The effect of musculus extensor digitorum brevis transfer for chronic lateral ankle instability.
Thirty-eight patients who had undergone surgery for instability of their ankles between 1980 and 1994 answered questionnaires regarding the results. In 32 of the 38 patients, clinical examinations were performed including practice on a balancing board, circle-running tests, and active and passive electromyographic measurements on the musculus extensor digitorum brevis (MEDB). The questionnaires showed that 90% of the patients with a median observation time of 9 years (range, 16 months-14 years) were content with the results of their operations, and the number of painful distortions of the ankle were reduced considerably in 96% of the patients. Within the group of active sportspersons with more than 4 hours of weekly exercise, 42% returned to their previous levels of sports activity. The tendency to have ankle pain disappeared in 90% of the patients. At the clinical examination, the time spent on the balancing board was reduced by 25% for the operated foot. When the patient ran in a circle with the operated leg toward the center, as compared with running with the nonoperated leg toward the center, the time was enhanced by 8%. We found electromyographic activity in the MEDB during active movement of the toes and with passive supination of the talocrural joint but not during passive pronation of the foot. The MEDB transfer procedure not only strengthens the lateral ligaments but also seems to add proprioceptive protection to the ankle to prevent distortions.