Chopart and Lisfranc joints divide the foot into three regions. The talus and the calcaneum comprise the hindfoot. The midfoot contains the cuneiforms, the cuboid, and the navicular. The metatarsals and the phalanges make up the forefoot (Figi.i...269-1). There are a total of 28 bones and 57 articular surfaces. Numerous intrinsic muscles and ligaments contribute to the integrity of the foot's structure. The biomechanical specifics of the foot involved in ambulation are extremely complex. In general, eversion and inversion occur about the subtalar and calcaneotarsal joints, whereas adduction-abduction and flexion-extension occur about the metatarsophalangeal and interphalangeal joints.
The body weight when standing is distributed about the heel to the rear and the five metatarsal heads to the front. The curved shape of the foot is held in position by three arches. The shape of the bones, the arrangement of the ligaments, and the tone of the muscles maintain the position of the arches. The plantar aponeurosis covers the sole of the foot and is a strong band of fascia that originates on the medial side of the calcaneum and fuses with the fibrous sheaths of the phalanges.
The blood supply of the foot comes from branches of the popliteal artery. The anterior tibial artery serves the dorsum of the foot, and its branch, the dorsalis pedis, can be palpated over the dorsum of the midfoot. Branches of the posterior tibial and the peroneal arteries serve the sole. The motor and sensory nerves of the foot include branches of both the femoral and sciatic nerves and include branches of the saphenous, sural (sensory), and deep and superficial peroneal nerves (both sensory and motor).
The essential parts of the anatomy of concern include, but are not limited to, the following. The first metatarsal bears twice the weight as any other metatarsal, and injuries to this bone require a more conservative approach. The blood supply to the foot is tenuous, and major fractures of the talus and subtalar dislocations are complicated by avascular necrosis. The base of the second metatarsal is the "keystone" of the Lisfranc complex, and any injury to this area has to be treated with caution.
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