terior branches of the radial nerve.
Note the medial and posterior
branches to the triceps. The main
stem of the radial nerve penetrates
the lateral intermuscular septum to
enter the anterior aspect of the
arm at approximately the junction
of the middle and distal thirds of
the arm. (continued on next page)
muscular septum (Fig. 6.15). It then descends anterior to the
medial head of the triceps, accompanied by the superior
ulnar collateral artery, to enter the cubital tunnel. The ulnar
nerve does not give off any muscular branches in the arm.
Musculocutaneous Nerve
This nerve arises from the lateral cord of the brachial plexus
opposite the inferior border of the pectoralis minor (Fig.
6.16). It supplies the coracobrachialis, both heads of the
biceps, and most of the brachialis. The branch to the coracobrachialis is given off before the musculocutaneous nerve
enters that muscle. Branches to the biceps and the brachialis
are given off after the nerve exits the coracobrachialis. The
nerve continues distally between the biceps and brachialis
muscles, and exits from the lateral margin of these muscles
to continue distally as the lateral antebrachial cutaneous
nerve.
Anatomic Detail of the Musculocutaneous Nerve. Based
on dissections in 24 cadavers, Yang et al. studied the muscular branches of the musculocutaneous nerve and
observed the distance from the coracoid, length, diameter, and number of fascicles of the various branches of the
musculocutaneous nerve (11). Their findings are presented in Table 6.1.
Innervation of the Biceps and Brachialis
Yang et al. also identified anatomic patterns of innervation
of the biceps and brachialis (11).
Biceps. The authors found three anatomic types of
biceps innervation: Type I, found in 20 cases, demonstrated a primary motor branch (mean length, 9 ± 2 mm)
that divided into two secondary branches, each of which
separately innervated the long and short heads of the
biceps. Type II, found in two cases, demonstrated two
primary motor branches from the main musculocutaneous trunk, with the proximal branch innervating the
short head and the distal branch the long head, with a
distance of 26 mm between the branches. Type III, found
in two cases, is a variation of type I, with a primary motor
branch from the main musculocutaneous nerve trunk
that divides into two secondary branches to innervate the
two heads of the biceps individually, plus an additional
primary branch distal to the former by an average distance of 85 mm that innervates the distal part of the
biceps at its common belly.
Brachialis. The motor branch to the brachialis demonstrated two anatomic patterns: Type I, found in 23 specimens, demonstrated a single primary branch innervating
336 Regional Anatomy
FIGURE 6.14. (continued) B: Fresh cadaver dissection of the
posterior aspect of the right arm showing the main stem of the
radial nerve and its posterior branches to the lateral head and
the lateral half of the medial head (green triangles). B
6 Arm 337
FIGURE 6.14. (continued) C: Lateral muscular (anterior) branches of the radial nerve. The
main stem of the radial nerve penetrates the
lateral intermuscular septum to enter the
anterior and lateral aspect of the arm at
approximately the junction of the middle and
distal thirds of the arm. Branches are given off
in this region to the lateral third or less of the
brachialis, the brachioradialis, and the extensor carpi radialis longus. The radial nerve may
divide into its radial and sensory branches 2.5
cm proximal or 3 cm distal to the interepicondylar line of Hueter.
338 Regional Anatomy
FIGURE 6.15. Ulnar nerve. The ulnar nerve arises from the medial cord of the plexus and, after
leaving the axilla, continues distally medial to the brachial artery to the midarm, where it penetrates the medial intermuscular septum and, accompanied by the superior ulnar collateral artery,
enters the posterior aspect of the arm on its way to the cubital tunnel. No muscular branches are
given off in the arm.
A
FIGURE 6.16. A: Musculocutaneous nerve (MSCN). This nerve arises from the lateral cord of the
brachial plexus opposite the inferior border of the pectoralis minor. It supplies the coracobrachialis, both heads of the biceps, and most of the brachialis. The branch or branches to the
coracobrachialis are given off before it enters the coracobrachialis, and the branches to the
biceps and brachialis are given off after it exits the coracobrachialis. After supplying these muscles, it continues distally between them to exit from their lateral margin as the lateral antebrachial cutaneous nerve.
6 Arm 339
FIGURE 6.16. (continued) B: Fresh cadaver dissection of the proximal and medial aspect of the
right arm. Note the MSCN (large green arrow) entering the coracobrachialis and three motor
branches arising superiorly and entering the proximal aspect of the muscle; and note the axillary
artery and the anterior (yellow arrowhead) and posterior (blue arrowhead) humeral circumflex
arteries and the median nerve. C: Fresh cadaver dissection of the MSCN in the right arm, middle
and distal thirds, as viewed from the lateral aspect. Note the green marker at left on the coracoid process, the cut tendon of the pectoralis major reflected laterally, the MSCN as it exits from
the coracobrachialis, the branches to the biceps and brachialis, and the continuation of the MSCN
as the lateral antebrachial cutaneous nerve. The biceps muscle is reflected superiorly and the lateral intermuscular septum (LIMS) inferiorly. Note the radial nerve (green rectangular marker)
exiting from the LIMS on its way to the forearm between the brachioradialis and the brachialis.
B
C
the brachialis; type II, found in 1 specimen, demonstrated
2 primary branches from the musculocutaneous innervating the brachialis, with a distance of 15 mm between the
branches.
Cross-Communications. Cross-communication between the
median nerve and the musculocutaneous nerve was found in
three cases, and in one specimen the musculocutaneous nerve
and the median nerve combined to form a common trunk
from the lateral and medial cords of the brachial plexus.
Motor Fascicles. The authors found that the primary motor
branch was contained in a continuous epineural sheath and
that independent motor fascicles could be dissected proximally between 9 and 103 mm for the biceps motor fascicles
and 53 mm for the brachialis motor fascicles.
Clinical Significance. The authors stated that this study was
done to assist the surgeon who has elected to reinnervate the
elbow flexors in brachial plexus injuries. They noted that one
of the major problems when using the intercostal nerves to
reinnervate the elbow flexors is the inadequate length and the
small number of fascicles. However, with mobilization of the
proximal motor fascicles to the biceps and brachialis, the
intercostal nerves reach the nerve ends to allow direct repair
without using a nerve graft. The suture site may be as proximal as 60 mm below the coracoid process (11).
Median Nerve
The median nerve arises from the medial and lateral cords,
which pass on either side of the third part of the axillary
artery and then unite anterior or lateral to it to form the
median nerve (Fig. 6.17). It enters the arm lateral to the
340 Regional Anatomy
FIGURE 6.17. Median nerve. The median nerve arises from the medial and lateral cords, which
pass on either side of the third part of the axillary artery and then unite anterior or lateral to it
to form the median nerve. It enters the arm lateral to the brachial artery near the insertion of
the coracobrachialis and then crosses in front of the artery to descend medial to it to the cubital
fossa, where it is posterior to the biceps tendon and anterior to the brachialis.
TABLE 6.1. MUSCULAR BRANCHES OF THE MUSCULOCUTANEOUS NERVE
Branch to Distance from Coracoida Length (mm) Diameter (mm) Fascicles
Biceps 122 ± 12 mm — 1.3 ± 0.3 —
Short head — 20 ± 8 0.9 ± 0.3 2.2
Long head — 29 ± 11 0.9 ± 0.3 2.4
Brachialis 170 ± 11 34 ± 14 0.8 ± 0.2 2.7
aMean length of humerus was 299 ± 11 mm.
Data from Yang Z-X, Pho RWH, Kour A-K, et al. The musculocutaneous nerve and its branches to the biceps and brachialis muscles. J Hand Surg
[Am] 20:671–675, 1995, with permission.
brachial artery near the insertion of the coracobrachialis and
then crosses in front of the artery to descend medial to it to
the cubital fossa, where it is posterior to the biceps tendon
and anterior to the brachialis. In the arm, the median nerve
gives branches to the brachial artery, and the branch to the
pronator teres is given off at a variable distance from the
elbow joint.
SURGICAL EXPOSURES
Anterior Approach to the Humerus
Indications
This approach can provide a comprehensive exposure of the
humerus, although only portions of the incision usually are
used. This approach may be used for fracture management
or osteotomy.
Patient Position
The patient is supine, the arm extended on a hand table,
and the forearm in supination or with the elbow flexed to
90 degrees and the forearm resting on the patient’s chest
(Fig. 6.18A).
Landmarks/Incision
Landmarks include the coracoid process, the long head of
the biceps tendon, the cephalic vein, the deltopectoral
groove, and the lateral margin of the mobile biceps muscle
(see Fig. 6.18B). The cephalic vein follows the lateral or
outer margin of the biceps and the medial or inner margin
of the deltoid. The comprehensive and complete approach
is described with the understanding that all or any portion
of the approach may be used as required. The incision
begins at the coracoid process and continues distally in the
deltopectoral groove to the lateral margin of the biceps
muscle, which it follows to the elbow flexion crease. The
lateral margin of the biceps may be identified by noting its
relative mobility compared with the underlying brachialis.
If the incision is carried one fingerbreadth lateral to the
outer margin of the biceps, the cephalic vein may be spared.
Proximal Technique
In the proximal part of the approach, the cephalic vein provides a useful landmark to identify the deltopectoral groove,
and the vein may be carried with either the deltoid or the
pectoralis as this plane is developed (see Fig. 6.18C). This
interval is followed down to the deltoid insertion, with
identification of the long and short heads of the biceps and
the coracobrachialis in the proximal portion of the wound
and the pectoralis major insertion into the crest of the
greater tuberosity. Beginning near the deltoid insertion, the
periosteum is incised just lateral to the pectoralis major tendon and the long head of the biceps and continued proximally to identify the anterior humeral circumflex artery,
which traverses the line of dissection. This artery is located
approximately 1 cm superior to the proximal edge of the
pectoralis major tendon and may be ligated to complete the
exposure. Dissection is subperiosteal, and the insertion of
the pectoralis major may be detached to obtain further
exposure.
Distal Technique
The approach to the distal half of the humerus is achieved
by locating the interval between the biceps and brachialis
and incising the fascia to develop the interval (Fig. 6.19). It
must be appreciated that the brachialis cloaks the distal and
anterior aspect of the humerus from the region of the deltoid insertion to the supracondylar region. The biceps is
retracted medially to reveal the underlying brachialis covering the humerus. The medial two-thirds or more of the
brachialis is innervated by the musculocutaneous nerve and
the remaining lateral portion by the radial nerve. The
brachialis muscle may be split longitudinally in the direction of its fibers, but not along its middle or anterior aspect
because this would denervate a significant portion of the
muscle. Splitting the muscle along its outer aspect not only
minimizes the potential for denervation but at the same
time protects the radial nerve, which lies along its lateral
border. The main nutrient artery to the humerus also is protected by this technique because its entrance into the
humerus usually occurs anteromedially near the junction of
the middle and distal thirds of the humerus. Flexion of the
elbow relaxes the muscle and facilitates the exposure. Gentle retraction of the lateral aspect of the brachialis protects
the radial nerve. The medial two-thirds of the brachialis
muscle, after subperiosteal dissection, is retracted medially
to expose the humerus.
Caution: The radial nerve is at risk in the posterior aspect
of the humerus as it leaves the spiral groove and enters the
anterior compartment in the distal third of the arm; care
must be exercised when retracting the soft tissues or when
inserting fixation devices.
Anterolateral Approach to the Distal
Humerus
Indications
This approach is useful to expose the distal fourth of the
humerus and, compared with the anterior approach, has the
added advantage that it can be extended proximally and distally.This approach may be used for management of fractures
of the distal humerus and for exploration of the radial nerve.
6 Arm 341
342 Regional Anatomy
FIGURE 6.18. A: Patient position for the anterior approach to the humerus. B: Landmarks and
incision. Landmarks are the coracoid process, the deltopectoral groove, the lateral biceps groove,
and cephalic vein. The incision begins at the coracoid process and continues distally in the deltopectoral groove to the lateral margin of the biceps, which it follows to the elbow flexion
crease.
Patient Position
The patient is supine, with the arm extended on a hand
table and the forearm in supination.
Landmarks/Incision
Landmarks include the biceps and brachioradialis muscles,
the biceps tendon, and the elbow flexion crease (Fig. 6.20).
The incision begins over the lateral border of the biceps in
the midarm and curves distally to end just proximal to the
elbow flexion crease in the interval between the biceps and
the brachioradialis. This interval is identified by noting the
comparative mobility of the biceps with regard to the fixed
brachialis.
Technique
The lateral margin of the biceps is used to find the more
deeply situated brachialis muscle (Fig. 6.21). Identification
of the interval between these two muscles is aided by noting the cephalic vein, which lies in this interval. The terminal extension of the musculocutaneous nerve, the lateral
antebrachial cutaneous, exits from the interval between the
6 Arm 343
C
FIGURE 6.18. (continued) C: Technique for anterior approach to the humerus. The cephalic
vein provides a useful proximal landmark to identify the deltopectoral groove. This interval is followed to the deltoid insertion with identification of the long and short heads of the biceps, the
coracobrachialis, and the pectoralis major. Beginning near the deltoid insertion, the periosteum
is incised just lateral to the pectoralis major tendon and continued proximally to identify the
anterior humeral circumflex artery approximately 1 cm superior to the proximal margin of the
pectoralis tendon.
344 Regional Anatomy
FIGURE 6.19. A: The approach to the distal half of the humerus is achieved by locating the interval between the biceps and brachialis and incising the fascia to develop the interval. B: The biceps
is retracted medially to reveal the underlying brachialis, which covers the humerus. The brachialis
muscle is split along its outer aspect. This not only minimizes the potential for denervation of the
brachialis but protects the radial nerve, which lies along its lateral border, and the entrance of
the main nutrient artery to the humerus located anteromedially. Flexion of the elbow relaxes the
muscle and facilitates the exposure. Gentle retraction of the lateral aspect of the brachialis protects the radial nerve. C: The medial two-thirds of the brachialis muscle, after subperiosteal dissection, is retracted medially to expose the humerus.
biceps and brachialis and should not be misidentified as the
radial nerve, which is situated deeper and more lateral
between the brachialis and brachioradialis. The radial nerve
is most easily identified near the elbow joint by gentle blunt
separation of the brachioradialis and brachialis using both
thumbs, one on each muscle belly, as advised by Henry (9).
The interval is widened between the brachioradialis and the
biceps and these muscles retracted to expose the radial nerve
and the brachialis. The radial nerve is traced proximally to
where it exits from the lateral intermuscular septum at
approximately the junction of the middle and distal thirds
of the arm. Dissection may be extended proximally between
the brachialis and the lateral head of the triceps with care
taken to protect the radial nerve in the spiral groove behind
the humerus. Distal extension is made in the interval
between the brachioradialis and the pronator teres. With
the radial nerve under constant view, the lateral margin of
the brachialis is released by subperiosteal dissection and
retracted medially to expose the anterolateral aspect of the
distal humerus.
6 Arm 345
FIGURE 6.20. A, B: Anterolateral approach to the distal humerus. The interval between the
biceps and brachialis is used to expose this region of the humerus. Identification of the interval
between these two muscles is aided by noting the cephalic vein, which lies in this interval, and
the mobility of the biceps compared with the more fixed brachialis.
Medial Approach to the Arm
Indications
This approach is useful for exposure of the brachial artery,
the median, ulnar, and radial nerves, and the MACN.
Patient Position
The patient is supine, with the arm extended on a hand
table and the forearm in supination.
Landmarks/Incision
The medial epicondyle, the medial biceps groove, and the
basilic vein are landmarks for placement of the skin incision (Fig. 6.22A). A longitudinal incision is made centered over the medial biceps groove and in line with the
medial epicondyle. The incision may extend from the
medial epicondyle to the axilla, depending on the need for
exposure.
Technique
Before making the skin incision, the course and location of
the basilic vein may be identified by applying a tourniquet
proximally and the skin marked as required (see Fig. 6.22B
and C). The skin and subcutaneous tissues are incised and
the basilic vein located in the subcutaneous tissue of the distal arm. This vein, which lies anteromedially at the elbow,
ascends proximally in the medial bicipital groove accompanied by the MACN. These structures are useful landmarks
346 Regional Anatomy
FIGURE 6.21. Anterolateral approach to the distal humerus, deep dissection. A: As the interval
between the biceps and brachialis is entered, the cephalic vein and the lateral antebrachial cutaneous nerve are noted to exit between these two muscles, and the latter should not be misidentified as the radial nerve, which is situated deeper and more lateral between the brachialis and
brachioradialis. B: The radial nerve is most easily identified near the elbow joint by gentle blunt
separation of the brachioradialis and brachialis using both thumbs, one on each muscle belly, as
advised by Henry (9). C: The radial nerve is traced proximally where it exits from the lateral intermuscular septum. With the radial nerve under constant view, the lateral margin of the brachialis
is released by subperiosteal dissection and retracted medially to expose the anterolateral aspect
of the distal humerus.
and guides to the more deeply situated neurovascular bundle. In the distal arm, the basilic vein is in the subcutaneous
tissue and enters the deeper zone of the arm through an
opening in the brachial fascia in the middle third of the
arm. As the vein enters this opening, the brachial fascia is
split proximally and the vein followed to the underlying
neurovascular bundle in the proximal half of the arm. The
sheath of the neurovascular bundle is incised to expose the
various components.
Another useful landmark is the medial intermuscular
septum located in the distal two-thirds of the arm. It
extends from the medial lip of the intertubercular sulcus
distal to the teres major to the medial epicondyle. It thus
divides the arm into anterior and posterior compartments,
and should be identified as an aid to location of the various
components of the neurovascular bundle.
In the proximal arm, the neurovascular bundle contains the brachial artery, basilic vein, and the median,
radial, and ulnar nerves. In the region of the teres major,
the radial nerve courses posteriorly, whereas the median
and ulnar nerves continue to accompany the brachial
artery. The median nerve is adjacent to the brachial artery
throughout the arm and crosses the artery from lateral to
medial as it descends from proximal to distal. The ulnar
nerve, situated medially in the sheath of the neurovascular bundle, pierces the medial intermuscular septum at
the mid-portion of the arm and descends posterior to the
medial intermuscular septum to pass posterior to the
6 Arm 347
FIGURE 6.22. A: Medial approach to the arm: landmarks and incision. Landmarks are the medial
epicondyle, the medial biceps groove, and the basilic vein. A longitudinal incision is made centered over the medial biceps groove and in line with the medial epicondyle. The incision may
extend from the medial epicondyle to the axilla, depending on the need for exposure. (continued on next page)
A
348 Regional Anatomy
FIGURE 6.22. (continued) B: Medial approach to the arm: technique. The skin and subcutaneous tissues are incised and the basilic vein located in the subcutaneous tissue of the distal arm.
In the distal arm, the basilic vein is in the subcutaneous tissue and enters the deeper zone of the
arm through an opening in the brachial fascia in the middle third of the arm. As the vein enters
this opening, the brachial fascia is split proximally and the vein followed to the underlying neurovascular bundle in the proximal half of the arm.
B
6 Arm 349
FIGURE 6.22. (continued) C: Medial approach to the arm: technique (continued). The sheath
of the neurovascular bundle is incised to expose the various components, including proximally,
the brachial artery, basilic vein, and the median, radial, and ulnar nerves. In the region of the
teres major, the radial nerve courses posteriorly, whereas the median and ulnar nerves continue
distally in the company of the brachial artery. The median nerve is adjacent to the brachial artery
throughout the arm and crosses the artery from lateral to medial as it descends from proximal to
distal. The ulnar nerve, situated medially in the sheath of the neurovascular bundle, pierces the
medial intermuscular septum at the mid-portion of the arm and descends posterior to the medial
intermuscular septum to pass posterior to the medial epicondyle.
C
350 Regional Anatomy
FIGURE 6.23. A, B: Posterior approach to the humerus: landmarks and incision. The acromion
and olecranon process are landmarks for placement of the skin incision, along with the long head
of the triceps. The long head of the triceps may be identified by noting its greater mobility compared with the lateral head and the deltoid. The skin incision begins over the lateral margin of
the long head of the triceps in a direct line from the acromion to the olecranon, and begins 6 to
8 cm distal to the acromion to end at the olecranon.
medial epicondyle. The superior ulnar collateral artery
and the ulnar collateral branch of the radial nerve accompany the ulnar nerve.
Posterior Approach to the Humerus
Indications
This approach is useful in the treatment of humeral fractures that may be associated with radial nerve palsy, for
exploration of radial nerve injuries in the spiral groove, or
for exposure of the posterior aspect of the middle and distal
thirds of the humerus.
Patient Position
The patient is prone with the arm extended on a hand
table.
Landmarks/Incision
The acromion and olecranon process are landmarks for
placement of the skin incision, along with the long head of
the triceps (Fig. 6.23A and B). The long head of the triceps
may be identified by noting its greater mobility compared
with the lateral head and the deltoid. The skin incision
begins over the lateral margin of the long head of the triceps
in a direct line from the acromion to the olecranon, and
6 Arm 351
FIGURE 6.23 (continued). C: Posterior approach
to the humerus: technique. The inferior margin of
the deltoid is retracted superiorly to reveal the “V”-
shaped opening between the two superficial heads
(long and lateral) of the triceps. The surgeon’s index
finger is used bluntly to separate the long and lateral heads of the triceps until sharp dissection is
required. The oblique fibers of the lateral head join
the vertically oriented fibers of the long head at a
fibrous tissue raphe, which is the appropriate plane
of dissection. The fibers of the lateral head are separated from this thick and prominent sheet of
fibrous tissue with a knife.
begins 6 to 8 cm distal to the acromion to end at the olecranon.
Technique
The inferior margin of the deltoid is retracted superiorly
to reveal the “V”-shaped opening between the two superficial heads (long and lateral) of the triceps (Figs. 6.24
and 6.25; see Fig. 6.23C). The surgeon passes a finger
between these two heads and lifts and begins bluntly to
separate the long and lateral heads of the triceps until
sharp dissection is required (9). The oblique fibers of the
lateral head join the vertically oriented fibers of the long
head at a fibrous tissue raphe that is the appropriate plane
of dissection. The fibers of the lateral head are separated
from this thick and prominent sheet of fibrous tissue with
352 Regional Anatomy
FIGURE 6.24. Posterior approach to
the humerus, radial nerve and deep
brachial artery. The radial nerve and
the deep brachial artery are identified in the spiral groove and their
course is parallel to the obliquely oriented origin of the medial or deep
head of the triceps. The medial head
of the triceps is split in the direction
of its fibers to expose the remainder
of the humerus. Denervation of the
medial head does not occur if the
medial head is split in its central
aspect by aiming directly for the olecranon (see text).
a knife. The radial nerve and the deep brachial artery are
identified in the spiral groove, and their course is parallel
to the obliquely oriented origin of the medial head or
deep head of the triceps. The medial head of the triceps
is split in the direction of its fibers to expose the remainder of the humerus. Denervation of the medial head does
not occur if the medial head is split in its central aspect
(aim directly for the olecranon) because the medial half of
the medial head is supplied by a long, slender radial nerve
branch called the ulnar collateral nerve (because of its
proximity to the ulnar nerve), and the lateral half of the
medial head is supplied by a posterior branch of the radial
nerve. Dissection always is subperiosteal to protect the
adjacent ulnar nerve, which pierces the medial intermuscular septum as it exits the anterior compartment to lie
medially along the medial head of the triceps. Limited
mobilization of the radial nerve may be performed if all
muscular branches are protected.
