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A diabetic patient complains to a physician of a sensation of walking on pebbles with bare feet. Physical examination demonstrates clawing of the toes with flexion of the interphalangeal
joints and extension of the metatarsophalangeal joints. Atrophy of which of the following muscles is most likely responsible for the observed changes?
A. Flexor digitorum longus
B. Lumbricals and interossei
C. Peroneus longus
D. Tibialis anterior
E. Tibialis posterior
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B. Lumbricals and interossei
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The correct answer is B. The condition described in the question stem is very common among diabetics, and is due to atrophy of lumbricals and interosseus muscles secondary to diabetic neuropathy. Another finding that may be seen is the presence of corns and callosities on the dorsal surface of the feet overlying the protuberant interphalangeal joints. All of these degenerative changes add to the diabetic's foot disease, predisposing for sores that heal poorly in the poorly vascularized diabetic foot, often leading to gangrene, requiring amputation of the distal foot.
Flexor digitorum longus (choice A) is an extrinsic muscle of the foot that flexes the distal phalanges of the lateral four toes and assists in plantar flexion of the foot.
Peroneus longus (choice C) is an extrinsic muscle of the foot that plantar flexes and everts the foot.
Tibialis anterior (choice D) is an extrinsic muscle of the foot that dorsiflexes and inverts the foot.
Tibialis posterior (choice E) is an extrinsic muscle of the foot that plantar flexes and inverts the foot.
