wrist

enables the hand to be placed in an infinite number of

positions relative to the forearm, and yet also enables the

hand to be essentially locked to the forearm in those positions to transfer the forces generated by the powerful forearm muscles.

Although the wrist truly is a mechanical marvel when it

is intact and functioning, loss of mechanical integrity of the

wrist inevitably causes substantial dysfunction of the hand

and thus the entire upper extremity. It is vital that a thorough understanding of the wrist be acquired by all who

treat the wrist, including efforts in diagnosis, treatment,

and rehabilitation. This chapter provides such a foundation

by exploring the general architecture of the wrist, the bones

and joints that compose the wrist, and the soft tissues that

stabilize, innervate, and perfuse the wrist. As with all

anatomic descriptions, a common nomenclature is desirable. Although the terms medial and lateral are the gold

standard from an anatomic point of view, to use them

requires the application of the “anatomic position,” in

which the dependent arm is held in neutral rotation, with

the elbow extended, the forearm supinated, the wrist in

neutral extension, and the digits extended. Because of the

mental gymnastics required to position the extremity in virtual space in this manner to determine whether the term

medial or lateral is appropriate, it is often easier simply to

refer to structures distal to the elbow in reference to a more

local coordinate system based on the position of the radius

and ulna. Therefore, the authors may often preferentially

use the term radial when referring to the lateral direction

and ulnar when referring to the medial direction. The term

dorsal is used preferentially to describe the posterior direction. Finally, because the glabrous skin of the palm indeed

covers the entire region of the wrist, the term palmar is used

to describe the anterior direction.

DESCRIPTIVE ANATOMY

Contents

Bone: Distal radius, ulna, and eight carpal bones.

Ligaments: Palmar and dorsal extraosseous carpal ligaments, intraosseous carpal ligaments, flexor retinaculum

(FR), extensor retinaculum (ER), and triangular fibrocartilage complex (TFCC).

Blood Vessels: Extraosseous and intraosseous carpal

blood supply from radial, ulnar, and interosseous arteries;

vascular supply of distal radius and ulna.

Nerves: Articular branches from radial, median, ulnar,

and interosseous nerves.

Tendons: Wrist and finger flexors and extensors.

Landmarks

Dorsal

Important landmarks on the dorsal aspect of the wrist

include Lister’s tubercle, the anatomic snuff-box, the lunate

fossa, the styloid process at the base of the middle finger

metacarpal, the radial styloid process, and the distal head of

the ulna (Fig. 9.1).

Lister’s Tubercle

This bony prominence on the dorsal aspect of the distal

radius is situated approximately 0.5 cm proximal to the dorsal margin of the articular surface of the radius. It is in line

with the cleft between the index and middle finger

metacarpals. The extensor pollicis longus (EPL), located in a

groove just ulnar to Lister’s tubercle, turns radialward around

Lister’s tubercle on its way to the dorsal aspect of the thumb.

The extensor carpi radialis brevis (ECRB) is just radial to Lister’s tubercle in a similar groove on the dorsum of the radius.

Anatomic Snuff-Box

The anatomic snuff-box, a narrow triangle with its apex

located distally, is bordered dorsoulnarly by the EPL, radi-

ally by the abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons, and proximally by the distal

margin of the ER. In its depths, it contains the dorsal

branch of the radial artery, and in the dorsoulnar corner, the

tendon of the extensor carpi radialis longus (ECRL); superficially, it contains one or more branches of the superficial

branch of the radial nerve (1,2).

Lunate Fossa

The lunate fossa is a palpable central depression located on

the dorsum of the wrist in line with the longitudinal axis of

the third metacarpal, just ulnar and distal to Lister’s tubercle, and begins immediately distal to the dorsal margin of

the radius. It is, on average, approximately the size of the

pulp of an examiner’s thumb and marks the location of the

carpal lunate. This palpable lunate fossa should not be confused with the “lunate fossa” of the distal radius, which is a

depression of the articular surface of the radius that accommodates the lunate (1).

Styloid Process of the Middle Finger Metacarpal

The styloid process of the middle finger metacarpal, located

on the dorsal and radial base of this metacarpal, points to

the articular interface between the capitate and the trapezoid and is just proximal to the point of insertion of the

ECRB tendon.

Radial Styloid

The distal projection of the radial side of the radius forms a

visible and easily examined landmark that is palpable both

9 Wrist 487

FIGURE 9.1. A, B: Dorsal landmarks of the wrist.

A B

palmar and dorsal to the APL and EPB tendons, which

course across its apex.

Distal Head of Ulna

The slightly expanded distal end of the ulna has a head and

styloid process. The head is most visible and palpable when

the forearm is in pronation; the posteroulnar styloid is most

readily palpable in supination and is approximately 1 cm

proximal to the plane of the radial styloid (1).

Palmar

Important landmarks on the palmar surface of the wrist

include the pisiform, hook process of the hamate, scaphoid

tubercle, the thenar and hypothenar eminences, and the

thenar and wrist flexion creases (Fig. 9.2).

Hook Process of the Hamate

The hook of the hamate, located on the ulnar and palmar

aspect of the distal carpus, can be palpated approximately 1

cm radial and distal to the pisiform. Because of its deep

location, it may be difficult to palpate in some individuals.

The hook of the hamate lies between the ulnar tunnel

(Guyon’s canal) and the carpal tunnel. It thus provides a

landmark for the ulnar nerve and artery (located just ulnar

to the hook), and the ulnar boundary of the carpal tunnel.

Point tenderness in this area may indicate a fracture of the

hook process, a common injury in sports that use racquets,

clubs, or bats, such as tennis, golf, or baseball.

Scaphoid Tubercle

The scaphoid tubercle is in the distal palmar aspect of the

scaphoid. It projects into the palm and the tubercle is palpable on the radial aspect of the base of the hand, usually

just distal to the distal palmar wrist crease. It becomes more

prominent with the wrist positioned in radial deviation,

since the scaphoid assumes a position of more palmar flexion in this position. Conversely, the scaphoid tubercle is less

prominent and possibly not palpable when the wrist is in

ulnar deviation, since the scaphoid assumes a position of

decreased palmar flexion and lies more in the plane of the

radius and ulna.

Pisiform Bone

The pisiform bone, located on the ulnar and palmar

aspect of the base of the hand provides a visible and palpable landmark that aids in the identification and location

of the flexor carpi ulnaris (FCU) tendon, the underlying

ulnar neurovascular bundle, and the hook process of the

hamate.

488 Regional Anatomy

FIGURE 9.2. A, B: Palmar landmarks of the wrist.

A B

Thenar and Hypothenar Eminences

The thenar eminence is formed by the abductor and the flexor

pollicis brevis, which overlie the opponens pollicis. The less

prominent hypothenar eminence on the ulnar side of the hand

is formed by the corresponding muscles of the little finger.

Flexion Creases

The wrist and palmar flexion creases are skin flexion lines

seen in the vicinity of synovial joints, where the skin is

attached to the underlying fascia (1). McGrouther has

shown that the fascial attachments in the palmar creases are

greatest adjacent to the creases rather than directly under

them (3). These creases have been recognized as useful

anatomic landmarks because of their relationship to underlying structures (4).

Thenar Crease. The thenar crease usually intersects the

lateral side of the proximal palmar crease and curves

obliquely across the palm to intersect the distal wrist crease

near the wrist center. In the mid-portion of the palm, the

thenar crease is located directly over the long finger

metacarpal over half the time. In the proximal palm, the

thenar crease crosses the capitate nearly half the time and

the trapezoid approximately one-third of the time. Mean

distance from the thenar crease to the center of the

trapeziometacarpal joint is 22.6 mm. The thenar crease

passes 18.7 mm from the hamate hook on the medial side

of the carpus (5).

Distal Wrist Crease. Although there usually are three wrist

flexion creases, only the distal crease is of sufficient consistency to be used as a reliable landmark. The distal wrist

crease is located over the proximal carpal row and passes over

the scaphoid waist in almost all instances and over the pisiform 80% of the time. The lunate is consistently proximal

to the distal wrist crease, with its center an average of 9.2

mm from the crease. The radiocarpal joint is 13.5 mm proximal to the distal wrist crease and the center point of the distal radioulnar joint (DRUJ) is 21.1 mm proximal to the

wrist crease. On the lateral side of the wrist, the distal wrist

crease is within 1 mm of the center of the scaphoid waist.

The mid-portion of the trapeziometacarpal joint averages

19.4 mm distal to the wrist crease. On the ulnar side of the

wrist, the pisiform is directly under or slightly distal to the

crease. The base of the ulnar styloid is on average 11.7 mm

proximal to the distal wrist crease (5) (Fig. 9.3).

9 Wrist 489

FIGURE 9.3. Flexion crease landmarks of the wrist.

SKELETAL ANATOMY

Distal Radius and Ulna

The distal surface of the radius articulates with the proximal carpal row through two articular fossae separated by a

fibrocartilaginous prominence oriented in the sagittal

plane, called the interfossal ridge. The scaphoid fossa is

roughly triangular and extends from the interfossal ridge

to the tip of the radial styloid process. The lunate fossa is

roughly quadrangular and extends from the interfossal

ridge to the sigmoid notch. On the dorsal cortex of the

distal radius, immediately dorsal and proximal to the

interfossal ridge, is a bony prominence called the dorsal

tubercle of the radius, or Lister’s tubercle. It serves as a

divider between the second and third extensor compartments, and functionally behaves as a trochlea for the tendon of the EPL. The sigmoid notch forms an articular

concavity on the ulnar, or medial, aspect of the distal

radial epiphysis. It has considerable variation in terms of

depth, anteroposterior dimension, and dorsopalmar orientation; however, it consistently exhibits an arc of curvature

greater than that of the corresponding ulnar head, with

which it articulates (Fig. 9.4). Under normal circumstances, the ulna does not articulate directly with the carpus. Rather, a fibrocartilaginous wafer called the triangular fibrocartilage (TFC) is interposed between the ulnar

head and the proximal carpal row. Even the ulnar styloid

process is hidden from contact with the carpus by the

ulnotriquetral ligament. The ulnar head is roughly cylindrical, with a distal projection on its posterior border

called the ulnar styloid process. Approximately threefourths of the ulnar head is covered by articular cartilage,

with the ulnar styloid process and the posterior one-fourth

exposed bone or periosteum. A depression at the base of

the ulnar styloid process is called the fovea and typically is

not covered in articular cartilage. A more comprehensive

description of the distal ulna is given later in the section

on the DRUJ.

Carpal Bones

There are eight carpal bones (Fig. 9.5), although many consider the pisiform to be a sesamoid bone in the tendon of

the FCU, and thus not behaving as a true carpal bone. The

bones are arranged in two rows (proximal and distal carpal

rows), each containing four bones. All eight carpal bones

are interposed between the forearm bones and the

metacarpals to form the complex called the wrist joint. The

wrist joint is subdivided into the mid-carpal joint, which

comprises the articulation between the proximal and distal

carpal row, and the radiocarpal joint, which comprises the

articulation between the distal radius and the scaphoid and

lunate. The ulnocarpal joint comprises the theoretical articulation between the distal ulna and the lunate and triquetrum and the interposed TFC.

Proximal Carpal Row

The proximal row is composed of, from radial to ulnar, the

scaphoid (navicular), lunate, triquetrum, and pisiform.

Scaphoid

Bony Architecture. The scaphoid is shaped somewhat like

a kidney bean. It is divided into regions called the proximal

pole, waist, and distal pole. The proximal pole has a convex

articular surface that faces the scaphoid fossa and a flat

490 Regional Anatomy

FIGURE 9.4. Articular surfaces of the distal radius.

9 Wrist 491

FIGURE 9.5. A, B: Osseous anatomy of the radiocarpal joint

and the carpus.

A

B

articular surface that faces the lunate. The dorsal surface of

the waist is marked by an oblique ridge that serves as an

attachment plane for the dorsal joint capsule. This ridge

passes from proximal-ulnar to distal-radial. The medial surface of the waist and distal surface of the proximal pole is

concave and articulates with the capitate. The distal pole

also articulates with the capitate medially, but distally it

articulates with the trapezium and trapezoid. Often, there is

a change in the curved geometry of the distal pole articular

surface, reflecting its dual articulation with the trapezium

and trapezoid.

Ligament Attachments. The radial aspect of the scaphoid

has nonarticular surfaces to which the radioscaphocapitate, dorsal intercarpal, and scaphotrapezium-trapezoid

(STT) ligaments attach. The palmar surface of the distal

pole serves as an attachment for the scaphocapitate ligament, whereas the palmar surface of the proximal pole

serves as an attachment for the palmar region of the

scapholunate interosseous ligament. The scapholunate ligament has a crescentic attachment zone along the palmar,

proximal, and dorsal edges of the ulnar surface of the

proximal pole of the scaphoid. Dorsally, the ridge serves as

an attachment for the dorsal joint capsule and the dorsal

intercarpal ligament.

Vascular Foramina. Most of the vascular foramina are

found along the radial aspect of the scaphoid at the termination of the dorsal ridge. There also may be foramina

on the palmar surface of the distal pole, and rarely along

the attachment zone of the scapholunate interosseous

ligament.

Lunate

Bony Architecture. The lunate is crescent-shaped in the

sagittal plane, such that the proximal surface is convex and

the distal surface concave, and somewhat wedge-shaped in

the transverse plane. With the exception of ligament attachment planes on its dorsal and palmar surfaces, the lunate is

covered with articular cartilage. It articulates with the

scaphoid laterally, the radius and TFC proximally, the triquetrum medially, and the capitate distally. In some individuals, the lunate has a separate fossa for articulation with

the hamate, separated from the fossa for capitate articulation by a prominent ridge.

Ligament Attachments. The palmar and dorsal surfaces

are the principal zones of ligament attachment. The palmar

surface serves as the attachment region for the long and

short radiolunate ligaments, the ulnolunate ligament, as

well as the palmar regions of the scapholunate and lunotriquetral interosseous ligaments. Dorsally, the lunate attaches

to the dorsal regions of the scapholunate and lunotriquetral

interosseous ligaments, as well as the deep fibers of the dorsal radiocarpal ligament.

Vascular Foramina. The dorsal and palmar (nonarticular)

surfaces have numerous vascular foramina. Otherwise, the

lunate is devoid of perforating vessels.

Triquetrum

Bony Architecture. The triquetrum has a complex shape,

with a flat articular surface on the palmar surface for articulation with the pisiform, a concave distal articular surface

for the hamate, a flat lateral surface for articulation with the

lunate, and three tubercles on the proximal, ulnar, and dorsal surfaces. The proximal tubercle is covered in hyaline cartilage for contact with the triangular disc, whereas the

medial and dorsal tubercles serve as ligament attachment

surfaces.

