Flexor hallucis longus tendoscopy: a technical note.

The course of the flexor hallucis tendon (FHL) is divided into three zones. Zone 1 is located behind the ankle joint, from the musculotendinous junction to the orifice of the tunnel underneath the sustentaculum tali. Zone 2 is located from the tunnel underneath the sustentaculum tali to the knot of Henry. Zone 3 is located from the knot of Henry to the tendon insertion to the base of the distal phalanx of the big toe. The zone 1 FHL tendon is examined with posterior ankle endoscopy with the posterolateral and posteromedial portals. The zone 2 FHL tendon can be examined through the posteromedial and the plantar portals. The zone 3 FHL tendon is examined with the toe flexor tendoscopy. By means of different endoscopic approach to the each zone of the FHL tendon, the complete course of the tendon can be examined from the musclotendinous junction to its insertion.