Hip contact forces and gait patterns from routine activities

In vivo loads acting at the hip joint have so F;rr only been measured in fe w patients and without detailed documentation of gait data. Such informatio n is required to test and improve wear, strength and fixation stability of hip implants. Measurements of hip contact forces with instrumented implants and synchronous analysts of gait patterns and ground reaction forces were performed in four patients during the most frequent activities of daily liv ing. From the individual data sets an average was calculated. The paper foc uses on the loading of the femoral implant component but complete data are additionally stored on an associated compact disc. It contains complete gai t and hip contact force data as well as calculated muscle activities during walking and stair climbing and the frequencies of daily activities observe d in hip patients. The mechanical loading and function of the hip joint and proximal femur is thereby completely documented. The average patient loade d his hip joint with 238% BW (percent of body weight) when walking at about 4 km/h and with slightly less when standing on one leg. This is below the levels previously reported for two other patients (Bergmann et al., Clinica l Biomechanics 26 (1993) 969-990). When climbing upstairs the joint contact force is 251% BW which is less than 260% BW when going downstairs. Inwards torsion of the implant is probably critical For the stem fixation. On aver age it is 23% larger when going upstairs than during normal level walking. The inter- and intra-individual variations during stair climbing are large and the highest torque values are 83% larger than during normal walking. Be cause the hip joint loading: during all other common activities of most hip patients are comparably small (except during stumbling), implants should m ainly; be tested with loading conditions that mimic walking and stair climb ing. (C) 2001 Elsevier Science Ltd. All rights reserved.