PEEK-OPTIMA™ as an alternative to cobalt chrome in the femoral component of total knee replacement: A preliminary study.

Raelene M Cowie,John Fisher,Louise M Jennings,Adam Briscoe

doi:10.1177/0954411916667410

Abstract

PEEK-OPTIMA™ (Invibio Ltd, UK) has been considered as an alternative joint arthroplasty bearing material due to its favourable mechanical properties and the biocompatibility of its wear debris. In this study, the potential to use injection moulded PEEK-OPTIMA™ as an alternative to cobalt chrome in the femoral component of a total knee replacement was investigated in terms of its wear performance. Experimental wear simulation of three cobalt chrome and three PEEK-OPTIMA™ femoral components articulating against all-polyethylene tibial components was carried out under two kinematic conditions: 3 million cycles under intermediate kinematics (maximum anterior-posterior displacement of 5 mm) followed by 3 million cycles under high kinematic conditions (anterior-posterior displacement 10 mm). The wear of the GUR1020 ultra-high-molecular-weight polyethylene tibial components was assessed by gravimetric analysis; for both material combinations under each kinematic condition, the mean wear rates were low, that is, below 5 mm3/million cycles. Specifically, under intermediate kinematic conditions, the wear rate of the ultra-high-molecular-weight polyethylene tibial components was 0.96 ± 2.26 mm3/million cycles and 2.44 ± 0.78 mm3/million cycle against cobalt chrome and PEEK-OPTIMA™ implants, respectively (p = 0.06); under high kinematic conditions, the wear rates were 2.23 ± 1.85 mm3/million cycles and 4.44 ± 2.35 mm3/million cycles, respectively (p = 0.03). Following wear simulation, scratches were apparent on the surface of the PEEK-OPTIMA™ femoral components. The surface topography of the femoral components was assessed using contacting profilometry and showed a statistically significant increase in measured surface roughness of the PEEK-OPTIMA™ femoral components compared to the cobalt chrome implants. However, this did not appear to influence the wear rate, which remained linear over the duration of the study. These preliminary findings showed that PEEK-OPTIMA™ gives promise as an alternative bearing material to cobalt chrome alloy in the femoral component of a total knee replacement with respect to wear performance.

Highlights

Polyether ether ketone (PEEK) is a thermoplastic polymer which has been used clinically in the spine and investigated for use as a biomaterial in trauma and orthopaedics due to its favourable mechanical properties and relative bioinertness.[1,2] There has been growing interest in its use as an arthroplasty bearing material either in its natural, unfilled form or reinforced with carbon fibres (CFR-PEEK)
The aim of this study was to assess the suitability of PEEK-OPTIMAä for use as an alternative bearing material to cobalt chrome in the femoral component of total knee replacements in terms of its wear performance
The surface topography of the PEEK-OPTIMAä femoral components was as-moulded; there was no additional post-processing of the articulating surfaces of the implants, and the geometry of the PEEK-OPTIMAä implant was based on the engineering drawing of the cobalt chrome component

Summary

Introduction

Polyether ether ketone (PEEK) is a thermoplastic polymer which has been used clinically in the spine and investigated for use as a biomaterial in trauma and orthopaedics due to its favourable mechanical properties and relative bioinertness.[1,2] There has been growing interest in its use as an arthroplasty bearing material either in its natural, unfilled form or reinforced with carbon fibres (CFR-PEEK). Natural PEEK has been used in the spine in PEEK-on-PEEK articulations, where pre-clinical studies have demonstrated an equivalent wear rate for PEEK cervical (NuNec)[3] and lumbar disc replacements (NuBac) compared to conventional materials,[4] and clinical follow-up has been relatively short term, the implants have shown promise.[5]. CFR-PEEK has been considered for use as acetabular cups in total hip replacement, and experimental wear simulation under standard gait conditions has shown lower wear rates than cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) against ceramic heads[6,7,8] a 5-year follow-up from clinical trials of the Mitch cup has yielded a revision rate of 4 in 25 due to loosening and squeaking.[9] CFR-PEEK has exhibited low wear experimentally in the tibial component of a highly conforming unicompartmental knee replacement.[10] despite promise from experimental wear simulation in low contact stress situations, in high contact stress environments, there are questions about the suitability of CFR-PEEK11,12 and PEEK13 and to date there are minimal clinical data.[14]

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Conclusion