Proximal Posterior Approach to the
Humerus
Indications
A more proximal approach has been described to expose
portions of the proximal humerus not accessible through
the standard posterior approach (12).
Patient Position
The patient is prone with the arm extended on a hand
table.
Landmarks/Incision
These include the posterior aspect of the acromion, the deltoid tuberosity, and the deltoid and lateral head of the triceps (Fig. 6.26). The incision begins 5 cm distal to the posterior aspect of the acromion and continues in the interval
between the deltoid and triceps muscles to the level of the
deltoid tuberosity.
Technique
The interval between the lateral head of the triceps and
the deltoid is developed by blunt dissection down to the
periosteum, which is incised longitudinally (Fig. 6.27).
The lateral head and the periosteal sleeve are retracted
medially with care taken to protect the radial nerve,
which lies beneath the lateral head as it comes in contact
with the periosteum approximately 3 cm proximal to the
level of the deltoid tuberosity. Next, the periosteum is elevated laterally and retracted with the deltoid. The axillary
nerve and posterior circumflex artery are at risk proximally and must be protected. Further exposure may be
obtained distally by partial release of the deltoid insertion. This approach allows exposure of approximately 8
cm of the proximal humerus and is limited proximally by
the axillary nerve and posterior circumflex artery and distally by the origin of the triceps muscle and the underlying radial nerve (12).
6 Arm 353
FIGURE 6.25. Posterior approach to the humerus, deep dissection. Dissection always is subperiosteal to protect the adjacent
ulnar nerve, which pierces the medial intermuscular septum as it
exits the anterior compartment to lie medially along the medial
head of the triceps. Limited mobilization of the radial nerve may
be performed if all muscular branches are protected.
354 Regional Anatomy
FIGURE 6.26. Posterior proximal approach to the humerus: landmarks and incision. Landmarks
include the posterior aspect of the acromion, the deltoid tuberosity, and the deltoid and lateral
head of the triceps. The incision begins 5 cm distal to the posterior aspect of the acromion and
continues in the interval between the deltoid and triceps muscles to the level of the deltoid
tuberosity.
CLINICAL CORRELATIONS
Radial Nerve Palsy in the Arm
Associated Injuries
Radial nerve palsy in the arm is associated most often with
fractures of the humerus in the middle third or at the junction of the middle and distal thirds. Radial nerve palsy at
this location is distinguished from the more proximal “Saturday night palsy” and “crutch palsy” seen in the upper arm
and axilla, respectively.
Anatomic Factors
At the level in the humerus under discussion, the radial nerve
is subject to injury based on at least two anatomic factors: (a)
the proximity of the radial nerve to bone in the spiral groove,
and (b) the relative fixation of the radial nerve in the spiral
groove and at the site of penetration of the nerve through the
lateral intermuscular septum on its way from the posterior to
the anterior aspect of the arm. Based on these anatomic findings, it is appropriate to postulate the etiology of the neurapraxia based on traction, contusion, or hematoma.
6 Arm 355
FIGURE 6.27. A, B: Proximal posterior approach to the humerus: technique. The interval
between the lateral head of the triceps and the deltoid is developed by blunt dissection down to
the periosteum, which is incised longitudinally. The lateral head and the periosteal sleeve are
retracted medially with care taken to protect the radial nerve, which lies beneath the lateral
head as it comes in contact with the periosteum approximately 3 cm proximal to the level of the
deltoid tuberosity. Next, the periosteum is elevated laterally and retracted with the deltoid. The
axillary nerve and posterior circumflex artery are at risk proximally and must be protected. Further exposure may be obtained distally by partial release of the deltoid insertion.
Surgical Exploration
Although much discussion has been generated around the
issue of early versus late exploration of radial nerve palsy
associated with humeral fracture, most palsies recover spontaneously, and early surgical exploration is recommended in
only three circumstances: (a) open fractures, (b) fractures
that require open reduction and or fixation, and (c) fractures with associated vascular injuries. The onset of radial
nerve palsy after fracture manipulation is not an indication
for early nerve exploration (13,14).
Surgical Exploration for the Holstein-Lewis
Fracture
In 1963, Holstein and Lewis described a spiral oblique fracture of the distal humerus in seven patients, with radial
nerve paralysis in five and paresis in two (15). They noted
radial angulation and overriding at the fracture site. As the
radial nerve courses anteriorly through the lateral intermuscular septum, it is less mobile and subject to being injured
by the movement of the distal fracture fragment. Because of
the high incidence of radial nerve dysfunction, early operative intervention was advised. In a larger and more recent
study of this fracture associated with radial nerve palsy, 11
of 15 patients were treated without exploration of the radial
nerve and had complete recovery; in the 4 patients who
were explored, the nerve was in continuity and also demonstrated complete recovery (14).
Radial Nerve Entrapment in the Arm
Etiology
Radial nerve entrapment in the arm is rare compared with
trauma-related palsy (6). Lotem et al. in 1971 described a
fibrous arch and accessory part of the lateral head of the triceps that they associated with nerve compression secondary
to swelling of the muscle after muscular effort (16). This
was a case report of exertional radial nerve palsy that was
not confirmed surgically, but the anatomic etiology was
postulated based on cadaver studies that found the radial
nerve passed through a fibrous tissue arch in the lateral head
of the triceps (16). Four other cases of radial nerve entrapment in this region of the lateral head of the triceps have
been reported, some spontaneous in onset and some following strenuous muscular activity (6,17–19). Two of the
four cases demonstrated a fibrous arch at the time of
surgery (6,19). What appears to be a familial radial nerve
entrapment syndrome has been reported in a 15-year-old
girl with a total and spontaneous radial nerve palsy. Her sister had recently sustained an identical lesion that was
improving spontaneously, and her father also suffered from
intermittent radial nerve palsy (20). The authors of this
report agreed with the concept of a genetically determined
defect in Schwann cell myelin metabolism, noting that sites
along the course of a nerve that were subject to chronic or
intermittent compression may undergo segmental demyelination with resultant nerve palsy (21).
Treatment
Although a patient with entrapment neuropathy with an
acute onset after overactivity sometimes recovers spontaneously, entrapment in the advanced stage should be surgically decompressed because prolonged compression might
result in intraneural fibrotic changes secondary to longterm compression (6,18). The surgical approach of choice is
posterior between the long and lateral heads of the triceps.
ANATOMIC VARIATIONS
Arcades
Arcades of Struthers’
John Struthers, an anatomist in Edinburgh, described a
series of nine abnormal arcades in the arm (Figs. 6.28
through 6.30). Eight were related to potential compression
of the median nerve/brachial artery, and one to the ulnar
nerve (22). Only two, or possibly three, of these arcades
have been found to be associated with clinical symptoms
(22–25). For the sake of clarity, these arcades are presented
in Table 6.2, followed by a more detailed discussion of the
three arcades that may have clinical significance.
Clinically Significant Arcades
The first six of the median nerve/brachial artery arcades are
of historical and anatomic interest, and at this time have no
reported clinical significance in terms of entrapment or
impingement of nerve or blood vessel. The following three
arcades are of clinical significance.
Arcade VII
Arcade VII is characterized by an abnormal proximal origin
of the superficial head of the pronator teres from the supracondylar ridge rather than the medial epicondyle (Fig.
6.31). This high origin also may be related to the presence
of a supracondylar process. This position results in lateral
displacement of the neurovascular bundle and has the
potential for compression of the underlying median nerve
and brachial artery. Arcade VII of Struthers should not be
confused with the so-called pronator teres syndrome as
described by Johnson and colleagues in 1977 (26). These
authors noted compression of the median nerve at one of
three levels, in the following order of frequency: the prona356 Regional Anatomy
6 Arm 357
FIGURE 6.28. Arcades of Struthers, I to
IVc. The arcades are median nerve/
brachial artery arcades. Arcade I is a
muscular slip from the latissimus dorsi to
the pectoralis major to the coracobrachialis muscle or biceps tendon;
arcade II is a muscular slip from the coracobrachialis to medial intermuscular septum; and arcade III is an anomalous third
head of the biceps from the medial
intermuscular septum that inserts into
the biceps aponeurosis. (continued on
next page)
358 Regional Anatomy
FIGURE 6.28. (continued) Arcade IVa
is a musculotendinous slip from the
biceps to the pronator teres aponeurosis; arcade IVb is a musculotendinous
slip from the bicipital tuberosity to the
pronator teres aponeurosis; and arcade
IVc is a musculotendinous slip from the
pectoralis major to the pronator teres
aponeurosis.
6 Arm 359
FIGURE 6.29. Arcades of Struthers, V to
VII. Arcade V is an accessory brachial
head of the biceps surrounding the neurovascular structures in the lower arm;
arcade VI is an accessory muscle slip from
the brachialis that inserts into the pronator aponeurosis; and arcade VII is an
abnormal origin of pronator teres from
the medial supracondylar ridge rather
than the medial epicondyle.
360 Regional Anatomy
FIGURE 6.30. Arcades of Struthers, VIII and ulnar nerve arcade. Arcade VIII is a ligament passing
from a supracondylar process to the medial humeral condyle; the ulnar nerve arcade is a fibrous
tissue band from the medial intermuscular septum to the medial head of the triceps located 8 cm
proximal to the medial epicondyle of the humerus. It is described in detail in Chapter 7.
TABLE 6.2. MEDIAN NERVE/BRACHIAL ARTERY ARCADES OF STRUTHERS
Arcade Abnormal Muscle/Ligament Complex
I Muscular slip from latissimus dorsi to pectoralis major, coracobrachialis, or biceps tendon
II Muscular slip from coracobrachialis to medial intermuscular septum
III Anomalous third head of the biceps from the medial intermuscular septum that inserts into the biceps aponeurosis
IVa Musculotendinous slip from biceps to pronator teres aponeurosis
IVb Musculotendinous slip from bicipital tuberosity to pronator teres aponeurosis
IVc Musculotendinous slip from pectoralis major to pronator teres aponeurosis
V Accessory brachial head of the biceps surrounding the neurovascular structures in the lower arm
VI Accessory muscle slip from brachialis that inserts into the pronator aponeurosis
VII Abnormal origin of pronator teres from the medial supracondylar ridge rather than the medial epicondyle
VIII Ligament of Struthers passing from a supracondylar process to the medial humeral condyle
Ulnar nerve Fibrous tissue band from the medial intermuscular septum to the medial head
arcade of the triceps located 8 cm proximal to the medial epicondyle of the humerus
tor teres, the flexor superficialis arch, and the lacertus fibrosus.
The pronator teres syndrome is discussed in detail in
Chapter 8.
Arcade VIII
Anatomy. This arcade, along with the ulnar nerve arcade
on the medial aspect of the arm, probably has the greatest clinical significance (Fig. 6.32; see Fig. 6.30). Arcade
VIII consists of a supracondylar process and ligament of
Struthers that spans between the supracondylar process
and the medial epicondyle, thus creating an arcade that
contains the median nerve and brachial artery (27). The
supracondylar process is a hook-shaped projection of
bone from the anteromedial aspect of the distal humerus.
It arises 3 to 5 cm proximal to the medial epicondyle and
is 2 to 20 mm in length (2). Its incidence is approximately 1%, and it is a rare cause of pressure on the underlying median nerve and brachial artery (2,27). In climbing animals, the supracondylar process normally is
present and forms a foramen called the end-epitrochlear
foramen that serves to protect the neurovascular bundle
and provides attachment for the pronator teres (27,28). If
the ligament of Struthers extends to the fibrous arch of
the two heads of the FCU as well as the medial epicondyle, it may produce compression of the median as
well as the ulnar nerve (29). The ligament of Struthers
6 Arm 361
FIGURE 6.31. Arcade of Struthers, VII. This arcade is characterized by an abnormal proximal origin of the superficial head of the pronator teres from the supracondylar ridge rather than the
medial epicondyle. This position results in lateral displacement of the neurovascular bundle and
has the potential for compression of the underlying median nerve and brachial artery.
FIGURE 6.32. The ligament of Struthers. The ligament of
Struthers spans between the anomalous supracondylar process
and the medial epicondyle and thus creates an arcade that contains the median nerve and brachial artery. The supracondylar
process is a hook-shaped projection of bone from the anteromedial aspect of the distal humerus that arises 3 to 5 cm proximal
to the medial epicondyle and is 2 to 20 mm long. If the ligament
of Struthers extends to the fibrous arch of the two heads of the
flexor carpi ulnaris as well as the medial epicondyle, it may produce compression of the median as well as the ulnar nerve.
has been reported without the usually associated supracondylar process, and the ligament alone may produce
median nerve compression (22,24). The humeral or
superficial head of the pronator teres may arise from the
supracondylar process and the ligament of Struthers in
some instances (24,27).
Clinical Picture. Symptoms may include aching pain in
the region of the elbow with proximal migration toward the
medial aspect of the arm and shoulder and diminished sensibility in the median nerve distribution in the hand. Weakness of grip may be noted, and sometimes the supracondylar process may be palpable (24,27). An oblique radiograph
of the distal humerus may demonstrate the anteromedially
placed supracondylar process (27).
Treatment. Excision of the supracondylar process and ligament of Struthers usually results in complete resolution of
the problem (24,25,27).
The Ulnar Nerve and Arcade of Struthers
This structure that occurs in the arm and which involves
the ulnar nerve must be distinguished from the ligament
of Struthers that involves the median nerve, usually in
association with a supracondylar process (see Fig. 6.30).
The arcade of Struthers as it relates to the ulnar nerve
occurs 8 cm proximal to the medial epicondyle and arises
from the medial intermuscular septum, crosses over the
ulnar nerve, and inserts into the fascial elements of the
medial head of the triceps (23). A detailed description of
the ulnar nerve arcade of Struthers is given in Chapter 7
in the section on surgical technique for ulnar nerve transposition.
Muscle
Biceps
In approximately 12% of arms, an accessory humeral head
is found in addition to the usual scapular sites of origin
(28). The most common accessory head arises from the
medial side of the brachialis and the medial intermuscular
septum near the insertion of the coracobrachialis, and
attaches to the medial side of the biceps aponeurosis and the
biceps tendon. A less common accessory head arises from
the proximal humerus in the region of the lesser tubercle
(2,28).
Clinical Significance
The most common form of an accessory head usually lies
behind the brachial artery as a single muscle belly, but
sometimes it has two heads or slips through which the neurovascular bundle may pass. The two-headed form of the
muscle may represent arcade III in Struthers’ description of
nine arcades in the arm (2,3,25).
Brachialis
This muscle may split into two parts in its distal aspect, or
may be fused with the brachioradialis, pronator teres, or
biceps. Aberrant distal attachments have included the
radius, the elbow joint capsule, and the biceps aponeurosis
(2,28).
Triceps
Medial Aspect of Elbow
An anomalous musculotendinous slip may arise from the
triceps and run through a groove behind the medial epicondyle. During elbow flexion, the patient experiences a
painful snapping over the medial aspect as the abnormal
slip snaps forward. In some cases there may be progressive
numbness in the ulnar nerve distribution of the hand
(28,30).
Clinical Significance
This condition must be distinguished from ulnar nerve
neuritis or cubital tunnel syndrome because the treatment
is markedly different. This topic is discussed in Chapter 7.
Coracobrachialis
The coracobrachialis, which normally inserts on the medial
mid-portion of the humerus, may extend as far distally as
the medial supracondylar or epicondylar region, and in
such instances the muscle is called the coracobrachialis inferior and coracobrachialis longus, respectively. The coracobrachialis brevis, in contrast, may insert on the bicipital
ridge of the humerus approximately 1 cm distal to the lesser
tuberosity (28).
Vasculature
Brachial Artery
The brachial artery extends from the distal margin of the
teres major to the antecubital fossa, where it normally
divides into the radial and ulnar arteries.
Variations
Superficial Brachial Artery. The superficial brachial
arises from the axillary or the proximal end of the brachial
artery and is superficial to the musculature of the arm. It
lies slightly more lateral than the normally placed brachial
artery. It divides into the radial and ulnar arteries in the
elbow region (28,31). Under these circumstances, the usual
brachial artery may be absent or give rise only to the deep
brachial and common interosseous arteries. The radial
artery, as a branch of the superficial brachial, has a normal
course, but the ulnar artery derived from the superficial
362 Regional Anatomy
brachial usually courses superficially across the forearm flexors to the medial side of the forearm (31).
High Origin of the Radial or Ulnar Artery. High origin
of the radial or ulnar artery is the most common variation
of the brachial artery (31). A high origin of the radial artery
may occur in 15% of individuals, and it may arise as high
as the axillary artery. A high radial artery usually lies anterior to the median nerve and medial to the biceps, but in
the forearm is in its normal position. In contrast, a high origin of the ulnar artery only occurs in approximately 2% of
individuals, and it may arise from the axillary or brachial
artery. It usually lies superficial to the brachial artery and
median nerve and remains superficial in the antecubital
fossa, where it lies on the forearm flexors.
High or Low Division of the Brachial Artery. A high
division of the brachial artery has been reported, usually
near its origin, in 12% of individuals (28), and a low division as late as 8 cm distal to the antecubital fossa also has
been noted (32).
Clinical Significance
High Origin of the Ulnar Artery. The ulnar artery courses
superficially across the forearm flexors and may be at risk
during venipuncture (33), as well as during surgical exposures in the proximal forearm or during elevation of a radial
forearm flap.
Low Origin of Radial Artery. In this configuration, the
radial artery usually passes deep to the pronator teres and
does not have its usual skin and subcutaneous tissue connections, which may be of significance in a radial forearm
flap (32).
Nerve
Musculocutaneous Nerve
Instead of piercing the coracobrachialis, the nerve may
travel with the median nerve for a variable distance and
then, either as a single branch or as several branches, pass
between the biceps and brachialis to innervate the biceps,
brachialis, and coracobrachialis (28). This variation was
found in 22% of arms. Sometimes, only a portion of the
musculocutaneous nerve pursues this course and then
rejoins the main trunk after penetrating and supplying the
coracobrachialis.
Other Variations
These include the finding that the musculocutaneous nerve
may be accompanied by fibers of the median nerve as it transits the coracobrachialis; instead of penetrating the coracobrachialis, the nerve may pass behind or between it and the
short head of the biceps; and, rarely, the lateral cord may
pierce the coracobrachialis and then divide into the musculocutaneous and the lateral head of the median nerve (28).
Median Nerve
In cases of high division of the brachial artery, when the
resulting radial and ulnar arteries lie along the medial side
of the arm, the median nerve lies between these two vessels
(3,28).
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6 Arm 363
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364 Regional Anatomy
7
ELBOW
JAMES R. DOYLE
The elbow joint is a compound synovial uniaxial joint that
allows a wide range of functional positions for the hand.
This joint permits 180 degrees of rotation of the forearm
and a flexion–extension arc of 140 degrees with intrinsic
stability that resists deformity in all planes in spite of long
moment arms and large forces acting through its joint axis.
Stability of this joint is based on its skeletal configuration as
well as its ligamentous support system (1). The ligaments
provide approximately 50% of the stability, and the exact
distribution varies between 45% and 55%, depending on
the flexion or extension position of the elbow (1). Strong
muscles and tendons also span this joint, which adds further stability. The hingelike motion of the joint is provided
for by the articulation between the proximal ulna and the
trochlea, whereas rotation is provided for by the round and
concave radial head that articulates with the capitulum and
the radial notch of the ulna, thus allowing rotation of the
radius around the longitudinal axis of the ulna. These seemingly contradictory movements are permissible because the
ulna flexes and extends only, whereas the radius not only
flexes and extends but rotates as well. Although the articulation between the ulna and trochlea is more intrinsically
stable than the articulation between the radius and capitulum, both joints are stabilized by strong ligaments (2).
DESCRIPTIVE ANATOMY
Contents
Bone: Distal humerus, proximal radius, and proximal ulna.
Blood Vessels: Brachial artery and its branches.
Nerves: Ulnar, median, radial, and cutaneous nerves.
Muscles: Elbow flexors and extensors, forearm flexor-pronators, forearm extensor-supinators.
Fat Pads, Capsule, and Ligaments: Anterior and posterior
fat pads, anterior and posterior joint capsule, and anterior,
medial, and lateral joint ligaments.
External Landmarks
The major landmarks about the elbow are the medial and
lateral epicondyles and the olecranon process of the ulna.
All of these landmarks are bony prominences that are easily
identified by visualization and palpation. These three landmarks form a triangle that allows for the accurate placement
of incisions and the identification of adjacent vital structures (Fig. 7.1).
Skeletal Anatomy
Articulations
The elbow joint includes three articulations: (a) the trochlea
of the humerus with the ulnar trochlear notch, (b) the
capitulum of the humerus with the radial head, and (c) the
proximal radioulnar joint (radial head to the radial notch of
the ulna). The trochlea is not a symmetric pulley because its
medial edge is approximately 6 mm longer than its lateral
counterpart; it also is wider posteriorly (2). The trochlear
notch of the ulna is not totally congruent with the humeral
trochlea because in flexion a portion of the lateral aspect of
the trochlear notch is not in contact with the humeral
trochlea, and in extension the medial part of the proximal
olecranon is not in contact with the humeral trochlea. The
proximal and distal halves of the trochlear notch are separated by an area devoid of articular cartilage and covered by
fibroadipose tissue and synovium. The capitulum and radial
head are reciprocally curved, and closest contact occurs in
semiflexion and mid-pronation. During flexion, the radial
head is accommodated by the groove between the humeral
trochlea and capitulum and in full flexion by the radial fossa
just proximal to the capitulum. The coronoid process of the
ulna is similarly accommodated in flexion by the coronoid
fossa. Posteriorly, the apex of the olecranon avoids impingement by entering the comparatively large olecranon fossa
when the elbow is extended.
