Wear analysis of cross-linked polyethylene inserts articulating with alumina and ion-treated cobalt-chromium femoral heads under third-body conditions

Aseptic implant loosening due to wear debris is the main cause of revision of total hip replacement. Since the presence of third-body particles in the joint gap can lead to highly increased amount of wear, the aim of this study was to evaluate wear of hard-on-soft couplings under third-body wear conditions. For this, alumina ceramic and nitrogen ion-treated cobalt-chromium femoral heads were coupled with sequentially cross-linked polyethylene inserts in a hip joint simulator following ISO 14242-1. Bone cement particles containing zirconium dioxide were added. After 5 million cycles, the amount of wear on the inserts was determined gravimetrically and compared to the amount of wear without third-body particles. The abrasion at the joint components was evaluated by digital microscope. The mean gravimetric wear rates of the polyethylene inserts under third-body wear conditions measured 16.57 +/- 5.98 mg per million cycles when coupled with nitrogen ion-treated CoCr heads and 15.14 +/- 3.30 mg per million cycles with alumina ceramic heads. The results revealed no significant differences between the material pairings. The amount of wear was approximately eight times higher in both cases than that resulting under standard wear test conditions. In the microscopic analysis, the ceramic femoral heads showed higher resistance against abrasive third-body wear.