Changes in tibiotalar joint contact areas following experimentally induced tibial angular deformities.

Six cadaveric legs were stripped of all soft tissue excluding the interosseous membrane and the tissues about the ankle joint and foot. Angular deformities were simulated in all planes to a maximum of 15 degrees for proximal, middle, and distal third levels following tibial resection and same-level fibular osteotomy. Anterior ankle arthrotomies allowed exposure to the tibiotalar joint so that contact area could be measured with pressure-sensitive film inserted between the tibia and talus. An angular deformity of 15 degrees or less produced no significant alteration in the contact area of the ankle joint for proximal and middle third tibial levels. Distal tibial deformities showed a dramatic change in the contact area, with as much as a 42% decrease in contact area for anterior deformities. The contact shape for distal third angular deformities of 10 degrees and 15 degrees in all planes also tended to elongate, with a shift to more lateral contact noted. Although minor degrees of angular malalignment had little effect on ankle contact for proximal and middle third levels, it would appear that distal third deformities produce a greater change in ankle joint contact; thus, fractures at the distal level should be managed to minimize the possibility of tibial malalignment.