Ligament Attachments. The dorsal tubercle serves as a

common attachment for the dorsal radiocarpal and intercarpal ligaments. The ulnar tubercle serves as an attachment

for the ulnotriquetral ligament. From the most palmar and

distal edge of the triquetrum emerge the triquetrohamate

and triquetrocapitate ligaments. The palmar region of the

lunotriquetral ligament and fibers from the ulnocapitate

ligament attach along the palmar and radial edge of the triquetrum, whereas the dorsal and radial edge of the triquetrum serves as an attachment zone for the dorsal region

of the lunotriquetral interosseous ligament. The palmar

region of the triquetrum has a horseshoe-shaped region of

attaching fibers from the pisotriquetral ligament along the

radial, distal, and palmar margins.

Vascular Foramina. Blood vessels enter the triquetrum

through the dorsal and ulnar tubercles.

Pisiform

Bony Architecture. The pisiform, which means “peashaped,” is oval in profile with a flat articular facet covering

the distal half of the dorsal surface for articulation with the

triquetrum. The general orientation of the oval is such that

the major (long) axis is in the proximodistal direction.

Ligament Attachments. The pisotriquetral ligament has a

horseshoe-shaped attachment on the dorsal surface of the

pisiform, surrounding the radial, distal, and ulnar margins

of the articular facet. Otherwise, it is entirely enveloped in

the tendon of the FCU and serves as a proximal origin of

the flexor digiti minimi muscle.

Vascular Foramina. The pisiform is encircled by a vascular ring from the ulnar artery, and thus has a variable number of foramina located circumferentially on the nonarticular surfaces.

492 Regional Anatomy

Distal Carpal Row

The distal carpal row is composed of, from radial to ulnar,

the trapezium, trapezoid, capitate, and hamate. Each bone

articulates with a metacarpal distally and a proximal row

bone proximally.

Trapezium

Bony Architecture. The trapezium has three articular surfaces. The proximal surface is slightly concave and articulates with the distal pole of the scaphoid. The dorsoulnar

articular surface is flat and articulates with the trapezoid.

The distal surface is saddle-shaped and articulates with the

base of the first metacarpal. The remaining surfaces are

nonarticular and serve as attachment areas for ligaments, as

described later. The anterolateral edge of the trapezium

forms an overhang, referred to as the beak or trapezial ridge,

that is part of the fibroosseous tunnel for the tendon of the

flexor carpi radialis (FCR). The trapezial ridge that forms a

longitudinal projection on the palmar surface of the trapezium serves as an attachment for a portion of the transverse

carpal ligament (TCL). The trapezial ridge is susceptible to

fracture and is best seen radiographically on carpal tunnel

views (6–8).

Ligament Attachments. Beginning on the radial surface,

the STT ligament partially attaches. There is essentially no

ligament on this surface that crosses the carpometacarpal

joint, immediately deep to the tendon of the APL. The dorsal surface has no prominent ligament attachment proximally, but distally the dorsoradial and posterior oblique ligaments of the carpometacarpal joint attach. In addition, the

dorsal trapeziotrapezoid ligament attaches. The palmar surface serves as an attachment for the deep and superficial

anterior oblique ligaments of the first carpometacarpal

joint, as well as the palmar trapeziotrapezoid ligament. It

also has been reported that discrete ligaments can be traced

out connecting the palmar surface of the trapezium to the

second and third metacarpals. Only the ulnar collateral ligament of the first carpometacarpal joint covers the distal

surface of the ulnar border of the trapezium.

Vascular Foramina. The dorsal, palmar, and radial surfaces have variable vascular foramina for transmission of

nutrient vessels originating from the radial artery and the

palmar and dorsal carpal arches.

Trapezoid

Bony Architecture. The trapezoid is a small bone with

articular surfaces on the proximal, lateral, medial, and distal surfaces for articulation with the scaphoid, trapezium,

capitate, and base of the second metacarpal, respectively.

There is an offset geometry on its ulnar articular surface,

which articulates with a similarly shaped radial articular

surface of the capitate. In the “notch” of the offset, the deep

trapeziocapitate ligament attaches.

Ligament Attachments. The palmar and dorsal surfaces

serve as ligament insertion areas. Dorsally, the dorsal

trapeziocapitate and trapeziotrapezoid ligaments, as well as

the distally oriented dorsal carpometacarpal ligaments

attach. The dorsal intercarpal ligament also attaches on the

dorsal surface of the trapezoid. Palmarly, a similar set of ligament attachments is found. Ulnarly, the deep trapeziocapitate ligament attaches to the trapezoid in the middle of the

articular surface of the trapezoid.

Vascular Foramina. Numerous foramina are found on the

dorsal and palmar nonarticular surfaces of the trapezoid.

Capitate

Bony Architecture. The capitate is the largest carpal bone

and is divided into head, neck, and body regions. The head

is almost entirely covered in articular cartilage and forms a

proximally convex surface for articulation with the scaphoid

and lunate. There often is a faint change in curvature on the

radial aspect of the head corresponding to the ridge on the

ulnar surface of the waist of the scaphoid. The neck is a narrowed region between the body and the head, and is

exposed to the mid-carpal joint without ligament attachment. The body is nearly cuboid, with articular surfaces on

its medial, lateral, and distal aspects for articulation with

the trapezoid, hamate, and base of the third metacarpal,

respectively. The radial surface, articulating with the ulnar

surface of the trapezoid, is “offset” with a ridge in the middle, which serves as an attachment of the deep trapeziocapitate ligament. Ulnarly, the articular surface of the capitate

for the hamate is shaped like a skillet, with the handle

extending distally along the dorsal third of the ulnar surface. This leaves a relatively large square area on the palmar

and distal aspect of the ulnar surface, which serves as an

attachment for the deep capitohamate and carpometacarpal

ligaments.

Ligament Attachments. The large, flat palmar and dorsal

surfaces serve as ligament attachment areas. There are no

ligament attachments on the head or neck. Dorsally, the

dorsal trapeziocapitate and capitohamate ligaments attach,

as well as the distally oriented carpometacarpal ligaments.

Palmarly, the body of the capitate can be divided into proximal and distal halves for the purposes of discussing ligament attachments. Beginning radially and progressing

ulnarly on the proximal half of the palmar surface, the

scaphocapitate, radioscaphocapitate, ulnocapitate, and triquetrocapitate ligaments attach. The distal half serves as an

attachment surface for the palmar trapeziocapitate, carpometacarpal, and capitohamate ligaments, respectively

progressing from radial to ulnar. The middle of the radial

9 Wrist 493

articular surface serves as the attachment for the deep

trapeziocapitate ligament, whereas the large square recess on

the ulnar articular surface serves a similar role for the deep

capitohamate and carpometacarpal ligaments.

Vascular Foramina. As with the other carpal bones, all

surfaces with ligament attachments also have numerous vascular perforations. The nonarticular neck of the capitate has

a variable number of small vascular foramina on the dorsal,

radial, and palmar surfaces. There are no foramina on the

head of the capitate.

Hamate

Bony Architecture. The hamate has a complex geometry,

with a pole, body and hamulus (hook). The pole is a conical, proximally tapering projection that is nearly entirely

covered in articular cartilage for articulation with the triquetrum, capitate, and variably with the lunate. The body

is relatively cuboid, with medial and distal articulations for

the capitate and fourth and fifth metacarpal bases, respectively. The dorsal and palmar surfaces serve as ligament

attachment areas, except the most medial aspect of the

body, where the hamulus arises. The hamulus forms a palmarly directed projection that curves slightly lateral at the

palmar margin. The radial articular surface is matched to

the corresponding ulnar surface of the capitate, with a

square recess, which is nonarticular, on the palmar and distal aspect of the hamate.

Ligament Attachments. The palmar surface of the hamate

serves as an attachment for the palmar capitohamate and

carpometacarpal ligaments. The proximal aspect of the palmar nonarticular surface of the hamate allows attachment

of the triquetrohamate ligament. The dorsal surface serves a

similar purpose for the dorsal counterparts of the capitohamate and carpometacarpal ligament systems. There is no

dorsal counterpart to the triquetrohamate ligament. As

noted previously, the deep capitohamate ligament attaches

to the hamate in the recess on the radial surface. The hamulus serves as an attachment for the pisohamate ligament (an

extension of the tendon of the FCU) and the FR.

Vascular Foramina. A large number of vascular foramina

are found on the body, as well as circumferentially about the

hamulus of the hamate. There are no foramina on the pole

of the hamate.

JOINT ANATOMY

Although 8 carpal bones comprise the wrist proper, the

wrist functionally should be considered as having a total of

15 bones. This is because of the proximal articulations with

the radius and ulna and the distal articulations with the

bases of the first through fifth metacarpals. The geometry of

the wrist is complex, demonstrating a transverse arch created by the scaphoid and triquetrum/pisiform column

proximally and the trapezium and hamate distally. In addition, the proximal carpal row demonstrates a substantial

arch in the frontal plane.

From an anatomic standpoint, the carpal bones are

divided into proximal and distal carpal rows, each composed of four bones. This effectively divides the wrist into

radiocarpal and mid-carpal joints. Although mechanically

linked to the DRUJ, the wrist normally is biologically separated from the DRUJ joint space by the TFC.

Radiocarpal Joint

The radiocarpal joint is formed by the articulation of confluent surfaces of the concave distal articular surface of the

radius and the TFC, with the convex proximal articular surfaces of the proximal carpal row bones. The radiocarpal joint

communicates with the pisotriquetral joint in approximately

80% of normal individuals. In addition to this orifice, there

is a consistent defect in the TFCC called the prestyloid recess.

It is filled with vascular villi and variably communicates with

the distal tip of the ulnar styloid process.

Mid-Carpal Joint

The mid-carpal joint is formed by the mutually articulating

surfaces of the proximal and distal carpal rows. Communications are found between the mid-carpal joint and the

interosseous joint clefts of the proximal and distal row

bones, as well as with the second through fifth carpometacarpal joints. Under normal circumstances, the midcarpal joint is isolated from the pisotriquetral, radiocarpal,

and first carpometacarpal joints by intervening membranes

and ligaments. The geometry of the mid-carpal joint is

complex. Radially, the STT joint is composed of the slightly

convex distal pole of the scaphoid articulating with the reciprocally concave proximal surfaces of the trapezium and

trapezoid. Forming an analog to a ball-and-socket joint are

the convex head of the capitate and the combined concave

contiguous distal articulating surfaces of the scaphoid and

the lunate. In 65% of normal adults, it has been found that

the hamate articulates with a medial articular facet at the

distal-ulnar margin of the lunate, which is associated with a

higher rate of cartilage eburnation of the proximal surface

of the hamate. The triquetrohamate region of the midcarpal joint is particularly complex, with the mutual articular surfaces having both concave and convex regions forming a helicoid-shaped articulation.

Interosseous Joints

Proximal Row

The interosseous joints of the proximal row are relatively

small and planar, allowing motion primarily in the flex494 Regional Anatomy

ion–extension plane between mutually articulating bones.

The scapholunate joint has a smaller surface area than the

lunotriquetral joint. Often, a fibrocartilaginous meniscus

extending from the membranous region of the scapholunate or lunotriquetral interosseous ligaments is interposed

into the respective joint clefts.

Distal Row

The interosseous joints of the distal row are more complex

geometrically and allow substantially less interosseous

motion than those of the proximal row. The capitohamate

joint is relatively planar, but the mutually articulating surfaces are only partially covered by articular cartilage. The

distal and palmar region of the joint space is devoid of articular cartilage, being occupied by the deep capitohamate

interosseous ligament. Similarly, the central region of the

trapeziocapitate joint surface is interrupted by the deep

trapeziocapitate interosseous ligament. The trapeziotrapezoid joint presents a small planar surface area with continuous articular surfaces.

Distal Radioulnar Joint

Osseous Anatomy

The DRUJ is a uniaxial pivot joint between the convex distal head of the ulna and the concave ulnar notch of the

radius (1) (Fig. 9.6A). It has been described as a trochoid

(wheel-like) joint (9). The convex distal ulna is covered by

hyaline cartilage for 270 degrees of its total circumference.

It varies in proximal to distal height from 5 to 8 mm. It

articulates with the adjacent radius in the sigmoid notch.

Distally, the dorsopalmar height of the sigmoid notch is 1.5

cm, and proximally it is 1 cm (10). In the dorsopalmar

plane, the semicylindrical sigmoid notch has an angular

inclination distally and ulnarly of 7.7 degrees (average) (11)

(see Fig. 9.6B). This concave sigmoid notch has three distinct margins: dorsal, palmar, and distal. The dorsal margin

is acutely angular in cross-section, and the palmar less so.

The palmar margin may have an osteocartilaginous lip in

some instances (12). The prominent palmar beak of the

radius seen on a lateral radiograph represents the sigmoid

notch as well as the lunate facet of the radius. Thus, fractures of the lunate facet are fractures of the DRUJ, and viceversa (9). The sigmoid notch and the lunate fossa of the

radius are separated by the attachment of the TFC to the

radius (6). The articular surface of the radius is inclined a

variable amount (15 to 21 degrees toward the ulna) (11).

The articulation of the ulnar head to the radius is not congruent in that the radius of the shallow arc of the sigmoid

notch is greater than that of the ulnar convexity (13,14).

Because of this, pronation and supination of the forearm

include both a sliding and a rolling (rotational) component

(9). In addition, because of the differences in radii of the

ulna and the sigmoid notch, there is significant translation

of this joint. The maximum limits of translation have been

measured at 2.8 mm dorsal and 5.4 mm palmar in the zero9 Wrist 495

FIGURE 9.6. A–C: Osseous anatomy of the distal radioulnar joint.

A

B

C

degree position of rotation (15) (see Fig. 9.6C). In this position, 60 to 80 degrees of the articular surface of the ulna is

in contact with the sigmoid notch. However, in the

extremes of rotation, less than 10% of the ulna may be in

contact with the dorsal (in pronation) or palmar (in supination) margins of the sigmoid notch. In addition, the radii of

the articular head of the ulna may vary and add a camlike

effect to the rotation (15). Also, the articular inclination of

the sigmoid notch and the ulnar seat may not match (11).

The semicylindrical head of the ulna that faces the TFC is

flattened. The periphery of this flattened dome is covered

with articular cartilage. An eccentric concavity of the dome

lies at the base of the styloid and is the area of attachment

for the apex of the TFC and ulnocarpal ligaments. This

concavity is confluent dorsally onto the shaft–head junction

with the sulcus for the extensor carpi ulnaris (ECU) tendon

(9) (see Fig. 9.6A). The ulnar styloid is a continuation of

the prominent subcutaneous ridge of the dorsal shaft of the

ulna that projects distally for a variable distance of 2 to 6

mm (16).

Ligamentous Anatomy

Radioulnar Joint Ligaments

The reader also is directed to the section on Clinical Significance: Stabilizing Factors of the DRUJ, later.

A description of the anatomy of the palmar and dorsal

radioulnar ligaments is required to understand the origin of

the ulnocarpal ligaments. The dorsal and palmar DRUJ ligaments are believed to be the major stabilizers of the DRUJ.

