Polyethylene wear in retrieved canine acetabular components - A tribological study

The aim of this pilot study was to define the mechanism and mode of polyeth ylene wear in acetabular components retrieved from seven dogs following the rapeutic total hip replacement. The articular surface of each acetabular co mponent was examined using contact profilometry and scanning electron micro scopy (SEM). Peak-to-valley distance (P-V) and arithmetic average surface r oughness (R-a) were calculated for each quadrant of the surface. Deformatio n of the regular profile of the machining lines was the least severe form o f surface alteration. Randomly orientated scratches, fine tapered filaments , ripples, and coarse surface shredding were common SEM observations. Gougi ng of the convex surface of the cup was seen in two cases following failure of the polyethylene-cement interface. Wear of the nonarticular acetabular rim suggested neck impingement in one case. P-V and R-a were significantly lower in the cranio-dorsal zone, compared to the average roughness of the o ther three quadrants (p < 0.05). Abrasion, adhesion and fatigue were the pr incipal mechanisms of polyethylene wear, and were implicated in the product ion of polyethylene particulate debris. Meticulous removal of abrasive thir d bodies at the time of surgery, and correct orientation of the acetabular component, should reduce early and severe wear.