EVALUATION OF ISCHIAL WEIGHT-BEARING ORTHOSES, BASED ON IN-VIVO HIP-JOINT FORCE MEASUREMENTS

The reduction of hip joint forces by ischial weight-bearing orthoses, used for the treatment of Legg-Perthes and other joint diseases, was measured in vivo in a patient with two instrumented endoprostheses. Three different types of orthoses reduced hip joint loading by about 30%, independent of their cuff design and the position in which the femur was held. The direction of the joint forces was changed in such a way that the size of the load-carrying joint areas decreased by up to 3.4% with two conventional orthoses. With the third model with improved containment of the femoral head this area increased by up to 8.2%. All the orthoses studied support the pelvis too close to the affected joint, leading to insufficient load reduction. A design concept is proposed which prevents tilting of the pelvis in the frontal plane and may improve the force reduction at the hip joint. Relevance Ischial weight-bearing orthoses are still widely used, although their clinical benefit is controversial. The observed reduction of the joint load is not better than achievable with two forearm crutches. New data about very large joint forces during fast walking and stumbling indicate that a potential benefit of orthoses for the course of Legg-Perthes disease may mainly be caused by the restrictions put on the patients' activities. With regard to the encumbrance of the patients, other methods of treatment should therefore be preferred.