Chapter 34 - MicroCT Analysis of Wear and Damage in UHMWPE

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) wear continues to be an important factor in the long-term survivability of orthopedic implants. UHMWPE wear volume and wear patterns must be fully evaluated to understand historic UHMWPE wear processes, to evaluate the efficacy of highly crosslinked UHMWPE, and to analyze future UHMWPE formulations that attempt to improve the clinical performance of UHMWPE. There are many methods to evaluate UHMWPE wear, including direct, gravimetric, radiographic, optical, fluid displacement, and more recently, microcomputed tomography (microCT)-based. MicroCT methods provide reliable, accurate, and relatively fast assessment of wear and damage of UHMWPE components. Like all methods of assessing wear, a drawback of these methods is that actual wear cannot be easily distinguished from creep. For that reason, the term penetration is used and refers to the cumulative effect of material removal (true wear) and creep deformation. Some of the microCT techniques discussed in this chapter require a priori knowledge of the nominal implant geometry, while others use measured geometric parameters obtained from unworn portions of the components. MicroCT methods provide three-dimensional quantification of the wear and damage patterns of UHMWPE components; they are extremely valuable in increasing the understanding of the relationships between UHMWPE formulation, loading conditions, mechanical design, and long-term performance.