Ankle dislocation without fracture

Abstract

Dislocation of the ankle without accompanying malleolar fracture has been regarded as a rare lesion, with few cases reported in the literature. To date, there has been no precedent for accurate descriptions of the mechanisms, optimum treatment, and long-term prognosis of this injury. Our goal was to evaluate these variables by a retrospective review of cases from our institution. We identified eight patients who had sustained ankle dislocation without fracture and were treated at the University of Iowa during the period 1958 to 1986. We interviewed and examined each patient and obtained ankle radiographs at an average of 11.5 years postinjury (range 2 to 24 years). After analyzing our cases and other reported in the literature, we have found that this injury is most common in young people (average age 31 years, range 10 to 73 years) and males (72%), and occurs most frequently in falls, motor vehicle accidents, and sports (86%). Medial displacement occurs most frequently (27%). Disruption of the mortise occurs variably. The most likely mechanism appears to be anterior or posterior extrusion of the talus from the mortise secondary to a force applied to the plantarflexed foot. Final displacement is then determined by the position of the foot and the direction of the force applied. Physical findings are commensurate with the deformity. Neurovascular compromise is uncommon (10%). Closed reduction is almost invariably accomplished easily unless the deformity is accompanied by posterior tibiofibular dislocation. Optimum treatment appears to be immobilization in a short leg cast for 6 weeks with no weightbearing for the first 3 weeks. Long-term follow-up revealed the following. Results were all good to excellent considering the following variables: return to work and sports activities, pain, instability, swelling, and ankle and subtalar joint motion. No patient reported instability and all returned to work and sports participation. We noted mild pain and swelling that was not severe enough to require medication in 25% of patients. Range of motion was normal in all but four patients; none of these lacked more than 10 degrees of motion in any plane. Radiographic abnormalities consisted of minor ligamentous or capsular calcification in all patients, small osteophytes in four patients, and minimal joint space narrowing in one patient. No patient had normal radiographs.