Anatomic Features of Patients With Recurrent Peroneal Tendon Dislocation.

Background: There are several anatomic variations of the peroneal muscles and lateral malleolus of the ankle that may play an important role in the onset of peroneal tendon dislocation.

Purpose: To investigate the anatomic variations of the retromalleolar groove and peroneal muscles in patients with and without recurrent peroneal tendon dislocation using magnetic resonance imaging (MRI) and computed tomography (CT).

Study Design: Cross-sectional study; Level of evidence, 3.

Methods: A total of 30 patients (30 ankles) with recurrent peroneal tendon dislocation who underwent both MRI and CT before surgery (PD group) and 30 age- and sex-matched patients (control [CN] group) who underwent MRI and CT were included in this study. The imaging was reviewed at the level of the tibial plafond (TP level) and at the center slice between the TP and the fibular tip (CS level). The appearance of a malleolar groove (convex, concave, or flat) and the posterior tilting angle of the fibula were assessed on CT images. The appearance of accessory peroneal muscles, height of the peroneus brevis muscle belly, and volume of the peroneal muscle and tendons were assessed on MRI scans.

Results: There were no differences in the appearance of the malleolar groove, posterior tilting angle of the fibula, or accessory peroneal muscles at the TP and CS levels between the PD and CN groups. The peroneal muscle ratio was significantly higher in the PD group than in the CN group at the TP and CS levels (both < .001). The height of the peroneus brevis muscle belly was significantly lower in the PD group than in the CN group ( = .001).

Conclusion: A low-lying muscle belly of the peroneus brevis and a larger muscle volume in the retromalleolar space were significantly associated with peroneal tendon dislocation. Retromalleolar bony morphology was not associated with peroneal tendon dislocation.