Radiographic diagnosis of acute peroneal tendon dislocation.

Acute dislocation of the peroneal tendons at the ankle is accompanied, in a significant proportion of cases, by a characteristic small shelllike avulsion fracture of the lateral malleolus, rendering the lesion diagnosable radiographically. This small fracture is usually best seen on internal rotation oblique or occasionally on anteroposterior films of the ankle. It is seen as a bone flake only a few millimeters thick but often 1 cm or more in vertical diameter lying adjacent to the posterolateral surface of the lateral malleolus. It is an infrequent injury, now usually the result of a ski accident. Failure to recognize and treat the lesion can result in chronic disability.