The flexor digitorum longus: an anatomic and microscopic study for use as a tendon graft.

Recent experimental studies have shown that intrasynovial donor tendons have the capacity to heal with minimal alteration in the gliding surface when grafted to an intrasynovial location. In order to evaluate the flexor digitorum longus of the foot as a potential matched donor tendon for use in flexor tendon grafting, we dissected 15 feet (75 toes) and 10 hands (50 fingers) to determine the intrasynovial lengths of the flexor digitorum longus and flexor digitorum profundus and to determine a method of tendon graft harvest. Specimens were taken from the intrasynovial portion of each tendon for evaluation by light and electron microscopy. The intrasynovial tendons of the hand and foot were similar in vascularity, cellularity, gliding surface, and ultrastructure. The flexor digitorum longus tendon of the foot was a mean length of 12 cm to the area of tendon confluence in the midfoot, which will usually provide enough tendon length for grafting from the distal phalanx to the palm of the hand. Because of the difference in length of the synovial sheaths of the fingers and toes, some extrasynovial tendon will be transferred to the synovial space when a flexor digitorum longus tendon is used.