The Carrying Angle
When the forearm is supinated and in full extension, it
deviates laterally by approximately 17 degrees (2). This socalled carrying angle is due to (a) the fact that the medial
trochlear edge is approximately 6 mm longer than its lateral edge; and (b) the matching obliquity of the coronoid’s
superior articular surface, which is not orthogonal to the
ulnar shaft (2). The carrying angle disappears when the
elbow is flexed because of slight spiral orientation of the
ridge in the trochlear notch and the companion groove in
the trochlea, and the fact that the tilt of the humeral and
ulnar articular surfaces is approximately equal (2). The
carrying angle is masked, if not obliterated, by pronation
of the forearm, which brings the hand into a more functional position.
Distal Humerus
The distal humerus is a modified condyle that is wider than
it is thick and has articular and nonarticular parts.
Articular Components
The lateral and convex capitulum is less than half a sphere
that has anterior and inferior but not posterior articular surfaces. It articulates with the discoid radial head, which abuts
the inferior surface in full extension. The trochlea, the
medial and pulley-shaped humeral surface, articulates with
the trochlear notch of the proximal ulna. The trochlear
notch of the ulna has a mid-articular ridge that extends
from front to back and corresponds to a groove in the
trochlea of the humerus. The articular surface of the
trochlea is anterior, inferior, and posterior and is separated
from the capitulum by a shallow groove (2).
Nonarticular Components
The nonarticular medial and lateral epicondyles and their
respective supracondylar ridges are sites of origin for the
flexor-pronator and extensor-supinator muscles, respectively. The smooth posterior surface of the medial epicondyle is traversed by the ulnar nerve through a groove
before its entrance into the flexor carpi ulnaris (FCU). The
radial and coronoid fossae provide space for the radial head
and coronoid process of the ulna, respectively, to accommodate flexion of the elbow without impingement. Posteriorly, the olecranon fossa accommodates the apex of the olecranon process when the elbow is extended (Fig. 7.2).
Radius
The radial head is discoid and its proximal surface is a shallow
cup to accommodate the adjacent capitulum. The disc is
widest medially, where it articulates with the ulna in the radial
notch (2). The neck is positioned between the head and the
medially placed biceps tuberosity (Fig. 7.3). The nonarticular
portion of the radial head is posterolateral when the arm is in
full supination. This nonarticular portion of the radial head is
characterized by a thin band of yellowish cartilage, in contrast
to the wider, white, and glistening cartilage of the articular
portion. This nonarticular zone is located in a 90-degree
quadrant as measured from the radial styloid and Lister’s
tubercle and projected proximally to the radial head (3).
366 Regional Anatomy
FIGURE 7.1. A: The major posterior bony landmarks about the elbow are the medial and lateral
epicondyles and the olecranon process of the ulna. B: These three bony landmarks form a triangle that allows for the accurate placement of incisions and the identification of adjacent vital
structures.
A B
Clinical Significance
This nonarticulating portion of the radial head represents a
safe zone for the application of a fixation device, such as a
plate and screws, without the danger of impingement.
Ulna
The proximal end of the ulna is a large hook process with a
trochlear or semilunar notch that is bounded proximally by
the apex of the olecranon process and distally by the coronoid process. Just distal to the coronoid process is the site
of insertion of the brachialis muscle, the ulnar tuberosity,
and a rough impression on the anterior aspect of the coronoid process (Fig. 7.4).
7 Elbow 367
FIGURE 7.2. Anterior and posterior views of the distal humerus.
FIGURE 7.3. The radial head and proximal radius. FIGURE 7.4. The proximal ulna.
ANATOMIC RELATIONSHIPS
Extraosseous and Intraosseous Arterial
Anatomy of the Adult Elbow
Yamaguchi et al., based on injection studies of 22 fresh
cadaver elbows, found consistent patterns of extraosseous and
intraosseous vascular anatomy that were organized into
medial, lateral, and posterior arcades (4). The intraosseous circulation of the elbow was derived mainly from perforating
branches from neighboring extraosseous arteries. The details
of this vascular complex are given in Figure 7.5 and Table 7.1.
The reader is referred to this comprehensive article for details.
368 Regional Anatomy
A B
FIGURE 7.5. The extraosseous and intraosseous arterial anatomy of the adult elbow. A: The anterior right elbow showing the superior ulnar collateral (SUC); inferior ulnar collateral (IUC); anterior
and posterior ulnar recurrent (AUR and PUR); common interosseous (CI) and its branches the anterior and posterior interosseous (AI and PI) and the interosseous recurrent (IR); and the radial recurrent (RR) arteries. B: The posterior right elbow showing the radial and medial collateral branches (RC
and MC); the radial recurrent artery (RR); the interosseous recurrent artery (IR); the posterior ulnar
recurrent artery (PUR); and the inferior and superior ulnar collateral branches (IUC and SUC).
7 Elbow 369
FIGURE 7.5 (continued). C: Medial view of the right
elbow showing superior and inferior ulnar collateral
branches (SUC and IUC); and the posterior and anterior
ulnar recurrent arteries (PUR and AUR). D: Lateral view of
the right elbow showing the radial and interosseous
recurrent arteries (RR and IR) and the medial and radial
collateral branches (MC and RC). (Redrawn after Yamaguchi K, Sweet FA, Bindra R, et al. The extraosseous and
intraosseous arterial anatomy of the adult elbow. J Bone
Joint Surg Am 79:1653–1662, 1997, with permission.)
C
D
Clinical Significance
The perforating branches from the extraosseous arteries are
the main source of the intraosseous blood supply to the
elbow and may be damaged by injury or indiscriminate dissection during surgery. The radial head has a dual
extraosseous blood supply; the first source is from a single
branch of the radial recurrent artery directly to the head,
and the second source is from vessels from both the radial
and interosseous recurrent arteries that penetrate the capsular insertion at the neck of the radius. The vessel to the
radial head enters at the noncartilaginous portion of the
head, which is the preferred area for placement of fixation
devices and may have vascular implications (4). The proximal ulna is well vascularized from posteromedial and posterolateral sources (4).
Elbow Capsule, Fat Pads, and Ligaments
The elbow joint is a compound uniaxial synovial joint with
capsular and ligamentous fibrous tissue support. The capsule is anterior and posterior; the fat pads are extrasynovial;
and the ligaments are anterior (annular ligament of radius),
medial (ulnar), and lateral (radial).
Capsule
The fibrous tissue capsule is comparatively thin anteriorly
and posteriorly compared with the more substantial medial
and lateral collateral ligaments. Anteriorly, the capsule
begins proximal to the coronoid and radial fossae and spans
the interval from the medial to the lateral epicondyle. Distally, it is attached to the coronoid process and the annular
ligament and spans the interval between the two condyles.
Posteriorly, the capsule is thin and its attachments proximally are from the margins of the olecranon fossa and distally from the olecranon process, the lateral epicondyle and
annular ligament, and the medial epicondyle. A synovial
membrane lines the articular capsule including the radial,
coronoid, and olecranon fossae (2).
Fat Pads
Between the capsule and synovial membrane are three fat
pads: the largest is at the olecranon fossa and is pressed into
the fossa by the triceps during flexion; the other two are at
the coronoid and radial fossae, and are compressed into the
fossa by the brachialis during extension (2).
Anterior Ligament
The annular ligament of the radius arises from the lateral
aspect of the coronoid process of the ulna and arches up and
over the head and neck of the radius to insert on the opposite side of the coronoid process. It is a strong band that
forms a fibroosseous ring with the ulnar radial notch and
maintains the radial head in this notch. The annular band
370 Regional Anatomy
TABLE 7.1. EXTRAOSSEOUS BLOOD SUPPLY TO THE ELBOW
Distance from
Medial Epicondyle
(cm)
Artery Origin Average Range Common Anastomoses Supplies
Profunda brachiia Brachial 21.6 18.2–25.2
Radial collateral Profundus 19.9 18.0–23.0 Radial recurrent Lateral aspect of trochlea,
capitellum, lateral epicondyle
Middle collateral Profundus 19.9 18.0–23.0 Interosseous recurrent Capitellum, medial aspect of
olecranon
Superior ulnar Brachial 17.2 13.5–23.0 Medial arcade, inferior Olecranon fossa, medial aspect
collateral ulnar collateral of trochlea
Inferior ulnar Brachial 6.7 2.0–11.5 Superior ulnar recurrent, Medial epicondyle, coronoid
collateral posterior ulnar fossa, medial aspect of
recurrent trochlea
Radial recurrent Radial 6.6 5.4–9.0 Radial collateral Radial head and neck,
capitellum
Interosseous recurrent Posterior interosseous 8.9 8.0–10.0 Middle collateral Lateral aspect of olecranon
recurrent radial neck, capitellum
Posterior ulnar Ulnar 7.3 5.8–9.7 Superior ulnar collateral, Medial aspect of olecranon
recurrent inferior ulnar medial aspect of trochlea
collateral
Anterior ulnar Ulnar 6.9 4.0–8.6 Inferior ulnar collateral Mostly muscular
recurrentb
aPresent in 19 (86%) of the 22 specimens.
bPresent in 11 (50%) of the 22 specimens.
forms approximately four-fifths of this ring. The radial collateral ligament blends with the outer layers of the annular
ligament, and a portion of the supinator attaches to the
annular ligament (2). This ligament also is considered to be
the ligament of the proximal radioulnar joint, just as the triangular fibrocartilage complex is considered to be the ligament of the distal radioulnar joint and the interosseous
membrane the ligament of the so-called middle joint of the
forearm (2). Many authors have considered the annular ligament to be part of the lateral ligament complex of the
elbow, although this differs from its classic description
(1,2,5–8). However, the fact that the fan-shaped radial lateral ligament blends with and attaches to the superior and
lateral portion of the annular ligament so extensively gives
support to the concept of including the annular ligament as
part of the lateral ligament complex.
Medial Ligaments
The medial or ulnar collateral ligament of the elbow consists of three parts, the anterior, posterior, and transverse ligaments (2) (Figs. 7.6 and 7.7).
Anterior Component of the Medial Ligament
This component is an obliquely oriented, cordlike segment
that arises from a depression in the inferior aspect of the
medial epicondyle of the humerus. It attaches to the coronoid process of the ulna adjacent to the sublimis tubercle
(9). The mean length of the anterior portion is 27.1 ± 4.3
mm and the mean width is 4.7 ± 1.2 mm (5). The anterior
ligament is divided into anterior and posterior parts. These
two parts tighten in reciprocal fashion as the elbow flexes
and extends. The anterior part is relaxed in flexion and tight
in extension and the reverse is true for the posterior part of
the anterior ligament (9). In general, the anterior part of the
anterior ligament is tight from full extension to 60 degrees
of flexion, and the posterior part of the anterior ligament is
tight from 60 to 120 degrees of flexion (5).
Posterior Component of the Medial Ligament
The fanlike posterior ligament arises posterior to the origin
of the anterior ligament, slightly posterior to the most inferior portion of the medial epicondyle, and inserts in a broad
depression on the ulna adjacent to the articular surface
(2,9). The mean length of the posterior portion is 24.2 ±
4.3 mm and the mean width is 5.3 ± 1.1 mm (5).
The posterior ligament resembles thickened joint capsule when the elbow is extended, but as the elbow flexes, the
posterior ligament tightens and fans out to form a sharp
edge (9).
Transverse Component of the Medial Ligament
The transverse segment consists of horizontally oriented
fibers between the coronoid and the olecranon and partially
overlays the insertion of the fanlike component. The transverse ligament is closely applied to the joint capsule and
contributes little or nothing to elbow stability because it
originates and inserts on the ulna (9).
Comparative Significance of the Anterior and
Posterior Ligaments of the Medial Ligament
The anterior component is the most prominent and can be
easily distinguished from the joint capsule (5,9,10). This
component of the medial collateral ligament resists valgus
as well as internal rotatory forces. Sequential sectioning of
7 Elbow 371
FIGURE 7.6. The medial collateral elbow ligaments.
the anterior and posterior parts of the anterior ligament and
the posterior ligament revealed that the anterior component
of the anterior ligament was the primary restraint to valgus
deformity at 30, 60, and 90 degrees of flexion, and was a
co-primary restraint at 120 degrees of flexion. The posterior
component of the anterior ligament was a co-primary
restraint at 120 degrees of flexion and a secondary restraint
at 30 and 90 degrees of flexion. The greatest amount of valgus deformity after sectioning of the anterior ligament was
with the elbow at 90 degrees of flexion. The anterior part of
the anterior ligament was more subject to valgus overload
when the elbow was extended and the posterior component
of the anterior ligament was more subject to overload when
the elbow was flexed. The posterior ligament was a secondary restraint at 30 degrees only and was not subject to
valgus overload unless the anterior ligament was completely
disrupted (9).
Clinical Significance
The authors of this study noted that the greatest amount of
valgus instability due to sectioning of the anterior ligament
was observed when the elbow was at 90 degrees of flexion.
They recommended that physical examination in patients
with a suspected injury to the anterior ligament of the
medial collateral ligament should be performed with the
elbow in 90 degrees of flexion for greatest sensitivity (9).
Lateral Ligaments
The lateral ligament complex of the elbow arises from a
bare area just distal to the lateral epicondyle and fans out
distally to insert on the annular ligament of the radius laterally and superiorly and on the lateral aspect of the coronoid process of the ulna inferiorly. It is blended with the
attachments of the supinator and the extensor carpi radialis
brevis (ECRB) (2). Its classic description is that of a single
triangular ligament called the radial collateral ligament (2).
Morrey and An identified three parts to the lateral ligament
complex: (a) the annular ligament, (b) the fan-shaped part
that originates from the lateral epicondyle and inserts into
and blends with the annular ligament, and (c) an invariably
present but often inconspicuous part of the inferior aspect
of the fan-shaped ligament that inserts on a tubercle of the
supinator crest of the proximal ulna. They named the latter
structure the lateral ulnar collateral ligament (LUCL) (5)
(Figs. 7.8 and 7.9). Based on studies of posterolateral rotatory instability of the elbow, some authors consider the
LUCL portion of the lateral collateral ligament complex the
most important in preventing posterolateral rotatory instability of the elbow (5,6). The lower than expected incidence
of objective varus laxity in cases of posterolateral rotatory
instability with varus stress when the LUCL is disrupted is
said to be due to the fact that the primary contributor to
stability is the ulnohumeral articulation rather than the
372 Regional Anatomy
FIGURE 7.7. Fresh cadaver dissection of
the medial collateral elbow ligaments
(medial aspect of the right elbow). The
probe is beneath the anterior ligament;
the green marker is beneath the transverse ligament, and the blue triangle is
beneath the proximal edge of the posterior ligament.
radial collateral ligament complex (5). The somewhat variable incidence of varus instability after radial head excision
may be due to the inadvertent release of the LUCL rather
than to radial head excision alone (5).
These findings and conclusions are compared with a study
that focused on the muscular and ligamentous anatomy of
the lateral aspect of the elbow as it relates to rotatory instability (6). The dissections in this study revealed a broad conjoined tendon of insertion of the lateral collateral and annular ligaments to the ulna. In 22 of the 40 specimens, the
insertion was bilobed, and it was broad in 18 specimens.
Cohen and Hastings (8) did not identify a discrete ligament
spanning from the epicondyle to the ulna, the so-called
LUCL described by Morrey and An (5). A standardized rotatory force on the elbow joint was used to evaluate the role of
the various stabilizers of the elbow joint as they related to
rotatory stability. The stabilizers evaluated included the
extensor carpi ulnaris (ECU) fascial band, the annular ligament, the lateral collateral ligament complex, the supinator
insertion, the supinator origin, and composite fibers of origin
of the extensors. Cohen and Hastings concluded that: (a) the
primary restraint to posterolateral rotatory instability of the
elbow is the combination of the lateral collateral and annular
ligaments that coalesce to insert broadly over a 2-cm area on
the proximal ulna; (b) the supinator tendon, which attaches
to the ulna and becomes confluent with the lateral collateral
ligament toward its origin, reinforces this structure; (c) the
principal secondary restraints of the lateral aspect of the
elbow are the extensor muscles with their fascial bands and
intermuscular septa; (d) rotatory instability involves attenuation or avulsion of both the ligamentous and muscular origins from the lateral epicondyle; and (e) posterolateral rotatory instability spontaneously reduced with the forearm in
pronation even when all the restraints had been sectioned (8).
Clinical Significance
Cohen and Hastings made several clinical observations
based on their understanding of the anatomy of the lateral
ligament complex and the muscles arising from the lateral
region of the elbow:
1. Patients with acute lateral ligament disruption may be
managed with a hinged brace with the forearm in pronation. If repair is elected, immobilization of the forearm
in pronation aids in protection of the repair.
7 Elbow 373
FIGURE 7.8. The lateral collateral ligaments of the elbow. LUCL,
lateral ulnar collateral ligament.
FIGURE 7.9. Fresh cadaver dissection of
the lateral collateral ligament of the
elbow (lateral aspect of the right elbow).
The green diamond-shaped marker is on
the lateral epicondyle, and the probe is
beneath the radial collateral ligament,
which attaches to the supinator crest
marked with a dotted line.
2. Overzealous debridement for recalcitrant lateral epicondylitis may result in posterolateral instability, and
may explain persistent complaints. Cohen and Hastings
advise debridement of tissue anterior to the palpable septum of the extensor digitorum communis and extensor
digiti quinti at the middle of the axis of the epicondyle.
This approach spares the posterior fibers of the lateral
collateral ligament and the extensor muscle origins and
maintains stability of the lateral aspect of the elbow (4).
3. The usual Kocher approach for radial head excision
between the anconeus and ECU muscles should be kept
in line with the fibers of the ECU to avoid section of the
fascial band of the ECU. Proximal extension of the
Kocher incision, if kept inferior to the epicondyle, preserves the integrity of the extensor tendon from the
condylar and epicondylar regions. Excision of the radial
head requires incision of portions of the lateral ligament
complex. An incision slightly anterior to the center of
the radial head and carried distally for a short distance
preserves the inferior portions of the complex. Careful
repair of the these fibers is important (8).
Loci of Origin of the Medial and Lateral
Elbow Ligaments and Axis of Joint Rotation
The origins and insertions of the medial and lateral ligaments as well as the axis of rotation of the elbow joint are
presented in Figure 7.10. Little variation is noted in the
three-dimensional distance between the origin and insertion of the radial collateral ligament complex from full
extension to 120 degrees of flexion. This is consistent with
the fact that the axis of rotation passes through the center
of this locus. The distance between the origin and insertion
of the anterior ligament of the medial collateral ligament
increased a mean of 4.8 mm from extension to 120 degrees
of flexion. This distance was even more pronounced in the
posterior ligament of the medial collateral ligament, which
demonstrated a mean distance of 9.4 mm after approximately 60 degrees of flexion. These changes are consistent
with the eccentric locus of the medial collateral ligament in
relationship to the elbow joint axis of rotation (5).
SURGICAL EXPOSURES
Posterior Approach
Indications
This approach is used for exposure of nonarticular and
intraarticular fractures of the distal humerus, removal of
loose bodies, and treatment of extension contractures of the
elbow requiring posterior capsulotomy and triceps lengthening.
Landmarks
The landmarks for this approach are the olecranon process
and the two humeral condyles, which are readily palpated
and visualized.
Position/Incision
The patient may be positioned prone with the arm resting
on a well padded arm table and the elbow flexed to 90
degrees, or supine with the elbow flexed to 90 degrees and
374 Regional Anatomy
FIGURE 7.10. Loci of origin of the medial and lateral
elbow ligaments and axis of joint rotation. A: Anterior
view of distal humerus showing radial collateral ligament
(RCL); anterior ligament of medial collateral ligament (AMCL); posterior ligament of medial collateral ligament
(P-MCL); and axis of joint rotation (Z); note that the
medial ligament originates from the epicondyle, not the
medial aspect of the trochlea. B: Lateral view of distal
humerus showing the concentric locus of the RCL compared with the eccentric locus of the MCL in relationship
to the elbow joint axis of rotation (Z). C: Anterior view of
proximal radius and ulna showing loci of insertion of PMCL, A-MCL, and RCL. D: Lateral view of proximal ulna
and radius showing loci of insertion of RCL, A-MCL, and
P-MCL. (Redrawn after Morrey BF, An K-N. Functional
anatomy of the ligaments of the elbow. Clin. Orthop
201:84–90, 1985, with permission.)
the forearm supported on a well padded Mayo stand over
the patient’s chest (Fig. 7.11). These positions allow for
comprehensive exposure of the elbow, but the arm also may
be positioned on an arm table with the elbow flexed to 90
degrees and resting on a soft pad. This third position, however, may make it difficult to see all aspects of the medial
areas of the elbow and may be better suited for exposure of
the posterolateral aspect of the elbow. A straight-line incision is begun in the posterior aspect of the distal arm,
curved distally across the lateral edge of the olecranon
process, and then curved distally to end over the medial
subcutaneous margin of the ulna. This incision is designed
to avoid the potential for a bothersome scar over the pressure or contact surface of the olecranon and also has the
7 Elbow 375
FIGURE 7.11. A–C: Patient positions and incision for posterior approach to elbow.
potential for providing better soft tissue cover over any fixation devices that may be used as part of the procedure.
Technique
The skin, subcutaneous tissue, and superficial fascia are
incised down to the triceps aponeurosis, which is the plane
of dissection and provides a thick flap for coverage of the
operative site.
Ulnar Nerve
The ulnar nerve is palpated beneath the deep fascia in the
interval between the long head of the triceps and the medial
intermuscular septum. The fascia is incised and the nerve
freed distally and gently retracted with saline-moistened,
0.5-inch-diameter Penrose drains. The nerve usually is
accompanied by the posterior ulnar recurrent artery and
one or more small veins; if possible, these vascular structures should be left with the nerve to preserve its blood supply (Fig. 7.12).
Olecranon Osteotomy
In nonarticular fractures or in cases that do not require
exploration of the joint, the triceps mechanism may be
released by an oblique nonarticular osteotomy of the proximal aspect of the olecranon (11) (Fig. 7.13A and B). If a
more complete exposure of the joint is required, as in
removal of loose bodies or in the management of intraarticular fractures, the joint is exposed through a transverse
chevron-shaped osteotomy approximately 2.5 cm distal to
the proximal edge of the olecranon process (11). The apex
of the chevron is distal to lessen the chances of splitting
the proximal olecranon during fixation. The chevron
modification of the osteotomy makes fixation of the
osteotomy more accurate at the close of the procedure.
