In vitro implant-bone interface pressure measurements for a cementless femoral implant. A preliminary study.
Implants endurance as well as a good clinical tolerance depends on the recovery of a physiological stress distribution within bone after implantation. The purpose of the present work was to develop an alternative technique using Force Sensing Resistors (FSR) to gather in vitro pressure values at the implant-bone interface for a cementless implant. Eight cementless femoral stems were instrumented with six calibrated FSR bonded on each facet and then implanted in eight cadaver femurs. Compression tests were performed until failure and FSR pressure values were recorded. The average failure load was 4241 N. The maximum contact pressure measured with the FSR averaged 1.965 MPa. FSR reached many of the requirements for an ideal implant-bone interfacial sensor. This experimentation provided in vitro quantitative data on contact pressure at the implant-bone interface, which could help understanding stress shielding phenomenon and developing relevant numerical model.