Design and development of a pre-clinical test for cemented femoral hip replacements

Abstract

Current state of the art testing methods do not allow implant performance to be assessed relative to known failure modes, prior to clinical use. Even clinically, it can take up to 5 years before implant performance can be readily quantified. This situation is not desirable for either the surgeons who have to chose from amongst the wide array of implants on the market, or for the engineers who are effectively selling a device of un-proven performance. Femoral hip implants loosen. The rate at which they loosen is determined by many factors, but dominated by implant design. Loosening has been correlated with the migration measured at 2 years post-operatively. This thesis presents a pre-clinical testing protocol which measures prosthesis migration, migration rates, and inducible displacement (i.e. amplitude of motion) in six degrees-of-freedom, for 2 million cycles. Using this protocol, the performance of two prostheses known to loosen at different rates clinically are assessed; the Muller Curved prosthesis, which has a high revision rate, and the Lubinus SPII prosthesis, which has a low revision rate.