Accurate replacement and fixation of either osteotomy is
aided by predrilling the olecranon process before the
osteotomy and by making a longitudinal mark on the
medial and lateral side of the olecranon at right angles to
the intended osteotomy with an osteotome or the cutting
current of the Bovie unit. These marks are then realigned
at the time of fixation of the osteotomy. The transverse
osteotomy is performed at right angles to the longitudinal
axis of the ulna using a power saw with a thin blade. The
olecranon is cut nearly completely through and then the
osteotomy is completed by a thin osteotome. Before making the osteotomy, a pilot hole is drilled in the ulna for
inserting a cancellous lag screw.
376 Regional Anatomy
FIGURE 7.12. Posterior approach to the elbow. A: Skin incision. B: Deep dissection.
Soft Tissue Release
After the osteotomy, it is necessary to release the soft tissues
both medially and laterally adjacent to the olecranon
process while taking care that the soft tissue attachments to
the olecranon process are not disrupted. Subperiosteal dissection of the triceps muscle from the humerus allows an
extensive exposure of the posterior humerus and the posterior articular surface of the elbow joint. Indiscriminate dissection of the muscle from bone is to be avoided because
the circulation to the bone may be compromised. Although
subperiosteal dissection may be performed around the
medial and lateral margins of the distal humerus to its anterior aspect, care should be taken to avoid disruption of the
blood supply to the bone or injury to the brachial artery
and median nerve, which are nearby in the antecubital fossa
(see Fig. 7.13C).
Radial Head Approach
Indications
This approach is used to expose the radial head for excision
or for management of fractures, including open reduction
and internal fixation.
Landmarks
Useful landmarks include the lateral epicondyle, the olecranon process and its proximal subcutaneous margin, and the
radial head, which usually is palpable with alternating
pronation and supination of the forearm.
Position/Incision
With the patient supine, the upper extremity draped free,
and the elbow resting on a well padded hand table, the forearm is placed in pronation and the elbow flexed to 90
degrees. The radial head is approached through an oblique
incision made from the lateral epicondyle to the ulna that
parallels the interval between the anconeus and the ECU
(Fig. 7.14).
Technique
The interval between the anconeus muscle and the ECU is
identified distally and then traced proximally because these
two muscles share a common fibrous origin. The origin of
the anconeus from the lateral epicondyle may be detached
to facilitate the exposure. The ECU and anconeus are
7 Elbow 377
FIGURE 7.13. Posterior approach to the elbow (comprehensive with osteotomy). A: Accurate
replacement and fixation of either osteotomy is aided by predrilling the olecranon process
before the osteotomy. B: Oblique (a) and transverse chevron-shaped (b) osteotomies of the proximal ulna. C: Subperiosteal dissection of the triceps muscle from the humerus allows an extensive
exposure of the posterior humerus and the posterior articular surface of the elbow joint.
retracted to reveal the underlying supinator muscle. Identification of the supinator is facilitated by noting that its
fibers run at approximately a 90-degree angle to the
anconeus fibers (Fig. 7.15).
Posterior Interosseous Nerve
The supinator contains the posterior interosseous nerve
(PIN), which enters the volar lateral face of the supinator
and courses obliquely in the fibers of the muscle to exit
dorsally near the distal margin of the supinator. The PIN
can be found on the back of the radius, three fingerbreadths distal to the radial head. Maintaining the forearm in pronation during this approach rolls the PIN away
from the operative site and aids in its preservation (see Fig.
7.15). Dissection that does not extend beyond the annular ligament also avoids the potential for injury to the
PIN.
Radial Collateral Ligament
The radial collateral ligament complex shares an attachment at the supinator crest with the supinator muscle. The
proximal margin of the supinator is incised and reflected
anteriorly to reveal more completely the lateral ligament
complex and elbow capsule. These structures are incised
longitudinally, beginning at the epicondyle, to enter the
joint. This incision is carefully repaired to maintain the
integrity of the lateral ligament. This approach is designed
to expose only the radial head and if exposure of the proximal radius is required, then another, more comprehensive
approach is used (see Chapter 8, Part 1, Flexor Forearm).
378 Regional Anatomy
FIGURE 7.14. Radial head approach; patient position (A) and incision (B). An oblique incision is
made from the lateral epicondyle to the ulna that parallels the interval between the anconeus
and the extensor carpi ulnaris.
Medial Approach
Indications
The medial approach may be used for removal of loose bodies in the medial side of the joint as well as for reduction
and fixation of fractures of the coronoid process of the ulna
and medial aspect of the humerus.
Landmarks
Landmarks include the medial epicondyle, the medial intermuscular septum, and the olecranon process.
Position/Incision
With the patient supine, the forearm in supination, and the
upper extremity resting on a hand table with a soft pad
under the elbow, an incision is made between the anterior
and posterior muscular compartments of the arm in line
with the medial intermuscular septum. The incision aims
directly for the medial epicondyle but curves anteriorly
above the condyle to avoid placing a scar directly over this
bony prominence, and continues distally over the anteromedial aspect of the forearm (Fig. 7.16).
Technique
In the arm, the muscular intervals used are between the
brachialis and the triceps, and in the forearm, between the
pronator teres (PT) and the brachioradialis.
Cutaneous Nerve Branches
Posterior branches of the medial cutaneous nerve of the
forearm are found in the subcutaneous tissues of the incision anywhere from 6 cm above to 6 cm below the medial
epicondyle, and should be preserved (12).
Ulnar Nerve
The ulnar nerve is found posterior to the medial intermuscular septum in the arm and in its groove behind the medial
epicondyle. The ulnar nerve is freed from above the elbow
to its entrance into the FCU muscle by incising the overlying fascia and gently retracting it posteriorly with a salinemoistened 0.5-inch Penrose drain.
Median Nerve/Brachial Artery
The interval between the PT and the brachioradialis is
entered and the median nerve and brachial artery identified.
7 Elbow 379
FIGURE 7.15. Radial head approach; deep dissection. A, B: The interval between the anconeus
muscle and the extensor carpi ulnaris (ECU) is identified distally and then traced proximally
because these two muscles share a common fibrous origin. The origin of the anconeus from the
lateral epicondyle may be detached to facilitate the exposure. The ECU and anconeus are
retracted to reveal the underlying supinator muscle. Identification of the supinator is facilitated
by noting that its fibers run at approximately a 90-degree angle to the anconeus fibers.
The underlying brachialis is gently separated from the PT
and all branches of the median nerve are noted and protected, including the branches to the PT.
Medial Epicondylotomy
These maneuvers are done as a preliminary to detachment of the PT and the common flexor origin from the
medial epicondyle by osteotomy. The plane of this
osteotomy is between the anterior component of the
underlying medial collateral ligament and the flexor origin (Fig. 7.17). These flexors then may be retracted distally and the interval between the brachialis and triceps
may be developed further to expose the anterior aspect of
the elbow joint and distal humerus. Before detachment,
the medial epicondyle is predrilled to facilitate reattachment with a screw.
380 Regional Anatomy
FIGURE 7.16. Medial approach to the elbow; patient position (A) and incision (B). The incision
aims directly for the medial epicondyle but curves anteriorly above the condyle and continues distally over the anteromedial aspect of the forearm
FIGURE 7.17. Medial approach to the elbow. Deep dissection. A, B: In the arm, the muscular
intervals used are between the brachialis and the triceps, and in the forearm, between the pronator teres (PT) and the brachioradialis (BR). The ulnar nerve is freed and gently retracted posteriorly. The interval between the PT and the BR is entered and the median nerve and brachial artery
identified. C: Medial epicondylotomy. The PT and the common flexor origin are detached from
the medial epicondyle by osteotomy. Before detachment, the medial epicondyle is predrilled to
facilitate reattachment with a screw.
7 Elbow 381
Lateral Approach
Indications
The lateral approach may be used for fractures of the lateral
aspect of the elbow and surgical treatment of tennis elbow.
Landmarks
Useful landmarks are the lateral epicondyle and the lateral
supracondylar ridge.
Position/Incision
The patient is supine and the arm is flexed on the chest or
on a hand table with the elbow semiflexed and the forearm
in pronation. A longitudinal incision is made 5 cm proximal to the lateral epicondyle over the lateral supracondylar
ridge and continued distally over the lateral epicondyle, to
end 5 cm distal to the epicondyle over the proximal portion
of the extensor digitorum communis muscle (Fig. 7.18).
Technique
To expose the lateral border of the humerus, the interval
between the triceps and brachioradialis/extensor carpi radialis longus (ECRL) is developed from distal to proximal by
subperiosteal dissection. Branches of the posterior antebrachial cutaneous nerve are identified and preserved. The
radial nerve is identified where it enters the interval
between the brachialis and brachioradialis muscles. In fractures of the lateral condyle, the common origin of the
extensors is attached to the fracture fragment, which facilitates the exposure. In nonfracture cases, the common origin
is removed by osteotome with a thin wafer of bone to facilitate reattachment, or the origin may be divided distal to
the lateral epicondyle with an adequate cuff of substantial
tissue for repair. With either method, the extensor origin
should be separated from the lateral collateral ligament
complex. An alternative to removal of the common extensor origin is to identify the interval between the anconeus
muscle and the ECU and retract these muscles to find the
underlying supinator. The origin of the anconeus from the
lateral epicondyle may be detached to facilitate the exposure. If removal of the common extensor origin is elected,
the extensors are reflected distally to reveal the supinator,
lateral ligament complex, and joint capsule. The supinator
contains the PIN, which enters the volar lateral face of the
supinator and courses obliquely in the fibers of the muscle
to exit dorsally near the distal margin of the supinator. The
382 Regional Anatomy
FIGURE 7.18. Lateral approach
to the elbow; patient position
(A) and incision (B). A longitudinal incision is made 5 cm proximal to the lateral epicondyle
over the lateral supracondylar
ridge and continued distally
over the lateral epicondyle to
end 5 cm distal to the epicondyle, over the proximal portion of the extensor digitorum
communis muscle.
PIN can be found on the back of the radius three fingerbreadths distal to the radial head. Maintaining the forearm
in pronation during this approach rolls the PIN away from
the operative site and aids in its preservation (see Fig. 7.14).
The radial collateral ligament complex shares an attachment at the supinator crest with the supinator muscle. The
proximal margin of the supinator is incised and reflected
anteriorly to reveal more completely the lateral ligament
complex and elbow capsule. These structures are incised
longitudinally, beginning at the epicondyle, to enter the
joint. The ligamentous and capsular incision is carefully
repaired to maintain the integrity of the lateral ligament. If
the common extensor origin was removed, it should be
securely reattached (Fig. 7.19).
7 Elbow 383
FIGURE 7.19. Lateral approach to the elbow, deep dissection. A: The interval between the triceps and brachioradialis/extensor carpi radialis longus is developed from distal to proximal by
subperiosteal dissection. The radial nerve is identified where it enters the interval between the
brachialis and brachioradialis muscles. The common extensor origin may be divided distal to the
lateral epicondyle with an adequate cuff of substantial tissue for repair. B: Alternatively, the common extensor origin may be removed by osteotome with a thin wafer of bone to facilitate reattachment. The radial collateral ligament and capsule are incised longitudinally beginning at the
epicondyle to enter the joint.
384 Regional Anatomy
FIGURE 7.20. The Kocher approach to the lateral aspect of the elbow. A: A longitudinal incision
is made 5 cm proximal to the lateral epicondyle over the lateral supracondylar ridge and continued distally over the lateral epicondyle to curve over the anconeus, ending posteriorly at the subcutaneous margin of the ulna. B: The origin of the brachioradialis, extensor carpi radialis longus,
and extensor carpi radialis brevis is elevated subperiosteally, as is the triceps muscle posteriorly,
to expose the lateral epicondyle and supracondylar ridge.
Kocher or Lateral “J” Approach
Indications
This approach may be used for elbow joint capsulotomy for
contracture, fractures of the lateral aspect of the elbow,
drainage of the elbow joint, or reconstruction of the lateral
ligament complex.
Landmarks
Landmarks include the lateral supracondylar ridge, the lateral epicondyle, the radial head, and the subcutaneous border of the proximal ulna.
Position/Incision
The patient is supine, with the elbow semiflexed and the
forearm in pronation. A longitudinal incision is made 5 cm
proximal to the lateral epicondyle over the lateral supracondylar ridge and continued distally over the lateral epicondyle to curve over the anconeus and end posteriorly at
the subcutaneous margin of the ulna. This approach is similar to the lateral exposure just described, but differs in its
distal aspect, which curves from the radial head medially
and posteriorly to end at the posterior border of the ulna.
Distally, the interval between the ECU and anconeus is
used to expose the proximal and extensor aspect of the forearm (Fig. 7.20).
Technique
Proximal dissection is over the lateral supracondylar ridge
between the triceps posteriorly and the brachioradialis and
ECRL anteriorly to expose the lateral epicondyle. Distally, the
interval between the anconeus and the ECU is used to expose
the lateral ligament complex, joint capsule, and ulna. The origin of the brachioradialis, ECRL, and ECRB is elevated subperiosteally, as is the triceps muscle posteriorly. Distally, the
anconeus is retracted posteriorly after removing its origin from
the lateral epicondyle, and the ECU is retracted anteriorly.
The common origin of the extensors at the lateral epicondyle
may be reflected by subperiosteal dissection or by detachment.
The incision in the radial collateral ligament and capsule is
longitudinal. This allows later repair of this important ligament at the time of closure (5). If it is necessary to dislocate
the joint, the lateral collateral ligament complex may be
removed from its proximal origin with a portion of bone to
facilitate reattachment. Dissection should be kept in line with
the fibers of the ECU to avoid section of the fascial band of
the ECU, which is a stabilizer of the joint (8). A modification
for proximal extension of the Kocher incision may be made by
staying inferior to the epicondyle. This preserves the attachments of the extensor tendon from the condylar and epicondylar regions (8). Excision of the radial head requires incision of portions of the lateral ligament complex. An incision
slightly anterior to the center of the radial head and carried
distally for only a short distance preserves the inferior portions
of radial lateral ligament complex. Careful repair of these
fibers also is important (8) (Fig. 7.21).
7 Elbow 385
FIGURE 7.21. The Kocher approach to the lateral
aspect of the elbow; deep dissection. Distally, the interval between the anconeus and the extensor carpi
ulnaris (ECU) is used to expose the lateral ligament
complex, joint capsule, and ulna. The anconeus is
retracted posteriorly after removing its origin from the
lateral epicondyle, and the ECU is retracted anteriorly.
The common origin of the extensors at the lateral epicondyle is detached and reflected distally to expose the
radial collateral ligament and capsule.
CLINICAL CORRELATIONS
Activities of Daily Living and Elbow
Motion
Activities of dressing and personal hygiene require elbow
positioning from approximately 140 degrees of flexion to
reach the occiput to 15 degrees of flexion to tie a shoe.
Most of these activities are performed with the forearm in
0 to 50 degrees of supination. Most of the activities of
daily living are accomplished with 30 to 130 degrees of
elbow flexion, 50 degrees of pronation, and 50 degrees of
supination (13).
Imaging
Radiographic Skeletal Relationships
The long axis of the radius should point to the capitulum
in all views. If it does not, a lateral condyle fracture, a Monteggia fracture or equivalent, or an elbow dislocation should
be considered. Normally, the radial neck may be in as much
as 15 degrees of valgus angulation and may be 10 degrees
anterior to the radial shaft (14) (Fig. 7.22).
The long axis of the ulna should be nearly parallel to and
slightly medial to the long axis of the humerus on a true
anteroposterior view (14). If it is not, and if the radial head
and capitulum remain in correct alignment, a transepiphyseal injury or displaced supracondylar fracture should be
considered. If the radius no longer is pointing to the capitulum, an elbow dislocation should be considered.
The anterior humeral line should bisect the capitulum in
a true lateral view of the distal humerus. If the center of the
capitulum falls posterior to this line, an extension-type
supracondylar fracture is likely; a transepiphyseal fracture is
possible but rare. If the capitulum is anterior to the line, the
less common flexion-type supracondylar fracture or a
transepiphyseal fracture is likely. A true lateral view of the
distal humerus must be obtained because any rotation makes
the capitulum appear posterior to the anterior humeral line
(14) (Fig. 7.23A). The humeral capitular angle (Baumann’s
angle; see Fig. 7.23B) is a sensitive indicator of varus angulation of the distal humerus and is used primarily to measure
386 Regional Anatomy
FIGURE 7.22. Radiographic skeletal relationships. A: The long axis of the radius should point to
the capitulum in all views. B: If it does not, a lateral condyle fracture, a Monteggia fracture or
equivalent, or an elbow dislocation should be considered. Normally, the radial neck may be in as
much as 15 degrees of valgus angulation, and may be 10 degrees anterior to the radial shaft. C:
If the radius no longer is pointing to the capitulum, an elbow dislocation should be considered.
D: The long axis of the ulna should be nearly parallel and slightly medial to the long axis of the
humerus on a true anteroposterior view. If it is not, and if the radial head and capitulum remain
in correct alignment, a transepiphyseal injury or displaced supracondylar fracture (see B) should
be considered.
the adequacy of reduction in supracondylar and transepiphyseal fractures (14,15). It ranges from 9 to 26 degrees in
95% of normal elbows and is relatively constant with respect
to humeral rotation, changing only 1.6 degrees for each 10
degrees of humeral rotation as long as a true anteroposterior
view of the humerus has been obtained (14–16).
Fat Pad Sign
Norell first described the fat pad sign in 1954 (17). Displacement of the extrasynovial but intracapsular fat pads
due to distention of the synovial–capsular membrane secondary to an effusion associated with infection, fracture, or
spontaneously reduced dislocation may be a useful diagnostic sign in infection or injuries about the elbow. Because of
the relative shallowness of the coronoid fossa, the anterior
fat pad may be seen under normal circumstances in a lateral
radiograph of the elbow taken at 90 degrees of flexion as a
triangular lucency just anterior to the humerus, in contrast
to the olecranon fat pad, which normally is not seen
because of the relative deepness of the olecranon fossa and
the containment of the fat pad by the overlying triceps muscle (18). When a posterior fat pad is visible, an intraarticular injury is present 90% of the time (19) (Fig. 7.24). If the
elbow is extended, the olecranon fat pad usually is displaced
from the olecranon fossa by the olecranon process.
Although the fat pad sign can be a useful indicator of effusion, it is not always present, and displacement of the olecranon fat pad may occur without associated displacement
of the anterior fat pad (18). An anterior and posterior fat
pad sign is demonstrated in Figure 7.24.
7 Elbow 387
FIGURE 7.23. Anterior humeral line and Baumann’s angle. A: The anterior humeral line should
bisect the capitulum in a true lateral view of the
distal humerus. B: The humeral capitular angle
(Baumann’s angle) is a sensitive indicator of varus
angulation and ranges from 9 to 26 degrees in
95% of normal elbows.
FIGURE 7.24. The fat pad sign. Note the relatively radiolucent
zones indicated by the white arrows adjacent to the anterior and
posterior aspect of the distal humerus in this contrast-enhanced
radiograph of the right elbow. This positive fat pad sign is due
to displacement of the extrasynovial but intracapsular anterior
and posterior fat pads secondary to joint effusion associated
with an undisplaced and barely detectable fracture of the neck
of the radius (lower right arrow).
Epicondylitis
Medial
Medial epicondylitis is much less common than its lateral
counterpart. Both conditions are characterized by epicondylar pain and tenderness and symptom aggravation by
movement against resistance of the respective flexor or
extensor muscle groups.
Pathology
The pathologic process includes a gross or microscopic tear
in the tendinous origin of the muscles involved due to
mechanical overload in normal or aging tendon fibers
(20,21). In medial epicondylitis, the fibers involved usually
are located in the flexor carpi radialis (FCR) and less frequently in the flexor digitorum superficialis (FDS) origins.
Ulnar neuropathy may be differentiated by the well localized findings of epicondylar tenderness and reproduction of
symptoms by resisted flexion of the wrist.
Treatment
Surgical treatment for those cases not responsive to conservative management consists of excision of the involved portion of the FCR or the FDS through a 4-cm incision that
begins over the medial epicondyle and continues distally
over the fibers of origin of the FCR. The tear usually is in
the substance of the tendon just distal to the epicondyle,
and the diseased portion of the tendon is excised through a
longitudinal incision and a small portion of the condyle
removed with an osteotome to produce a raw cancellous
surface, after which the tendon defect is closed, including
the portion over the raw portion of the condyle (21). Care
is taken to avoid injury to the anterior portion of the medial
collateral ligament complex.
Lateral
Provocative Test
A recognized provocative test for lateral epicondylitis is
reproduction of symptoms by resisted dorsiflexion of the
wrist with the elbow in extension, compared with the usual
absence of symptoms with the elbow in flexion.
Differential Diagnosis
This condition must be differentiated from radial tunnel
syndrome, although the two conditions may coexist. Differentiation may be aided by noting in tennis elbow that the
site of maximum tenderness is at the lateral epicondyle, in
contrast to radial tunnel syndrome, in which the tenderness
is in the region of the radial head and proximal forearm
(22). In radial tunnel syndrome, some authors have noted
that pain may be produced by resisted dorsiflexion of the
long finger, which is said to produce secondary stress on the
ECRB, the leading edge of which can compress the radial
nerve (22,23). Radial tunnel pain also has been reported to
be reproduced by resisted supination of the extended forearm (22). The radial tunnel syndrome is discussed in detail
in Chapter 8, Part 2, Dorsal Forearm.
Treatment
Surgical treatment for those cases not responsive to conservative management is performed through a longitudinal
incision beginning at the lateral epicondyle and continuing
distally for 5 cm to expose the common extensor origin.
The usual site of pathology is in the substance of the ECRB
origin just distal to the lateral epicondyle. The common origin is split longitudinally for a distance of approximately 1
cm and reflected off the lateral epicondyle superiorly and
inferiorly. The tear along with necrotic tendon and granulation tissue is excised. A small osteotome is used to remove
a portion of the lateral epicondyle, and then the defect is
sutured to overlay the raw bone on the epicondyle. Care
must be taken to avoid injury to the lateral ligament complex because injury to this structure may result in posterolateral instability of the elbow (see discussion to follow,
under Lateral Insufficiency of the Elbow) (6).
Cubital Tunnel Syndrome
Definition
The term cubital tunnel syndrome was proposed in1958 to
identify a specific site of entrapment of the ulnar nerve and
to distinguish it from tardy ulnar palsy associated with posttraumatic cubitus valgus (24).
