CHAPTER TWELVE LOWER LEG, ANKLE, AND FOOT

AXIOMS IN ASSESSING THE LOWER LEG, ANKLE, AND FOOT

• Pain in the ankle and foot can arise from the bones and joints, periarticular soft tissues, nerve roots and peripheral nerves, or vascular structures.

• Pain in the foot can also be referred from the lumbar spine or knee joint.

• The greatest majority of painful foot conditions result from inappropriate footwear, weak intrinsic muscles, foot deformities, or static disorders.

INTRODUCTION

The leg, ankle, and foot are subject to static deformities more than any other skeletal unit. The weight-transmitting and propulsive functions of these structures are restricted daily by nonyielding foot coverings. Anatomic variations in the shape and stability of joint surfaces may predispose, resist, or modify the deforming force of common footwear.

Modern civilization disregards the physiologic features of the ankle and foot. Fashion and eye appeal rather than function determine shoe design, especially in the fore part of the shoe, where most disabilities and deformities of the foot occur.

ORTHOPEDIC GAMUT 12-1 IMPORTANT SHOE DESIGN FEATURES

1. The arch support can reduce muscle fatigue in the calf and disperse arch pressure.

2. Outsoles with 1.5-cm thickness in the metatarsal zone tend to produce lower metatarsal pressure and vertical impact force and to reduce low back discomfort.

3. A shoe upper with soft leather and mid-sole made with ethylene vinyl acetate or polyurethane materials are helpful to increase whole-body and foot comfort.

4. An outsole with heel height between 1.8 and 3.6 cm tends to generate lower heel pressure and vertical impact force in the forefoot and to reduce ankle discomfort.

The restrictive force of poorly fitting shoes produces little deformity on the tarsus because the tarsus is made up of short, heavy bones. Normal movement in the tarsal joints is limited because the articular surfaces of the tarsal joints are flat. However, the phalanges and metatarsals are long thin bones with a normally wide range of joint motion. Restrictive force on these bones produces most of the static deformities of the forefoot. These static deformities include first metatarsophalangeal joint deformities, hammertoe, tailor’s bunion, overlapping toes, and many other conditions that are deviations from the normal (Table 12-3).

TABLE 12-3 ANKLE AND FOOT DIFFERENTIATION BY ONSET

Articular	Trauma, sprain Arthritis Metatarsalgia Congenital disorders (e.g., clubfoot)
Neurologic	Entrapment of lumbosacral nerve roots form herniated lumbar disc Entrapment of the lateral popliteal nerve behind the neck of the fibula Tarsal tunnel syndrome (posterior tibial nerve) Interdigital (Morton) neuroma Peripheral neuropathy and insensitive foot
Periarticular	Cutaneous and subcutaneous Plantar fascia Tendons and tendon sheaths Bursitis Acute calcific periarthritis
Osseous	Fracture Epiphysitis (osteochondritis) Bone neoplasms, infection Painful accessory ossicles
Vascular	Ischemic foot pain Vasospastic disorders with Raynaud phenomenon Cholesterol embolization with purple toes

TABLE 12-1 LOWER LEG, ANKLE, AND FOOT CROSS-REFERENCE TABLE BY ASSESSMENT PROCEDURE

TABLE 12-2 LOWER LEG, ANKLE, AND FOOT CROSS-REFERENCE TABLE BY SYNDROME OR TISSUE

Achilles tendon	Thompson test
Atrophy	Calf circumference test
Calcaneus fracture	Hoffa test Thompson test
Fibular fracture	Keen sign
Foot pronation	Helbings sign
Metatarsalgia	Morton test Strunsky sign
Neuroma	Morton test
Peroneal nerve paralysis	Duchenne sign
Talofibular ligament	Anterior drawer sign of the ankle
Tarsal tunnel syndrome	Tinel foot sign
Thrombophlebitis	Homans sign Moses test
Vascular	Buergers test Claudication test Foot tourniquet test Homans sign Moszkowicz test Moses test Perthes test

The human foot is uniquely specialized. The metatarsals and toes enable the body to stand erect. The versatility of the forefoot permits the human to retain an upright stance and allows for grace during walking, dancing, and athletics.