These ligaments form the dorsal and palmar margins of the

TFCC in the region between the sigmoid notch of the

radius and the styloid process of the ulna. They attach radially at the dorsal and palmar corners of the sigmoid notch,

and converge ulnarly to pass in a cruciate manner such that

the dorsal ligament attaches near the tip of the styloid

process and the palmar ligament attaches near the base of

the styloid process in the region called the fovea. The palmar ligament has substantial connections to the carpus

through the ulnolunate, ulnotriquetral, and ulnocapitate

ligaments. The dorsal ligament integrates with the sheath of

the ECU (Fig. 9.7).

The Triangular Fibrocartilage Complex

The center of this complex (TFC and ulnocarpal ligaments)

has been called the ulnocarpal complex by Taleisnik (17), the

TFCC by Palmer and Werner (18), and the ulnocarpal ligament complex by Bowers (19). Based on historical and common usage, the TFC and ulnocarpal ligaments, taken

together, have been called the TFCC in this chapter.

Triangular Fibrocartilage. The anatomic structure that

spans the distal (carpal-facing) aspect of the DRUJ is called

the TFC. It should not be confused with the DRUJ meniscus (see section on Meniscus, later). The TFC is part of an

extensive fibrous system that arises from the carpal margin

of the sigmoid notch of the radius, cups the lunate and triquetral bones, and extends to the palmar base of the small

finger metacarpal (9). The TFC is, as its name implies, triangular and 1 to 2 mm thick at its base, which is attached

to the distal margin of the sigmoid notch. The biconcave

body of the TFC crosses the articular dome of the distal

ulna and its apex attaches to the eccentric concavity of the

head and projecting concavity, where it may be as thick as

5 mm (9) (see Fig. 9.7).

Microstructure of the Triangular Fibrocartilage. The

peripheral margins of the TFC are thick lamellar collagen

that is structurally adapted to bear tensile loading (20).

These often are referred to as the dorsal and palmar radioul496 Regional Anatomy

FIGURE 9.7. Dorsal and palmar distal radioulnar

ligaments and the triangular fibrocartilage.

nar ligamentous margins, and the thin central portion as the

articular disc. The articular disc is chondroid fibrocartilage,

a type of tissue seen in structures that bear compression

loads (9,21). This central area occasionally is absent and

often so thin as to be translucent (22).

There is avascular, random criss-crossing of collagen

fibers in the central aspect of the TFC consistent with compression load bearing, in contrast to a highly organized and

well vascularized collagen arrangement in the peripheral

marginal ligaments of the TFC (21).

Ulnocarpal Ligaments

The ulnocarpal ligament is discussed here because of its

close anatomic proximity to the TFC (Fig. 9.8). The ulnocarpal ligament arises largely from the palmar margin of the

TFC, the palmar radioulnar ligament, and, in a limited

fashion, from the head of the ulna. It courses obliquely and

distally toward the lunate, triquetrum, and capitate. There

are three divisions of the ulnocarpal ligament, designated by

their distal bony insertions.

Ulnolunate Division. The ulnolunate ligament is essentially continuous with the short radiolunate ligament, forming a continuous palmar capsule between the TFCC and

the lunate.

Ulnotriquetral Division. Confluent with these fibers is

the ulnotriquetral ligament, connecting the TFC and the

palmar rim of the triquetrum. In 60% to 70% of normal

adults, a small orifice is found in the distal substance of the

ulnotriquetral ligament, which leads to a communication

between the radiocarpal and pisotriquetral joints. Just proximal and ulnar to the pisotriquetral orifice is the prestyloid

recess, which usually is lined by synovial villi and variably

communicates with the underlying ulnar styloid process.

Ulnocapitate Division. The ulnocapitate ligament arises

from the foveal and palmar region of the head of the ulna,

where it courses distally, palmar to the ulnolunate and

ulnotriquetral ligaments, and passes palmar to the head of

the capitate, where it interdigitates with fibers from the

radioscaphocapitate (RSC) ligament to form an arcuate ligament to the head of the capitate. A few fibers from the

ulnocapitate ligament insert to the capitate.

Meniscus

This structure often may be confused with the TFC (9). It

is found in a minority of wrists and, when present, lies in

the ulnocarpal joint. The meniscus is concave and has a

free margin similar to the knee meniscus (9). When fully

developed, it overlies the TFC–ulnocarpal ligament–styloid complex and extends from the dorsal aspect of the

TFC to the palmar and ulnar aspect of the triquetrum.

When the meniscus is more developed, it may contain an

ossicle (os lanula, 4%) that may be misdiagnosed as a styloid fracture (9).

Arterial Anatomy

The vascular supply of the DRUJ/TFCC is from the anterior interosseous and ulnar arteries (20) (Fig. 9.9). The

9 Wrist 497

FIGURE 9.8. The three divisions of the ulnocarpal

ligament: ulnotriquetral, ulnocapitate, and ulnolunate.

anterior interosseous divides into palmar and dorsal

branches proximal to the DRUJ. The dorsal branch supplies

most of the dorsal margin of the TFC and the palmar

branch the palmar margin near the radius. Dorsal and palmar branches of the ulnar artery supply the styloid and the

ulnar half of the palmar margin of the TFC. Terminal

branches of these vessels penetrate only the outer 15% to

20% of the TFC, thus leaving its central portion avascular

(9,23).

Ulnar Variance

The relative lengths of the radius and ulna at the DRUJ

may vary, and this has been referred to as Hulten’s variance

(24). Ulna zero indicates equal length of the radius and

ulna in the anteroposterior plane; ulna minus indicates

the ulna is 1 to 6 mm shorter than the radius; ulna plus

indicates that the ulna is 1 to 5 mm longer than the

radius. The importance of ulnar variance is that positive

ulnar variance may be associated with Kienböck’s disease

(25) and degenerative changes in the ulnolunate joint

(18).

Clinical Significance: Stabilizing Factors

of the Distal Radioulnar Joint

William H. Bowers has best described the stabilizing factors

of the DRUJ, so we quote his work directly (9):

The TFC and the ulnocarpal ligaments provide the heart of

the TFCC. Stability of the radioulnar-carpal unit is additionally influenced by the conformation of the sigmoid notch (12),

the interosseous membrane (9), the ER, the dynamic forces of

the ECU and the pronator quadratus (PQ), as well as the dorsal carpal ligament complex. The latter can be visualized as a

“star” centered over and blending with the dorsal peripheral

margin of the TFCC. The proximal and distal legs are the

ECU sheath extending from the ECU groove to the dorsal

base of the fifth metacarpal. The radial legs are the proximal

and distal radiotriquetral ligaments and the dorsal TCL. The

ulnar leg is a wide ligament band proceeding from the center

of the star around the ulnar aspect of the triquetrum distal to

the styloid and attaching to the pisotriquetral joint capsule.

I [Bowers] attach no functional or anatomical significance

to the oft-described “ulnar collateral ligaments” and “dorsal

and volar radioulnar ligaments,” except as terms used to

describe the dorsal and volar margins of the TFC. In my [Bowers] opinion there are no structures that deserve this designation and they probably represent figments of the imagination.

The DRUJ capsule is uniformly thin and cannot be construed to offer stability in the usual sense. Dorsally, the capsule

is minimally reinforced by the obliquely passing radiotriquetral capsular ligament. It offers no coverage to the ulnar head.

Spinner and Kaplan (26) have called attention to the importance of the ECU musculotendinous unit in stabilizing the

joint. The emphasis is warranted but should be shared by both

the rather strong sheath system through which it runs and the

strong volar ligament complex. Johnson and Shrewsbury (27)

have demonstrated that the dual structure of the PQ stabilizes

the radioulnar joint actively by maintaining coaptation of the

ulnar head in the notch in pronation and passively by viscoelastic forces in supination.

LIGAMENT ANATOMY

The ligaments of the wrist have been described in a number

of ways, leading to substantial confusion in the literature

regarding a variety of features of the carpal ligaments. Several general principles have been identified to help simplify

the ligamentous architecture of the wrist. No ligaments of

the wrist are truly extracapsular. Most can be anatomically

classified as capsular ligaments with collagen fascicles clearly

within the lamina of the joint capsule. The ligaments that

are not entirely capsular, such as the interosseous ligaments

between the bones in the carpal row, are intraarticular. This

implies that they are not ensheathed in part by a fibrous

capsular lamina. The wrist ligaments show consistent histologic features, which are to a degree ligament specific. Most

capsular ligaments are composed of longitudinally oriented

laminated collagen fascicles surrounded by loosely orga498 Regional Anatomy

FIGURE 9.9. The vascular supply of the triangular fibrocartilage.

AIA, anterior interosseous artery.

nized perifascicular tissue, which in turn is surrounded by

the epiligamentous sheath. This sheath usually is composed

of the fibrous and synovial capsular lamina. The perifascicular tissue has numerous blood vessels and nerves aligned

longitudinally with the collagen fascicles. The function of

these nerves currently is not well understood. It has been

hypothesized that these nerves are an integral part of a proprioceptive network, following the principles of Hilton’s

law of segmental innervation. The palmar capsular ligaments are more numerous than the dorsal, forming almost

the entire palmar joint capsules of the radiocarpal and midcarpal joints. The palmar ligaments tend to converge

toward the midline as they travel distally, and have been

described as forming an apex-distal “V.” The interosseous

ligaments between the individual bones in a carpal row usually are short and transversely oriented, and with specific

exceptions, cover the dorsal and palmar joint margins. Specific ligament groups are briefly described in the following

sections, and are divided into capsular and interosseous

groups.

Palmar Radiocarpal Ligaments

The palmar radiocarpal ligaments arise from the palmar

margin of the distal radius and course distally and ulnarly

toward the scaphoid, lunate, and capitate (Fig. 9.10).

Although the course of the fibers can be defined from an

anterior view, the separate divisions of the palmar radiocarpal ligament are best appreciated from a dorsal view

through the radiocarpal joint. The palmar radiocarpal ligament can be divided into four distinct regions.

Radioscaphocapitate Ligament

Beginning radially, the RSC ligament originates from the

radial styloid process, forms the radial wall of the radiocarpal joint, attaches to the scaphoid waist and distal pole,

and passes palmar to the head of the capitate to interdigitate with fibers from the ulnocapitate ligament. Very few

fibers from the RSC ligament attach to the capitate.

Long Radiolunate Ligament

Just ulnar to the RSC ligament, the long radiolunate (LRL)

ligament arises to pass palmar to the proximal pole of the

scaphoid and the scapholunate interosseous ligament to

attach to the radial margin of the palmar horn of the lunate.

The interligamentous sulcus separates the RSC and LRL

ligaments throughout their courses. The LRL ligament has

been called the radiolunotriquetral ligament historically, but

the paucity of fibers continuing toward the triquetrum

across the palmar horn of the lunate renders this name misleading.

9 Wrist 499

FIGURE 9.10. Palmar radiocarpal ligaments: the

radioscaphocapitate, long and short radiolunate,

radioscapholunate, pisohamate, triquetrocapitate,

ulnocapitate, ulnotriquetral, and palmar radioulnar.

Radioscapholunate Ligament

Ulnar to the origin of the LRL ligament, the radioscapholunate “ligament” emerges into the radiocarpal joint space

through the palmar capsule and merges with the scapholunate interosseous ligament and the interfossal ridge of the

distal radius. This structure resembles more a “mesocapsule”

than a true ligament because it is composed of small-caliber

blood vessels and nerves from the radial artery and anterior

interosseous neurovascular bundle. Very little organized collagen is identified in this structure. The mechanical stabilizing effects of this structure have been shown to be minimal.

Short Radiolunate Ligament

The final palmar radiocarpal ligament, the short radiolunate ligament, arises as a flat sheet of fibers from the palmar

rim of the lunate fossa, just ulnar to the radioscapholunate

ligament. It courses immediately distally to attach to the

proximal and palmar margin of the lunate.

Dorsal Capsular Ligaments

The dorsal wrist capsule is reinforced by two well defined

ligaments (Fig. 9.11). Otherwise, it is composed of a highly

pliable joint capsule, which no doubt contributes to the

range of motion allowed by the wrist during palmar flexion.

The two ligaments are referred to as the dorsal radiocarpal

(DRC) and dorsal intercarpal ligaments.

Dorsal Radiocarpal Ligament

The DRC ligament arises from the dorsal rim of the radius,

essentially equally distributed on either side of Lister’s

tubercle. It courses obliquely distally and ulnarly toward the

triquetrum, to which it attaches on the dorsal cortex. There

are some deep attachments of the DRC ligament to the dorsal horn of the lunate. Loose connective and synovial tissue

forms the capsular margins proximal and distal to the DRC

ligament. It is sometimes called the dorsal radiotriquetral ligament.

Dorsal Intercarpal Ligament

The dorsal intercarpal ligament, originating from the dorsal

cortex of the triquetrum, crosses the mid-carpal joint

obliquely to attach to the scaphoid, trapezoid, and capitate.

The attachment of the dorsal intercarpal ligament to the triquetrum is confluent with the triquetral attachment of the

DRC ligament. In addition, a proximal thickened region of

the joint capsule, roughly parallel to the DRC ligament,

extends from the waist of the scaphoid across the distal margin of the dorsal horn of the lunate to the triquetrum. This

band, called the dorsal scaphotriquetral ligament, forms a

“labrum” that encases the head of the capitate, analogous to

the RSC and ulnocapitate ligaments palmarly.

500 Regional Anatomy

FIGURE 9.11. Dorsal radiocarpal ligaments: dorsal intercarpal, dorsal scaphotriquetral, and dorsoradiocarpal

(dorsoradiotriquetral).

Ulnocarpal Ligaments

[Note: The ulnocarpal ligaments also are discussed earlier in

the section on the TFCC (under the main Distal Radioulnar Joint section; see Fig. 9.8)].

The ulnocarpal ligament arises largely from the palmar

margin of the TFCC, the palmar radioulnar ligament, and

in a limited fashion from the head of the ulna. It courses

obliquely distally toward the lunate, triquetrum, and capitate. There are three divisions of the ulnocarpal ligament,

designated by their distal bony insertions.

Ulnolunate Ligament

The ulnolunate ligament is essentially continuous with the

short radiolunate ligament, forming a continuous palmar

capsule between the TFCC and the lunate.

Ulnotriquetral Ligament

Confluent with these fibers is the ulnotriquetral ligament,

connecting the TFCC and the palmar rim of the triquetrum. In 60% to 70% of normal adults, a small orifice

is found in the distal substance of the ulnotriquetral ligament that leads to a communication between the radiocarpal and pisotriquetral joints. Just proximal and ulnar to

the pisotriquetral orifice is the prestyloid recess, which usually is lined by synovial villi and variably communicates

with the underlying ulnar styloid process.

Ulnocapitate Ligament

The ulnocapitate ligament arises from the foveal and palmar region of the head of the ulna, where it courses distally,

palmar to the ulnolunate and ulnotriquetral ligaments, and

passes palmar to the head of the capitate, where it interdigitates with fibers from the RSC ligament to form an arcuate

ligament to the head of the capitate. A few fibers from the

ulnocapitate ligament insert to the capitate.

Mid-Carpal Ligaments

The mid-carpal ligaments on the palmar surface of the carpus are true capsular ligaments, and as a rule are short and

stout, connecting bones across a single joint space (Fig.

9.12).

