Trimalleolar fractures with impaction of the posteromedial tibial plafond: implications for talar stability.

BACKGROUND: Trimalleolar fractures usually include a lateral malleolar fracture, a triangular fracture of the posterolateral corner of the tibial plafond, and a horizontal or oblique fracture of the medial malleolus. A subtype of a trimalleolar fracture is reported, differing in the shape and extent of the medial malleolar fracture and the posterior lip fracture, with implications for treatment.
METHODS: In a 3-year period, 10 patients were treated for a trimalleolar fracture with a multifragmentary transverse fracture of the entire posterior tibial lip, including the posterior colliculus of the medial malleolus. The radiographs of all patients showed a pathognomonic double-contour or flake-fragment sign above the medial malleolus. One patient's posteromedial fracture was not initially recognized and he had a standard lateral fracture repair. A double posterior approach was used in nine patients, with fracture repair proceeding from medial to lateral. Intraoperatively, eight of nine patients had impacted osteochondral fragments at the posteromedial corner of the tibial plafond that blocked anatomic reduction and allowed posteromedial subluxation of the talus.
RESULTS: Nine patients had anatomic reconstruction of the posteromedial corner. All fractures healed, and function was normal at one year. One patient had moderate loss of joint space. The patient with the malunited fracture developed symptomatic posteromedial instability of the talus and required an osteotomy of the malunited fragment. He had a good result at 18 months.
CONCLUSIONS: This unique subtype of trimalleolar fracture has distinct radiological features and implications for the strategy of the operative treatment. If recognized immediately and treated appropriately, the results were excellent. If missed initially, reconstructive osteotomy was possible and led to a good result.