Purpose: Subtalar dislocation is an exceptional finding. En bloc dislocation under the talus leads to talocalcaneal talonavicular luxation, generally observed in young active adults. Prognsosis is related to the risk of infection and talar necrosis. We report a retrospective series searching for featues influencing long-term clinical outcome.

Material and methods: Between 1984 and 1990, twelve cases of subtalar dislocation were treated in our unit. There were nine lateral and three medial cases. Six lateral dislocations were open injuries, the head of the talus exposed medially. Treatment consisted in emergency orthopaedic reduction associated with debride-ment and closure in case of open injury. Temporary pinning (45 days) between the talus and the calcaneus was used in six cases. There were two lesions of the posterior tibial bundle which were repaired in the emergency setting. A supramalleolar lateral flap (Masquelet) was needed in one patient who developed cutaneous necrosis exposing the anterior tibial. Postoperative immobilisation consisted in a plaster boot for 45 days in all cases.

Results: Mean follow-up was ten years. Clinical outcome was good in eleven patients (slightly limited dorsal flexion, 10°) and fair to poor in one. We did not have any case of talar necrosis or subtalar degeneration.

Discussion: This series confirms data in the literature. Pure dislocation has as a rule a good prognosis although there is some discrepancy in the literature. In our series, lateral dislocation was more frequent than medial dislocation. Skin opening is frequent and is not a factor of poor prognosis. The absence of talar necrosis is related to preservation of the deltoid branch of the posterior tibial artery and respect of the fibular artery collaterals which supply the posteriolateral tubercle and the tarsal sinus. Emergency reduction of peritalar dislocations eliminates vascular suffering and limits the risk of infection. A temporary talocalcaneal pin is indispensable if the joint is unstable after reduction.