Biomechanical effects on osseointegration of implants in a weight-bearing animal model

Macrostructured femoral stem prostheses (cobalt-chrome alloy) were implante d in a weight-bearing dog model in order to study implant osseointegration as a function of biomechanical bone loading conditions. Time until sacrific e was 6 months in almost all dogs. 5 implants showed roentgenologically pro ximal new bone formation. In accordance to a distal force transmission to t he bone of a stiff femoral implant 13 of 16 stems demonstrated an extensive distal new bone formation with a microradiographical and microscopical sta ble fixation of the distal tip of the implant without lucent lines. Proxima lly as well osseous integration as a circumferential fibrous tissue encapsu lation lead to bone atrophy. The results prove that osseointegration depend s as well on loading conditions as on biocompatibility.