Findings
Clinical findings include complaints of medial elbow pain,
numbness and tingling or burning in the ring and little fingers, hand clumsiness, and weakness of pinch. Physical
findings may include tenderness behind the medial condyle
over the course of the ulnar nerve and a positive Tinel’s sign
over the nerve 2 cm proximal and distal to the cubital tunnel (22). Other physical findings include decreased sensibility in the ring and little fingers, and decreased pinch and
grip strength. Claw deformity of the ring and little fingers
as well as intrinsic muscle atrophy are seen in severe and
prolonged cases.
Pathomechanics
The ulnar nerve at the elbow is subcutaneous throughout
much of its course and also is partially fixed in a
fibroosseous canal. Because of its exposed position and the
fact that it wraps around the medial condyle in flexion, prolonged elbow flexion, which stretches the nerve and narrows the tunnel, combined with resting the elbow on a hard
surface may result in paresthesias in the ring and little fingers even in normal persons (22). When swelling or elbow
388 Regional Anatomy
inflammation or congestion of the flexor-pronator muscles
is added to this stretch–compression, the vascular supply of
the ulnar nerve may be compromised and nerve symptoms
may result (22). Sustained elbow flexion combined with
vigorous finger and wrist motion such as a musician might
perform also can result in ulnar nerve symptoms. The
motions used to throw a ball or to serve a tennis ball are
similar and can place significant stress on the ulnar nerve,
and may be associated with ulnar nerve symptoms (22).
Perioperative ulnar neuropathies are more common in men
than in women, and although there is no gross anatomic
difference between sexes regarding the course of the ulnar
nerve in the upper extremity, there is a significantly larger
(2 to 19 times greater) fat content on the medial aspect of
the elbow in women compared with men. Also, the tubercle of the coronoid process on the ulna is 1.5 times larger in
men. The tubercle of the coronoid process is a likely area for
ulnar nerve compression and secondary ischemia of the
nerve because the nerve and its blood supply from the ulnar
recurrent artery are minimally covered in this area (25).
Sites of Compression
Surgical treatment of cubital tunnel syndrome is facilitated
by knowledge of the potential sites of compression and the
anatomy specific to each of those areas. The ulnar nerve
enters the posterior aspect of the arm at approximately the
midpoint of the arm and continues distally toward the
elbow behind the medial intermuscular septum on the
medial head of the triceps muscle.
Arcade of Struthers
There is a potential site of entrapment of the ulnar nerve
8 cm proximal to the medial epicondyle called the arcade
of Struthers (26). When the arcade is present, both the
ulnar nerve and the superior ulnar collateral vessels pass
through it. In a study of 25 arms, the arcade of Struthers
was present in 68% of the arms (26). The arcade has a roof
that faces medially, formed by the deep investing fascia of
the arm, superficial muscle fibers from the medial head of
the triceps, and the internal brachial ligament arising from
the coracobrachialis tendon. The floor, which is lateral, is
formed by the medial aspect of the humerus covered by
the deep muscular fibers of the medial head of the triceps.
The anterior border is the medial intermuscular septum
(Fig. 7.25). Atypical features of the arcade included multiple ligamentous bands arising from thickened deep fascia and the medial intermuscular septum passing both
superficial and deep to the ulnar nerve. Thus, after incision of the roof of the arcade, these ligaments, which
remain deep to the nerve, can still compress the nerve.
7 Elbow 389
FIGURE 7.25. The arcade of Struthers. A: This potential site of entrapment of the ulnar nerve is
located 8 cm proximal to the medial epicondyle. (continued on next page)
The same applies to the internal brachial ligament (Fig.
7.26C; see Fig. 7.25), which courses deep to the ulnar
nerve. Although the arcade of Struthers is a recognized
anatomic entity, it is said to be a rare cause of ulnar nerve
compression (26,27). However, Spinner and Kaplan
showed that the arcade can produce recurrent ulnar neuropathy after anterior transposition of the nerve because
of tethering, and thus recommended lysis of the arcade as
part of the transposition (28). They also recommended
lysis of the arcade when mobilizing a lacerated ulnar nerve
in the forearm to reduce the gap in the nerve.
Medial Head of Triceps
Another atypical feature relates to the finding that when the
ulnar nerve is buried in the medial head of the triceps, the
overlying muscular roof may be a source of compression
and should be incised.
390 Regional Anatomy
FIGURE 7.25. (continued) B: Detail of components.
FIGURE 7.26. Fresh cadaver dissection of the arcade of Struthers (medial view of right elbow).
A: The arcade of Struthers is present but not readily apparent in this view of the ulnar nerve and
medial intermuscular septum.
A
Elbow (Cubital Tunnel)
The ulnar nerve in its passage from the arm to the forearm
transits the cubital tunnel, which is an osseous canal
formed by the medial epicondyle and the proximal ulna
and covered by a retinaculum formed by the deep investing fascia of the arm that is attached to the medial epicondyle and the olecranon. This cubital tunnel retinaculum (CTR) is 2-3 cm wide (from proximal to distal), 0.5
to 0.75 mm thick and its distal margin blends with the
investing fascia of the humeral and ulnar heads of the
FCU. Osborne’s band and the arcuate ligament are other
names often used to describe this fibrous tissue roof of the
ulnar tunnel (29). Because of the somewhat eccentric origin of this fascial roof, the cubital tunnel changes contour
and volume during elbow flexion and extension. In flexion, the cross-sectional contour changes from slightly
ovoid to elliptical (22). Any swelling in the canal or
inflammation or thickening of the fascial roof may compress the nerve or its vasculature (22) (Fig. 7.27).
7 Elbow 391
FIGURE 7.26. (continued) B: Further dissection reveals the arcade of Struthers. Its proximal and
distal edges are marked with small triangles. Note the underlying ulnar nerve and the medial
intermuscular septum. C: The arcade has been incised and reflected anteriorly; note the internal
brachial ligament, which courses deep to the ulnar nerve.
B
C
Forearm
At the distal end of the cubital tunnel the ulnar nerve enters
the forearm through the flexor pronator group of muscles,
usually between the humeral and ulnar heads of the FCU.
The flexor-pronator muscles are arranged in two groups.
The superficial group is formed by five muscles (PT, FCR,
PL, FDS, and FCU) that originate from a common origin
created by the fusion of several fibrous septa that arise from
the anterior surface of the medial humeral epicondyle, the
ulnar collateral ligament, and medial surface of the coronoid process. These fibrous tissue septa form well defined
fascial compartments for the muscles as well as a common
aponeurosis from which adjacent muscles originate. These
septa fuse beginning approximately 3.5 to 4 cm distal to the
epicondyle (30). This fused structure is commonly known
as the flexor-pronator origin or the flexor-pronator aponeurosis. Inserra and Spinner identified an additional aponeurosis
in this area between the FDS to the ring finger and the
humeral head of the FCU that did not fuse with the previously described common flexor pronator origin but rather
arose from the medial surface of the coronoid process 0.3 to
0.5 cm medial to it. They found it was not possible to transpose the ulnar nerve adjacent to the median nerve in a relatively straight course unless this septum was detached
along with the radial two-thirds of the flexor-pronator
group (28). Amadio and Beckenbaugh identified a structure
deep to the FDS and superficial to the flexor digitorum profundus (FDP) and FCU that provided a point of origin for
all of these muscles and that extended approximately 5 cm
distal to the epicondyle. They advised that this deep
aponeurosis of the FCU, which bridged and formed a common origin for muscle fibers of the FCU, FDS, and FDP,
should be released by separating the two heads of the FCU
and exploring the deep surface of the muscle for at least 5
cm distal to the epicondyle (31).
Surgical Technique for Cubital Tunnel
Release and Ulnar Nerve Transposition
The common denominator in ulnar nerve transposition is
elimination of compression or traction problems by
removal of the nerve from the fibroosseous tunnel and permanent transposition to an anterior location. Permanent
transposition has been achieved by subcutaneous transposition, subcutaneous transposition with some form of tether
to prevent the nerve from assuming its original position, or
submuscular or intramuscular transposition (22,32–35).
The sine qua non of ulnar nerve transposition is permanent
realignment of the ulnar nerve in an anterior position without entrapment (absence of compression) or fixation (traction), which would prevent gliding of the nerve. It also
must be recognized that the ulnar nerve remains subcutaneous throughout most of its new course, and that even
submuscular or intramuscular transposition eliminates only
a portion of this subcutaneous position. The effectiveness of
transposition is based on decompression of the nerve and
elimination of any potential for traction injury.
Author’s Comment: The debate concerning the best technique for ulnar nerve transposition and the role of in situ
ulnar nerve neurolysis without transposition (with or without medial epicondylectomy) is not addressed in this text.
Subcutaneous Transposition
Position/Incision
With the patient supine and the upper extremity supported
on an arm board and the elbow resting on a soft pad, a 14-
cm incision is begun on the medial aspect of the arm and
continued distally through the interval between the medial
epicondyle and olecranon process, to end on the flexor and
medial side of the forearm. The incision begins at least 8 cm
proximal to the medial epicondyle to verify the presence or
absence of the arcade of Struthers (26) (see Fig. 7.28A and B).
Technique
Cutaneous Nerves. After incision of the skin and subcutaneous tissue and superficial fascia, the posterior branches of
the medial antebrachial cutaneous nerve are identified on
the distal aspect of the wound. One to three branches may
be present and may cross the incision anywhere from 6 cm
proximal to 6 cm distal to the medial humeral condyle (12).
Injury to these branches may result in hypesthesia, a painful
scar, or hyperalgesia.
392 Regional Anatomy
FIGURE 7.27. Changes in the cubital tunnel with flexion.
Because of the somewhat eccentric origin of the fascial roof of
the cubital tunnel, its contour and volume change during elbow
flexion and extension. In flexion, the cross-sectional contour
changes from slightly ovoid to elliptical.
Ulnar Nerve. At this level in the distal arm, the ulnar nerve
lies posterior to the medial intermuscular septum and anterior
to the medial head of the triceps, having pierced the medial
intermuscular septum at approximately the midshaft of the
humerus. The nerve is most easily identified just proximal to
its entrance into the osseous groove and can be traced proximally from this area. The deep fascia is incised and the nerve
is noted to lie on the medial head of the triceps just posterior
to the medial intermuscular septum. The anterior flap is raised
at least 5 cm anterior to the medial epicondyle and the ulnar
nerve is dissected free a minimum of 8 cm proximal to the
medial epicondyle and 6 cm distal to the epicondyle to ensure
complete release of the nerve from the various structures as
previously described, including the arcade of Struthers, if present proximally, the CTR, the FCU fascia, and additional
aponeuroses as previously described distal to the medial
condyle (22,26–28,30–32,36) (see Fig. 7.29A–C).
Vascular Plexus Accompanying Nerve. As the ulnar
nerve descends toward the elbow, it is accompanied by a
longitudinally oriented venous plexus with feeder veins
that may be mobilized with the nerve. Mobilization and
preservation of this plexus is said to promote optimum
postoperative microcirculation, and immediate postoperative dysesthesias appear to be greatly reduced (22,32).
The superior ulnar collateral branch of the brachial artery
also accompanies the nerve and joins the inferior ulnar
collateral artery in the region of the medial epicondyle,
passes posterior to the medial supracondylar ridge, and
ends deep to the FCU by anastomosing with the posterior ulnar recurrent artery. Preservation of these arterial
vessels is discussed later in the section on Medial Intermuscular Septum. Details of the arterial circulation of the
elbow were presented earlier, in the section on Anatomic
Relationships.
7 Elbow 393
FIGURE 7.28. Subcutaneous transposition of the ulnar nerve; patient position (A) and incision
(B). A 14-cm long incision begins on the medial aspect of the arm and continues distally through
the interval between the medial epicondyle and olecranon process to end on the flexor and
medial side of the forearm. The incision begins at least 8 cm proximal to the medial epicondyle
to verify the presence or absence of the arcade of Struthers.
Cubital Tunnel. The nerve enters the cubital tunnel in a
groove in the posterior aspect of the medial condyle that is
bordered medially by the medial epicondyle and laterally by
the olecranon.
The roof of the tunnel is formed by the CTR. Distally,
the nerve enters the area between the humeral and ulnar
heads of the FCU, where it is covered by thickened transverse fascial fibers that join these two heads. Motor
branches to the FCU are given off at this level (see Fig.29).
Medial Intermuscular Septum. After complete release of
the nerve and performance of a trial anterior transposition,
394 Regional Anatomy
FIGURE 7.29. The Cubital Tunnel Retinaculum (CTR) and the Medial Intermuscular Septum (MIS).
A: The Cubital Tunnel Retinaculum (CTR), the FCU fascia and Medial Intermuscular Septum (MIS)
prior to release or excision. B: Release of the CTR and proposed (dotted lines) release of the FCU
fascia and excision of the MIS.
it is readily apparent that the ulnar nerve will impinge on
the medial intermuscular septum as it crosses over the septum. Therefore, complete excision of the medial intermuscular septum is required for a distance of 8 cm proximal to
the medial epicondyle (see Fig. 7.30A and B). The superior
ulnar collateral artery from the brachial artery runs along
the posterior surface of the medial intermuscular septum in
company with the ulnar nerve and may be dissected off the
nerve before transposition, or, if it is elected to attempt to
carry the artery with the nerve, the perforating vessels into
the septum must be dealt with as well as the anastomosis to
the inferior ulnar collateral artery. On the anterior surface
of the medial intermuscular septum, the inferior ulnar collateral artery from the brachial artery is encountered along
with its branch, the anterior ulnar recurrent artery. The
inferior ulnar collateral artery pierces the medial intermuscular septum near the mid-portion of the medial epicondylar ridge and may require ligation as the septum is resected
from the humerus (see Fig. 7.30C).
Author’s Comment: The concept of preservation of the
mesentery-like vessels from the ulnar collateral and ulnar
recurrent arteries to the ulnar nerve may be academic
because of the rich anastomotic microcirculation of the
nerve. Kleinman noted that it is this rich intrinsic blood
supply composed of an interconnecting meshwork of vessels running among the fascicular bundles as well as along
each fascicle that allows microscopic hemodynamics to continue normally in spite of the elimination of multiple
mesentery-like feeding vessels (37).
After removal of the medial intermuscular septum and
with the elbow flexed to 90 degrees, the nerve is transposed
anteriorly at least 3 cm anterior to the medial epicondyle to
lie on the muscle fascia. The nerve is inspected for impingement points, and then the anterior flap is positioned over
the nerve.
Permanent Transposition of Nerve. The nerve may be
maintained in its new position by one of two methods (Fig.
7.31A and B): With the nerve in its new anterior position,
three polyglycolic acid sutures are placed in the superficial
fascia of the flap and the muscle fascia to make a fat-covered
tunnel overlying the nerve. The length of this tunnel should
be at least 6 cm, and it must be large enough to admit the
surgeon’s little finger throughout its length. The elbow
should be flexed and extended to verify that the nerve is not
trapped or constrained in the new tunnel. The second
method is to raise a proximally based strip of antebrachial
fascia 1 cm wide and long from the region of the medial
epicondyle, which is then passed medial to the nerve and
sutured to the superficial fascia of the anterior flap (22,33).
This fascial curtain or septum in the mid-lateral plane lies
posterior and medial to the transposed nerve and prevents
the ulnar nerve from migrating back to its original site,
allows gliding of the nerve, and covers the nerve with fatty
subcutaneous tissue.
Submuscular Transposition. Submuscular transposition of
the ulnar nerve as described by Learmonth (35) has as its
7 Elbow 395
FIGURE 7.29. (continued) C: After excision of the MIS and with the elbow flexed to 90
degrees, the nerve is transposed anteriorly at least 3 cm anterior to the medial epicondyle to
lie on the muscle fascia.
396 Regional Anatomy
FIGURE 7.30. Subcutaneous transposition of the ulnar nerve; deep dissection. A: The ulnar nerve
lies posterior to the medial intermuscular septum, covered by fascia, and is most easily identified
just proximal to its entrance into the osseous groove. For clarity, the fascia that hides the nerve
has been removed in this depiction. Motor branches to the flexor carpi ulnaris are given off at
this level. B: After release of the nerve, excision of the medial intermuscular septum is performed
for a distance of 8 cm proximal to the medial epicondyle. After removal of the medial intermuscular septum and with the elbow flexed to 90 degrees, the nerve is transposed anteriorly at least
3 cm anterior to the medial epicondyle to lie on the muscle fascia.
A
B
7 Elbow 397
FIGURE 7.31. Methods of maintaining the
transposed ulnar nerve in its new position,
and submuscular transposition. A: The
nerve is placed in its new anterior position,
the anterior flap is placed over the nerve,
and three polyglycolic acid sutures are
placed in the superficial fascia of the flap
and the muscle fascia. B: The second
method is to raise a proximally based strip
of antebrachial fascia 1 cm wide and long
from the region of the medial epicondyle,
which is then passed medial to the nerve
and sutured to the superficial fascia of the
anterior flap. This fascial curtain or septum
in the mid-lateral plane lies posterior and
medial to the transposed nerve. C: Submuscular transposition. The flexor-pronator
muscle group is removed from the medial
epicondyle with an osteotome and a small
amount of bone. The origin is reflected at
least 6 cm distal to the medial epicondyle.
The nerve is then transposed anteriorly and
the flexor-pronator origin reattached while
the elbow is flexed to 90 degrees.
strongest indication revision surgery for ulnar neuropathy at
the elbow (32). Lesser indications include young, vigorous
people such as athletes and very thin individuals in whom
subcutaneous positioning of the ulnar nerve might make it
liable to repeat injury (22). Submuscular transposition is
identical to subcutaneous transposition with regard to the
release and mobilization of the nerve and removal of the
medial intermuscular septum (see Fig. 7.31C). The next step
in submuscular transposition is to define the antecubital
fossa margin of the PT and the brachial artery and median
nerve in the antecubital fossa before elevation of the origin
of the flexor-pronator group from the medial epicondyle. An
osteotome is used to remove the flexor-pronator origin from
the medial epicondyle with a small amount of bone, and
then the remainder of the origin is reflected for a distance of
at least 6 cm distal to the medial epicondyle. Part of the
flexor-pronator origin is from the medial collateral ligament
of the elbow, and care must be taken to avoid disruption of
this important structure. The nerve is then transposed anteriorly and the flexor-pronator origin reattached while the
elbow is flexed to 90 degrees. Because of the need for muscle healing and restoration of elbow motion and strength,
the time for return to full activity is longer with this technique compared with subcutaneous transposition.
Intramuscular Transposition. Permanent positioning of
the transposed ulnar nerve has been achieved by placing the
nerve in a 5-mm-deep muscular trough cut into the flexorpronator mass, followed by tension-free closure of the muscle fascia over the nerve. A recent report of this technique,
first described in 1918 (38), revealed a high percentage of
good to excellent results (34).
Snapping Elbow
To many physicians, snapping sensations or sounds about
the medial aspect of the elbow are synonymous with the relatively common recurrent dislocation of the ulnar nerve
(39). However, the medial head of the triceps muscle or tendon also may dislocate over the medial epicondyle and
result in snapping as the elbow either is flexed or as it is
extended from a flexed position. Dislocation of the medial
head of the triceps can occur in combination with ulnar
nerve dislocation to produce the clinical finding of two
snaps at the elbow. This condition may be present with or
without ulnar neuropathy and with or without discomfort.
Physical Examination
Both passive and active flexion and extension from a flexed
position are performed while palpating the medial aspect of
the elbow (39–41). In a patient who has snapping of the
medial head of the triceps and dislocation of the ulnar nerve,
the ulnar nerve dislocates at 90 degrees and the medial head
of the triceps dislocates at approximately 110 degrees (39).
Sequential palpation of the ulnar nerve in the cubital tunnel
and the medial head of the triceps may allow the examiner to
determine if one or both of these structures is dislocating. The
diagnosis may be confirmed by magnetic resonance imaging
(MRI) or computed tomography (CT), or both (39).
Associated Conditions
Abnormalities confirmed by operative findings include
hypermobility of the ulnar nerve, varying amounts of triceps muscle fibers extending distal to the medial epicondyle
that dislocated over the medial epicondyle with the elbow
in flexion, thickening of the fascial edge of the medial head
of the triceps, accessory triceps tendon, and posttraumatic
cubitus varus deformity (39). Dislocation of the medial triceps and ulnar neuropathy has been reported in three generations of one family (42).
Clinical Significance
Dislocation of the medial head of the triceps may occur in
combination with dislocation of the ulnar nerve. Failure to
recognize that these two conditions can occur concurrently
may be the reason for persistent symptoms after an otherwise successful transposition of the ulnar nerve. Patients
who have an ulnar nerve transposition, especially those who
have dislocation of the ulnar nerve, should be examined
during surgery with the elbow in flexion and extension to
be certain that the medial head of the triceps does not snap
over the medial epicondyle (39).
Snapping of the Triceps Tendon over the
Lateral Epicondyle
This unusual condition is manifested by anterior dislocation of the lateral head of the triceps with passive or active
flexion beyond 90 degrees. The differential diagnosis may
include posterolateral rotatory instability, loose bodies,
intraarticular adhesions, osteochondral defects, ruptured
annular ligaments, and synovial folds or plicae (43).
Acute Elbow (Ulnohumeral) Dislocation
Complete
A complete dislocation may be either straight posterior or
posterolateral with the coronoid posterior to the trochlea
(44). Based on clinical experience, there is deficiency of the
medial collateral ligament observed with valgus stress and disruption of the ligament found at the time of surgery (44).
Incomplete
An incomplete dislocation or subluxation (so-called
perched subluxation) is characterized by the trochlea being
398 Regional Anatomy
“perched” or balanced on the coronoid process (44). This
incomplete type of dislocation occurs in less than 10% of
elbow dislocations and has been shown experimentally to be
possible with disruption of the lateral collateral ligament
and maintenance of some continuity of the medial collateral ligament (44).
Treatment
Treatment is immediate reduction. After reduction, stability of the joint is tested through a range of motion to determine if instability is present and at what position. The
elbow is placed in the position of stability and range of
motion started in 5 to 7 days in the previously defined arc.
If the elbow is markedly unstable, it is placed in sufficient
flexion to obtain stability and brought into extension after
5 to 7 days, with progression of the extension over the next
3 to 4 weeks (44).
Surgical intervention has very little value in the management of elbow dislocation without fracture (44,45).
Subluxation of the Radial Head (Pulled
Elbow Syndrome)
This injury occurs most commonly in children 2 to 3 years
of age when a longitudinal pull is applied to the upper
extremity. The child fails to use the extremity and the forearm is most often in pronation. Plain radiographs usually are
normal. This condition is due to slippage of the annular ligament over the head of the radius so that the ligament is
interposed between the radial head and the capitulum.
