CALCANEAL FRACTURES CAUSE A LATERAL LOAD SHIFT IN CHOPART JOINT CONTACT STRESS AND PLANTAR PRESSURE PATTERN IN-VITRO

In order to evaluate the effects of the anatomical changes after calca neal fractures on joint loading characteristics we investigated the ef fects of simulated calcaneal fractures on intra-articular loading in t he Chopart joint and on plantar pressure patterns in vitro. Five fresh -frozen lower leg specimens were axially loaded with 500 N in three po sitions: neutral, 10 degrees plantarflexion and 10 degrees dorsiflexio n. The loading characteristics were determined before and after creati ng a tongue-type fracture by osteotomy. Plantar loading patterns were measured with a capacitive pressure distribution platform. Intra-artic ular contact areas and pressures were recorded on pressure sensitive f ilm introduced into the talonavicular and calcaneocuboid joint. Increa sed loading in the calcaneocuboid joint (+25%, p = 0.005) and decrease d loading in the talonavicular joint (-16%, p = 0.01) corresponded to increased loading of the lateral aspects of the plantar surface. These findings were independent of the foot position. The results suggest t hat the effects of increased lateral foot loading which have been obse rved in calcaneal fracture patients (Rosenbaum et al., Clin. Biomech. 10, 345-351, 1995) are caused by changes in joint kinematics and do no t appear to result from a protective gait pattern established after th e injury. Copyright (C) 1996 Elsevier Science Ltd.