Analysis of the fixation quality of cementless hip prostheses using a vibrational technique

Vibration analysis can be used as a more sensitive alternative to conventional techniques for the detection of loosening of total hip replacement (THR) components. The vibration modes of the human femur and of selected THR prosthetic stems were studied by experimental modal analysis using a CADA-X system and by finite element simulation using MARC/Mentat software. Two hypotheses were formulated: (1) the differences between the vibrational behaviour of an intact femur and of the system formed by a femur and an implanted prosthesis will increase with increasing complexity of the mode shapes of the system; (2) when a prosthesis is implanted in a femur, the vibration modes of the prosthesis will be more affected by this interaction than the modes of the femur. After confirming these hypotheses, a method for peroperative assessment of the fixation quality of a THR stem was derived, based on the frequency shifts of the vibration modes of the system.