ABSTRACT
Polymeric wear debris generated from total hip arthroplasties (THA) has been suggested as a major cause of osteolysis, which may lead to loosening of implants. As the polyethylene wear depends on several parameters a parametric mathematical model has been developed to preview wear volume and localisation. In this paper we focus on an experimental work that has been carried out to measure, on retrieved cups, the wear volume. Experimental results will help in setting the mathematical model. Several ultra high molecular weight polyethylene (UHMWPE) cups coupled to the relevant femoral heads were obtained from hip revisions. The surface roughness was measured on each femoral head. Two linear voltage displacement transducers (LVDT) were mounted on a mobile support to allow planar geometric measurements inside the cups while 10 degree step rotations of the cup allowed to gain 36 equi-spaced transpolar tracks of the worn surface. The measurements enabled 3D reconstruction of the actual cup surface and the evaluation of both shape and dimensions of the worn polyethylene by comparison to the original spherical cup surface. The wear maps were compared to those generated by the mathematical model. The comparison shows similar patterns, with the maximum located near the cup superior borderline.
