Intraarticular contact stresses with simulated ankle malunions.

Peak contact stresses were evaluated in a human cadaver ankle model of ankle fracture malunion. In one set of experiments, changes in peak contact stresses were evaluated for ankles loaded with lateral displacements of the talus and fibula of 1, 2, 3, and 4 mm. In a second set of experiments, peak contact stresses were evaluated after removal of posterior malleolar fragments. Peak contact stresses were concentrated over the anterior medial talar dome in normal specimens, and in specimens with stimulated malunions. There were relatively low stresses beneath the medial malleolus. Peak stresses for ankles without talar displacements ranged from 1.9 MPa to 12.4 MPa (eliminating one disparate specimen). There was no increase in peak stresses with lateral displacements of the talus or with removal of posterior malleolar fragments. The fact that peak stresses with simulated ankle malunions were not elevated suggests that factors other than the magnitude of normal contact stresses are of greater importance in the pathogenesis of posttraumatic arthritis.