Review Question - QID 5503

The fixation of the medial malleolus in the figure consists of a contoured reconstruction plate placed in buttress (antiglide) mode with screws running parallel to the joint surface and perpendicular to the fracture line. This fixation is indicated for vertical fractures of the medial malleolus from a supination-adduction (SA) shearing force.

A vertical fracture of the medial malleolus is characteristic of a Lauge-Hansen SA fracture. Bimalleolar SA fractures will also demonstrate a distal fibular avulsion. Another characteristic is impaction of anteromedial distal tibia by the talar dome. An anteromedial surgical approach allows visualization of this region, elevation of impaction, and bone grafting of the defect if necessary.

Dumigan et al. analyzed 4 different methods of treating vertical shear fractures with polyurethane models. They found that fixation with a 4 hole 1/3 tubular plate with 2 screws in the distal fragment was stiffer than fixation with the same plate with 1 screw in the distal fragment (3 in the proximal), fixation with two 3.5mm cortical screws with washers, and fixation with two 4mm cortical screws with washers. They recommend plating over screw-alone constructs.

McConnell et al. reported 8 cases of anteromedial marginal impaction in SA fractures. They note that 44 fractures were SA type. Following reduction and fixation, all 8 patients had excellent outcome and no arthritis. They recommend an anteromedial approach to the medial malleolus for visualization.

Figure A is a lateral radiograph showing fixation of both malleoli with reconstruction plates. Illustration A is an postoperative AP fluoroscopy image. Illustration B is an injury film demonstrating the same SA ankle fracture. Illustration C shows articular impaction at the medial shoulder of the ankle joint typical of SA injuries. Illustration D shows marginal impaction in SA fractures.

Incorrect Answers
Answer 1: Bimalleolar pronation-abduction fractures comprise an avulsion fracture of the medial malleolus and comminuted fibula fracture proximal to the syndesmosis (with a butterfly fragment).
Answer 3: Bimalleolar pronation-external rotation fractures comprise a transverse medial malleolar fractures and a spiral fibula fracture (anterosuperior to posteroinferior) above the syndesmosis.
Answer 4: Bimalleolar supination-external rotation fractures comprise a transverse medial malleolar fracture and short oblique fibula fracture (anteroinferior to posterosuperior).
Answer 5: Axial loading leads to pilon fractures. A dorsiflexed position leads to anterior plafond injury.