To find out the factors affecting prognosis after surgical decompression of tarsal tunnel syndrome.

We investigated and followed 11 patients in 12 cases with tarsal tunnel syndrome who underwent surgical decompression in our hospital over a 2-year and 6-month period. Diagnosis was based on the history, thorough physical examination and electrodiagnostic study. Recently, Magnetic Resonance Imaging has also been used to show in extraordinary detail both bony and soft tissue structures of ankle. Operation removed etiologic factors, decompression of flexor retinaculum and neurolysis of the posterior tibial nerve and its medial and lateral plantar nerve branches. It was particularly vital that the mobilization of the posterior tibial nerve be carried out distal to the overlying abductor hallucis.

Electrodiagnostic evaluation showed reduced amplitude, increased duration of motor evoked potentials and decreased sensory conduction velocity, The postoperative result was assessed according to Takakura's rating scale. It was excellent in 3 cases, good in 6 cases, fair in 2 cases and poor in 1 case.

The prognosis seemed to be related with age, duration of symptom and definite space occupying lesion.