Ankle and Foot — Surgical Anatomy and Approaches

Introduction

The ankle and foot together form an intricate anatomical complex with 28 bones, more than 30 joints, and a dense network of tendons, ligaments, and neurovascular structures organized into a region of complex weight-bearing and propulsive function. The surgical approaches to the region must navigate this complexity, with attention to the thin soft- tissue envelope (particularly around the medial and anterior ankle), the principal neurovascular structures (anterior tibial artery and deep peroneal nerve anteriorly, posterior tibial artery and tibial nerve in the tarsal tunnel, saphenous vein and nerve medially, sural nerve laterally, superficial peroneal nerve crossing anterolaterally), and the multiple distinct compartments of the foot. The principal approaches — anterior ankle, anterolateral ankle, posterolateral ankle, medial ankle, sinus tarsi, extensile lateral calcaneal, dorsal foot, plantar foot, and the multiple specific approaches to particular bones and joints — each provide access to specific regions. This chapter draws on Orthopaedic Surgical Approaches, Netter’s Concise Orthopaedic Anatomy, and Gray’s Anatomy.

Bony Anatomy

The ankle joint comprises the tibial plafond, medial malleolus, lateral malleolus (distal fibula), and the talar dome (Topic Trauma-28). The subtalar joint is between the talus (superiorly) and the calcaneus (inferiorly), with three articular facets (anterior, middle, and posterior) separated by the tarsal canal. The midfoot comprises the navicular, cuboid, and three cuneiforms (Topic Trauma-29). The forefoot comprises the five metatarsals and the phalanges (similar to the hand pattern, with two phalanges in the great toe and three in the lesser toes). Key surgical landmarks include the medial and lateral malleoli, sustentaculum tali (medial calcaneus), tibialis anterior tubercle of the navicular, and the fifth metatarsal tuberosity.

Neurovascular Anatomy

The anterior ankle structures, from medial to lateral, are: tibialis anterior, extensor hallucis longus (EHL), anterior tibial artery and deep peroneal nerve, extensor digitorum longus (EDL), peroneus tertius. The medial ankle contains the tarsal tunnel posterior to the medial malleolus, with the contents (deep to the flexor retinaculum, from anterior to posterior): tibialis posterior, flexor digitorum longus, posterior tibial artery and tibial nerve, flexor hallucis longus — the “Tom, Dick, And a Nervous Harry” mnemonic.

The lateral ankle contains the peroneus brevis anteriorly and peroneus longus posteriorly behind the lateral malleolus, with the sural nerve running posterolaterally. The superficial peroneal nerve crosses the anterolateral ankle and dorsum of the foot subcutaneously, providing most of the dorsal foot sensation; injury produces a recognizable sensory deficit and is a recognized concern in anterolateral ankle approaches. The saphenous nerve descends along the medial side of the ankle and foot, providing medial sensation; injury produces medial dorsal sensory deficit.

Anterior Ankle Approach

The anterior ankle approach is used for anterior ankle arthrodesis, total ankle arthroplasty, distal tibial osteotomy, tumor resection, and other anterior procedures. A longitudinal incision is made over the anterior ankle in the line of the second metatarsal, approximately 10 to 15 cm in length. The superficial peroneal nerve crosses the lateral aspect of the incision (most surgeons make the skin incision medial to the SPN crossings). The deep dissection develops the interval between the tibialis anterior (medial) and the extensor hallucis longus / extensor digitorum longus (lateral), with the anterior tibial artery and deep peroneal nerve retracted laterally. The ankle capsule is opened to access the joint.

Anterolateral Ankle Approach

The anterolateral approach is the standard for lateral plafond (pilon) fractures (Topic Trauma-27). A longitudinal incision is made over the anterolateral ankle, between the EHL/EDL medially and the peroneus tertius laterally. The deep peroneal nerve and the anterior tibial vessels are identified and retracted medially. The ankle joint and the distal tibia are exposed. The approach provides excellent visualization of the anterior ankle joint and the distal tibial articular surface.

Posterolateral Ankle Approach

The posterolateral approach is used for posterior malleolar fracture fixation, posterior pilon fractures, and exposure of the peroneal tendons and the lateral aspect of the posterior ankle. A longitudinal incision is made over the posterolateral leg behind the fibula. The sural nerve and small saphenous vein are identified and protected. The interval between the peroneal tendons (laterally) and the flexor hallucis longus (medially) is developed, with the FHL retracted medially. The posterior aspect of the ankle joint and the posterior malleolus are exposed.