Reduction is achieved by supination of the forearm; if this
fails to produce the characteristic snapping sensation of
reduction, the elbow is brought into maximum flexion until
the snapping sensation occurs (46).
Collateral Ligament Injuries
Acute Medial
An acute tear of the medial collateral ligament is the most
frequent isolated ligamentous injury of the elbow. It is seen
most commonly in throwing athletes such as baseball pitchers and javelin throwers (47).
Diagnosis
The diagnosis is suspected by the history and mechanism of
injury. Regional ecchymosis and tenderness over the anterior band of the medial collateral ligament just inferior to
the medial epicondyle are characteristic findings (44).
Instability Test
With the patient’s hand placed in the examiner’s axilla, the
elbow flexed to 25 degrees (Jobe test), and the humerus externally rotated and abducted, valgus stress is applied to the
elbow to demonstrate laxity or localized pain. This degree of
flexion unlocks the olecranon from its fossa (47,48). Morrey
flexes the elbow approximately 10 degrees to relax the anterior capsule and remove the coronoid and olecranon from
their respective fossae (44) (Fig. 7.32). Stress views are useful
if there is any question about the diagnosis.
7 Elbow 399
FIGURE 7.32. Test for medial collateral ligament
instability. With the patient’s hand placed in the
examiner’s axilla, the elbow flexed to 25 degrees, and
the humerus externally rotated and abducted, valgus
stress is applied to the elbow to demonstrate laxity or
localized pain.
Other Diagnostic Tests
Azar et al. evaluated their patients with suspected ulnar collateral ligament injuries by valgus stress testing and as well
as radiographic stress views, CT arthrograms, and, in some
instances, saline-enhanced MRI (49).
Treatment
Acute injury in patients with low-demand activities is best
managed by immobilization of the elbow for 3 weeks followed by a hinged splint for another 4 to 5 weeks. The
splint is fashioned to promote slight varus angulation of
the elbow and the forearm is placed in supination. At 8
weeks, unrestricted flexion and extension exercises are
allowed, but valgus load is avoided (44). In patients with
high-demand activities, such as competitive pitchers,
immediate repair or reconstruction may be appropriate.
The surgical management is discussed later, under Medial
Insufficiency.
Acute Lateral
This is an infrequent acute injury because varus stress is not
often generated from routine or sports activities (44).
Diagnosis
Diagnosis is made after a history of acute varus stress associated with point tenderness and varus instability on examination.
Treatment
Nonoperative management is similar to that for medial collateral ligament acute tears, with the exception that the
forearm is pronated rather than supinated because this position provides the optimum position for stability and healing. Protection for 3 months is provided because the lateral
collateral ligament often displays residual laxity (44).
Medial Insufficiency
In chronic medial collateral insufficiency, there may be no
frank instability but the patient may note pain at the medial
aspect of the elbow with stress, as in throwing.
Diagnosis
The diagnosis is confirmed by noting tenderness over the
anterior bundle of the medial collateral ligament and reproduction of pain or palpable instability with valgus stress.
Not surprisingly, approximately 40% of patients may experience ulnar nerve symptoms (47).
Treatment
Treatment is through ligament reconstruction (Jobe technique) (48). The medial aspect of the elbow is opened and
care is taken to protect the ulnar nerve and sensory nerves
in the skin. The flexor-pronator muscle group is split longitudinally and the anterior portion of the ulnar collateral
ligament exposed. Additional exposure is obtained by
detachment and distal reflection of the flexor-pronator
mass. The ulnar nerve is mobilized 2.5 cm distal to the
epicondyle to well above the medial epicondyle. The
medial intermuscular septum is removed to the point at
which no impingement on the ulnar nerve can be palpated
or visualized. These maneuvers are in preparation for submuscular transposition of the ulnar nerve after ligament
reconstruction. A drill is used to make a tunnel in the epicondyle and ulna that corresponds to the points of attachment of the original ligament. The tunnel in the ulna is 1
cm distal to the joint. The tunnel in the medial epicondyle
is at the point of isometry. A tendon graft from either the
palmaris longus or plantaris, or a strip of Achilles tendon
is used to pass through the tunnels to form a figure-ofeight. The graft is pulled taut and sutured to itself. The
flexor-pronator origin is reattached and the elbow immobilized in 90 degrees of flexion for approximately 2 weeks,
followed by a hinge splint for an additional 2 weeks (Fig.
7.33).
Lateral Insufficiency (Posterolateral Rotatory
Instability)
Posterolateral rotatory instability of the elbow was first
described in 1991 and is distinguished from recurrent radial
head dislocation (the radioulnar joint) or dislocation of the
elbow joint (the ulnohumeral and radiohumeral joints) (6).
This condition also has been observed after lateral release
for tennis elbow (6).
Diagnosis
The diagnosis is made from a history of elbow dislocation
followed by symptoms of chronic instability characterized
by complaints of a pop, catch, or “clunk” as the elbow goes
from full extension to flexion or from flexion to extension.
In some cases, pain over the lateral aspect of the joint may
be a more prominent feature than the symptoms of instability. Although the patient may complain of posterolateral
elbow pain, a varus stress test often is negative unless gross
instability is present (6,44).
Diagnostic Maneuver.
The test is performed with the patient supine and the arm
over the patient’s head (6,44). The diagnostic maneuver
involves supination of the forearm and application of a valgus moment and axial compression while simultaneously
flexing the elbow from a position of full extension. This
maneuver produces a rotatory subluxation of the ulnohumeral joint as the semilunar notch of the ulna is displaced from the trochlea of the humerus. This rotation dislocates the radiohumeral joint posterolaterally, and as the
elbow is flexed to approximately 40 degrees, the rotatory
displacement is at its maximum and a posterior prominence
400 Regional Anatomy
with an associated dimple in the skin is noted proximal to
the radial head (Fig. 7.34). Additional flexion results in a
sudden reduction of the radiohumeral and ulnohumeral
joints accompanied by disappearance of the dimple, and the
radius and ulna visibly and palpably snap into place on the
humerus. Although the reduction can be performed by
pronation of the forearm, the reduction is not as dramatic
as that described in the standard maneuver. In some
instances, the patient notes only pain with this maneuver,
without demonstrable pivot. This type of response is
reported as “positive for pain” and is highly suggestive of the
presence of this lesion (44). Full external rotation of the
shoulder provides a counterforce for the supination of the
forearm and leaves one hand of the examiner free for application of valgus stress. Routine physical examination is negative and the elbow joint is stable to varus and valgus stress
even under anesthesia. In no instance can the ulnohumeral
joint be frankly dislocated (6).
7 Elbow 401
FIGURE 7.33. Ligament reconstruction for medial insufficiency (Jobe technique). A: The medial
aspect of the elbow is opened and the flexor-pronator muscle group is split longitudinally and
the anterior portion of the ulnar collateral ligament exposed. B: Additional exposure is obtained
by detachment and distal reflection of the flexor-pronator mass. C: A tendon graft is passed
through tunnels to form a figure-of-eight, pulled taut, and sutured to itself.
Abnormal Findings at Surgery
According to Nestor et al. (6), anatomic findings at time of
surgery consistently demonstrated laxity or avulsion of that
portion of the radial collateral ligament that they have
named the LUCL. Treatment depends on the status of the
LUCL and includes advancement and imbrication or
reconstruction with autogenous tendon graft.
Treatment/Surgical Technique
With the patient supine, the elbow semiflexed, and the
forearm in pronation on an arm board, a longitudinal
incision is made 5 cm proximal to the lateral epicondyle
over the lateral supracondylar ridge and continuing distally over the lateral epicondyle to curve over the
anconeus, ending posteriorly at the subcutaneous margin
of the ulna. Distally, the interval between the ECU and
anconeus is used to expose the proximal and extensor
aspect of the forearm, the supinator crest, and the insertion of the LUCL. Two 3- to 4-mm drill holes are placed
at the tubercle on the proximal aspect of the supinator
crest approximately 7 to 10 mm apart. To determine the
proximal point of origin of the new ligament, the point
of isometry is determined by passing a suture through the
tunnel made in the proximal ulna and clamping the two
ends of the suture with a hemostat, which is used as a
pointer to identify the isometric point. This point usually
is in the mid-portion of the lateral epicondyle (6,44). A
tunnel is then made in the epicondylar ridge centered
about the isometric point and a free tendon graft using
the palmaris longus or the plantaris passed through these
tunnels so that a three-ply graft is obtained (Fig. 7.35).
The elbow is placed in 30 degrees of flexion and the graft
sutured to itself under tension. The elbow is immobilized
for 2 weeks, followed by protection in a hinge splint for
4 to 6 weeks. Thereafter, progressive activities are
allowed, but varus stress is avoided for 4 to 6 months
(44).
Flexion Contracture
Flexion contracture of the elbow may be associated with significant loss of upper extremity function. An arc of motion
from 30 degrees short of full extension to 120 degrees flexion (90 degrees of motion) is said to be essential for most
activities of daily living (50).
Etiology
Flexion contracture may be due to a variety of causes,
including fractures and dislocations about the elbow, burns,
heterotopic ossification, spasticity, or congenital or developmental conditions about the joint (50,51). This discussion of anterior capsulotomy focuses on the release of flexion contracture secondary to trauma.
Surgical Approaches
Although anterior capsulotomy may be performed through
an anterior (46) approach as well as a combined medial and
lateral (52) approach, there are several compelling reasons to
perform it through a lateral approach (50). These include the
ability to release both anterior and posterior structures
402 Regional Anatomy
FIGURE 7.34. Diagnostic maneuver for posterolateral rotatory instability (lateral insufficiency
test). The maneuver involves supination of the forearm and application of a valgus moment and
axial compression while simultaneously flexing the elbow from a position of full extension. This
maneuver dislocates the radiohumeral joint posterolaterally, and as the elbow is flexed to
approximately 40 degrees, the rotatory displacement is at its maximum and a posterior prominence with an associated dimple in the skin is noted proximal to the radial head.
through the same incision, the fact that the olecranon fossa
may be cleared or part of the olecranon excised to obtain
additional extension, and any enlargement of the coronoid
process that might produce impingement can be excised. Posteriorly, tenolysis of the triceps and capsulotomy can be done
to increase flexion. After surgery, the lateral incision, which is
in the neutral axis of flexion–extension, is less likely to produce an unacceptable scar, and if immediate continuous passive motion is used, it will be less subject to tension (50).
Technique of Lateral Approach
Position/Incision
With the patient supine, the elbow flexed to 60 degrees,
and the forearm pronated, a Kocher approach is used beginning along the lateral supracondylar ridge of the humerus
and continuing across the lateral epicondyle, to end at the
subcutaneous border of the ulna between the ECU and
anconeus (Fig. 7.36).
7 Elbow 403
FIGURE 7.35. Ligament reconstruction for posterolateral rotatory instability (lateral insufficiency). A: A longitudinal incision is made 5 cm proximal to the lateral epicondyle over the lateral supracondylar ridge and continued distally over the lateral epicondyle to curve over the
anconeus, ending posteriorly at the subcutaneous margin of the ulna. The interval between the
extensor carpi ulnaris and anconeus is used to expose the proximal and extensor aspect of the
forearm, the supinator crest, and the insertion of the radial collateral ligament. B, C: Drill holes
are placed at the tubercle on the proximal aspect of the supinator crest approximately 7 to 10
mm apart, and the point of isometry is determined by passing a suture through the tunnel made
in the proximal ulna to identify the isometric point. A second tunnel is then made near the epicondylar ridge centered about the isometric point, and a free tendon graft is passed through
these tunnels so that a three-ply graft is obtained.
FIGURE 7.36. Lateral approach for elbow flexion contracture. A: A Kocher approach is used
beginning along the lateral supracondylar ridge of the humerus and continued across the lateral
epicondyle to end at the subcutaneous border of the ulna between the extensor carpi ulnaris
(ECU) and anconeus. B: Subperiosteal stripping is used to elevate the brachioradialis (BR) and
extensor carpi radialis longus (ECRL) from the supracondylar ridge to reveal the brachialis muscle
and the anterior capsule. C: Distally, the interval between the ECU and anconeus is used to
expose the lateral aspect of the elbow joint. Retractors are placed deep to the BR, ECRL, and
brachialis to expose the anterior capsule, which is incised from lateral to medial. D: The elbow is
brought into maximum extension and, if extension is incomplete, the triceps is dissected free and
retracted to look for soft tissue or bone in the olecranon fossa that might block full extension.
Deep Dissection
Subperiosteal stripping is used to elevate the brachioradialis and ECRL from the supracondylar ridge to reveal the
brachialis muscle and the anterior capsule. Distally, the
interval between the ECU and anconeus is used to expose
the lateral aspect of the elbow joint. Retractors are placed
deep to the brachioradialis, ECRL, and brachialis to expose
the anterior capsule, which is incised from lateral to
medial. The fascia on the underside of the brachialis may
be incised as needed. The elbow is brought into maximum
extension and, if extension is incomplete, the triceps is dissected free and retracted to look for soft tissue or bone in
the olecranon fossa that might block full extension or
enlargement of the olecranon. Flexion may be improved by
tenolysis of the triceps and posterior capsulotomy as
required. If adequate flexion still is not obtained, the coronoid fossa should be inspected and cleared, or if the coronoid process is enlarged, it should be trimmed as indicated
proximal to the brachialis insertion. The extensive nature
of this release requires careful reattachment of the lateral
sleeve of tissues, and the authors recommend drill holes in
the humerus to facilitate closure to restore lateral stability
to the elbow (50). The senior author (Hastings) of this
technique has noted that when radical debridement of the
joint is not required, preservation of the origin of the lateral collateral ligament on the lateral epicondyle is recommended (8). If this is possible, no postoperative protection
of the lateral ligamentous structures is required in the rehabilitation phase of recovery.
Myositis Ossificans and Heterotopic
Calcification and Ossification
True myositis ossificans should be differentiated from heterotopic calcification, the latter being a dystrophic process
(46). Myositis ossificans is ossification in the muscle (most
often the brachialis) after trauma such as an elbow dislocation. This condition may lead to significant loss of
motion of the elbow and usually is seen 3 to 6 weeks after
injury (53). This condition is rare compared with heterotopic calcification in the ligaments and capsule of the
elbow joint, which is common, but rarely results in loss of
elbow function. The incidence of myositis ossificans can
be lessened by gentle and prompt reduction of elbow dislocations and by using gentleness during the rehabilitation
process (46). Heterotopic ossification is manifested clinically as an intense inflammatory reaction about the joint
with redness, increased warmth, severe pain, and rapidly
decreasing range of motion (54,55). It is a complication of
traumatic brain injury and usually is detected within 2
months after the injury. The incidence of periarticular
heterotopic ossification after traumatic brain injury is
11%. The hips are involved most commonly, followed by
the shoulder and elbows (55). An increased incidence to
85% is noted in patients with concomitant musculoskeletal injuries (55).
ANATOMIC VARIATIONS
Muscle
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 (56,57). It has been reported to have
a variable incidence as high as 25% (56). 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 supplied 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 anconeus
epitrochlearis, this ligament is believed to be a rudiment of
the muscle (58).
Clinical Significance
This muscle crosses over the ulnar nerve in the region of
the cubital tunnel and has been reported to be a source of
compression of the ulnar nerve in cubital tunnel syndrome (56,57). 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 (57).
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406 Regional Anatomy
CHAPTER
FOREARM
JAMES R. DOYLE
PART
FLEXOR FOREARM
The proximal and distal ends of the two-bone configuration of the forearm are uniquely suited to allow a large arc
of flexion–extension movement while at the same time
permitting almost 180 degrees of rotation of the forearm.
The functional implications of this unique system are but
minimally illustrated by the use of a screwdriver or the act
of passing a curved surgical needle, which requires repetitive and alternating pronation and supination of the forearm in association with a stable elbow and wrist joint. The
radius, so aptly named, rotates around the long axis of the
ulna while the stability of the two bones is maintained by
their bony architecture, the interosseous membrane, and
proximal and distal ligamentous and muscular support.
The uniqueness of the forearm is further illustrated by the
relative ease of surgical exposure of the ulna, which is subcutaneous throughout its length, compared with the
radius, which is surrounded by muscles and nerves that
make surgical approaches to this bone significantly more
complex.
The functional and purposeful movement of this bony
scaffold is effected by means of two forearm muscle groups,
the dorsolateral and the ventromedial, and also by the
biceps brachii, which is an elbow flexor as well as a primary
supinator of the forearm.
FOREARM MUSCLE GROUPS
Dorsolateral
The dorsolateral group arises from the lateral epicondyle of
the humerus and extends to the dorsal aspect of the forearm, wrist, and hand. When the forearm is in neutral, isolated contraction of the dorsolateral group tends to supinate
the forearm. This is especially true of the brachioradialis,
which inserts on the radial styloid and was formerly known
as the supinator longus.
1
Ventromedial
Similarly, the ventromedial group arises from the medial
epicondyle and extends to the ventral aspect of the forearm,
wrist, and hand. These two groups sometimes are described
as the flexor-pronator and extensor-supinator groups because
of their combined functional roles in movement of the wrist
and forearm. The ventromedial group assists in pronation
of the forearm.
Pronation/Supination
The respective actions of pronation and supination are
facilitated by the oblique orientation and pull of the two
muscle groups. Although the biceps and supinator are recognized as the major supinators of the forearm, just as the
pronator teres (PT) and pronator quadratus (PQ) are recognized as the major pronators of the forearm, the fact that
other muscle groups also may participate in a given motion
illustrates the complex nature of movement in the upper
extremity. This complexity is further illustrated by the fact
that these two muscle groups that originate from the
humerus also may act as flexors of the elbow.
DESCRIPTIVE ANATOMY OF THE FLEXOR
FOREARM
Contents
Bones: The forearm contains the radius and ulna.
Blood Vessels: The forearm contains the brachial, radial,
ulnar, and interosseous arteries and superficial veins.
Nerves: The forearm contains the median, ulnar, and
radial nerves and cutaneous nerves.
Interosseous Membrane: The interosseous membrane
(IOM) spans the space between the radius and ulna.
Muscles: The forearm contains the primary flexors and
extensors of the wrist and fingers, the extrinsic finger and
thumb flexors and extensors, and the pronators and supinators of the forearm.
External Landmarks
Important landmarks for the volar forearm include the
medial and lateral epicondyle, the biceps tendon, the
8
“mobile wad of three” [brachioradialis, extensor carpi radialis longus (ECRL), and extensor carpi radialis brevis
(ECRB)] (1), the flexor-pronator group, the flexor carpi
ulnaris (FCU) tendon, the flexor carpi radialis (FCR) tendon, the pisiform bone, the radial styloid, and, if present,
the palmaris longus (PL) tendon (Fig. 8.1).
Skeletal Anatomy
Although the radius and ulna represent the major osseous
components of the forearm, the distal humerus also must be
included because of the important relationships between
these three bones (Fig. 8.2).
8
408 Regional Anatomy
Distal Humerus
The distal humerus is a modified condyle that is wider than
it is thick and has articular and nonarticular parts.
Articular Components
The lateral and convex capitulum is less than half a sphere
that has anterior and inferior but not posterior articular surfaces. It articulates with the discoid radial head that abuts the
inferior surface in full extension. The trochlea, the medial
and pulley-shaped humeral surface, articulates with the
trochlear notch of the proximal ulna. The trochlear notch has
a mid-articular ridge that extends from front to back and corresponds to a groove in the trochlea. The articular surface of
FIGURE 8.1. A, B: Flexor aspect of the right forearm, showing prominent landmarks.
A B
the trochlea is anterior, inferior, and posterior and is separated from the capitellum by a shallow groove (2).
Nonarticular Components
The nonarticular medial and lateral epicondyles and their
respective supracondylar ridges are sites of origin for the
flexor-pronator and extensor-supinator muscles, respectively.
The smooth posterior surface of the medial epicondyle is traversed by the ulnar nerve through a groove before its entrance
into the FCU. The radial and coronoid fossae provide space
for the radial head and coronoid process of the ulna to
accommodate flexion of the elbow without impingement.
8.1 Flexor Forearm 409
FIGURE 8.2. Radius and ulna. Note the bony landmarks
and changes in cross-sectional morphology from proximal to distal. Note the radial bow that allows rotation
of the radius about the long axis of the ulna without
impingement.
Posteriorly, the olecranon fossa accommodates the apex of the
olecranon process when the elbow is extended. A line in the
coronal plane drawn from the most external aspects of the
medial to the lateral epicondyle is called the interepicondylar
line or Hueter’s line, and is a useful landmark for identification of the lateral antebrachial cutaneous nerve of the forearm
and the site of division of the radial nerve into motor and
sensory components (2,3).
Radius
The radius has expanded proximal and distal ends. The
shaft is convex laterally and concave anteriorly in the distal
one-half, a probable requirement of impingement-free
motion from full supination to full pronation. This biplane
bowing must be maintained in the treatment of fractures to
prevent loss of pronation or supination. The radial head is
discoid and its proximal surface is a shallow cup to accommodate the adjacent capitulum. The disc is widest medially,
where it articulates with the ulna in the radial notch (2).
The neck is positioned between the head and the medially
placed biceps tuberosity. A prominent anterior oblique line
extends from the tuberosity to the junction of the proximal
and middle thirds of the radius and is the site of origin of
the flexor digitorum superficialis (FDS). The middle third
of the radial shaft is triangular, in contrast to the proximal
third, which is more or less round, and the distal third,
which is a broad, four-sided oval. The radial styloid on the
lateral surface is a prominent landmark and projects beyond
that of the ulna. The complex distal articulation of the
radius and ulna is presented in Chapter 9.
Ulna
The proximal end of the ulna is a large hook and the ulna
progressively diminishes in size from its larger proximal end
to its distal end, which expands into a small, rounded head
and styloid process. The head of the distal ulna is visible in
pronation and its convex articular surface fits into the radial
ulnar notch. The styloid process of the ulna is a short,
round posterolateral projection of the end of the ulna. The
trochlear or semilunar notch is bounded proximally by the
apex of the olecranon process and distally by the coronoid
process. Just distal to the coronoid process is the site of
insertion of the brachialis muscle, the ulnar tuberosity. The
shaft is triangular in cross-section, in contrast to the
rounded distal end and the quadrangular proximal end.
Interosseous Membrane
The radius and ulna are joined by a syndesmosis called the
interosseous membrane (Fig. 8.3).