9 Wrist 501

FIGURE 9.12. Palmar mid-carpal and proximal and distal row interosseous ligaments. Mid-carpal

interosseous: STT, scaphotrapezium-trapezoid; SC, scaphocapitate; TC, triquetrocapitate; TH, triquetrohamate. Proximal row interosseous: SL, scapholunate; LT, lunotriquetral. Distal row

interosseous: TT, trapeziotrapezoid; TC, trapeziocapitate; CH, capitohamate.

Scaphotrapezium-Trapezoid Ligament

Beginning radially, the STT ligament forms the palmar capsule of the STT joint, connecting the distal pole of the

scaphoid with the palmar surfaces of the trapezium and

trapezoid. Although no clear divisions are noted, it forms an

apex-proximal “V” shape.

Scaphocapitate Ligament

The scaphocapitate ligament is a thick ligament interposed

between the STT and RSC ligaments, coursing from the

palmar surface of the waist of the scaphoid to the palmar

surface of the body of the capitate. There are no formal connections between the lunate and capitate, although the

arcuate ligament (formed by the RSC and ulnocapitate ligaments) has weak attachments to the palmar horn of the

lunate.

Triquetrocapitate Ligament

The triquetrocapitate ligament is analogous to the scaphocapitate ligament. It is a thick ligament, passing from the

palmar and distal margin of the triquetrum to the palmar

surface of the body of the capitate.

Triquetrohamate Ligament

Immediately adjacent to the triquetrocapitate ligament, the

triquetrohamate ligament forms the ulnar wall of the midcarpal joint, and is augmented ulnarly by fibers from the

TFCC.

Proximal Row Interosseous Ligaments

The scapholunate and lunotriquetral interosseous ligaments

form the interconnections between the bones of the proximal carpal row and share several anatomic features (see Fig.

9.12). Each forms a barrier between the radiocarpal and

mid-carpal joints, connecting the dorsal, proximal, and palmar edges of the respective joint surfaces. This leaves the

distal edges of the joints without ligamentous coverage.

Scapholunate Interosseous Ligament

The dorsal region of the scapholunate ligament is relatively

thick and composed of transversely oriented collagen fibers.

It merges distally with the scaphotriquetral band of the dorsal intercarpal ligament, and proximally with the fibrocartilaginous membrane of the scapholunate ligament. The

fibrocartilaginous membrane forms the proximal region of

the scapholunate ligament. It often is wedge shaped in

cross-section, extending into the scapholunate joint cleft

much as a meniscus. Palmarly, the radioscapholunate ligament interrupts the continuity of the scapholunate ligament, again with vascular villi extending into the palmar

aspect of the scapholunate joint cleft. The palmar region of

the scapholunate ligament is quite thin and obliquely oriented in the transverse plane, from the relatively dorsal palmar edge of the scaphoid to the more palmar anterior edge

of the lunate. It is completely separate from the dorsal surface of the LRL ligament.

Lunotriquetral Interosseous Ligament

The dorsal region of the lunotriquetral interosseous ligament is quite thin, transversely oriented, and superficially

integrated with the overlying dorsal radiocarpal ligament.

The proximal region is composed of fibrocartilage, similar

to the proximal region of the scapholunate interosseous ligament. Palmarly, the lunotriquetral ligament is quite thick

and interdigitates with the longitudinally oriented fibers of

the ulnocapitate ligament.

Distal Row Interosseous Ligaments

The bones of the distal carpal row are rigidly connected by

a complex system of interosseous ligaments (see Fig. 9.12).

As is discussed in the following sections, these ligaments are

largely responsible for transforming the four distal row

bones into a single kinematic unit. The trapeziotrapezoid,

trapeziocapitate, and capitohamate joints each are bridged

by palmar and dorsal interosseous ligaments. These ligaments are composed of transversely oriented collagen fascicles and are covered superficially by the fibrous capsular

lamina, also composed of transversely oriented fibers. This

lamina gives the appearance of a continuous sheet of fibers

spanning the entire palmar and dorsal surface of the distal

row.

Trapeziotrapezoid Interosseous Ligament

The trapeziotrapezoid ligament is composed of parallel dorsal and palmar sheets, spanning from the dorsal and palmar

cortices of each respective bone.

Trapeziocapitate Interosseous Ligament

The trapeziocapitate ligament is similar to the trapeziotrapezoid ligament; however, the trapeziocapitate has an

additional component called the “deep” trapeziocapitate ligaments. This ligament is entirely intraarticular, spanning

the respective joint spaces between voids in the articular

surfaces. It is a true ligament, with dense, colinear collagen

fascicles, but also is heavily invested with nerve fibers. The

deep trapeziocapitate ligament is located midway between

the palmar and dorsal limits of the joint, obliquely oriented

from palmar-ulnar to dorsoradial, and measures approximately 3 mm in diameter. The respective attachment sites

of the trapezoid and capitate are angulated in the transverse

502 Regional Anatomy

plane to accommodate the orthogonal insertion of the ligament.

Capitohamate Interosseous Ligament

The dorsal and palmar bands of the capitohamate

interosseous ligament are similar to those of the other distal

row interosseous ligaments. As with the trapeziocapitate

interosseous ligament, there is a “deep” component to the

capitohamate interosseous ligament. The deep capitohamate interosseous ligament is found transversely oriented at

the palmar and distal corner of the joint. It traverses the

joint from quadrangular voids in the articular surfaces and

measures approximately 5 × 5 mm in cross-sectional area.

RETINACULAR ANATOMY AND THE CARPAL

CANAL

Flexor Retinaculum

Nomenclature

Based on the observations of Cobb and associates, the

restraining or retinacular structure on the palmar aspect of

the wrist is most appropriately called the flexor retinaculum.

They noted, however, that others have considered the TCL

and FR to be synonymous (28). Cobb and associates identified three distinct and continuous segments that extended

from the distal part of the radius to the distal aspect of the

base of the long finger metacarpal. The proximal portion of

the FR is continuous with the deep investing forearm fascia

that lies deep to the antebrachial fascia. The TCL represents

the central portion of the FR and is defined by its bony

attachments ulnarly to the pisiform and hook process of the

hamate, and radially to the tuberosity of the scaphoid and

ridge of the trapezium, and serves as the roof of the carpal

canal. The distal portion of the FR is composed of an

aponeurosis between the thenar and hypothenar muscles.

Anatomic Layers/Divisions

Two separate layers of fascia are present over the palmar

aspect of the carpal canal. The more superficial layer is the

thickened antebrachial fascia proximally and the palmar fascia distally. The deeper layer, the FR, has three continuous

portions. The most proximal is represented by a thickening

in the deep investing fascia of the forearm. The central portion is the TCL and the distal portion is formed by an

aponeurosis between the thenar and hypothenar eminences

(Fig. 9.13). Anteriorly, the proximal portion of the FR is

inseparable from the thickened antebrachial fascia. On the

ulnar and radial aspects, these two layers become separated.

The antebrachial fascia is more superficial and encloses the

FCR, FCU, and the ulnar neurovascular bundle. The deep

investing fascia encloses only the contents of the carpal

canal (28).

Dimensions of the Transverse Carpal Ligament

Portion of the Flexor Retinaculum

Based on the study of Cobb et al., the TCL portion of the

FR begins an average of 11 mm distal to the capitate-lunate

joint and extends an average of 10 mm distal to the car9 Wrist 503

FIGURE 9.13. The flexor retinaculum.

pometacarpal joint of the long finger. The mean width of

the carpal tunnel was 25 ± 1.2 mm proximally, 20 ± 1.2

mm at the hook of the hamate, and 25 ± 1.5 mm at its distal extent. The thickness of the TCL ranged from 0.8 to 2.5

mm, with a mean of 1.52 mm (28).

Histology

The fibers of the FR demonstrated large numbers of transversely oriented collagen fibers and an overall thickness

approximately 10 times the thickness of the antebrachial

fascia. In contrast, the fibers of the antebrachial fascia were

oriented longitudinally.

Clinical Significance

Anatomically, there are two areas in the carpal canal where

median nerve compression may occur. The first is at the

level of the proximal edge of the TCL, where compression

is produced by acute flexion of the wrist. The comparative

thickness of the TCL relative to the adjacent fascia results in

impingement on the nerve. This configuration offers one

explanation for a positive Phalen’s test (wrist flexion test) in

carpal tunnel syndrome. The second area of potential compression is at the level of the hook of the hamate, where the

canal is narrowest in both palmar-dorsal and ulnar-radial

planes. This second site of potential compression corresponds to the authors’ clinical observation of the location of

the hourglass deformity in the median nerve seen at carpal

tunnel release in long-standing cases of carpal tunnel syndrome. The site of maximum indentation of the median

nerve is adjacent to the hook process of the hamate.

Carpal Canal

Boundaries

This fibroosseous canal is bounded ulnarly by the hook

process of the hamate, the triquetrum, and the pisiform,

and radially by the scaphoid, trapezium, and the fascial elements over the FCR tendon. The floor is formed by the

underlying portions of the scaphoid, lunate, capitate,

hamate, and trapezoid; the roof is formed by the FR (Fig.

9.14).

Contents

The contents of the carpal canal are the four tendons of the

flexor digitorum profundus, the four tendons of the flexor

digitorum superficialis (FDS), the FPL tendon, and the

median nerve. The FPL tendon is the most radial of the

flexors and the median nerve is the most palmar structure

in the canal. The finger flexor tendons in the carpal canal

are covered by a common sheath and the FPL by its own

synovial sheath. These synovial sheaths begin approximately

2.5 cm proximal to the proximal edge of the FR. Details of

the synovial tissues in the wrist and palm are presented in

Chapter 10.

The Carpal Canal as a Compartment

Although the carpal tunnel, as its name implies, is open

proximally and distally, it may act like a physiologic compartment and has its own distinct compartment pressure

levels (29–31). Cobb and associates studied the pressure

dynamics of the carpal tunnel and flexor compartment of

the forearm and found that it functions as a relatively closed

compartment with respect to transfer of pressure from the

flexor compartment of the forearm under conditions that

mimic elevated tissue pressure (32).

Clinical Significance of the Carpal Tunnel as a

Physiologic Compartment

When carpal canal pressure rises above a critical threshold

level, capillary blood flow is reduced below the level

required for median nerve viability and irreparable nerve

damage is likely to result (33).

Extensor Retinaculum

Anatomy

The wrist, thumb, and finger extensors gain entrance to the

hand beneath the ER through a series of six tunnels, five

fibroosseous and one fibrous [the fifth dorsal compartment,

which contains the extensor digiti minimi (EDM)] (34)

(Fig. 9.15). The ER is a wide, fibrous band that prevents

504 Regional Anatomy

FIGURE 9.14. The carpal tunnel.

bowstringing of the tendons across the wrist joint. Its average width is 4.9 cm (range, 2.9 to 8.4 cm) as measured over

the fourth compartment (34). At this level, the extensor

tendons are covered with synovial sheath. The ER consists

of two layers: the supratendinous and the infratendinous.

The infratendinous layer is limited to an area deep to the

ulnar three compartments. The six dorsal compartments are

separated by septa that arise from the supratendinous retinaculum and insert onto the radius (35). Three distinct layers have been identified: (a) an inner gliding layer with high

hyaluronic acid–secreting cells with isolated areas of chondroid metaplasia; (b) a thick middle layer with collagen

bundles oriented in various directions, fibroblasts, and

elastin fibers; and (c) an outer layer of loose connective tissue with vascular channels. This is the same histologic

arrangement seen in anatomic pulleys throughout the body

that provides a smooth gliding surface with mechanical

strength (36).

Function

The basic function of the ER is to avoid bowstringing of the

extensor tendons; this explains the presence of chondroid

metaplasia, which is an adaptation in response to friction

and the dorsal forces produced by extensor tendon action.

The ER has been found to be a useful tissue for flexor tendon pulley reconstruction because of its histologic similarity to the native pulley in the fingers (37).

Tendon Anatomy

The tendons that cross the wrist can be divided into two

major groups: those that are responsible primarily for mov9 Wrist 505

FIGURE 9.15. The six compartments of the extensor retinaculum.

ing the wrist and those that cross the wrist in their path to

the digits. Both groups impart some movement to the wrist,

but obviously those that are primary wrist motors have a

more substantial influence on motion of the wrist. The five

primary wrist motors can be grouped as either radial or

ulnar deviators and as either flexors or extensors.

The ECRL and ECRB muscles are bipennate and originate from the lateral epicondyle of the humerus from a

common tendon. Over the distal radius epiphysis, they are

found in the second extensor compartment, from which

they emerge to insert into the radial cortices of the bases of

the second and third metacarpals, respectively. The ECRL

imparts a greater moment for radial deviation than the

ECRB, whereas the opposite relationship is found for wrist

extension. Both the ECRL and the ECRB muscles are

innervated by the radial nerve.

The ECU muscle is bipennate, originates largely from

the proximal ulna, and passes through the sixth extensor

compartment. In the sixth extensor compartment, the ECU

tendon is contained in a fibroosseous tunnel between the

ulnar head and the ulnar styloid process. Distal to the ER,

the ECU tendon inserts into the ulnar aspect of the base of

the fifth metacarpal. The ECU muscle is innervated by the

radial nerve.

The FCR muscle is bipennate and originates from the

proximal radius and the interosseous membrane. The tendon of FCR enters a fibroosseous tunnel formed by the distal pole of the scaphoid and the “beak” of the trapezium,

and then angles dorsally to insert into the base of the second metacarpal. This fibroosseous tunnel is separate from

the carpal tunnel. The FCR muscle is innervated by the

median nerve.

The FCU muscle is unipennate and originates from the

medial epicondyle of the humerus and the proximal ulna. It

is not constrained by a fibroosseous tunnel, in contradistinction to the other primary wrist motors. It inserts into

the pisiform and ultimately continues as the pisohamate ligament. The FCU muscle is innervated by the ulnar nerve.

VASCULAR ANATOMY

Vascular Anatomy of the Carpus

There are three dorsal and three palmar carpal arches from

the radial, ulnar, and anterior interosseous arteries. These

arches are named (proximal to distal) the radiocarpal, intercarpal, and basal metacarpal transverse arches (38). Anastomoses often are found between the arches, the radial and

ulnar arteries, and the interosseous artery system. All carpal

bones, with the exception of the pisiform, receive their

blood supply through dorsal and palmar entry sites, and

usually through more than one nutrient artery. Usually, a

number of small-caliber penetrating vessels are found in

addition to the major nutrient vessels. Intraosseous anastomoses can be found in three basic patterns. First, a direct

anastomosis can occur between two large-diameter vessels

in the bone. Second, anastomotic arcades may form with

similar-sized vessels, often entering the bone from different

areas. A final pattern, although rare, has been identified

where a diffuse arterial network virtually fills the bone.

Although the intraosseous vascular patterns of each carpal

bone have been defined in detail, studies of the lunate, capitate, and scaphoid are particularly important because of

their predilection to the development of clinically important avascular problems.

