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 ยฎ , 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.