2001 OITE Question 97

Question

Figure 25 shows the AP radiograph of a 20 year old man who sustained a twisting injury to his foot. An attempt at closed reduction is unsuccessful, most likely because of

1. buttonholing of the talar head through the extensor retinaculum

2. osteochondral fracture of the posterior facet of the talus

3. interpositioning of the peroneal tendons

4. interpositioning of the posterior tibial tendon

5. fracture of the talar neck

Figures

Answer (click for answer)

The correct answer is 4. Subtalar dislocations involve a dislocation of the subtalar joint as well as of the talonavicular joint. Open subtalar dislocation should be taken to the operating room and irrigated and debrided before reduction. These dislocations are classified as medial, lateral, anterior and posterior according to which position the dislocated calcaneus has taken. Medial dislocation involves an injury of the lateral ankle ligaments, with the calcaneus dislocated medially. The talonavicualr joint is dislocated so the talar head is dislocated laterally. Closed reduction may be impossible if the talar neck gets entrapped by the extensor retinaculum or peroneal tendons or there is impaction of the talus onto the lateral aspect of the navicular. In lateral dislocations the calcaneus dislocated laterally, and the talar head and neck dislocate medially. Failure of closed reduction can be caused by the talar neck and head entangled in the posterior tibial tendon or by a small fracture involving the head of the talus. (Miller)

Reference: Miller MD, Brinker MR: Review of Orthopeadics, 3rd edition Pp301-303