Extraosseous Vascular Patterns

The extraosseous vascularity of the carpus is from a series of

three dorsal and palmar transverse arches formed by the

radial, ulnar, and anterior interosseous arteries (38).

Dorsal Carpal Vascularity

The vascularity to the dorsal carpus is from three dorsal

transverse arches: the radiocarpal, the intercarpal, and the

basal metacarpal transverse arches (38,39) (Fig. 9.16). The

presence of each arch is variable. These arches are approximately 1 mm in diameter and their branches are less than 1

mm (40).

Radiocarpal Arch. The dorsal radiocarpal arch is the most

proximal and is present 80% of the time (38). It is located

at the level of the radiocarpal joint and lies deep to the

extensor tendons. This arch provides the main nutrient vessels to the lunate and triquetrum. This arch usually is

formed by branches from the radial and ulnar arteries and

the dorsal branch of the anterior interosseous artery. Occasionally, the radial and ulnar arteries supply the dorsal

radiocarpal arch alone, or it is supplied by the radial and

anterior interior osseous arteries (38).

Intercarpal Arch. The dorsal intercarpal arch is the largest

of the dorsal transverse arches and is consistently present

(38). It runs transversely across the carpus between the

proximal and distal carpal rows and supplies the distal

carpal row, as well as joining the radiocarpal arch to supply

the lunate and triquetrum. This arch is supplied by the

radial, ulnar, and anterior interosseous arteries 53% of the

time, by the radial and ulnar arteries alone in 20%, and by

the ulnar and anterior interosseous arteries in 7% (38).

Basal Metacarpal Arch. This is the most distal of the dorsal transverse arches and is located at the base of the

metacarpal just distal to the carpometacarpal joints. It is the

smallest of the dorsal arches and is represented by a series of

vascular retia; its presence is the most variable and is complete in 27%, absent in 27%, and present in its radial aspect

alone in 46% (38). This arch is supplied by perforating

arteries from the second through fourth interosseous spaces

and contributes to the vascularity of the distal carpal row

506 Regional Anatomy

through anastomoses with the intercarpal arch. The dorsal

arches are connected centrally by the dorsal branch of the

interosseous artery and radially and ulnarly by the radial

and ulnar arteries.

Palmar Carpal Vascularity

Like its dorsal counterpart, the palmar carpal vascularity is

formed by three transverse arches: the palmar radiocarpal,

the palmar intercarpal, and the deep palmar arch (38) (Fig.

9.17).

Palmar Radiocarpal Arch. This arch is the most proximal; it courses transversely 5 to 8 mm proximal to the

radiocarpal joint at the level of the distal metaphysis of the

radius and ulna and lies in the wrist capsule. It is consistently present and is formed by branches of the radial, anterior interosseous, and ulnar arteries in 87% of specimens,

and by the radial and ulnar arteries alone in 13%. This arch

supplies the palmar surface of the lunate and triquetrum

(41).

Palmar Intercarpal Arch. This arch, located between the

proximal and distal carpal rows, is the most variable in

occurrence and is present 53% of the time. It is formed by

branches of the radial, ulnar, and anterior interosseous

arteries in 75% of specimens and by the radial and ulnar

arteries alone in 25%. This small arch is not a major source

of vessels to the carpus (38).

9 Wrist 507

FIGURE 9.16. Schematic drawing of the arterial supply of the dorsal wrist. (After Gelberman RH,

Panagis JS, Taleisnik J, et al. The arterial anatomy of the human carpus. Part I: the extraosseous

vascularity. J Hand Surg [Am] 8:367–375, 1983, with permission.)

Deep Palmar Arch. This most distal palmar arch is

located 5 to 10 mm distal to the palmar carpometacarpal

joints. It is consistently present and contributes to the

radial and ulnar recurrent arteries, as well as sending perforating branches to the dorsal basal metacarpal arch and

to the palmar metacarpal arteries (41). These three palmar

arches are connected longitudinally by the radial, ulnar,

anterior interosseous, and deep palmar recurrent arteries

(38).

Specific Vessels

The five major arteries that supply the carpus are the radial,

ulnar, anterior interosseous, deep palmar arch, and the

accessory ulnar recurrent (40). These arteries are discussed

separately as they relate to the vascularity of the carpus.

Radial Artery

The radial artery is the most consistent artery that supplies

the carpus. It has seven major branches, including three dor508 Regional Anatomy

FIGURE 9.17. Schematic drawing of the arterial supply of the palmar wrist. (After Gelberman

RH, Panagis JS, Taleisnik J, et al. The arterial anatomy of the human carpus. Part I: the

extraosseous vascularity. J Hand Surg [Am] 8:367–375, 1983, with permission.)

sal, three palmar, and a terminal branch that continues distally (40) (Fig. 9.18). The most proximal branch is the

superficial palmar artery, which leaves the main stem of the

radial artery 5 to 8 mm proximal to the tip of the radial styloid, passes between the FCR and brachioradialis, and continues distally to contribute to the superficial palmar arch.

The second branch, which contributes to the palmar radiocarpal arch, leaves the radial artery approximately 5 mm distal to the superficial palmar artery and courses toward the

ulna. A third branch originates at the level of the radiocarpal

joint and courses dorsally and ulnarly to penetrate the radiocarpal ligament deep to the extensor tendons. This branch

supplies the dorsal radiocarpal arch. The fourth branch arises

palmarly at the level of the scaphotrapezial joint and supplies

the tubercle of the scaphoid, the trapezium, and the

radiopalmar surface of the trapezium. It then anastomoses

with the superficial palmar artery. This vessel is absent in

25% of specimens; in 25% it anastomoses with a branch of

the superficial palmar artery before entering the scaphoid

tubercle (38). The fifth branch of the radial artery, the

branch to the dorsal ridge of the scaphoid, originates directly

from the radial artery in 75% of specimens and from the

radiocarpal or intercarpal arch in 25%. It courses in an ulnar

retrograde fashion to supply the scaphoid. The sixth branch

leaves the radial artery 5 mm distal to the branch to the

scaphoid and contributes to the dorsal intercarpal arch. This

arch courses ulnarly across the trapezoid and the distal onehalf of the capitate and then branches and anastomoses with

the dorsal branch of the anterior interosseous artery and the

dorsal branches of the ulnar artery. The last branch of the

radial artery originates at the level of the trapezium and

courses distally to supply the trapezium and the lateral

aspect of the thumb metacarpal (38).

Ulnar Artery

At the level of the carpus, the ulnar artery gives off a latticework of fine vessels that span the dorsal and palmar

aspects of the medial carpus (see Figs. 9.16 and 9.17). Proximal to the end of the ulna, there are three branches: a

branch to the dorsal radiocarpal arch, one to the palmar

radiocarpal arch, and one to the proximal pole of the pisiform and to the palmar aspect of the triquetrum. Several

small branches supply the lateral aspect of the pisiform, and

one branch joins the palmar intercarpal arch. Distally, a

branch supplies the distal pisiform and the medial hamate

and continues dorsally between the pisohamate and

pisometacarpal ligaments to contribute to the dorsal intercarpal arch. At the mid-carpal joint level, the medial branch

of the ulnar artery contributes to the intercarpal arch (see

Fig. 9.16). Distally, at the level of the metacarpal bases, the

basal metacarpal arch receives its contribution from the

medial branch of the ulnar artery. The medial branch of the

ulnar artery then continues distally toward the base of the

fifth metacarpal. A distal branch of the ulnar artery arises

proximal to the origin of the superficial palmar arch and

continues dorsally to supply the basal metacarpal arch. A

deep palmar branch is given off distally that contributes to

the deep palmar arch. The ulnar artery continues distally

and radially to contribute to the superficial arch.

Anterior Interosseous Artery

At the proximal border of the PQ muscle, the anterior

interosseous artery bifurcates into dorsal and palmar

branches. The dorsal branch continues distally on the

interosseous membrane to the carpus, where it supplies the

dorsal radiocarpal arch in 89% of specimens (38). Small

branches extend radially to supply the lunate and anasto9 Wrist 509

FIGURE 9.18. Schematic drawing of the arterial supply of the radial aspect of the wrist. (After

Gelberman RH, Panagis JS, Taleisnik J, et al. The arterial anatomy of the human carpus. Part I: the

extraosseous vascularity. J Hand Surg [Am] 8:367–375, 1983, with permission.)

mose with several small radial artery branches supplying the

dorsal ridge of the scaphoid. The dorsal branch of the anterior interosseous artery bifurcates at the intercarpal level,

each branch contributing to the intercarpal arch in 83% of

specimens (38). The dorsal branch of the interosseous

artery ends by anastomosing with recurrent vessels from the

basal metacarpal arch at the third and fourth interosseous

spaces in 70% of the specimens (38). The palmar branch of

the anterior interosseous artery continues deep to the PQ

and bifurcates 5 to 8 mm proximal to the radiocarpal arch.

It usually contributes at least one branch to the palmar

radiocarpal arch to supply the ulnar aspect of the lunate and

triquetrum, and then ends by anastomosing with recurrent

vessels from the deep palmar arch (41).

Deep Palmar Arch

The deep palmar arch provides the primary arterial supply

to the distal carpal row by means of two branches, the radial

and ulnar recurrent arteries (see Fig. 9.17). These branches

run in a distal-to-proximal direction and are consistently

present (38). The radial recurrent artery is slightly smaller,

originates from the arch just lateral to the base of the index

metacarpal, and courses proximally to bifurcate on the palmar aspect of the trapezoid. It anastomoses with the ulnar

recurrent artery in 45% of the specimens. The ulnar recurrent artery originates from the deep arch between the bases

of the third and fourth metacarpals. It courses proximally in

the ligamentous groove between the capitate and the

hamate, supplying both bones. It anastomoses with the terminal portion of the anterior interosseous artery in 80% of

the specimens (41).

Accessory Ulnar Recurrent Artery

In 27% of specimens, an ulnar recurrent artery is present

that originates from the deep arch 5 to 10 mm medial to the

ulnar recurrent artery and supplies the medial aspect of the

hook process of the hamate. When this vessel is absent, the

medial aspect of the hamate is supplied by direct branches

from the ulnar artery (38).

Posterior Interosseous Artery

The posterior interosseous artery does not reach the carpus

and thus does not contribute to the vascularity of the carpus (38). The contributions of the major arteries and arches

to the vascularity of the carpus are shown in Figures 9.19

and 9.20.

Intraosseous Vascular Patterns

Vascularity of the Scaphoid

The scaphoid receives most of its blood supply from the

radial artery by means of vessels that enter in limited areas

dorsally and palmarly that are nonarticular areas of ligamentous attachment (42). The dorsal vascular supply

accounts for 70% to 80% of the internal vascularity of the

bone, all in the proximal region (42). On the dorsum of the

510 Regional Anatomy

FIGURE 9.19. Schematic drawing of the dorsal wrist showing the various arterial contributions to the carpal bones.

(After Gelberman RH, Panagis JS, Taleisnik J, et al. The arterial anatomy of the human carpus. Part I: the extraosseous

vascularity. J Hand Surg [Am] 8:367–375, 1983, with permission.)

scaphoid, there is an oblique ridge that lies between the

articular surfaces of the trapezium and trapezoid, and the

major dorsal vessels enter the scaphoid through small

foramina located on this ridge (42). The dorsal ridge is in

the region of the scaphoid waist. At the level of the intercarpal joint, the radial artery gives off the intercarpal artery,

which immediately divides into two branches. One branch

courses transversely to the dorsum of the wrist and the

other courses vertically and distally over the index

metacarpal. Approximately 5 mm proximal to the origin of

the intercarpal vessel, at the level of the styloid process of

the radius, another vessel is given off that runs over the

radiocarpal ligament to enter the scaphoid through its waist

along the dorsal ridge. In 70% of specimens, the dorsal vessel arises directly from the radial artery. In 23%, the dorsal

branch has its origin from the common stem of the intercarpal artery. In 7%, the scaphoid receives its dorsal blood

supply directly from the branches of the intercarpal artery

and the radial artery. There are consistent major communications between the dorsal scaphoid branch of the radial

artery and the dorsal branch of the anterior interosseous

artery in each specimen. No vessels enter the proximal dorsal region of the scaphoid through the dorsal scapholunate

ligament, and no vessels enter through dorsal cartilaginous

areas (42). Although the dorsal vessels usually enter the

scaphoid through foramina located on the dorsal ridge at

the level of the scaphoid waist, in a few specimens the vessels entered just proximal or distal to the waist. The dorsal

vessels usually divide into two or three branches soon after

entering the scaphoid, and these branches run palmarly and

proximally, dividing into smaller branches to supply the

proximal pole as far as the subchondral region. The palmar

vascular supply accounts for 20% to 30% of the internal

vascularity, all in the region of the distal pole (42). At the

level of the radioscaphoid joint, the radial artery gives off

the superficial palmar branch, and just distal to the origin

of the superficial branch, several smaller branches course

obliquely and distally over the palmar aspect of the

scaphoid to enter the region of the tubercle (39,42). These

branches, called the palmar scaphoid branches, divide into

several smaller branches just before entering the bone. In

75% of the specimens, these arteries arise directly from the

radial artery (42). In the remainder of the specimens, they

arise from the superficial palmar branch of the radial artery.

Consistent anastomoses exist between the palmar division

and the anterior interosseous artery and the palmar

scaphoid branch of the radial artery, when the latter arises

from the superficial palmar branch of the radial artery.

9 Wrist 511

FIGURE 9.20. Schematic drawing of the palmar aspect of the wrist showing the various arterial

contributions to the carpal bones. (After Gelberman RH, Panagis JS, Taleisnik J, et al. The arterial

anatomy of the human carpus. Part I: the extraosseous vascularity. J Hand Surg [Am] 8:367–375,

1983, with permission.)

There are no apparent communicating branches between

the ulnar artery and the palmar branches of the radial artery

that supply the scaphoid. Vessels in the scapholunate ligament do not penetrate the scaphoid. The palmar vessels

enter the tubercle and divide into several smaller branches

to supply 20% to 30% of the scaphoid. There are no apparent anastomoses between the palmar and dorsal vessels (39).

Vascularity of the Lunate

The lunate receives its blood supply from either palmar and

dorsal sources or from the palmar aspect alone. In 80% of

specimens, the lunate receives nutrient vessels from palmar

and dorsal aspects. In 20% of the specimens, it receives

nutrient vessels from the palmar surface alone (42). Besides

these relatively small dorsal and palmar surfaces, the lunate

is covered by articular cartilage, and no other vessels enter

the bone. The vessels entering the dorsal surface are from

branches from the dorsal radiocarpal arch, the dorsal intercarpal arch, and occasionally from smaller branches of the

dorsal branch of the anterior interosseous artery (42–44).

On the palmar aspect, the lunate nutrient vessels are supplied by the palmar intercarpal arch, the palmar radiocarpal

arch, communicating branches from the anterior

interosseous artery, and the ulnar recurrent artery. The vessels that enter the lunate dorsally are slightly smaller than

those entering palmarly. Major vessels branch proximally

and distally after entering the bone and end in the subchondral bone. The dorsal and palmar vessels anastomose

intraosseously just distal to the mid-portion of the lunate.

