No abstract

Lateral ankle instability results from a tear of the fibular collateral ligaments, which are the major ankle stabilizing structures against adduction stress.' The anterior talofibular ligament usually ruptures first, with a concomitant disruption of the calcaneofibular ligament occurring in about 40% of patients.' When the calcaneofibular ligament does rupture, there is often an associated tear of the common peroneal sheath.Isolated ruptures of the superior peroneal retinaculum with dislocation of the peroneal tendons is an uncommon injury.&dquo; 11.13,18,21.24,26-28.31,36 The mechanism of injury is a forced dorsiflexion of the foot along with a contraction of the peroneal muscles that ruptures the superior peroneal retinaculuml (Figs. 1 and 2). The peroneal tendons can then snap anteriorly over the lateral malleolus. Many cases are misdiagnosed acutely and become chronic. The patients present with snapping, ankle stiffness, pain, and instability. It has been stated by some authors4 that habitual dislocations do not need treatment, but most advocate surgical reconstruction. Numerous procedures have been described', 1,1,6 that successfully prevent the tendons from dislocating. However, most of these reconstructions do not provide adequate support for an unstable ankle joint since they do not address the calcaneofibular or anterior talofibular ligament anatomy.Inversion instability associated with dislocation of the peroneal tendons indicates that the fibular collateral ligaments are injured in addition to the superior peroneal retinaculum. If the superior peroneal retinaculum is ruptured (allowing the peroneal tendons to dislocate), but the fibular collateral ligaments remain intact, then the ankle should be stable to inversion stress. There are numerous reports on lateral ankle instability and dislocating peroneal tendons as separate entities, but we have found no previous reports that focus on these as combined injuries. ANATOMYEdwards' performed an anatomical study of the posterior peroneal sulcus (fibular groove) and found significant variations in the contour, depth, and length. He found a definite sulcus on the posterior surface of the lateral malleolus in 146 (82%) of 178 fibulae, a transverse flat surface in 19 specimens (11% ), and in the remaining 13 (7%) the groove actually had a convex surface. The convex surface provided no support to the bone or the cartilage in retaining the tendons within the sulcus. The average width of the sulcus was 6 mm. The groove was usually shallow, but occasionally reached a depth of 3 mm. The lateral ridge of the distal fibula, when present, was usually not of substantial mass to retain the tendons in the groove, even when augmented by cartilage. CASE REPORT AND SURGICAL TECHNIQUEA 29-year-old male presented with a history of multiple left ankle sprains occurring over the past 6 years. He complained of a popping sensation over the lateral aspect of the ankle as well as lateral ankle pain and instability. Physical examination showed anterior dislocation of the peroneal ten...