We report the cases of six patients (seven feet) who had tarsal tunnel
syndrome in association with an anomalous muscle that was located deep to
the flexor retinaculum of the ankle. An accessory flexor digitorum longus
muscle was present in six of the ankles and a tibiocalcaneus internus
muscle, in one. All of the patients had a release of the tarsal tunnel and
a neurolysis of the posterior tibial nerve and its branches in addition to
a resection of the anomalous muscle. The duration of follow-up averaged
forty-one months (range, twenty-eight to eighty-three months). Although the
pain was reduced in four of the six patients, only one patient was
completely free of symptoms at the time of the most recent follow-up
examination. Four of the six patients were satisfied with the result of the
operation.