Separated muscle belly of the flexor digitorum brevis for the fifth toe: a case report

This case report describes a variation of the flexor digitorum brevis (FDB) with a separated muscle belly and tendon at the fifth toe. The narrow tendon and muscle belly for the fifth toe arose from the intermuscular septum between the FDB and abductor digiti minimi adjacent to the arising fibers of the FDB, separating from its other fibers. The tendon and muscle belly for the fifth toe became wider at the base of the metatarsal bones and narrower as it coursed toward the toes in a fusiform shape. The tendon and muscle belly for the fifth toe became thin at the midfoot and coursed just beneath the flexor digitorum longus tendon and entered the digital tendinous sheath. FDB variations including that described herein should be considered when performing various surgical procedures and evaluating the biomechanics of the foot.