Influence of contact pressure, cross-shear and counterface material on the wear of PEEK and CFR-PEEK for orthopaedic applications

C.L Brockett,S Carbone,A Abdelgaied,J Fisher,L.M Jennings

doi:10.1016/j.jmbbm.2016.06.005

C.L Brockett, S Carbone + Show 3 more

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https://doi.org/10.1016/j.jmbbm.2016.06.005

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Abstract

Total joint replacement is a successful surgical intervention for the treatment of the degeneration of many joints, particularly the hip and knee. As the demand for joint replacement grows, and the life expectancy of the population increases, the performance requirements of these implants also changes. New materials, to improve longevity and enhance performance have been explored including PEEK and CFR-PEEK.This study investigated whether CFR-PEEK and PEEK were appropriate materials for total joint replacement by examining wear performance in simple configuration studies articulating against cobalt chrome under a range of cross-shear and contact pressure conditions. Simple geometry pin on plate studies were conducted for one million cycles for each test condition, with the contact pressure and cross-shear conditions representing a range in which the material may need to operate in-vivo.The wear factor for PEEK was significantly higher than CFR-PEEK and conventional polyethylene under all test conditions. Both PEEK and CFR-PEEK wear were influenced by contact pressure, with the highest wear factors for both materials measured at the highest pressure conditions. PEEK appeared to have a cross-shear dependent wear response, but this was not observed for the CFR-PEEK material.This study has further characterised the wear performance of two materials that are gaining interest for total joint replacement. The wear performance of the PEEK material showed poorer wear performance compared to polyethylene when articulating with a metal counterface, but the performance of the CFR-PEEK material suggested it may provide a suitable alternative to polyethylene in some applications. The wear performance of CFR-PEEK was poorer than polyethylene when it was used as the plate, when there was translation of the contact zone over the surface of the CFR-PEEK plate. This has implications for applications in low conforming contacts, such as lower conformity knee replacement.

Highlights

Total joint replacement has been a successful surgical intervention for joint degeneration for decades
This study investigated whether CFR-poly ether-ether ketone (PEEK) and PEEK were appropriate materials for total joint replacement by examining wear performance in simple configuration studies articulating against cobalt chrome under a range of cross-shear and contact pressure conditions
The wear factors for both PEEK and CFR-PEEK appeared to increase with increasing contact pressure, and reducing contact area, this was not statistically significant for either material (p1⁄4 0.21 and p1⁄4 0.09 respectively)

Summary

Introduction

Total joint replacement has been a successful surgical intervention for joint degeneration for decades. Each year more than 90 000 replacement hips and knees are implanted in the UK alone (12th Annual Report National Joint Registry for England, 2015). Hip and knee replacements are both considered successful surgical procedures, with less than 10% failure within the first ten years of implantation for most designs (Mäkelä et al, 2014; Engh et al, 2012; Argenson et al, 2013). The majority of total joint replacements utilise an ultra-high molecular weight polyethylene (UHMWPE) bearing, articulating with either a metallic or ceramic counterface. It is well documented that the wear of polyethylene releases small particles into the surrounding tissue that elicit a dose-dependent osteolytic response (Ingham and Fisher, 2000; Tipper et al, 2000; Fisher et al, 2009). In order to improve implant longevity and reduce wear, alternative bearing materials have been sought

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