A well-developed and strong foot withstands surprising abuse. Morbid changes take place only when maltreatment becomes excessive. An underdeveloped and frail foot, ankle, and lower-leg mechanism may fail under ordinary stress and strain.

The ankle and foot are inspected in both the resting and standing positions for evidence of swelling, deformity, and skin abnormalities such as edema, erythema, tophi, subcutaneous nodules, or ulcers. Abnormalities of gait are observed while the patient is walking. The gait or walking cycle can be divided into two phases: the stance or weight-bearing phase and the swing or non–weight-bearing phase.

ORTHOPEDIC GAMUT 12-2 ETIOLOGY OF ACHILLES TENDON SWELLING

1. Tendon rupture

2. Calcaneal bursitis

3. Rheumatoid nodules

4. Urate tophi

In the standing position, the calcaneus normally maintains the line of the Achilles tendon. Deformities of the subtalar joint, resulting in eversion (calcaneovalgus) or inversion (calcaneovarus) of the heel, are best observed from behind. Equinus and calcaneus refer to angulation of the ankle in plantar and dorsiflexion, respectively. Inspection while the patient is standing may reveal lowering of the longitudinal arch (pes planus) or increased height of the arch (pes cavus).

ESSENTIAL ANATOMY

The leg is divided by fascial septa into posterior, lateral, and anterior compartments. Because they have a common nerve supply, the anterior and lateral compartments are often considered to be one. The posterior compartment is further divided into a superficial and deep area. Although each compartment of the leg has a specialized vascular and nerve supply, the nerves and vessels are sometimes not physically within the compartment they supply (e.g., the lateral compartment is supplied by the peroneal artery, which lies in the posterior compartment).

The anterior leg muscles attach to the area between the tibia and fibula.

ORTHOPEDIC GAMUT 12-3 MUSCLE OF THE ANTERIOR COMPARTMENT OF THE LEG

1. Tibialis anterior

2. Extensor hallucis longus

3. Extensor digitorum longus

ORTHOPEDIC GAMUT 12-4 ANKLE JOINT

Structures crossing the ankle joint:

ANTERIORLY

• Tendons of the tibialis anterior

• Extensor hallucis longus

• Anterior tibial vessels

• Deep peroneal nerve

• Extensor digitorum longus

• Peroneus tertius

POSTEROMEDIALLY

• Tibial vessels

• Tibial nerve

• Flexor hallucis longus

POSTEROLATERALLY

• Tendons of the peroneus longus and brevis

ESSENTIAL MOTION ASSESSMENT

For the sake of simplicity, motions are tested along three different axes. Dorsiflexion and plantar flexion are movements at the ankle joint that occur around a transverse axis that passes through the body of the talus. Inversion and eversion are movements of rotation of the foot along its long axis. Abduction and adduction of the forefoot, occurring along a vertical axis, are movements of the midtarsal joints. Pronation and supination refer to a weight-bearing foot. The complex movements of eversion and inversion indicate changes in the form of the whole foot when it is not bearing weight.

ORTHOPEDIC GAMUT 12-5 ANKLE AND FOOT

Activities for testing range of motion of the ankle and foot:

1. Point the foot up toward the ceiling.

2. Point the foot down toward the floor.

3. With the foot bent at the ankle, point the medial side of the foot toward the floor (eversion) and repeat with the lateral side (inversion).

4. Rotate the ankle, turning the foot away from and then toward the other foot.

Movements of the lesser toes can be measured in a similar manner. Clinically, the examiner should note whether fixed contractures exist or if the joints are supple. Restriction of joint motion can be the result of soft-tissue contractures, bony abutment, or intraarticular adhesions. Motion may be restricted because of pain that results from inflammation or injuries (Figs. 12-1 and 12-2).

