Anatomical Features of Dislocation of the Peroneal Tendon

Abstract

Category: Ankle Introduction/Purpose: Dislocation of the peroneal tendons is one of the major injuries of the ankle. However, the pathology underlying this condition is still unclear. The purpose of this study was to evaluate the anatomical features of dislocation of the peroneal tendon using MRI. Methods: We compared twenty cases of dislocation of the peroneal tendon and twenty three controls. Both groups were matched for age, gender and BMI. The following patients were excluded: those with an acute injury within the past three weeks and/or findings of peroneal tendon tears or a dislocated peroneal tendon on MRI. MRI axial images of the ankle were retrospectively observed and the shape (concave, convex or flat) of the posterior fibular malleolar groove and the soft tissue dimensions within the peroneal tendon sheath at the level of the ankle joint (joint level) and the middle level between the ankle joint and the fibular malleolar tip (lower level) were investigated. The measurement was performed using a Konica i-pacs SX measurement system (Konica Minolta Health Care, Tokyo, Japan). Results: No significant differences were observed in the shape of the posterior fibular malleolar groove at both levels (Joint level, peroneal dislocation: concave, convex, flat = 2, 10, 8 cases vs. control: 4, 12, 7 cases. P=0.70. Lower level, peroneal dislocation: concave, convex, flat = 3, 6, 11 cases vs. control: 6, 6, 11 cases. P=0.36, Chi-square test for independence). However, a significant difference was confirmed in the soft tissue dimensions within the peroneal tendon sheath (Joint level, peroneal dislocation: 144.6±41.4mm2 vs. control: 97.5±29.1mm2. P < 0.0001. Lower level, peroneal dislocation: 120.2±36.1mm2 vs. control: 84.3±26.8mm2. P < 0.0001, Student's t-test). Conclusion: These results suggest that a larger amount of soft tissue inside of the peroneal tendon sheath at the level of the distal fibula is a significant anatomical feature associated with peroneal tendon dislocation, and could be a potential risk factor for unstable peroneal tendons. It remains unclear whether the soft tissue was bulky prior to injury. However, the presence of enlarged soft tissue within the peroneal tendon sheath is considered to be involved in the pathology of recurrent dislocation of the peroneal tendon.