Abstract
Introduction
Concerns regarding UHMWPE wear particle induced osteolysis in total hip replacement (THR, [1]) have led to alternative materials to be sought. Carbon-fibre reinforced poly-ether-ether-ketone (CFR-PEEK) has shown reduced wear in hip and knee configurations compared with conventional polyethylene [2-4]. The aim of this study was to investigate the wear performance of a ceramic-on-CFR PEEK THR through a simulator study.
Methodology
Five 36mm diameter Biolox Delta heads were paired with extruded CFR-PEEK cups and tested in a hip wear simulator (Simulator Solutions, UK) for 10 million cycles (Mc). Tests were performed in a Prosim hip simulator, which applied a twin peak loading cycle, with a peak load of 3kN. Flexion-extension of −15 to +30 degrees was applied to the head and internal-external rotation of +/− 10 degrees was applied to the cup, components were mounted anatomically. The lubricant was 25% (v/v) calf serum supplemented with 0.03% (w/v) sodium azide. Wear was assessed gravimetrically at several intervals adjusted for moisture uptake using loaded and unloaded soak controls.
Results
The volumetric wear of the CFR-PEEK cups was calculated from weight loss, corrected for fluid uptake by a mean value of the loaded and unloaded soak controls. The CFR-PEEK bearings exhibited step-like wear behaviour throughout the study (Figure 1), with periods of ‘higher’ wear rate (between 0.4mm–1.4mm3/Mc) and periods of a ‘lower’ wear rate (less than 0.4mm3/Mc), a phenomenon that has previously been observed with this material [3]]).
Discussion
The wear of a novel ram-extruded CFR-PEEK cup, articulating with a Biolox Delta ceramic head was assessed through a 10Mc experimental wear study. The mean wear rate over the period of the study was very low, with less than 1mm3/Mc measured. The wear rates observed in this study are comparable with reported wear rates for 36mm diameter hard-on-hard bearings [5], and lower than wear rates measured for a highly cross-linked polyethylene bearing [6]. The wear rates reported in this study are lower than those previously reported [3], however, as CFR-PEEK operates within a boundary lubrication regime, the reduced head diameter in the present study would result in reduced sliding distance and lower surface wear.
