Biomechanical assessment of patients treated by joint surgery.

Surgical replacement of lower limb joints has been practised for twenty years although there is little quantitative information on loads transmitted either by implants or by other related joints. The results of tests are presented which evaluate the variation in external forces developed between the ground and foot during walking, together with the configuration of the lower limbs and the moments acting about the hips and knees. Two groups of patients were investigated; patients who were assessed prior to joint replacement and at intervals thereafter, and patients for whom the Girdlestone procedure was performed following a failed implant. The results area compared with those from similar tests on clinically normal subjects. There is a significant improvement post-operatively in the mechanical aspects of hip function for the replacement patients. The improvement continues after the first six months post-operatively and may result in abnormally high loading at other joints. At twelve months the performance of the patients with joint replacement differs significantly from the normal subjects and is generally better than the Girdlestone patients.