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 m easured in vivo in a patient with two instrumented endoprostheses. Thr ee 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 co ntainment of the femoral head this area increased by up to 8.2%. All t he 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 imp rove the force reduction at the hip joint. Relevance Ischial weight-be aring orthoses are still widely used, although their clinical benefit is controversial. The observed reduction of the joint load is not bett er than achievable with two forearm crutches. New data about very larg e joint forces during fast walking and stumbling indicate that a poten tial benefit of orthoses for the course of Legg-Perthes disease may ma inly be caused by the restrictions put on the patients' activities. Wi th regard to the encumbrance of the patients, other methods of treatme nt should therefore be preferred.