Clinical outcome of closed isolated subtalar dislocations

Subtalar dislocation (SD) is an uncommon injury accounting for 1-2% of all dislocations. It involves simultaneous disruption of the talocalcaneal and talonavicular joints, without involvement of the calcaneocuboid or tibiotalar joints or talar neck fracture. We present a retrospective study of pure medial and lateral SDs treated conservatively and discuss the pathogenesis, classification, prognostics and therapeutic aspects of SD.

Thirty patients, 24 men and 6 women (mean age 33 years; range 18-55) with closed isolated SD were treated conservatively and re-evaluated at 5-12 years. There were 20 medial and 10 lateral dislocations. All patients were managed with immediate closed reduction under general anaesthesia. Open dislocations and SDs associated with fractures were excluded.

The mean AOFAS Ankle-Hindfoot score was 78.8. Seven patients (all with medial SDs) had an AOFAS score of 100; 14 patients (11 with medial and 3 with lateral SD) had a mean AOFAS score of 85; 6 patients (three with medial and three with lateral SD) had a mean AOFAS score of 65; and 3 patients (all with lateral SDs) had a mean AOFAS score of 28. The latter patients subsequently underwent subtalar fusion, with a fair outcome. The mean AOFAS scores of patients with lateral and medial SD were not significantly different (P = 0.05).

Various factors adversely affect outcome, including type of dislocation (lateral/medial, open/closed), severity of the injury, associated fractures, length of immobilization. Management of closed isolated SD is by immediate conservative treatment in order to avoid or reduce the incidence of early soft-tissue and vascular complications and poor long-term outcomes due to post-traumatic arthritis, talus necrosis and subtalar joint stiffness. However, complications may still arise despite correct treatment.