3-Dimensional Sliding/Contact Computational Simulation of Total Hip Wear

Abstract

Polyethylene wear in total hip replacements is a complex, multifactorial process. A tribologically grounded finite element formulation was developed to make quantitative estimates of polyethylene wear in total hip arthroplasty, incorporating the combined influences of contact stress, sliding distance, and a surface specific wear coefficient. For loading and sliding distance inputs taken directly from human gait data, the computational model showed a strong direct proportionality between femoral head size and volumetric wear rate. Other factors being equal, reducing the thickness of the polyethylene liner led to increases in the computed wear rates, but the effect was far less pronounced than the strong increases in wear rate that accompanied head size increases. Compared with human gait inputs, the load and sliding distance inputs for a 23° biaxial rocking hip simulator led to computed wear rates that were 1.7 times as large, and in which the direction of wear was near the cup apex rather than within the posterosuperolateral quadrant. In general, the finite element model's results emphasize the importance of articulation kinematics, especially sliding distance, in the complex process of polyethylene wear in total hip arthroplasty.