Determination of Total Hip Replacement stem insertion endpoint and stability assessment by vibration analysis: first experiences with per-operative measurements

The assessment of the primary stability of cementless implants still remains a subjective factor in total hip replacement (THR) and, as a consequence, the excessive press-fitting of a THR component can be the cause of intra-operative fractures. Objective information about the stability of implant-bone structures can be obtained using methods based on vibration analysis. After extensive in vitro studies, a per-operative protocol was designed to detect the insertion endpoint and/or to assess the stability of custom made hip prostheses. The experiments were performed on cementless hip stems and on hybrid hip stems that were partially cemented distally. This paper presents the frequency response function evolution during the hip stem insertion in the femur, in per-operative conditions.