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Extensor expansions of foot


The extensor expansions of the foot are similar to those of the hand but in miniature. They are complex, triangular aponeurotic sheaths, with a hood-like appearance, that function as the compound tendinous attachment of the extensor digitorum longus, lumbrical, plantar interossei, and dorsal interossei muscles. The hood-like base of this triangular aponeurosis covers the metatarsophalangeal joint dorsally and wraps around the lateral aspects of the joint. This broad base tapers to the apex of the triangular aponeurosis to attach to the base of the distal phalanx. The central axis of the aponeurosis is thick and contains the strong, flat tendon of the extensor digitorum longus muscle. The borders of the triangle are also thick, as the tendons of the lumbricals and interossei enter the aponeurosis from the sides. Between these thickened regions, the aponeurosis is thin and translucent. The central extensor digitorum longus tendon gives rise to two collateral slips at the level of the proximal interphalangeal joint, which angle to the sides of the expansion to join with the thick margins and then converge again to the midline to attach to the distal phalanx. Each of the toes has an extensor expansion.


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