Acute tarsal tunnel syndrome following partial avulsion of the flexor hallucis longus muscle: a case report.

An acute posterior tibial nerve compression from a partially ruptured flexor hallucis longus (FHL) muscle is reported. This etiology for acute tarsal tunnel syndrome has not been previously described. A 17-year-old male sustained multiple injuries in a motor vehicle accident, including a tibial shaft fracture and a posterior medial right ankle laceration of the same limb. The injured limb had no sensation on the plantar aspect of the foot and heel, decreased active great toe flexion, and associated leg pain. Exploration of the posterior tibial nerve for presumed laceration revealed the nerve to be intact, but compressed in a tense tarsal tunnel from a retracted partially ruptured flexor hallucis longus tendon. Decompression of the tunnel and resection of the devascularized muscle resulted in complete neurologic recovery.