Vibration Analysis of the Biomechanical Stability of Total Hip Replacements

In cases of severe rheumatoid arthritis or osteoarthritis, the hip joint is substituted by an artificial joint composed of a femoral stem fitted with a spherical head that can rotate inside a cup inserted in the acetabulum. This procedure is called total hip replacement (THR) and is one of the most frequently performed orthopaedic surgeries. For a cementless femoral implant, the fixation is achieved by preparing a slightly undersized bone bed, and the implant is forcefully hammered into the bone. The initial stability at the time of surgery is one of the most important factors to establish long survival of the implant. With each surgical hammer blow, the fixation of the implant in the bone increases. However, introducing an implant with a diameter wider than the bone’s inner canal contour (i.e. press fit) introduces stresses in the cortical bone which can cause femoral fracture. In response to mechanical excitations (i.e. hammer blows or external vibrations), a femur-implant structure will display vibration modes and frequencies, just like any other mechanical structure. Changes in material properties or boundary conditions of a femur-implant structure will change its vibration modes and frequencies, which can be obtained numerically and experimentally. Therefore, this chapter explains how to perform vibration analysis on a THR component (i.e. the femoral implant) in order to assess femur-implant stability, as well as how to analyze, present, and interpret results.edition: 1status: publishe