An instrumented brace for study of legg-calve-perthes disease

Abstract

The accepted clinical method for treating children with Legg-Calve-Perthes disease is by means of abduction bracing. To evaluate the effectiveness of this method, one major necessary step is solving the three-dimensional inverse dynamics problem for the intersegmental loads at the hip joint. In order to provide part of the external loading data on the lower limb required to solve this problem, an instrumented abduction brace has been designed. The instrumented brace duplicates the mechanical behavior of the Scottish Rite Atlanta treatment brace, currently a clinically popular device. Instrumentation of the actual Atlanta brace was not considered, since its complicated mechanism couples forces applied by the brace to the thighs, resulting in moments difficult to measure. The new design eliminates all moments and simply applies one single force to the center of the femur. This single force is measured by a strain gage dynamometer. To assess the utility of the instrumented brace, the brace was fitted to three test subjects and the brace force was recorded while children walked through multiple trials. Testing of the brace demonstrates that it can be considered a dependable tool in studying the mechanical interactions between the brace and patient.