Gross Anatomy
The IOM begins proximally, approximately 2 to 3 cm distal to the radial tuberosity, and spans the space between the
radius and ulna from this area down to the distal articulation. The proximal opening allows passage of the posterior
interosseous artery, and distally an opening is present to
allow passage of the anterior interosseous artery to the back
of the forearm (2). The oblique cord is a small, inconstant
flat band on the deep head of the supinator that extends
from the lateral side of the ulnar tuberosity to the radius a
short distance distal to its tuberosity (2). The IOM provides
attachments for the flexor pollicis longus (FPL) laterally
and the flexor digitorum profundus (FDP) medially on its
volar surface, and dorsally to the supinator, abductor pollicis longus (APL), extensor pollicis longus (EPL), extensor
pollicis brevis (EPB), and extensor indicis proprius (EIP).
The maximum thickness of 1 mm is noted 1 cm proximal
to the midpoint of the radius (4). This area of relative thickness is called the central band (CB) and is three to four times
as thick as the IOM proximally and distally. The width of
this band is approximately 1 cm as measured perpendicular
to its fibers. In the metaphyseal region of the distal forearm,
the IOM is dorsal to accommodate the deep head of the PQ
(5). The fibers of the IOM originate on the radius (proximal) and insert on the ulna (distal) (6). Skahen et al.
described the IOM as a complex composed of a membranous portion, a CB, accessory bands, and a proximal
interosseous band (6). The average length of the radial origin is 10.6 cm (range, 6 to 19.5 cm) and that of the ulnar
insertion, 10.6 cm (range, 8 to 13.5 cm). The CB has an
average width of 1.1 cm (range, 0.5 to 2.5 cm) measured
perpendicular to its fibers. The average site of origin is 7.7
cm (range, 6.5 to 8.7 cm) distal to the articular surface of
the radial head, and the insertion on the ulna is 13.7 cm
(range, 10 to 18.5 cm) distal to the tip of the olecranon.
The average fiber angle is 21 degrees (range, 11 to 38
degrees) to the longitudinal axis of the ulna. Accessory
bands were variable as to occurrence and number and were
less substantial than the CB, but fiber orientation was similar to the CB. The proximal interosseous band was more
likely (17 of 20 specimens) to be present and, when present,
was found exclusively on the proximal dorsal surface of the
forearm. Its fibers are oriented nearly perpendicular to the
CB. The radial attachment is 7.7 cm (range, 6.7 to 8.7 cm)
from the articular surface of the radial head and the ulnar
attachment is an average of 9.6 cm (range, 7.7 to 11.8 cm)
distal to the tip of the olecranon. The width of the proximal
interosseous band is 0.4 cm as measured perpendicular to
its fibers (range, 0.2 to 0.8 cm).
Histology, Ultrastructure, and Biochemical
Composition
Based on histologic sections, the IOM appears to be composed mostly of collagen with very little elastin (7). The collagen fiber bundles are organized in a parallel arrangement
surrounded by an elastin covering. The collagen bundles
provide the tensile strength of the IOM and the elastin
sheath provides support and some elasticity. Electron
microscopy of portions of the CB revealed parallel collagen
410 Regional Anatomy
fibers with a varying distribution of fibril diameters. The
biochemical composition, assessed using hydroxyproline
assay, yielded an average collagen content of 93.2% ± 7.1%.
Based on these findings of large amounts of collagen and an
ordered structure, McGinley and Kozin proposed that the
IOM functions similar to a tendon (7).
Function and Biomechanics
The CB of the IOM acts as a ligament and probably tethers the radius longitudinally to prevent proximal migration
of the radius after radial head excision (4). Skahen et al.
agreed with Hotchkiss et al., who found that the CB was
responsible for 71% of the longitudinal stiffness of the
IOM after radial head excision (4,6). Rabinowitz et al. have
identified the mid-portion of the IOM as the most crucial
structural subdivision (8). They noted that although the
intact radius has been identified as the primary restraint to
proximal radial migration, both the triangular fibrocartilage
complex (TFCC) and the IOM have been identified as
important secondary forearm stabilizers. Based on their biomechanical study and the observation that some patients
gradually acquire wrist symptoms after radial head excision,
it has been postulated that with subsequent dynamic physiologic loading stretching of the IOM and TFCC may
8.1 Flexor Forearm 411
FIGURE 8.3. The interosseous membrane (IOM). In addition to providing attachment areas for
several forearm muscles, the IOM, and especially the central band, is a secondary forearm stabilizer and load transfer structure (see text).
occur, allowing further proximal radial migration. This
study found that after radial head excision, if either the
TFCC or IOM alone were disrupted, little additional proximal migration would occur. However, if both the mid-portion of the IOM and the TFCC were incompetent, further
proximal radial migration would occur. They noted that
proximal migration of the radius greater than 6 to 7 mm
while under axial load implied disruption of both the
TFCC and the mid-portion of the IOM (8). Maximum
strain in the CB of the intact IOM occurs in neutral forearm rotation. Absence of the radial head is associated with
increased strain throughout the arc of forearm rotation, and
maximum strain is noted in pronation (6). The interactive
dynamic anatomy of the IOM, radius, and ulna may be
summarized as follows: (a) normally, the IOM transfers
load from the distal radius to the proximal ulna, as manifested by decreasing loads in the radius from distal to proximal and increasing load values in the ulna from distal to
proximal, whereas after IOM division the proximal and distal load values become equal (9); (b) normally, the radial
head serves as the primary restraint to proximal migration
of the radius; (c) the CB and TFCC serve as secondary
restraints when the forearm is loaded; and (d) when the
radial head is absent, the CB and TFCC become the primary restraints as they attempt to resist proximal migration
of the radius by transferring load to the ulna (6,8).
Clinical Significance
The ability of the IOM to transfer load from the radius to
the ulna through fibers that run from the proximal radius
to the distal ulna and exert a proximal pull on the ulna
might explain patterns of injury as seen in both-bone fractures of the forearm, Galeazzi and Monteggia fracture–dislocations, and the Essex-Lopresti injury, which are characterized by a pattern of proximal radius to distal ulna
forearm injury (9).
Both-Bone Fractures. Linking of the radius and ulna by
the obliquely oriented IOM, especially the CB, may explain
the finding that the radial fracture is most often proximal
and the ulnar fracture distal. Synostosis is less common in
this configuration but more common if the ulnar fracture is
proximal. This is said to be due to the fact that in the more
proximal ulnar fracture, the IOM injury is perpendicular
412 Regional Anatomy
FIGURE 8.4. The carrying angle. The carrying angle is most noticeable in supination and extension, and disappears in flexion and pronation.
rather than parallel to the fibers of the IOM. The small vessels that course parallel to these fibers are more likely to be
torn and form a hematoma in the interosseous space, leading to synostosis.
Galeazzi and Monteggia Fracture–Dislocations and
Essex-Lopresti Injury. In a fall on the outstretched hand,
the radius is impacted between the ground and the capitulum. Force transfer (mediated by the IOM) to the proximal
ulna would result in displacement of the ulnar column distally toward the ground and increased tension in the IOM.
The specific injury or lesion produced depends on the site
of force concentration; if proximal to the CB, it may result
in a Monteggia or Essex-Lopresti injury, and if distal, it may
result in a Galeazzi injury (9).
The Carrying Angle
When the forearm is supinated and in full extension, it
deviates laterally by approximately 17 degrees (2). This socalled carrying angle is due to (a) the fact that the medial
trochlear edge is approximately 6 mm longer than its lateral edge; and (b) the matching obliquity of the coronoid’s
superior articular surface, which is not orthogonal to the
ulnar shaft (2). The carrying angle disappears when the
elbow is flexed because of slight spiral orientation of the
ridge in the trochlear notch and the companion groove in
the trochlea, and because the tilt of the humeral and ulnar
articular surfaces is approximately equal (2,10). The carrying angle is masked, if not obliterated, by pronation of the
forearm, which brings the hand into a more functional
position (Fig. 8.4).
ANATOMIC RELATIONSHIPS
For the sake of clarity, the superficial structures on the volar
side of the arm, elbow, and forearm are included in this section on the volar forearm.
Veins
Although the dorsal veins of the hand and wrist are more
prominent than the volar veins, the opposite is true on the
volar aspect of the forearm, elbow, and arm. Three veins are
prominent in the forearm: the laterally placed cephalic vein,
the more centrally placed median vein of the forearm, and
the medially located basilic vein. In the region of the antecubital fossa, the median vein of the forearm usually joins
the cephalic, which continues into the arm on its anterolateral aspect near the interval of the biceps and brachialis
muscles, the so-called biceps groove. Sometimes, however,
the median vein of the forearm may join the basilic vein,
which continues into the arm along the medial biceps
groove. In the proximal forearm, a branch from the cephalic
or the median vein of the forearm, depending on the particular configuration, called the median cubital vein, courses
proximally and medially to join the basilic vein on the
medial aspect of the arm. The confluence of these veins
often, but not always, forms an “M”-shaped pattern (Fig.
8.5A). The median cubital vein often is the site for
venipuncture because of its size and prominence. This vein
also crosses over the biceps tendon in the region of the
elbow flexion crease. These superficial veins are connected
to the deeper venous system by communicating veins that
may require ligation during surgery. Such a communicating
branch often is found near the junction of the cephalic and
median cubital veins. Much variation can occur in the size
and orientation of veins throughout the upper extremity,
and the preceding discussion is intended to depict some
common patterns or configurations. These veins are discussed in this section because they often must be retracted
or ligated in surgical approaches in the upper extremity, and
sometimes may represent landmarks for location of other
superficial structures, such as the lateral antebrachial cutaneous nerve of the forearm.
Cutaneous Nerves
Medial Antebrachial Cutaneous Nerve
The medial antebrachial cutaneous nerve (MACN) originates in the axilla between the axillary artery and vein and
courses down the arm medial to the brachial artery (see Fig.
8.5B). Based on a study of 50 cadavers, it was found to arise
from the medial cord in 78% and from the lower cord in
22% (11). In the distal arm, the MACN is adjacent to the
basilic vein and pierces the deep fascia in the middle or distal arm to become subcutaneous. In the distal arm, the
MACN divides into posterior and anterior branches at an
average of 14.5 cm proximal to the medial epicondyle; these
branches continue with the basilic vein for a variable distance before the posterior branch turns ulnarward and posteriorly to cross over the medial intermuscular septum and
the ulnar nerve (11,12). Ninety percent of the posterior
branches cross at or proximal to the medial epicondyle, and
the number of branches ranges from one to four. The anterior branch sends cutaneous branches to the anterior arm
distally, antecubital fossa, and proximal anterior forearm.
These branches are variable in number (two to five) and
location. Most of these cutaneous branches arise between 6
cm proximal and 5 cm distal to the elbow. The anterior
branch crosses the elbow anteriorly between the medial epicondyle and biceps tendon, usually lying 2 to 3 cm anterolateral to the epicondyle. The main anterior branch continues distally superficial to the FCU to within an average of
5.6 cm from the wrist flexion crease. The cutaneous distribution of the MACN in the forearm is the antecubital fossa,
posterior olecranon region, and the medial half of the flexor
8.1 Flexor Forearm 413
side of the forearm, as well as proximal portions of the
extensor surface of the forearm (11,12).
Clinical Significance
This nerve and its branches are at risk during surgical exposures in this area of the forearm and should be identified
and preserved. The use of the MACN as a nerve graft is discussed in Chapter 6.
Lateral Antebrachial Cutaneous Nerve of the
Forearm
The lateral antebrachial cutaneous nerve of the forearm (the
cutaneous branch of the musculocutaneous nerve) enters
the antecubital fossa between the biceps and brachialis muscles (see Fig. 8.5B). It emerges from beneath the lateral
aspect of the biceps tendon at the level of the interepi414 Regional Anatomy
FIGURE 8.5. A: Veins of the arm and forearm. In the forearm, the cephalic and basilic veins flank
the median antebrachial vein in the forearm. Note the median cubital vein in the region of the
antecubital fossa.
A
condylar line (a line drawn between the medial and lateral
epicondyles) (13). It then becomes progressively more
superficial as it continues distally beneath the cephalic vein.
Because of the variability in the configuration of the veins
in this area, its relationship with the biceps tendon is a more
reliable landmark.
Clinical Significance
The lateral antebrachial cutaneous nerve has been found to
be a highly suitable autograft donor for digital nerve grafts,
and the resultant sensory loss is not considered to be clinically significant (14). As it exits from between the biceps
and brachialis in the distal arm, it is deep in the lateral
8.1 Flexor Forearm 415
FIGURE 8.5. (continued) B: Cutaneous nerves of the arm and forearm.
B
aspect of the arm and should not be confused with the adjacent radial nerve, which is in the interval between the
brachialis and the brachioradialis.
Volar Forearm Muscle Groups
There are three groups or layers of flexor forearm muscles:
superficial, intermediate, and deep. The muscular components of the volar forearm are:
Superficial
n Brachioradialis
n Pronator teres
n Flexor carpi radialis
n Palmaris longus
n Flexor carpi ulnaris
Intermediate
n Flexor digitorum superficialis
Deep
n Flexor pollicis longus
n Flexor digitorum profundus
n Pronator quadratus
n Supinator
Superficial Group
Brachioradialis
The unipennate brachioradialis is the most superficial muscle on the radial border of the forearm and arises from the
proximal two-thirds of the supracondylar ridge and from
the anterior surface of the lateral intermuscular septum
(Fig. 8.6). The muscle fibers end in the mid-forearm in a
flat tendon that continues distally to insert over a large area
on the radial styloid. The brachioradialis is an elbow flexor
and acts most effectively in this capacity when the forearm
is in mid-pronation. It is easily demonstrated when the
semipronated forearm is flexed against resistance. The brachioradialis is minimally active in slow, easy flexions or with
the forearm in supination, but is very active in both flexion
and extension when movement is rapid and is a stabilizing
force during rapid movements of the elbow (15).
Pronator Teres
The PT has two heads of origin: the humeral, the larger and
more superficial of the two, arises just proximal to the medial
epicondyle from the common tendon of origin of the flexor
muscles, and from the intermuscular septum between it and
the FCR; the ulnar head arises from the medial side of the
coronoid process of the ulna, distal to the attachment of the
FDS (see Fig. 8.6). The median nerve usually enters the forearm between these two heads. The muscle ends in a flat tendon that inserts on the middle third of the radius at the “summit” of its lateral bow. The PT forms the medial or ulnar side
of the antecubital fossa and the brachioradialis forms the lateral or radial side. The PT acts as a pronator of the forearm
in rapid or forceful pronation, and because of its location at
the medial epicondyle it also is an elbow flexor.
Flexor Carpi Radialis
The FCR lies ulnar to the PT and arises from the medial
epicondyle via the common flexor tendon, the antebrachial
fascia, and adjacent intermuscular septa (see Fig. 8.6). Its
fusiform belly ends in a tendon at the middle third of the
forearm. This tendon passes through a groove in the trapezium and inserts on the palmar surface of the base of the
index metacarpal, with an additional slip of attachment to
the middle finger metacarpal. In the distal aspect of the
arm, the radial artery lies radial to the FCR tendon. The
FCR is a wrist flexor and, in conjunction with the radial
wrist extensors, may aid in radial deviation of the hand.
Palmaris Longus
The PL is a fusiform muscle ulnar to the FCR that arises
from the medial epicondyle by the common flexor tendon
as well as adjacent intermuscular septa and deep fascia (see
Fig. 8.6). Its configuration and incidence are variable, and
it usually ends as a long tendon that inserts into the palmar
fascia. The PL may be an accessory wrist flexor.
Flexor Carpi Ulnaris
The FCU is the most ulnar of the superficial flexor group
and arises from two heads: the humeral and ulnar (see Fig.
8.6). The small humeral head arises from the medial epicondyle by the common tendon and the ulnar head arises
from the medial margin of the olecranon and the proximal
two-thirds of the posterior border of the ulna by an aponeurosis shared with the extensor carpi ulnaris (ECU) and FDP
and from the intermuscular septum between it and the
FDS. The two heads are joined by a tendinous arch beneath
which the ulnar nerve and the posterior ulnar recurrent
artery pass. This arch, may be a source of compression of
the ulnar nerve.
A thick tendon forms radially in the mid-aspect of the
muscle and continues distally to attach to the pisiform bone
and then to the hamate and base of the little finger
metacarpal by means of the pisohamate and pisometacarpal
ligaments. Muscle fibers continue nearly to the level of the
pisiform. The FCU is a major wrist flexor and, along with
the ECU, ulnar deviates the hand.
Intermediate Group
Flexor Digitorum Superficialis
The superficial portion (middle and ring fingers) of the
FDS arises from the medial epicondyle, the proximal ulna,
and the proximal radius (Fig. 8.7). The deep portion (index
and little fingers) of the FDS arises from the medial epicondyle only. The deep portion of the FDS is trigastric with
a single proximal belly and two distal bellies that give tendons to the index and little finger. The proximal and distal
416 Regional Anatomy
8.1 Flexor Forearm 417
FIGURE 8.6. The superficial layer of the forearm flexor muscles in longitudinal and cross-sectional views.
418 Regional Anatomy
FIGURE 8.7. The intermediate layer of forearm flexor muscles. Note the relationship of the two
layers of the superficialis and the trigastric superficialis to the index and little fingers.
bellies of the deep portion are joined in the mid-aspect of
the forearm by a prominent fibrous tissue linkage (Fig. 8.8).
After leaving the antecubital fossa, the median nerve
becomes a “satellite” of the deep part of the FDS (1). It lies
first to the radial side of the proximal belly 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 muscle bellies
and tendons of the middle and index fingers. Thus, the
median nerve stays with the FDS when the FDS and FDP
muscles are separated, as in the McConnell approach (see
section on Surgical Exposures, later). The median nerve can
be relied on to exit consistently from beneath the radial side
of the muscle belly of the middle finger in the distal forearm. This is a useful reference point in identifying and
locating this structure when exploring wounds about the
wrist. A fibrous tissue arch is present in the proximal margin of the superficial portion of the FDS, and as the median
nerve and anterior interosseous nerve (AIN) course beneath
this arch, they may be subject to compression (Fig. 8.9).
8.1 Flexor Forearm 419
FIGURE 8.8. The trigastric flexor digitorum superficialis (FDS) to the index and little fingers.
Fresh cadaver dissection of the right forearm viewed from the ulnar-flexor aspect. Note the
ulnar nerve in the near foreground, the 9satellite9 median nerve coursing between Gantzer’s
muscle (accessory flexor pollicis longus), and the trigastric FDS to the index and little finger.
Note also the fibrous tissue linkage between the proximal and distal muscle bellies of this FDS.
FIGURE 8.9. Fibrous tissue arch of the superficial component of the flexor digitorum superficialis
(FDS). Fresh cadaver dissection of the proximal and flexor aspect of the right forearm (distal is to the
left). Note the median nerve and the anterior interosseous nerve coursing beneath the fibrous edge
of the FDS. A yellow marker is beneath the median nerve proximally and distally. A red marker is
beneath the collapsed brachial artery proximally; a red vessel loop is around the recurrent branch of
the radial artery; both the ulnar and radial arteries are immediately ulnar to this vessel loop.
FIGURE 8.10. The deep layer of the forearm flexor muscles. Note the side-by-side configuration
of the flexor pollicis longus (FPL) and flexor digitorum superficialis tendons. Note also the accessory FPL (Gantzer’s muscle).
420
The FDS inserts on the base of the proximal phalanges and
is a flexor of all the joints it passes over, including the proximal interphalangeal (PIP), metacarpophalangeal (MCP),
and wrist joints. The fact that the FDS has independent
muscle slips to all four fingers accounts for its ability to flex
one PIP joint at a time (2).
Deep Group
Flexor Pollicis Longus
The FPL arises from the grooved flexor surface of the radius
in an oblique line of origin beginning just distal to the
biceps tuberosity to near the proximal margin of the PQ
(Fig. 8.10). Its proximal oblique origin is opposite the insertion of the supinator. It also has origins from the adjacent
IOM and frequently by a variable slip from the lateral or,
more rarely, medial border of the coronoid process, or from
the medial epicondyle of the humerus (2). Its tendon arises
from the ulnar side of the muscle belly, courses through the
carpal canal, and then passes between the opponens pollicis
and the oblique head of the adductor pollicis to insert on
the palmar base of the distal phalanx of the thumb. The
anterior interosseous neurovascular bundle descends on the
IOM between the FPL and the FDP. The FPL is the deepest and most radial of the flexor tendons.
Flexor Digitorum Profundus
The FDP arises deep to the FDS from the anterior and
medial proximal two-thirds of the ulna. Its origin begins
near the attachment of the brachialis and ends just proximal
to the proximal margin of the PQ (see Fig. 8.10). It also has
origins from a depression on the medial side of the coronoid process, from the proximal two-thirds of the posterior
ulnar border by an aponeurosis shared with the flexor and
ECU, and from the ulnar half of the IOM. The four FDP
tendons lie in a single layer, in contrast to the two layers of
the FDS. The FDP tendons insert on the distal phalanges.
The portion of the muscle directed to the index finger usually is distinct throughout its course, which accounts for its
often independent action compared with the other fingers.
Pronator Quadratus
The PQ, as its name implies, is a quadrilateral muscle that
spans the flexor aspect of the distal ulna and radius (Fig.
8.11). It has two heads: the superficial, which arises from a
short tendon on the dorsoulnar border of the ulna and
inserts on a broad, flat facet on the volar surface of the
radius; and the deep, which also arises from the ulna, but
from a slightly less distinct tendon of origin and slightly
more volar than the superficial head. The insertion of the
deep head is to the ulnar border of the distal radius from the
IOM and filling the “axilla” of the distal radioulnar joint
(5). The nerve and blood supply is from the anterior
interosseous bundle, which consistently runs in a plane
deep to the head of the muscle on the IOM. The muscle
bellies are supplied from deep to superficial. Some branches
run in a longitudinal direction between the two heads after
piercing the deep head before entering the superficial.
Function. Electromyography has clearly shown that the
PQ is the main pronator of the forearm, with the PT functioning only in maximal pronation and resisted pronation.
These studies also revealed that the deep head consistently
functioned during supination and grip (5). These findings
confirm the concept of Johnson and Shrewsbury that the
deep head is a significant factor in preventing distal radioulnar joint diastasis during forearm rotation and grip (16).
Clinical Significance. Operative procedures have been
designed that use the PQ as a muscle or vascularized osseous
graft, as well as as a transfer to stabilize the distal radioulnar
joint or the distal ulna after partial resection (17,18).
