follow-up instructions and timing should be discussed if specialist referral is indicated. Discharge instructions should

emphasize the importance of returning for signs of infection,

neurovascular compromise, or compartment syndrome.

SUGGESTED READING

Carson S, Woolridge DP, Colletti J , e t al. Pediatric upper extremity injuries. Pediatr Clin North Am. 2006;53:41-67.

Falcon-Chevere JL, Mathew D, Cabanas JG, et al. Management

and treatment of elbow and forearm injuries. Emerg Med Clin

North Am. 201 0;28:765-787.

Menkes JS. Initial evaluation and management of orthopedic

injuries. In: Tintinalli JE, Stapczynski JS, Ma OJ, Cline DM,

Cydulka RK, Meckler GD. Tintinalli's Emergency Medicine: A

Comprehensive Study Guide. 7th ed. New York, NY: McGrawHlill, 201 1, pp. 1 783-1796.

Ufberg JW, Vilke GM, Chan TC, et al. Anterior shoulder

dislocations: Beyond traction-countertraction. J Emerg Med.

2004;27:301-306.

Lower Extremity Inj u ries

Esther H. Chen, MD

Key Points

• If a hip fracture is suspected in an elderly patient, but

plain radiog raphs are negative, obtain a computed

tomography scan or magnetic resonance imaging.

• Delay in the reduction of a hip dislocation increases the

likelihood of avascu lar necrosis of the femoral head.

INTRODUCTION

Lower extremity injuries are frequently caused by motor

vehicle collisions (MVCs), pedestrian auto accidents,

sports, and falls. These mechanisms often involve large

forces, so concurrent torso injuries may be present.

Fractures in patients with osteopenia and pathologic

fractures occur after minor trauma. This chapter reviews

lower extremity injuries from the hip to the foot and

highlights some of the pitfalls in managing these o rthopedic

emergencies.

� Hip Injuries

Fractures at the hip are classified based on their location.

Femoral neck (ie, subcapital) fractures are intracapsular

and more likely to occur in elderly osteoporotic women.

Displaced femoral neck fractures cause a hemarthrosis

that compresses the femoral neck vessels and compromises the blood flow to the hip. This leads to avascular

necrosis of the bone in 1 5-35% of cases and potential

long-term disability. Intertrochanteric, subtrochanteric,

and femoral shaft fractures are more likely to occur in

young patients after a fall or direct blow to the knee

(Figure 91-1).

Hip dislocations are posterior in 90o/o of cases. They are

caused by high-energy trauma, such as striking the flexed

knee on the dashboard during an MVC.

397

• The presence of normal dista l pulses after a knee dislo ­

cation does not exclude popl iteal artery inju ry.

• A fracture at the base of the second metata rsal should

raise suspicion for a Lisfra nc fracture-dislocation.

.A. Figure 91-1. A displaced intertrochanteric fracture

of the hip.

CHAPTER 91

..... Knee Injuries

The knee is stabilized by 4 ligaments, the anterior and

posterior cruciates and the medial and lateral collateral

ligaments. Maneuvers such as cutting, squatting, and

twisting motions can cause ligamentous and meniscus

injuries. The popliteal fossa contains the popliteal artery

and vein, the common peroneal nerve, and the tibial nerve,

so fractures involving the femoral condyles or proximal

fibula may be associated with popliteal artery or deep pero ­

neal nerve injury, respectively. Likewise, popliteal artery

injuries may be seen with knee dislocations, even if distal

pulses are palpable.

Tibial plateau fractures, seen more commonly in older

patients even after minor trauma, can be difficult to detect

on plain radiography. A proximal fibula fracture occurs

from direct impact or when an external r otational force is

applied to the foot or ankle that tears the interosseous

membrane between the tibia and fibula, also called a

Maisonneuve fracture.

..... Ankle and Foot Injuries

Anatomically, the foot is divided into the hindfoot (talus,

calcaneus), midfoot (cuneiforms, navicular, cuboid), and

forefoot (metatarsals, phalanges). The Chopart j oint separates the hindfoot from the midfoot, whereas the Lisfranc

joint divides the midfoot from the forefoot. A fracture of

the second metatarsal base is associated with disruption of

the ligaments that stabilize the Lisfranc joint. This results

in dislocation of the other metatarsal bones. A Lisfranc

fracture-dislocation occurs after severe plantar flexion of

the foot with an abduction force, such as stepping off a

sidewalk curb. Calcaneus fractures are often bilateral

because the most frequent mechanism is a fall from

height, landing on both feet. Lumbar spine fractures occur

in 1 0% of patients with calcaneal fractures.

The ankle is stabilized by the deltoid ligament, lateral

ligament complex (anterior and posterior talofibular, and

calcaneofibular ligaments), and syndesmosis. The most

common injury is an ankle sprain, 90% of which are inversion injuries. Ligamentous injuries and laxity is difficult

to detect hours after an acute injury because of the

surrounding ligamentous tension and muscle spasm.

