Anatomy of the Superior Peroneal Tunnel

Background: Standard texts of anatomy provide cursory and varied descriptions of the superior peroneal retinaculum and the contents of the tunnel formed by it. The available clinical literature suggests that the boundaries and contents of the superior peroneal tunnel have a direct bearing on the causation of peroneal tendinopathies. Knowledge of the anatomy of this region is essential for successful diagnosis and treatment. Methods: Fifty-eight embalmed lower limbs were dissected and the boundaries and contents of the superior peroneal tunnel were ascertained. Sixty dry fibulas were also studied to observe the contour of the retromalleolar groove. Results: The tunnel was spacious, with the superior peroneal retinaculum forming its roof. The floor of the tunnel has an osseous and a nonosseous component. The osseous component is formed by the retromalleolar groove of the fibula, and the nonosseous component is formed by the lower part of the posterior intermuscular septum of the leg. Muscle fibers of the peroneus brevis muscle were the most frequent additional contents followed by an aberrant muscle, termed the peroneus quartus. A split peroneus brevis tendon, a double peroneus longus tendon, and an accessory peroneal nerve were some of the variants observed. In the study of the dry fibulas, it was observed that the contour of the retromalleolar groove was constantly concave. Conclusions: The study suggests that frequent additional structures can normally exist within the spacious superior peroneal tunnel. The retromalleolar groove has a concave contour and forms only a part of the floor of the tunnel and so is an unlikely cause of tendinopathies. The findings may facilitate radiographic evaluation of the tunnel and lead to improvements in the treatment of peroneal tendinopathies.