The proximal pole has relatively less vascularity. There are

three major intraosseous patterns of vascularity that occur

in the lunate (43) (Fig. 9.21).

These patterns are formed in the shape of the letters “Y,”

“X,” or “I.” The “Y” pattern is the most common, with an

incidence of 59%. The stem of the “Y” may occur dorsally

or palmarly with equal frequency. The “I” pattern occurs in

approximately 30% of specimens and consists of one dorsal

and one palmar vessel that anastomose in a straight line to

form an “I”-shaped pattern. The “X” pattern occurs in 10%

of specimens and consists of two dorsal and two palmar vessels that anastomose in the center of the lunate to form the

“X”-shaped pattern (41,43,44). In 20% of specimens studied, one palmar supply was present and consisted of one

large vessel that entered on the palmar surface of the lunate

and branched in the lunate to provide the only blood supply (41,43,44).

Vascularity of the Triquetrum

The triquetrum receives its blood supply from branches

from the ulnar artery, and the dorsal and palmar intercarpal

arches. Nutrient vessels enter through the intercarpal arch

as on its dorsal and palmar nonarticular surfaces. The dorsal surface of the triquetrum is rough for attachment of

associated carpal ligaments, and this dorsal surface contains

a ridge that runs from ulnar to radial. Two to four vessels

enter this dorsal ridge and radiate in multiple directions to

supply the dorsal 60% of the bone. This network is the predominant blood supply of the triquetrum as observed in

60% of the specimens (41,44). The palmar surface contains

an oval facet that articulates with the pisiform. One or two

vessels enter proximal and distal to the facet. The vessels

have multiple anastomoses with each other and supply the

palmar 40% of the triquetrum. This palmar vascular network is predominant in 20% of specimens, and significant

anastomoses have been identified between the dorsal and

palmar networks in 86% of specimens (4).

Vascularity of the Pisiform

The pisiform receives its blood supply through the proximal

and distal poles from branches of the ulnar artery. The proximal blood supply enters in the area where the FCU

attaches to the pisiform. One to three vessels enter the bone

inferior to the triquetral facet and divide into multiple

branches. Two superior branches run parallel beneath the

articular surface of the facet. One or two branches run

along the palmar cortex and anastomose with the superior

512 Regional Anatomy

FIGURE 9.21. Patterns of interosseous blood supply to the carpal lunate.

branches (44). The distal vascular supply includes one to

three vessels that enter inferior to the articular facets and

divide into superior and inferior branches that run parallel

to the palmar cortex. These distally entering vessels anastomose with the proximal vessels. The superior vessels run

deep to the articular facet and communicate with the proximal superior vessels, forming an articular ring deep to the

facet. There are multiple anastomoses between the proximal

and distal vascular networks.

Vascularity of the Hamate

The hamate has three main sources of supply: the dorsal

intercarpal arch, the ulnar recurrent artery, and the ulnar

artery. The vessels enter through the three nonarticular surfaces of the hamate, including the dorsal surface, the palmar

surface, and the ulnar aspect through the hook process of

the hamate. The dorsal surface is triangular and receives

three to five vessels that branch in several directions to supply the dorsal 30% to 40% of the hamate (41,44). The palmar surface also is triangular and usually receives one large

vessel that enters through the radial base of the hook

process of the hamate. It then branches and anastomoses

with the dorsal vessels in 50% of the specimens (41,44).

The hook process of the hamate receives one or two small

vessels that enter through the ulnar base and tip of the

hook. These vessels anastomose with each other but usually

not with the vessels to the body of the hamate.

Vascularity of the Capitate

The capitate receives its blood supply from dorsal and palmar sources. The main vascularity arises from vessels from

the dorsal intercarpal and dorsal basal metacarpal arches

and from significant anastomoses between the ulnar recurrent and palmar intercarpal arches. The vessels that enter

the capitate do so through the two nonarticular surfaces on

the dorsal and palmar surfaces. This dorsal surface is relatively wide and contains a deeply concave portion where

two to four vessels enter its distal two-thirds. Smaller vessels

occasionally enter more proximally near the neck. The dorsal vessels course palmarly, proximally, and ulnarly in a retrograde fashion to supply the body and head of the capitate.

This dorsal supply continues palmarly and proximally,

eventually to reach the convex, rough palmar surface. Terminal vessels reach the proximal palmar head and terminate

just deep to the articular surface (41,44). The palmar vascular contribution is through one to three vessels that enter

on the distal one-half of the capitate and course proximally

in a retrograde fashion. In 33% of the specimens, the vessels to the capitate head originate entirely from the palmar

surface. There are notable anastomoses between the dorsal

and palmar vessels in 30% of the specimens (41,44).

Vascularity of the Trapezoid

This bone is supplied by branches from the dorsal intercarpal arch, the basal metacarpal arch, and the radial recurrent artery that enter the trapezoid through its two nonarticular parts on the dorsal and palmar surfaces. The main

blood supply of this bone is dorsal, by means of three to

four small vessels that enter the rough dorsal surface in the

central aspect. These vessels supply the dorsal 70% of the

trapezoid (44). The palmar blood supply is by means of one

to two small vessels that enter the central portion and

branch after entering to supply the remaining 30% of the

trapezoid. No anastomoses are present between the palmar

and dorsal vessels.

Vascularity of the Trapezium

This bone is supplied by vessels from distal branches of the

radial artery that enter the trapezium through its three

nonarticular surfaces. These nonarticular surfaces are dorsal, palmar, and lateral. Dorsally, one to three vessels enter

and divide to supply the entire dorsal aspect of the bone.

Palmarly, one to three vessels enter the trapezium at its midportion and anastomose with the dorsal vessels. Laterally,

three to six very fine vessels penetrate the lateral surface and

anastomose with the dorsal and palmar vessels. The dorsal

vascular supply is dominant, and all three systems anastomose (44).

Clinical Significance and Clinical Correlations of the

Intraosseous Vascularity of the Carpus

Based on their comprehensive studies of the intraosseous

blood supply of the carpal bones, Gelberman and associates

noted that carpal bones were divided into three groups

based on the number and location of their entry blood vessels, the existence of large areas of bone supplied by a single

vessel, and the presence or absence of intraosseous anastomoses. Group I consisted of those carpal bones with vessels

entering only one surface or bones with large intraosseous

areas dependent on one artery. These bones were considered

to be at “greater risk” for avascular necrosis based on their

intraosseous vascular patterns. The capitate and scaphoid

are in this group, as well as those lunate bones supplied by

a single palmar vessel (20% of the cases in their studies)

(44,45).

Postfracture Osteonecrosis of the Carpus. One of the

most important clinical applications of the vascularity of

the carpus is the understanding it may give relative to posttraumatic osteonecrosis. Some, but not all, of these conditions are discussed. Based on vascular studies and clinical

correlations of osteonecrosis, the scaphoid, capitate, and

lunate are considered the bones most likely at risk for posttraumatic osteonecrosis (45). The proximal pole of the

scaphoid has been compared with the head of the femur

and the talus because it is almost completely covered with

hyaline cartilage and has a vascular source that may be

interrupted by fracture (45). The common anatomic findings in these bones at risk are either vessels that enter on

only one surface, or large portions of the bone that are

9 Wrist 513

dependent on one vessel, or both. The viability of the proximal pole of the scaphoid depends on the dorsal ridge vessels that flow in a retrograde fashion to supply the entire

proximal 70% to 80% of the bone. Thus, disruptions from

fracture may result in osteonecrosis of the scaphoid (46,47).

Idiopathic Osteonecrosis of the Scaphoid (Preiser’s Disease). Preiser in 1910 described five patients with what he

called rarefying osteitis of the scaphoid that was not associated

with fractures (48). Although scaphoid fractures were not

apparent in his cases, trauma was believed to be the cause.

There is no generally accepted definition of Preiser’s disease,

and several authors believe that it may develop only when

an occult fracture of the scaphoid has occurred (40). Ferlic

and Morin proposed a possible variant in vascularity that

predisposes patients to osteonecrosis with minimal trauma

(49).

Idiopathic Osteonecrosis of the Lunate (Kienböck’s Disease). This condition was first described by Peste in 1843

(50). However, it is Kienböck’s name that is most commonly associated with this condition (51). Many theories

have been proposed as to the etiology, but the exact cause of

the condition remains unknown. Studies support the concept that repetitive trauma with compression fracture of the

lunate may cause vascular interruption, leading to Kienböck’s disease. Biomechanical studies support the concept

of abnormal radiocarpal loading patterns leading to the disease. Kramer and Lichtman believe that repetitive loading

or acute trauma to an at-risk lunate (the 20% of lunate

bones that are supplied by a single palmar vessel) is the

cause in most cases (44,52).

Vascular Anatomy of the Distal Radius

and Ulna

The arterial blood supply of the distal radius and ulna is

quite constant. The extraosseous vessels that contribute

nutrient vessels to the distal radius and ulna are consistently

spatially related to the surrounding landmarks and supply

bone with predictable groups of arteries. The interosseous

blood supply is less uniform, but has a recognized pattern

of regional bone supply for any given extraosseous vessel

(53). The distal radius and ulna receive contributions from

the radial, ulnar, and anterior and posterior interosseous

arteries. The radial, ulnar, anterior and posterior

interosseous arteries are consistently present, and the radial

artery is the largest, followed by the ulnar, anterior

interosseous, and posterior interosseous arteries. The anterior interosseous artery has anterior and posterior divisions

that are consistently present. The posterior division of the

anterior interosseous artery consistently anastomoses with

the posterior interosseous artery over the dorsal distal ulna

by means of a small arch (53,54). The vessels supplying the

dorsal radius and ulna are best described by their relationship to the extensor compartments and retinaculum. The

following detailed description of the vascular anatomy of

the radius and ulna is taken from a comprehensive study by

Sheetz and associates (53).

Dorsal Blood Supply

The vessels supplying the dorsal radius and ulna are best

described by their relationship to the extensor compartments of the wrist and the ER. There are two compartmental arteries (one in the fourth and one in the fifth extensor

compartments) and two intercompartmental arteries superficial to the ER between the first and second and second and

third compartments. These extracompartmental vessels are

located where the ER is adherent to the underlying bony

tubercle separating their respective compartments, and they

send nutrient vessels through the ER to penetrate bone. The

dorsal distal ulna is supplied by an artery coursing across the

diaphysis and neck of the ulna, called the oblique dorsal

artery of the distal ulna. The first/second intercompartmental

artery originates proximally from the radial artery a mean of

48 mm (range, 24 to 85 mm) proximal to the radiocarpal

joint and usually courses deep to the brachioradialis muscle.

It proceeds distally to become superficial to the ER at the

first/second intercompartmental septum and sends nutrient

vessels through the ER to enter cortical bone. Distal to the

ER, it passes beneath the extensor tendons of the first compartment and rejoins the radial artery (52%), the radiocarpal

arch (52%), or the intercarpal arch (19%). Thirteen percent

of the specimens have distal connections with both the radial

artery and radiocarpal arch. In addition, there is always at

least one anastomosis to other vessels running parallel to the

radial shaft via a portion of the dorsal supraretinacular arch,

and usually a second anastomosis proximal to the ER that

courses deep to the extensor tendons. In 56% of the specimens, the first/second intercompartmental supraretinacular

artery has a branch that originates proximal to the ER and

proceeds onto the floor of the second extensor compartment. The second/third intercompartmental supraretinacular artery originates proximally from the anterior

interosseous artery (48%), the posterior division of the anterior interosseous artery (48%), or the anterior division of the

anterior interosseous artery (4%) and courses superficial to

the ER directly on the dorsal radial tubercle (Lister’s tubercle) to anastomose with the dorsal intercarpal arch (94%),

the dorsal radiocarpal arch (52%), or the fourth extensor

compartment artery (38%). In addition, it has superficial

and deep transverse anastomoses with the first/second intercompartmental supraretinacular artery, as described previously. The nutrient arteries from the second/third intercompartmental supraretinacular artery often penetrate

cancellous bone. The more proximally the nutrient artery

enters the bone, the more likely it is to penetrate cancellous

bone and proceed proximally. In 91% of the specimens, the

second/third intercompartmental supraretinacular artery has

514 Regional Anatomy

a proximal branch that enters the second extensor compartment and penetrates the bone in the floor of the compartment. All the specimens studied have a fourth extensor compartment artery that has a variable relationship to the

septum between the third and fourth compartments and lays

directly adjacent to the posterior interosseous nerve at the

radial aspect of the fourth compartment. Thirty-three percent of specimens have this artery in the septum for most of

its course, and in 70% the artery is located in the compartment. Proximally, this artery is supplied directly by the posterior division of the anterior interosseous artery (55%) or

by the fifth extensor compartment artery (45%). It anastomoses with the dorsal intercarpal arch (94%), the dorsal

radiocarpal arch (59%), the second/third intercompartmental supraretinacular artery (38%), or the fifth extensor compartment artery (34%). The fourth extensor compartment

artery is the source of numerous nutrient vessels to the floor

of the fourth compartment that frequently penetrate cancellous bone. The vessels entering more distally tend to supply

only a small area of cortical bone or go transversely into cancellous bone to supply the distal end of the metaphysis;

those more proximal are more likely to penetrate cancellous

bone and proceed proximally. All of the specimens studied

have a fifth extensor compartment artery that usually is the

largest of all the dorsal vessels supplying nutrient branches.

It has a variable relationship with the radial side of the

fourth/fifth septum. Thirty-three percent are in the septum

for most of their course, and 67% are located in the compartment. This vessel is supplied proximally by the posterior

division of the anterior interosseous artery and anastomoses

distally with the dorsal intercarpal arch in all of the specimens. Distally, it also anastomoses with the fourth extensor

compartment artery (34%), the dorsal radiocarpal arch

(23%), the second/third intercompartmental supraretinacular artery (9%), or the oblique dorsal artery of the distal ulna

(9%). Thirty-nine percent of the fifth compartment arteries

have a branch that usually originates proximal to the ER and

supplies one or two nutrient vessels to the floor of the fourth

compartment. The nutrient arteries from this branch frequently penetrate cancellous bone and are the only contribution of the fifth extensor compartment to the intraosseous

blood supply.

A series of arches across the dorsum of the hand and

wrist provide anastomoses between the intercompartmental

and compartmental arteries. The dorsal intercarpal arch is

present in all specimens, always receives contributions from

the radial, ulnar, and fifth extensor compartment arteries,

and frequently anastomoses with the second/third intercompartmental supraretinacular artery (94%), fourth

extensor artery (94%), dorsal radiocarpal arch (67%), and

the first/second intercompartmental supraretinacular artery

(19%). The dorsal intercarpal arch does not contribute

nutrient vessels to the distal radius or ulna except indirectly

through arteries with which it anastomoses. The dorsal

radiocarpal arch is present in all specimens and always

receives a contribution from the radial artery and at least

two additional sources such as the dorsal intercarpal arch

(67%), fourth extensor compartment artery (59%), the second/third intercompartmental supraretinacular artery

(52%), the first/second intercompartmental supraretinacular artery (52%), or the fifth extensor compartment artery

(23%). Unlike the other dorsal arches, the dorsal radiocarpal arch contributes significantly to the dorsal distal

radius through small nutrient arteries. These nutrient

branches usually enter bone just proximal to the radiocarpal

joint line and course perpendicularly to supply cancellous

bone in the extreme distal end of the metaphysis. All of the

specimens studied have a dorsal supraretinacular arch that

provides anastomoses between the arteries running parallel

to the radial and ulnar diaphyses. It originates from the

first/second intercompartmental supraretinacular artery

and proceeds transversely across the ER to the ulnar artery.