Medial Ankle Approach

The medial ankle approach is used for medial malleolus fracture fixation, deltoid ligament repair, tarsal tunnel release, and posterior tibial tendon procedures. A longitudinal or curved incision is made over the medial malleolus and the medial ankle, depending on the planned procedure.

For medial malleolus fixation, a vertical incision over the malleolus provides direct access. For tarsal tunnel release, a curved incision behind the medial malleolus provides access to the tarsal tunnel; the flexor retinaculum is incised, decompressing the tibial nerve. For posterior tibial tendon procedures (PTTD reconstruction with FDL transfer), a longitudinal incision along the course of the tendon provides access from the medial malleolus to the navicular insertion.

Sinus Tarsi Approach to the Calcaneus

The sinus tarsi approach has largely supplanted the extensile lateral approach for calcaneal fracture fixation (Topic Trauma-29), because of substantially lower wound complication rates. A small oblique incision is made over the sinus tarsi (a depression palpable just anterior to the lateral malleolus). The peroneal tendons are retracted, and the calcaneocuboid joint and the posterior facet of the subtalar joint are exposed.

Extensile Lateral Approach to the Calcaneus

The extensile lateral approach (Letournel/Benirschke) is the historical standard for calcaneal fracture fixation. An L-shaped or hockey-stick incision is made along the lateral calcaneus, with vertical and horizontal limbs. The skin and subcutaneous tissue are reflected, with the peroneal tendons elevated as a single soft-tissue flap. The lateral wall of the calcaneus is exposed for plating. The wound complication rates of 5 to 25 percent have led to the substantial preference for the sinus tarsi approach.

Approaches to the Foot

Dorsal Foot Approaches Dorsal foot incisions are used for forefoot procedures (bunion surgery, lesser toe deformity correction, foot fracture fixation). The incisions are placed to avoid the dorsal sensory nerves (branches of the superficial peroneal nerve) and the dorsalis pedis artery and deep peroneal nerve (which runs in the first dorsal interspace). Medial Foot Approach A medial foot incision along the medial border of the foot provides access to the medial column (navicular, medial cuneiform, first metatarsal base). The approach is used for medial column fractures, hallux valgus surgery, and medial column arthrodesis. Lateral Foot Approach A lateral foot incision along the lateral border provides access to the cuboid, the fourth and fifth metatarsals, and the lateral column. The approach is used for cuboid fracture fixation, lateral column lengthening, and lateral column reconstructive procedures.

Plantar Approaches Plantar incisions are generally avoided because of the thick plantar fat and the risk of painful scars on the weight-bearing surface. When necessary (for plantar fascia release, deep plantar abscess), incisions are placed along the medial or lateral plantar non-weight- bearing surface.

Foot Compartments and Fasciotomy

The foot has 9 compartments (medial, central, lateral, calcaneal, and four interosseous, with some classification variants). Foot compartment syndrome requires recognition and fasciotomy through dorsal incisions (over the second and fourth metatarsals to release the dorsal and palmar interossei) with additional medial incision if the medial compartment is involved.

Summary and Take-Home Points

The ankle and foot offer a wide variety of surgical approaches, each tailored to specific regional pathology. The anterior ankle approach uses the interval between TA and EHL/EDL, retracting the anterior tibial vessels and deep peroneal nerve laterally. The anterolateral approach is the standard for pilon fractures, between EHL/EDL and peroneus tertius. The posterolateral approach with sural nerve protection accesses the posterior malleolus and posterior pilon. The medial ankle approach is used for medial malleolar fixation, tarsal tunnel release, and posterior tibial tendon procedures. The sinus tarsi approach has largely supplanted the extensile lateral approach for calcaneal fracture fixation, with substantially lower wound complication rates. The dorsal foot approaches for forefoot procedures must avoid the superficial peroneal nerve branches and the dorsalis pedis artery. The medial and lateral foot approaches access the respective columns of the midfoot. Foot fasciotomy through dorsal incisions releases the multiple foot compartments in compartment syndrome. The principal neurovascular structures include the anterior tibial artery and deep peroneal nerve (anterior ankle, becoming the dorsalis pedis vessels and DPN in the foot), the posterior tibial artery and tibial nerve in the tarsal tunnel (medial ankle), the superficial peroneal nerve (subcutaneous over the dorsum of the foot), the sural nerve (subcutaneous posterolaterally), and the saphenous nerve (medially). The next and final chapter turns to pediatric bone, the last anatomical region of the syllabus.