A spatial dynamic model to investigate hip squeaking and contact point path in hip implants

Abstract

The present paper hypothesises firstly that stick-slip, negative-damping effects and alteration in contact force induces a three-dimensional vibration of the head within the cup; and secondly that this friction-induced vibration alters the head/cup contact point sliding track in both micro and macro domains. A spatial multibody dynamic approach was developed taking into account three-dimensional physiological forces and motion of the human body. Tangential and normal contact forces were incorporated into nonlinear motion equations as external forces. Governing dynamic equations were solved using numerical methods and FFT analysis used to extract hip squeaking frequencies. The approach was found to be robust and fast with respect to computation time and accuracy and the results validated by comparing with outcomes available in the literature. Moreover, hip squeaking frequencies obtained from the present procedure are consistent with in-vivo results.