It usually connects to the first/second and second/third

intercompartmental supraretinacular arteries (97%) and

continues toward the ulnar artery, penetrating the ER at

two or more points to connect with the fifth (80%) or

fourth (62%) extensor compartment arteries as well as the

intercarpal arch (80%). It is not a single artery, but rather

an anastomotic arch connecting the dorsal arteries.

The dorsal distal ulna is supplied proximally by one to

three oblique dorsal arteries. In 78% of specimens, one of

these arteries originates from the anastomotic arch between

the anterior and posterior interosseous arteries. Other

sources include the anterior division of the anterior

interosseous artery (26%), the posterior division of the

anterior interosseous artery (13%), or the fifth extensor

compartment artery (9%). Distally, this artery frequently

ends by penetrating bone, but it usually anastomoses with

the fifth extensor compartment artery, the ulnar artery, or

the ulnar half of the palmar carpal arch. The oblique dorsal

artery to the distal ulna gives off nutrient vessels that usually enter the ulnar head and neck adjacent to joint cartilage

and frequently penetrate cancellous bone. The further proximal that the vessel enters the metaphysis, the more likely it

is to penetrate cancellous bone. Any diaphyseal branches, if

present, supply a part of the ulna that is almost entirely cortical bone (53).

Palmar Blood Supply

In contrast to the vascular patterns on the dorsal aspect of the

distal radius and ulna, where the arteries roughly parallel the

long axis of the bones and give off nutrient arteries, the palmar side of the distal radius is supplied primarily by two large

transverse arches that course between the major arteries of the

forearm. In the study by Sheetz and associates, every specimen had at least one palmar metaphyseal arch that coursed

through the PQ muscle (53). Occasionally, instead of one primary proximal arch, two or more smaller arches were

observed. Its proximal source was either from the anterior

9 Wrist 515

division of the anterior interosseous artery (96%) or the anterior interosseous itself (4%). It then arched across the palmar

aspect of the distal radius to anastomose with the radial artery

(100%), and usually sent a branch to the palmar radiocarpal

arch as well (57%). It supplied nutrient arteries to variable

locations on the palmar side of the radial metaphysis. Every

specimen in their study had a palmar carpal arch that consisted of radial and ulnar halves bifurcated by the anterior

division of the anterior interosseous artery. The radial half of

the palmar carpal arch originated from the anterior division

of the anterior interosseous artery that arches across the distal

radius to anastomose with the radial artery. Frequently, there

were one or more branches that anastomosed with the palmar

metaphyseal arch (57%). The ulnar half of the palmar carpal

arch originated from the anterior division of the anterior

interosseous artery more proximally than the radial half of the

arch. It coursed obliquely across the distal ulna toward the

ulnocarpal joint and anastomosed with the ulnar artery

(69%) or the oblique dorsal artery to the distal ulna (25%),

or simply ended by penetrating bone (6%). Ninety-one percent of the specimens studied had one or two arteries that

entered the ulna between the head and the styloid process at

the attachment of the TFCC and supplied the cancellous

bone in the head and styloid process of the ulna (53). The various arteries and arches of the dorsal and palmar blood supply of the distal radius and ulna are depicted in Figure 9.22.

516 Regional Anatomy

FIGURE 9.22. Extraosseous blood supply to the distal radius and ulna. A: Dorsal: AIA, anterior

interosseous artery; aAIA, anterior branch anterior interosseous artery; pAIA, posterior branch

anterior interosseous artery; PIA, posterior interosseous artery; RA, radial artery; UA, ulnar artery;

ODA, oblique dorsal artery of distal ulna; dICA, dorsal intercarpal arch; dRCA, dorsal radiocarpal

arch; dSRA, dorsal supraretinacular arch; SRA, 1–2, supraretinacular artery between first and second extensor compartments; SRA, 2–3, supraretinacular artery between second and third extensor compartments; 2nd EC br of SRA, 1–2, second extensor compartment branch of supraretinacular artery between the first and second extensor compartment; 2nd EC br of SRA, 2–3, second

extensor compartment branch of the supraretinacular artery between the second and third

extensor compartments; 4th ECA, fourth extensor compartment artery; 5th ECA, fifth extensor

compartment artery; 4th EC br of 5th ECA, fourth extensor compartment branch of the fifth compartment artery.

A

Clinical Significance

A detailed knowledge of the vascular anatomy of the distal

radius has allowed for the development of several vascularized

bone grafts used in the management of scaphoid nonunions,

avascular necrosis lesions of the carpus, or intercarpal

arthrodesis. The reader is invited to review the comprehensive articles by Sheetz and associates and Shin and Bishop for

details of this complex anatomy and the current techniques

of vascularized bone graft based on this anatomy (53,54).

SURGICAL EXPOSURES

Dorsal Approach to the Wrist (Standard)

Indications

Dorsal approaches to the wrist joint provide excellent exposure to the wrist and finger extensors, the dorsal aspect of

the wrist including the radiocarpal, intercarpal, and carpometacarpal joints, the distal radioulnar joint, and the distal radius and ulna, for the management of fractures, fractures and dislocations, tendon disruption, extensor and

wrist synovitis, tumors, and infections.

Landmarks

Landmarks include the radial and ulnar styloid, Lister’s

tubercle, and the lunate fossa.

Patient Position/Incision

The upper extremity is positioned on a well padded arm table

with the forearm in pronation. The length of the incision

depends on the planned procedure, but often is 8 to 10 cm.

It is centered longitudinally over the dorsum of the wrist in

line with the middle finger metacarpal and begins 4 to 5 cm

proximal to the radiocarpal joint. Alternatives to the straight

longitudinal incision are a gently curved or an “S”-shaped

incision. A transverse incision also may be used if a less comprehensive exposure is required. The selection of the incision

is based on the requirements of the procedure and the personal preference and experience of the surgeon (Fig. 9.23).

9 Wrist 517

FIGURE 9.22. (continued) B: Palmar: pMeta, palmar metaphyseal arch; rPCA, radial half of palmar carpal arch; uPCA, ulnar

half of palmar carpal arch. (After Sheetz KK, Bishop AT, Berger

RA. The arterial blood supply of the distal radius and its potential use in vascularized pedicled bone grafts. J Hand Surg [Am]

20:902–914, 1995, with permission.)

B

FIGURE 9.23. Dorsal approach to the wrist: landmarks and skin

incisions.

Technique

Because of the thinness of the dorsal skin and the minimal

subcutaneous tissue on the dorsum of the hand and wrist,

the dissection down to the ER should be made cautiously.

The flaps are reflected at the level of the ER to keep them

as thick as possible and to carry the sensory branches of the

radial and ulnar nerves in the substance of the flaps. The

nature of the surgical procedure determines the site and

direction of entry into the ER. In those cases where minimal exposure is needed, the ER may be incised transversely

in line with its fibers. In rheumatoid synovectomy, it is

helpful to detach the ER over the lateral aspect of the ulna

and then reflect it radially as an intact structure. At closure,

the ER can be divided into proximal and distal halves; the

proximal half is placed beneath the extensor tendons and

used to cover any raw bone surfaces, such as the distal ulna,

that may have been resected or hemiresected. The ulnar

aspect of the ER also may be used as a soft tissue imbrication over the distal radioulnar joint for stability. The

remaining (distal) half of the ER is placed over the extensor

tendons and sutured to its site of original release to prevent

bowstringing of the extensors (Fig. 9.24). In other

instances, the ER may be divided in the direction of the

longitudinal skin incision over the fourth extensor compartment and reflected to each side to expose the distal

radius and the dorsal capsule of the wrist joint. The capsule

is incised in the direction of the skin incision to expose the

joint. The ER is carefully repaired at time of closure.

Bowers Approach to the Distal

Radioulnar Joint

Indications

This approach is designed specifically for operative exposure of the DRUJ, as proposed and used by Bowers. It

allows visualization of the dorsal 60% of the ulnar head

and the carpal face of the TFC, the lunotriquetral ligament, the meniscus (if present), the prestyloid recess, and

most of the DRUJ synovial cavity. If carefully dissected and

replaced, this exposure should not alter joint mechanics or

stability (9).

Landmarks

The landmarks are the ulnar head and styloid, the ECU

tendon, and the dorsal base of the small finger metacarpal.

Patient Position/Incision

The patient is supine, the arm is extended on a padded arm

table, and the forearm pronated. The incision begins three

fingerbreadths proximal to the styloid along the ulnar shaft

and curves gently around the distal side of the ulnar head,

to end dorsally at the mid-carpus; for further distal extension, the incision can be curved back ulnarly. The incision

lies just dorsal to the dorsal sensory branch of the ulnar

nerve, which must be found and protected.

Technique

The dissection is carried to the ER. Beneath the proximal

border of the ER, the capsule of the ulnar head passes

between the EDM and ECU tendons (Fig. 9.25). The

proximal and ulnar half of the ER is released at its ulnar

margin and reflected radially to uncover the ECU and

EDM tendons. Care is taken to avoid entering the fourth

extensor compartment, if possible. The EDM is retracted

radially to reveal the TFC and the dorsal margin of the

sigmoid notch of the radius. The capsule is sharply

divided at the radius, leaving a 1-mm cuff for repair at closure, and reflected ulnarly. Further exposure of the TFC

518 Regional Anatomy

FIGURE 9.24. A, B: Dorsal approach to the wrist:

A B deep dissection.

may be obtained by releasing the EDM and EDC from

their compartments by reflecting the distal half of the ER

toward the ulna opposite the first flap of ER. This flap of

ER is divided along the EDM septum, and the base of this

flap is the attachment of the ECU compartment nearest

the ulna. The ECU should be fully released only if it is

pathologically involved. The unviolated sixth compartment should be subperiosteally dissected from the ulnar

shaft for exposure without disturbing its stabilizing function. The dorsal radiotriquetral ligament may be incised

for a better view of the lunate and triquetral surfaces of the

TFC. Exposure of the ulnar styloid may be achieved by

full supination of the forearm. Important components of

the closure include returning the ECU to its anatomic

position in its dorsal groove over the ulna, and the first ER

flap may be used to stabilize its position as needed. Bowers has proposed and used a more comprehensive dorsal

ulnar approach for TFCC repair that uses subperiosteal

reflection of the ECU in its compartment to provide

greater exposure.

Palmar Radial Approach to the Wrist

Indications

This approach may be used for the palmar approach to

scaphoid fractures or bone grafts, excision of the radiocarpal

ganglion, open reduction and internal fixation of distal

radius fractures, and for lacerations of the radial artery.

Landmarks

These include the FCR tendon, the radial artery, and the

distal wrist flexion crease.

Patient Position/Incision

The patient is supine with the arm extended on a well

padded arm table and the forearm in supination. The longitudinal incision (straight or slightly curved) begins at the

distal wrist crease and is carried proximally 6 to 8 cm or

longer as needed in the interval between the radial artery

9 Wrist 519

FIGURE 9.25. A–C: Bowers approach to the distal radioulnar joint (DRUJ).

A B C

and the FCR tendon. An alternative to the longitudinal

incision is a 3- to 4-cm-long transverse incision approximately 1 cm proximal to the distal wrist flexion crease. The

same interval of dissection between the radial artery and

FCR tendon is followed. Such a transverse incision may

limit the exposure and should be used based on the needs

of the procedure and the experience and preference of the

surgeon. The longitudinal incision may be extended distally

as needed by an oblique radial extension from the distal

wrist crease to the base of the thumb metacarpal. Before

inflation of the tourniquet, the course of the radial artery

may be identified by palpation and its course indicated by

a skin marker to aid in placement of the incision.

Technique

The wrist and forearm fascia is incised in the interval

between the radial artery and FCR tendon (Fig. 9.26).

Under tourniquet control, the inexperienced surgeon may

not appreciate how closely the radial artery resembles a

vein. In the distal half of the wound, the radial artery passes

dorsally and radially beneath the APL and EPB tendons

onto the floor of the anatomic snuff-box, and gains the dorsal aspect of the wrist. The palmar branch exits from the

ulnar side of the main stem of the radial artery before it

ascends into the snuff-box, and may be electively ligated at

the surgeon’s discretion. The FRC tendon sheath may be

incised and the FRC tendon retracted ulnarly for exposure.

Excision of a palmar carpal ganglion may be aided by injection of the cyst with a small amount of a dilute solution of

methylene blue using a 30-gauge needle passed obliquely

through the capsule of the ganglion to avoid leakage of the

dye. Marking the cyst in this manner facilitates complete

excision, including the neck and base of the lesion. In treating fractures of the radius with open reduction and internal

fixation, the proximal portion of the longitudinal incision

may need to be extended and the PQ muscle released from

its radial attachments and reflected ulnarly as needed for

exposure of the radius. For exposure of the scaphoid, the

capsule is incised longitudinally with the intent to minimize

injury to the RSC and LRL ligaments.

Palmar Central Approach to the Wrist

Indications

This approach is useful in tumors or lacerations of the

median nerve, exposure of the PQ muscle, and in procedures

on the distal radius that may require wider exposure, including the distal radius and portions of the palmar DRUJ.

Landmarks

These include the FCR tendon, the radial artery, the palmaris longus (PL) tendon, if present, and the distal wrist

flexion crease and the thenar flexion crease.

Patient Position/Incision

The patient is supine with the arm extended on a padded

arm table and the forearm in supination. For limited expo520 Regional Anatomy

FIGURE 9.26. A, B: Palmar radial approach to the wrist.

A B

sure of the distal forearm/wrist, the incision begins at the

distal wrist flexion crease and continues proximally for 6 to

8 cm or more, depending on the requirements of the procedure. The incision begins over the PL tendon, if present,

and if not, it begins at the intersection of the thenar crease

and the wrist flexion crease. The incision may be straight

longitudinal, curved, or slightly “S”-shaped. Procedures

that require opening of the carpal canal require extension of

the incision to the midpalm. This is accomplished by crossing the wrist flexion crease obliquely or by offsetting the

palmar and wrist/forearm components of the incision and

joining them by a transverse limb at or near the wrist flexion (Fig. 9.27A).