Other important lower extremity injuries to diagnose

include Achilles tendon rupture and patella and quadriceps

tendon rupture.

CLINICAL PRESENTATION

Patients with lower extremity injuries present with pain

over the injured site, swelling, ecchymosis, deformity,

limited range of motion, and/or inability to ambulate.

During the primary survey, stabilizing the limb may

limit blood loss, and reducing a fracture/dislocation may

restore neurovascular function. The joints above and

below the injury should be examined for deformities,

shortening, rotation, lacerations, ligamentous instability,

and neurovascular status. The physical exam can be very

limited after an acute injury due to the pain associated with

movement.

Intertrochanteric fractures of the hip may leave the leg

shortened, abducted, and externally rotated because of

traction on the iliopsoas. Patients with nondisplaced hip

fractures may be ambulatory, so physicians should have a

low threshold for obtaining imaging. A posterior hip

dislocation presents with a shortened, adducted, and

internally rotated leg.

A knee exam begins with inspecting for swelling,

effusion, ecchymosis, and patella location, using the

uninjured knee for comparison. Knee injuries, whether

from a fracture, dislocation, or ligamentous injury, typically

present with a hemarthrosis. Anterior cruciate ligament (ACL)

tears cause the majority of hemarthrosis (75%), but other

etiologies include meniscal tears and fractures. The mechanism of injury for an ACL tear is a deceleration, hyperextension, or internal rotation of the tibia on the femur,

associated with a "pop" and swelling that develops within

hours. Ligamentous testing of the knee is outlined in

Table 91-1. A history of locking of the knee suggests a

meniscal tear.

Knee dislocations are associated with tremendous

ligamentous disruption. About half of all knee dislocations

will have spontaneously reduced before presentation.

Despite spontaneous reduction, there is still a high

likelihood of popliteal artery and peroneal nerve injury.

Palpation of the distal pulses is performed to assess the

popliteal artery, but normal pulses are not sensitive enough

to exclude arterial injury. In patients without evidence of

vascular injury, an ankle brachial index (ABI) of >0.9

allows for safe observation without angiography. The deep

peroneal nerve is assessed by testing sensation on the

dorsal aspect of the foot between the first and second toes.

Ligament

Anterior cruciate

ligament (ACL)

Posterior cruciate

ligament (PCL)

Medial collateral

ligament (MCL)

Latera I collateral

ligament (LCL)

Stress Test

Lachman

Posterior

drawer

Valgus stress

test

Varus stress

test

Description

Knee flexed to 30°, pull tibia

forward; anterior displacement is positive

Knee flexed to 90°, tibia

pushed backwards; posterior

displacement is positive

Knee flexed 30° and hanging

off lateral aspect of bed;

valgus force applied to leg

while palpating the MCL

Knee flexed 30° and hanging

off lateral aspect of bed;

varus force applied to leg

while palpating the LCL

LOWER EXTREMITY I NJURI ES

Some lacerations overlying the knee may be deep

enough to extend into the joint capsule (ie, traumatic

arthrotomy) . The knee is the most common joint to be

affected. Once an underlying fracture has been excluded,

the joint will need to be injected with saline or dilute

methylene blue. If fluid flows out of the laceration when

the joint is injected, then the joint has been violated and

requires a wash out in the operating room.

Patients with patella fractures and patella and quadriceps

tendon rupture may be able to ambulate normally, but the

extensor function of the knee is affected (ie, the patient

would not be able to perform a straight leg raise). The position of the patella is notably altered on exam in patients with

tendon rupture, particularly after a patella tendon rupture.

Posttraumatic compartment syndrome causes severe

pain that starts within a few hours after the injury (but can

occur up to 48 hours), worsens with passive range of

motion, and is associated with progressive swelling around

the injured area. In the lower extremity, the most common

location to develop compartment syndrome is the leg,

usually after a tibia fracture. The 4 compartments of the leg

are the anterior, lateral, posterior, and deep posterior.

The most common ankle injury is a lateral ankle sprain.

Patients will present with tenderness and swelling around

the anterolateral aspect of the ankle and difficulty bearing

weight. Grade I ankle sprains present with minimal

functional loss, pain, and swelling. Grade II and III sprains

involve partial and complete tear of the ligaments and

result in significant functional loss.

Achilles tendon rupture most commonly occurs after a

weekend warrior (ie, middle-aged man who infrequently

performs strenuous activities) applies a force to the

dorsiflexed foot and then has sudden severe pain in the

back of the leg. On examination, the calf is tender and

swollen and there is a gap in the tendon about 2-6 em

proximal to the calcaneus. The Thompson test is performed

with the patient lying prone, knees bent at 90 degrees. If

the foot does not dorsiflex when the calf is squeezed, then

the tendon is completely tom.