Hip simulator evaluation of the effect of femoral head size on sequentially cross-linked acetabular liners

Abstract

Larger femoral head size reduces the incidence of hip dislocation, which is a major complication after total hip arthroplasty. However, acetabular liner wear is a function of contact area and therefore head size. Larger heads also reduce liner thickness and there is a general concern about increased wear. This study evaluates the influence of polyethylene thickness and femoral head size on the wear performance of sequentially cross-linked acetabular inserts. A sequential cross-linking and annealing process for treating ultra-high molecular weight polyethylene (UHMWPE) has been developed (X3 ®, Stryker Orthopaedics). This material was compared to conventional UHMWPE in hip simulator wear testing. Liners varying from 32 mm to 52 mm in diameter and 3.8–7.9 mm in thickness were evaluated here. An MTS (Eden Prairie, MN) multi-station hip simulator was used for wear testing. All components were tested at 1 Hz under a joint reaction profile (2450 N maximum) and 50% diluted Alpha Calf Fraction Serum (Hyclone, Logan, UT). Results show no statistically significant effect of head size or liner thickness on wear rate of sequentially cross-linked liners. Analysis shows poor correlation between head size and wear rate ( R 2 = 0.2751), and between liner thickness and wear rate ( R 2 = 0.0055). An average of all tested sizes show a reduction of 96% in wear rate compared to control. The excellent wear performance of the sequentially cross-linked liners studied here increases the potential for use of large head components in total hip arthroplasty.