Technique

The technique for the more comprehensive exposure is

given (see Fig. 9.27B). After opening the skin in the palm

and wrist/forearm, the subcutaneous tissue in the

wrist/forearm is incised and the median nerve identified as

it exits from beneath the radial aspect of the muscle belly of

the middle finger FDS (55). The palmar cutaneous branch

of the median nerve (PCBMN) is identified as it leaves the

main stem of the median nerve on its radial aspect; it is variously reported as originating in a range of 4 to 8 cm proximal to the distal wrist crease (56–58). The median nerve is

retracted with a saline-moistened Penrose drain to either

side, depending on the exposure and needs of the procedure. This approach also allows exposure of the underlying

finger flexor tendons, which may be retracted radially or

ulnarly to expose the floor of the distal forearm. The anterior interosseous nerve and vessels are found on the

interosseous membrane before their entry into the PQ muscle. Release of the FR is facilitated by identification of its

proximal and distal ends. Distally, the superficial palmar

arch is a reasonably reliable deep landmark that is located

distal to the distal edge of the FR. The FR is released on its

ulnar aspect. A smooth elevator may be placed in the canal

before incision of the FR gently to retract and protect the

nerve. The various configurations of the median nerve

about the wrist are presented in Chapter 10 (Palmar Hand),

and the reader is referred there for these details.

9 Wrist 521

FIGURE 9.27. A, B: Palmar central approach to the wrist.

A B

Approach to the Carpal Tunnel

Indications

This approach is useful in tumors or lacerations of the

median nerve in the carpal canal, and for carpal tunnel

release.

Landmarks

These include the FCR and PL (if present) tendons, the

pisiform, hook process of the hamate bone, the distal wrist

flexion crease, the thenar flexion crease, and the thenar and

hypothenar eminences.

Patient Position/Incision

The patient is supine with the arm extended on a padded

arm table and the forearm in supination. Authors vary in

their recommendation for placement of this incision

(56,57). There is no truly internervous plane in the region,

and four cutaneous nerves are at risk, including the

PCBMN, the palmar cutaneous branch of the ulnar nerve

(PCBUN), branches from the nerve of Henle, and transverse branches of the PCBUN. Watchmaker et al., in an

effort to find the ideal location of the incision for carpal

tunnel release, identified the depression between the thenar

and hypothenar eminences in the proximal palm as a useful

landmark, and noted that the PCBMN traveled an average

of 5 mm radial to this interthenar depression (57). The

reader is referred to the section on Cutaneous Innervation

of the Palm in Chapter 10 (Palmar Hand) for a comprehensive review of this topic. Our recommended incision

begins at the mid-palmar crease in line with the central axis

of the ring finger and continues proximally to the distal

wrist flexion crease, where it angles ulnarward for 2 cm. The

incision may be straight longitudinal or slightly curved (Fig.

9.28A).

Technique

After incision of the skin and subcutaneous fat, the underlying FR is noted as a transversely oriented fibrous tissue

layer that is contiguous radially with the thenar muscles and

ulnarly with the hypothenar fat pad (see Fig. 9.28B). The

PL, if present, is freed from the underlying FR and retracted

ulnarly. The distal edge of the FR is identified by noting a

fat pad at its distal margin. This fat pad hides the median

nerve and its branches centrally and radially and the transversely oriented superficial palmar arterial arch distally.

Gentle blunt dissection is used to identify these structures,

and a blunt probe or curved mosquito clamp is passed proximally along the ulnar side of the carpal canal (see Fig.

9.28C). The canal may be identified by noting the prominent hook process of the hamate bone, which provides the

ulnar and distal anchor point for the FR. The TCL portion

of the FR is incised along its ulnar border using the probe

or clamp as a guide. The TCL is relatively thick compared

with the proximal portion of the FR, and their junction is

near the distal wrist flexion crease (see Fig. 9.28D). The

proximal portion of the FR is exposed through the ulnar

oblique limb of the incision and may be incised with a

scalpel under direct vision or divided by scissors after first

freeing the adjacent tissues palmarly and dorsally. The surgeon’s little finger should pass freely from the distal wrist

flexion crease to at least 3 cm into the distal forearm to

ensure complete division of the proximal portion of the FR.

Both the recurrent or motor branch of the median nerve

and the superficial palmar arterial arch should be inspected

before release of the tourniquet and wound closure (see Fig.

9.28E).

Approach to Guyon’s Canal

Indications

This approach is useful for exposure of the ulnar neurovascular bundle in the wrist and hand, the FCU tendon, the

pisiform, and the hook process (hamulus) of the hamate.

Landmarks

The FCU tendon is easily demonstrated by asking the

patient forcefully to flare or abduct the fingers, and the pisiform as well as the hook process of the hamate may be palpated. The ulnar artery may be palpable before inflation of

the tourniquet.

Patient Position/Incision

The patient is supine with the arm extended on a well

padded hand table and the forearm in supination. The incision begins in the distal and ulnar aspect of the palm and

courses proximally over the proximal hypothenar eminence

in the interval between the hook process of the hamate and

the pisiform to gain the distal wrist flexion crease. It continues proximally just radial to the FCU tendon for a distance of 6 to 8 cm, as required by the procedure (Fig.

9.29A).

Technique

The subcutaneous tissues and antebrachial fascia are incised

just radial to the FCU tendon to expose the neurovascular

bundle, which is deep and radial to the FCU tendon. The

ulnar artery, like its radial counterpart, usually is accompanied by venae comitantes. The sheath surrounding the

ulnar artery and nerve is incised to facilitate following these

structures into Guyon’s canal. The ulnar artery approaches

the wrist just beneath and radial to the FCU tendon, is

radial to the ulnar nerve, and lies in the interval between the

522 Regional Anatomy

9 Wrist 523

FIGURE 9.28. Approach to the carpal tunnel, fresh cadaver dissection, right hand and wrist. A:

Landmarks and skin incision. B: The transverse carpal ligament (TCL) portion of the flexor retinaculum (FR). C: A curved mosquito clamp has been passed from distal to proximal, and the

green triangle points to the dotted incision line.

(continued on next page)

A

B

C

524 Regional Anatomy

FIGURE 9.28. (continued) D: The TCL has been incised and the probe is tenting up the proximal portion of the FR. E: The FR has been completely incised, the blue marker to the right is

beneath the main stem of the median nerve, and the blue triangle points to the superficial palmar arch and the green triangle to the motor branch of the median nerve. F: The blue markers

indicate the origin and course of the palmar cutaneous branch of the median nerve (PCBMN;

note that the recommended carpal tunnel release (CTR) incision has been extended proximally to

define the course of this nerve).

D

E

F

9 Wrist 525

FIGURE 9.29. Approach to Guyon’s canal: fresh cadaver dissection of the left wrist/hand. A:

Landmarks and incision. B: Incision of roof of Guyon’s canal. C: Division of the ulnar nerve.

(continued on next page)

A

B

C

526 Regional Anatomy

FIGURE 9.29. (continued) D: Branches of the ulnar nerve in Guyon’s canal. E: Course of the

deep motor branch of the ulnar nerve around the hamulus.

D

E

FCU and the FDS to the ring and little fingers. It enters the

hand accompanied by the ulnar nerve on top of the FR

radial to the pisiform bone. This entryway, called the loge de

Guyon or Guyon’s canal, is a triangular space that begins at

the proximal edge of the palmar carpal ligament and

extends to the fibrous arch of the hypothenar muscles. The

anatomic details of Guyon’s canal and its contents are discussed in Chapter 10 (Palmar Hand). The palmar carpal

ligament (formed by the antebrachial and fascial elements

from the FCU) is incised along with the palmaris brevis

tendon, if present, to continue the exposure (see Fig.

9.29B). The neurovascular structures in Guyon’s canal are

surrounded by a thick fat pad and must be carefully identified in this fat. The ulnar nerve divides into its motor and

sensory components in the region of the pisiform (see Fig.

9.29C). Just distal to this division there are numerous

branches to the skin as well as to the palmaris brevis muscle

(see Fig. 9.29D). The motor component courses dorsally

around the base of the hook process (hamulus) of the

hamate, where it is at risk for injury during excision of the

hamulus (see Fig. 9.29E). The main trunk of the ulnar

artery continues distally after this branch to form the superficial palmar arch (59).

ANATOMIC VARIATIONS

Fourth Carpometacarpal Joint

Of the second to fifth carpometacarpal joints, the fourth

articulation demonstrates the greatest skeletal morphologic

variability (60,61). Viegas and colleagues have described

five different shapes to the base of this metacarpal: (a) a

broad base that articulates with the hamate and one dorsal

facet extension that articulates with the capitate (39% of

specimens); (b) a broad base that articulates with the

hamate and two facet extensions (one dorsal and one palmar) that articulate with the capitate (8% of specimens); (c)

a relatively narrow base that articulates only with the

hamate (9% of specimens); (d) a relatively narrow base that

articulates with the hamate and a separate single dorsal facet

that articulates with the capitate (34% of specimens); and

(e) a large base that articulates with the hamate and the capitate but without any separate dorsal or palmar facets (9%

of specimens) (60,61).

Mid-Carpal Joint

In addition to double ossification centers for the lunate

(62,63), total absence of the lunate has been reported

(64). Carpal coalitions of the lunate are discussed in a following section. Ossification of the lunate may be delayed

in syndromes such as epiphyseal dysplasias and homocystinuria (65). Two types of lunates have been identified

based on the presence or absence of a medial facet and the

alignment of the lunate to the capitate (60,66). Type I

does not have a medial facet, and type II has a medial

(ulnar) facet that articulates with the hamate (Fig. 9.30).

The size of this medial facet may range from a shallow, 1-

mm facet to a deep, 6-mm facet (66). In type II lunates,

Viegas et al. noted significant cartilage erosion with

exposed subchondral bone at the proximal pole of the

hamate in 44% of their dissections, compared with a 0%

to 2% incidence in type I lunates (66). A companion

study of the kinematics of wrist has shown significant differences between wrists with type I and type II lunate

bones (67).

9 Wrist 527

FIGURE 9.30. Type I and II lunate configurations. (After Viegas SF. Variations in the skeletal morphological features of the wrist. Clin Orthop 383:21–31, 2001, with permission.)

A second area of variability in the mid-carpal joint has

been found at the distal articulation of the scaphoid (68). In

81% of the scaphoids studied, there was a distinct and separate facet for the trapezoid articulation and another distinct facet for the trapezium, with an interfacet ridge that

was visible and palpable in 56% of the wrists. In the

remaining 19% of the scaphoids, there was a smooth distal

articular surface without an interfacet ridge (68).

A third area of variability relates to the variations in the

shape of the lunate at its proximal aspect. Based on the

studies of Shepherd, Taleisnik, and Atuna Zapico, three

types of lunate have been identified (69–71). In a study of

100 lunate bones, Atuna Zapico noted that when viewed

from the palmar aspect, some lunates were largely rectangular, whereas in others the proximal and ulnar surfaces

formed a peak or apex, resulting in a conical shape. Atuna

Zapico proposed an angle of inclination as an expression of

these variations. The angle is drawn between the lateral

(scaphoid) and proximal (radial) surfaces (Fig. 9.31). Based

on this concept of angles, Atuna Zapico classified the lunate

into three types: in type I, the angle of inclination was 130

degrees or more (30% of his specimens); in type II, the

angle of inclination was approximately 100 degrees (50%);

and type III, the least common (18%), was characterized by

two distinct proximal facets, one for the radius and one for

the TFC (71).

Proximal Wrist Joint

Viegas et al. identified a plica in the proximal wrist arising

from the dorsal capsule and the interfossal ridge of the

radius in 4% of 393 wrists (72).

Clinical Significance

This plica can be seen arthroscopically, and the arthroscopist who is not aware of its existence may be disoriented

the first time it is encountered (60,72).

Carpal Coalitions

Carpal coalitions usually are diagnosed as asymptomatic,

incidental radiologic findings, and are more common in

blacks than whites. Familial predisposition and bilaterality

are common (73). Lunotriquetral coalition is the most

common carpal coalition, and has been divided into four

types by de Villiers Minaar (74). Type I is a proximal

pseudarthrosis of the lunotriquetral junction; type II is a

528 Regional Anatomy

FIGURE 9.31. Lunate angles of inclination, types I to III. (After Atuna Zapico JM. Malacia del

semilunar. Doctoral Thesis, Universidad de Valladolid, Spain, 1966, with permission.)

proximal osseous bridge with a distal notch; type III is a

complete fusion; and type IV is fusion with other “carpal

anomalies.” In a series of 36 cases, Delaney and Eswar

found 32 cases of lunotriquetral coalition, 2 capitohamate,

1 scapholunate, and 1 trapeziocapitate (73). Bilateral capitohamate coalition has been reported as a rare coincidence

with extensor digitorum brevis manus (75).

Bipartite Scaphoid

True or congenital bipartite scaphoid is a developmental

anomaly of the carpal scaphoid that was first described by

Gruber in 1877 (76). Its existence has been challenged by

others who have suggested that it represents a pseudarthrosis after a fracture of the waist of the scaphoid (77). A documented bilateral case followed from early ossification to

skeletal maturity has established a more objective basis for

suggesting that congenital bipartite scaphoid is a true developmental condition (78). On magnetic resonance imaging,

this bilateral case revealed cartilage surrounding the circumference of the bipartite scaphoids and the absence of

degenerative changes. The incidence of congenital bipartite

scaphoid probably is less than 0.5% (78).

Bipartite Hamulus (Hook Process of the

Hamate)

Although the name hamate is derived from the Latin hamulus, meaning “hook,” hamulus as used in this brief discussion refers to the hook process of the hamate bone. The

hamate normally has one ossification center that begins to

ossify at the end of the third month. Bipartite hamulus is a

rare condition. Bogart reported 1 case in 1,452 routine

wrist radiographs over an 8-year period (79). Dwight in

1907 stated that Thelineus might have been the first to

describe this condition (80). Both Wilson and Hart and

Gaynor reported single cases of bipartite hamulus, and recommended carpal tunnel views to make this diagnosis

(81,82). A bipartite hamulus has been reported in association with ulnar tunnel syndrome (83). Kohler and Zimmer

in 1956 described several peculiarities of the hamate,

including the fact that the hamulus (hook process) may

remain separate from the body of the hamate to form an os

hamuli proprium, which may give the impression of an

accessory bone or fracture at first glance (63) (see the discussion of the hamate in Chapter 1).

Clinical Significance

A bipartite hamulus may be confused with a fracture of the

normal hamulus. It is important to distinguish between

these two conditions because excision of displaced or

nonunited fractures of the hook process currently is the

treatment of choice to avoid late complications such as tendon rupture (84).

Accessory Ossicles

Accessory ossicles are discussed with each upper extremity

bone in Chapter 1, and only one carpal accessory bone is

discussed here.

Os Centrale Carpi

This bone is said to be the most common carpal accessory

bone (85). The os centrale is an additional or accessory ossification center located at the distal and ulnar aspect of the

scaphoid that fails to unite with the scaphoid and thus

forms an accessory carpal bone. It rarely may fuse with the

capitate or trapezoid (86). It usually appears in the sixth

week of gestation and fuses with the main body of the

scaphoid in the eighth week. It remains as a small, irregular

prominence in the adult scaphoid on the distal and ulnar

aspect (70).

Clinical Significance

An os centrale carpi may be confused with a scaphoid

nonunion or bipartite scaphoid. A tomogram or computed

tomography scan is recommended to differentiate these

entities (86,87).

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