FIG. 12-1 A normal ankle allows 20 degrees of dorsiflexion (A) and 40 degrees of plantar flexion from this position (B).

FIG. 12-2 A normal joint allows 20 degrees of eversion (A) and approximately 30 degrees of inversion (B).

ESSENTIAL MUSCLE FUNCTION ASSESSMENT

The main muscles of the calf are the soleus and gastrocnemius. The soleus acts purely as a flexor of the ankle, and the gastrocnemius flexes both the ankle and the knee. The flexor digitorum longus and flexor hallucis longus flex the toes and big toe, respectively. The anterior compartment muscles include the tibialis anterior, extensor digitorum longus, and extensor hallucis longus. The tibialis anterior inverts the foot and dorsiflexes the ankle.

The motions in the ankle joint are plantar flexion and dorsiflexion. The muscles in the posterior compartment, which are innervated by the tibial nerve, are responsible primarily for plantar flexion motion. The major muscles for plantar flexion are the gastrocnemius and soleus, and they are supplemented by the tibialis posterior, peroneus longus, flexor digitorum longus, and hallucis longus. The power of the gastrocnemius-soleus group is weakened when the knee is in flexion because the gastrocnemius is a two-joint muscle. However, while the knee is in flexion, the passive range of ankle dorsiflexion increases slightly. The muscles of the anterior compartment, innervated by the deep peroneal nerve, are responsible primarily for dorsiflexion motion. Dorsiflexion is performed by the tibialis anterior and the extensor digitorum longus. When these two muscles act together, their individual actions of inversion and eversion are neutralized. The extensor hallucis longus and peroneus tertius also aid in dorsiflexion (Figs. 12-3 to 12-6).

FIG. 12-3 The soleus is evaluated by applying a dorsiflexion force to the foot while the patient plantar flexes the foot (A). The tibialis anterior is tested by exerting a counterforce to the dorsiflexion and inversion movement of the foot and ankle (B).

FIG. 12-4 The tibialis posterior is evaluated by exerting a counterforce to the foot while the patient inverts and plantar flexes the foot (A). The peroneus longus is tested by exerting a counterforce to a foot that is held in plantar flexion while the patient actively everts it (B).

FIG. 12-5 Flexion of the metatarsophalangeal joint is achieved primarily by the lumbricales, interossei, and flexor hallucis brevis, which are augmented by the flexor hallucis longus and the flexor digitorum longus and brevis (A). Extension of these joints is achieved primarily by the extensor digitorum longus and the extensor hallucis longus, which are supplemented by the extensor digitorum brevis and the extensor hallucis brevis (B).

FIG. 12-6 The muscle power of the long toe extensors is tested by exerting a counterforce to the toes while the patient extends the metatarsophalangeal joints (A and B). The long toe flexors are tested by exerting a counterforce to the tip of the toes while the patient flexes the interphalangeal joints (C and D).

ESSENTIAL IMAGING

The standard views of the ankle are the anteroposterior (AP), medial oblique (Mortise view), and lateral views. The AP ankle view includes the collimate field from the distal tibia and fibula through the talocalcaneal junction. The primary purpose of the AP ankle view is to illustrate the coronal relationship of the talocrural articulation and its surrounding bony elements of the tibia, fibula, and talus. The AP and oblique projections of the ankle are sensitive for ruling out sites of injury along the lower tibia and fibula. The lateral ankle view includes the lower tibia and fibula. In cases of suspected ligamentous instability, eversion and inversion stress views can be performed. Inversion will test the lateral collateral ligament, whereas eversion will check the medial collateral (deltoid) ligament.

ORTHOPEDIC GAMUT 12-6 VIEWS OF THE FOOT

Three basic plain-film views of the foot are:

1. AP or dorsoplantar view

2. Oblique view

3. Lateral view

ANTERIOR DRAWER SIGN OF THE ANKLE

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