Supinator
Although the supinator is considered to be a deep extensor
of the forearm, it is included here because it often is
encountered in approaches to the anterior or flexor aspect
of the forearm (Fig. 8.12). 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 PT. Its oblique insertion
parallels the origin of the FPL. The posterior interosseous
8.1 Flexor Forearm 421
FIGURE 8.11. The deep layer of the forearm muscles, pronator
quadratus. Note the two heads of this quadrilateral muscle and
the anterior interosseous nerve and vessels that supply this muscle from deep to superficial.
nerve (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.
“Mobile Wad of Three”
Henry found it useful to identify the brachioradialis,
ECRL, and ECRB as the “mobile wad of three” on the
dorsolateral side of the forearm (1). Although only the
brachioradialis in this group of muscles is considered to be
a flexor or volar muscle, it is part of this “mobile wad,”
which is an important landmark. These muscles can be
grasped between the examiner’s thumb and index finger
just distal to the lateral epicondyle, and when moved to
and fro, provide a useful guide to the deeper structures in
the forearm (Fig. 8.13). Henry also used a “manual
mnemonic” to aid identification and location of the volar
and medial superficial muscle group arising from the
medial epicondyle, which includes the PT, FCR, PL, and
FCU (1). This mnemonic is illustrated in Figure 8.14.
Identification of the interval between the laterally situated
mobile wad of three and the medial superficial flexors permits safe access to the deeper structures in the antecubital
fossa, including the radial, median, and ulnar nerves and
the vascular structures.
Antecubital Fossa
Landmarks/Boundaries
Entry into this area is facilitated by identification of the
biceps tendon, which bisects the base of the triangular antecubital fossa. Using the biceps tendon as a guide, the lateral
and medial boundaries of the antecubital fossa are noted to
be formed by the brachioradialis and the PT, respectively
(Fig. 8.15).
Zones of the Antecubital Fossa
The biceps tendon is an important landmark or partition
that divides the antecubital fossa into a relatively “safe” lat422 Regional Anatomy
FIGURE 8.12. The deep layer of the forearm muscles, supinator.
Note the deep and superficial heads that wrap around the proximal one-third of the radius. The posterior interosseous nerve
(PIN) traverses the supinator between these two heads; note the
proximal branch to the deep head and the entrance of the main
stem of the PIN beneath the superficial head and its arcade of
Frohse.
FIGURE 8.13. The “mobile wad of three.” The brachioradialis
(BR), extensor carpi radialis longus (ECRL), and extensor carpi
radialis brevis (ECRB) form this mobile wad, which is an important guide to surgical approaches in this area.
eral zone and a more hazardous medial zone. The medial
zone contains the brachial, radial, and ulnar arteries and
their branches as well as the median nerve and its branches.
It also is helpful to remember that most of the branches
from the median nerve arise from its medial side (1).
Contents of the Antecubital Fossa
Reflection of the skin envelope and the superficial fascia
reveals the prominent biceps tendon and its aponeurosis,
called the lacertus fibrosus, coursing from the biceps tendon
to fan out medially and distally over the flexor-pronator
muscles. Incision of this aponeurosis allows a deeper view
into the antecubital fossa, where it is noted that the brachial
artery is immediately beneath the lacertus fibrosus. From
lateral to medial, the structures are the brachioradialis, the
biceps tendon, the brachial artery with its venae comitantes,
the median nerve, and the PT.
Neurovascular Structures
Arteries in the Antecubital Fossa
Just distal to the lacertus fibrosus, the brachial artery divides
into the radial and ulnar arteries (Fig. 8.16).
Radial Artery Branches
Multiple arterial branches arise on the lateral side of the
radial artery, the largest of which is the radial recurrent
artery (see Fig. 8.16). 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 (1). 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 making up 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, 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).
Ulnar Artery Branches
Ulnar artery branches include the medially situated anterior
and posterior ulnar recurrent arteries and the laterally
placed common interosseous artery, which divides into the
anterior and posterior interosseous arteries (see Fig. 8.16).
Identification of the Radial and Ulnar Arteries in the
Antecubital Fossa
The radial artery, a continuation of and in the same plane
as the brachial artery, is easily identified in the interval
between the brachioradialis and the FCR and on top of the
PT. In contrast to the more superficial radial artery, the
8.1 Flexor Forearm 423
FIGURE 8.14. Henry’s 9manual mnemonic9: The thumb through
the ring finger of the examiner’s hand, when laid on the forearm
as depicted, correspond to the four underlying superficial muscles.
ulnar artery, immediately after its origin from the brachial
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. What must be
appreciated when exposing the radial and ulnar arteries in
the proximal forearm is that the radial artery, an easily identified extension of the brachial artery, is more superficial
than the deeply situated ulnar artery. The usual graphic
depiction of the ulnar artery indicates that it is medial to
the radial artery (it is) and in the same plane (it is not).
Unfortunately, the limitations of two-dimensional graphics
fail to characterize its true course, which is to descend
quickly into the depths of the antecubital fossa, which it
exits on the medial side beneath the deep head of the PT.
Major Forearm Nerves in the Antecubital
Fossa
The three major nerves leave the arm and enter the forearm
by coursing through or between a muscle belly: the ulnar
nerve through the two heads of the FCU, the median
between the two heads of the PT, and the radial (but only
the motor branch) through the supinator. Only the median
and radial nerves pass through the antecubital fossa (Fig.
8.17).
Identification of the Median and Radial Nerves in the
Antecubital Fossa
Identification of the median nerve in the antecubital fossa
usually is not a problem because it is on the same plane and
just medial to the brachial artery. However, identification of
the radial nerve is not as easy. The key to finding this nerve
is to identify the brachioradialis and the adjacent brachialis.
The brachialis lies just beneath the biceps, and it is in the
interval between the brachioradialis and the brachialis that
the radial nerve is found (1). Gentle and blunt separation of
these two muscle bellies reveals the radial nerve. The surgeon must not misidentify the musculocutaneous nerve,
which exits nearby between the lateral margins of the biceps
and brachialis muscle bellies, for the radial nerve.
424 Regional Anatomy
FIGURE 8.15. The antecubital fossa/landmarks and
zones. The biceps tendon divides the antecubital fossa
into medial and lateral zones bounded by the pronator
teres (PT) and brachioradialis (BR), respectively.
8.1 Flexor Forearm 425
FIGURE 8.16. A: Arterial branches in the
antecubital fossa. Note the division of
the brachial artery into radial and ulnar
arteries and their multiple branches. B:
Fresh cadaver dissection of this region.
The probe in the lower foreground is
tenting up the ulnar artery; the green
vessel loop is around the radial artery;
the green marker adjacent to the midfield retractor is beneath the radial recurrent artery; the green marker to the left
(distal) is beneath the radial artery; the
remaining vessels are either veins or
small arteries from the adjacent muscles.
Clinical significance: there are multiple
vessels in this region in addition to the
radial recurrent vessel.
A
B
Radial Nerve
Site of Division into Motor and Sensory Branches.
Based on a study of 50 fresh cadaver upper extremities, Fuss
and Wurzl noted that the radial nerve divides into motor
and sensory branches near the lateral epicondyle at a level
that may range from 2.5 cm above or 3 cm below Hueter’s
line (a line drawn in the coronal plane between the tips of
the medial and lateral epicondyles) (3) (Fig. 8.18).
Radial Nerve Branches Proximal to the Division. Radial
nerve branches proximal to the division into motor and
sensory components (excluding the nerve to the anconeus,
which is even more proximal) were one to three branches to
the brachialis muscle that were 3 to 9 cm above Hueter’s
line; one to three branches to the brachioradialis that arose
2 cm below to 7.5 cm above Hueter’s line, but in most
instances arose 3 to 6 cm above Hueter’s line; and one to
three branches to the ECRL 2.5 below to 6 cm above
Hueter’s line, but in most instances these branches arose 0.5
to 4.5 cm above Hueter’s line (3) (see Fig. 8.18).
Fuss and Wurzl concluded that there is great variability
in the both the number and level of nerve branches to these
three muscles, and therefore it is impossible to assume a
strict sequence of muscle innervation, which may be of clinical importance when trying to determine the level or site of
nerve injury or patterns of muscular weakness after nerve
injury (3).
Radial Nerve Branching and Muscle Innervation
Sequence. These findings are compared with the study of
Abrams et al., who dissected the radial nerve motor
branches in 20 upper extremities and measured the shortest
and longest distances along the main radial trunk of the various radial nerve branches with respect to a point 10 cm
proximal to the medial epicondyle, the mean number of
branches, and innervation order or sequence (19). Their
findings are summarized in Tables 8.1 and 8.2. The only
nearly constant (19 of 20 specimens) consecutive order of
innervation was ECRL, supinator, ECRB. The ECRL
branch origin was variable; in 9 of 20 (45%), it originated
from the PIN; in 6 of 20 (30%), it originated from the
radial nerve as one branch of a trifurcation (the other
branches were the PIN and sensory branch of the radial
nerve). The ECRB branch came from the sensory branch of
the radial nerve in 5 of 20 (25%). Abrams et al. noted that
the innervation order is quite variable. Nonvariable findings
426 Regional Anatomy
FIGURE 8.17. Entrance of the three major nerves to the forearm. These nerves leave the arm and
enter the forearm by coursing through or between a muscle belly: the ulnar nerve through the
two heads of the flexor carpi ulnaris, the median between the two heads of the pronator teres,
and the radial (but only the motor branch) through the supinator. Only the median and radial
nerves pass through the antecubital fossa.
included the fact that the extensor digitorum communis
(EDC) always was innervated before the EIP, APL, and
EPL, and almost always before the extensor digiti minimi.
The extensor digiti minimi was innervated before the EIP,
and the APL before the EPB. In 19 of 20 specimens, the
APL was innervated before the EPL. Regarding the question of variation in branch number, Abrams et al. found
that regression analysis demonstrated a positive nonlinear
correlation between both muscle mass and branch number
and physiologic cross-sectional area and branch number,
but no correlation between fiber length and branch number. The muscle with the highest branch number was the
EDC, and Abrams et al. stated that this might be a mechanism for regional muscle control unique to the EDC, which
has multiple, independently functioning tendon slips originating from a common muscle belly.
Origin of Extensor Carpi Radialis Brevis Branch. In a
study of 111 limbs regarding the origin of the motor
branch of the ECRB, Colborn et al. found that the most
common origin (56.7%) was from the PIN, followed by
31.5% from the sensory branch and 11.7% from the
8.1 Flexor Forearm 427
FIGURE 8.18. Division of the radial nerve into motor and sensory components. The interepicondylar line (Heuter’s line) is a useful landmark to begin a search for this division because the
nerve divides in a zone 2.5 cm above or 3 cm below this line.
region of the bifurcation of the radial nerve (20). In contrast to the one to three nerve branches that innervate the
brachialis, brachioradialis, and ECRL, Colborn et al.
found that the ECRB has only one nerve branch. This
nerve branch was found to arise within 1 cm of the distal
edge of the humeroradial joint and to pass distally approximately 3.5 cm before entering the ECRB muscle (20).
Regardless of its origin, the nerve to the ECRB is intimately related to the radial recurrent artery, which may be
used to guide the surgeon to the location of the nerve to
the ECRB (20). The finding of a single nerve branch to the
ECRB is in contrast to the findings of Abrams et al., who
428 Regional Anatomy
TABLE 8.1. MEAN DISTANCESa AND NUMBER OF RADIAL NERVE BRANCHES
Shortest Distance Longest Distance Mean Number
Muscles (mm/SD) (mm/SD) (Branches/SD)
BR 97.2/15.5 112.6/12.3 2.9/1.1
ECRL 117.4/11.5 132.6/13.9 3.8/1.4
SUP 157.3/10.5 172.8/13.8 3.9/1.4
ECRB 182.1/15.9 206.4/16.1 3.4/1.2
EDC 215.8/13.1 237.4/17.7 4.6/1.3
ECU 219.5/16.0 228.2/17.7 2.8/0.8
EDM 229.2/15.8 236.0/17.1 1.6/0.8
APL 235.0/12.5 253.0/17.1 2.7/0.7
EPL 253.3/11.6 278.4/22.4 2.5/1.2
EPB 285.8/21.9 289.0/23.1 1.3/0.5
EIP 299.8/17.3 300.7/18.0 1.1/0.3
aDistances measured along main trunk of radial nerve 10 cm proximal to the lateral humeral condyle.
APL, abductor pollicis longus; BR, brachioradialis; ECRB, extensor carpi radialis brevis; ECRL, extensor
carpi radialis longus; ECU, extensor carpi ulnaris; EDC, extensor digitorum communis; EDM, extensor
digiti minimi; EIP, extensor indicis proprius; EPB, extensor pollicis brevis; EPL, extensor pollicis longus;
SUP, supinator.
From Abrams RA, Ziets RJ, Lieber RL, et al. Anatomy of the radial nerve motor branches in the
forearm. J Hand Surg [Am] 22:232-237, 1997, with permission.
TABLE 8.2. PROXIMAL-TO-DISTAL RADIAL NERVE INNERVATION ORDER OF
20 SPECIMENS
Specimen Number Innervation Order
1 BR, ECRL, SUP, ECRB, EDC, APL, ECU, EPL, EDM, EPB, EIP
2 BC, BR, ECRL, SUP, ECRB, ECU, EDC, EDM, APL, EPB, EPL, EIP
3 BR, ECRL, SUP, ECRB, EDC, ECU, EDM, APL, EPB, EPL, EIP
4 BR, ECRL, SUP, ECRB, ECU, EDC, EDM, APL, EPL, EPB, EIP
5 BR, ECRL, SUP, ECRB, ECU, EDC, EDM, APL, EPB, EPL, EIP
6 BR, ECRL, SUP, ECRB, EDC, ECU, APL, EDM, EPL, EIP, EPB
7 BR, ECRL, SUP, ECRB, ECU, EDM, EDC, APL, EPL, EPB, EIP
8 BR, ECRL, SUP, ECRB, ECU, EDC, EDM, EPL, APL, EIP, EPB
9 BR, ECRL, SUP, ECRB, EDC, ECU, EDM, APL, EPL, EPB, EIP
10 BC, BR, ECRL, SUP, ECRB, EDC, ECU, EDM, APL, EPL, EPB, EIP
11 BC, BR, ECRL, SUP, ECRB, ECU, EDC, APL, EDM, EPL, EPB, EIP
12 BC, ECRL, BR, SUP, ECRB, EDC, ECU, APL, EDM, EPL, EIP, EPB
13 BC, BR, ECRL, SUP, ECRB, ECU, EDC, APL, EDM, EPL, EPB, EIP
14 BC, BR, ECRL, SUP, ECRB, ECU, EDC, EDM, APL, EPL, EPB, EIP
15 BR, BC, ECRL, SUP, ECRB, EDC, EDM, ECU, APL, EPL, EIP, EPB
16 BC, BR, ECRL, SUP, ECRB, EDC, ECU, EDM, APL, EPL, EPB, EIP
17 BC, BR, ECRL, SUP, ECRB, EDC, EDM, ECU, APL, EPL, EPB, EIP
18 BR, BC, ECRL, SUP, ECRB, EDC, ECU, EDM, APL, EPL, EPB, EIP
19 BR, ECRL, SUP, ECRB, EDC, ECU, APL, EDM, EPL, EPB, EIP
20 BR, ECRL, SUP, ECRB, EDC, ECU, APL, EDM, EPL, EIP, EPB
APL, abductor pollicis longus; BR, brachioradialis; ECRB, extensor carpi radialis brevis; ECRL, extensor
carpi radialis longus; ECU, extensor carpi ulnaris; EDC, extensor digitorum communis; EDM, extensor
digiti minimi; EIP, extensor indicis proprius; EPB, extensor pollicis brevis; EPL, extensor pollicis longus;
SUP, supinator; BC, brachialis.
From Abrams RA, Ziets RJ, Lieber RL, et al. Anatomy of the radial nerve motor branches in the
forearm. J Hand Surg [Am] 22:232–237, 1997, with permission.
noted a mean number of branches of 3.4 with a standard
deviation of 1.2 (19). The nerve branch to the ECRB is
superficial to its fascial origin (3).
Distal Course of the Sensory Branch of the Radial Nerve.
The radial nerve sensory branch travels beneath the mobile
wad of three and continues distally under cover of the brachioradialis, exiting dorsally from between the tendons of
the brachioradialis and the ECRL a mean of 9 cm proximal
to the radial styloid (21). Complete absence of the sensory
branch has been noted, with most of the area normally
innervated by the radial nerve supplied by the lateral antebrachial cutaneous nerve (3).
Branches to the Supinator Arising Proximal to the
Arcade of Frohse. Two to five branches (most often two or
three branches) arise 0.5 cm above to 4.5 cm below Hueter’s
line. An anterior group of branches innervates the superficial portion of the supinator and a posterior group (usually
only one branch) innervates the muscle layer deep to the
PIN (3).
Fibrous Arcades Relative to the Posterior Interosseous
Nerve. Extensor Carpi Radialis Brevis Fascial Origin. A fascial layer that constitutes the fascial origin of the ECRB is
consistently present 0.5 to 1 cm proximal to the arcade of
Frohse (3). If tendinous, the proximal border of the fascia
may compress the PIN as well as its branches to the supinator muscle (3). In some cases, this fascial origin may be laterally positioned and not overlie the PIN or the arcade of
Frohse, but in most instances it covers the arcade of Frohse.
The inexperienced surgeon may confuse this arch with the
arcade of Frohse (22) (Fig. 8.19).
Arcade of Frohse. The arcade of Frohse is found 3 to 5 cm
distal to Hueter’s line. The proximal edge of the superficial
8.1 Flexor Forearm 429
FIGURE 8.19. Fibrous tissue arcades relative to the posterior interosseous nerve (PIN). A: Artist’s
depiction of the fascial origin of the extensor carpi radialis brevis (ECRB) and the arcade of
Frohse, potential sites of compression of the PIN.
(continued on next page)
A
430 Regional Anatomy
FIGURE 8.19. (continued) B: Fresh cadaver dissection of the proximal and flexor aspect of the right
forearm. The probe to the right (proximal) is tenting
up the main stem of the radial nerve; the sensory
branch is coursing obliquely to the left; the blue
marker is beneath the fibrous edge of the ECRB and
the green marker beneath the fibrous edge of the
supinator (the arcade of Frohse); the green marker
rests on the PIN as it begins its traverse of the supinator. C: Same dissection as B. The small hook is retracting the fibrous edge of the ECRB; the green marker
remains beneath the arcade of Frohse (fibrous tissue
edge of the superficial component of the supinator).
D: The fibrous edge of the ECRB is tented up on the
retractor; the smaller green marker is beneath the
leading edge of the supinator; fat has been removed
from around the PIN for clarity, and it rests on the
larger green marker; note the fibers of the deep
head of the supinator muscle just radial to the PIN.
B
C
D
layer of the supinator is fibrous, especially the lateral side.
This fibrous tissue edge forms the arcade of Frohse, which
may compress the anterior radial nerve branches to the
supinator as well as the PIN.
Distal Course of the Posterior Interosseous Nerve. After
entering the supinator, the PIN continues distally between
the superficial and deep layers of the supinator on its way
to the dorsal or extensor surface of the forearm, where it
innervates the thumb and finger extensors as well as the
ECU.
Median Nerve
The median nerve exits the antecubital fossa through the
interval between the superficial and deep heads of the PT,
which arise from the medial epicondyle and proximal ulna,
respectively. It then becomes a “satellite” of the deep portion of the FDS, lying first to the radial side of the proximal belly and then to the radial side of the fibrous tissue
linkage between the proximal and distal portions of the
FDS. Below this level, fascia binds the median nerve in a
lateral groove between the muscle bellies and tendons of the
middle and index fingers (Fig. 8.20). The superficial portion of the FDS contains the middle and ring finger flexors
and the deep portion contains the index and little finger
flexors. In the distal forearm, the median nerve exits from
beneath the radial side of the muscle belly of the middle finger superficialis, where it is quite superficial and near to the
PL tendon, and it remains in this superficial position until
it enters the carpal canal.
Palmar Cutaneous Branch. The palmar cutaneous
branch of the median nerve arises from the distal and lateral
aspect of the median nerve 3 to 4 cm proximal to the flexor
retinaculum and provides sensation to the skin over the
thenar eminence (10).
Anterior Interosseous Nerve. The AIN branch arises posteriorly from the main median trunk approximately 5 to 8
cm distal to the medial epicondyle (23) (Fig. 8.21). Its origin usually is just distal to the branches to the superficial
forearm flexors and just distal to the proximal border of the
superficial head of the PT (2,23). It then passes through the
two heads of the PT and continues distally beneath the
fibrous tissue arcade of the FDS to lie on the IOM. At
approximately the level of the junction of the PT and the
FCR, it sends one to several motor branches to the FPL.
Motor branches have been identified as far distal as 1 cm
proximal to the proximal edge of the PQ. These motor
branches are anterior and along the medial margin of the
FPL, and may be preserved during exposure of the radius by
keeping to the lateral side of the muscle. The FPL and FDP
of the index are exclusively innervated by the AIN. The
FDP of the long finger is innervated by the AIN exclusively
only approximately half the time. In the remaining
instances, the FDP of the long finger is at least partially supplied by branches from the ulnar nerve (23). The AIN continues distally on the volar surface of the IOM, where it
enters the proximal margin of the PQ and branches onto its
deep surface.
Ulnar Nerve
The ulnar nerve enters the forearm through the two heads
of the FCU, which it soon exits to lie on the FDP muscle
belly, where it is joined by the ulnar artery in the middle
third of the forearm (Fig. 8.22).
Dorsal Sensory Branch. The ulnar nerve gives off an
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 (24).
Arteries of the Forearm
Radial Artery
The radial artery begins on the medial side of the biceps
tendon and continues its distal course along the lateral
aspect of the PT, which it soon overlies, and continues
under the muscle belly of the brachioradialis, to which it
sends multiple branches (see Fig. 8.22). The radial artery
courses away from the brachioradialis near its myotendinous junction and becomes superficial in its course to the
radial aspect of the wrist, where it lies just lateral to the FCR
muscle belly and tendon.
Ulnar Artery
The ulnar artery, after giving off the medially situated anterior and posterior ulnar recurrent arteries and the laterally
oriented common interosseus branch, which divides into
the anterior and posterior interosseous arteries, courses distally and ulnarward in the interval between the FDS and
the FDP, where it joins the ulnar nerve on its radial side in
the middle third of the forearm. The artery and nerve lie on
the FDP and continue distally as the ulnar neurovascular
bundle to the flexor and ulnar side of the wrist (see Fig.
8.22)
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