Alternative Bearing Surfaces for Arthroplasty

Abstract

Abstract Elastomeric materials have been suggested for use in total joint arthroplasty as an alternative to ultra high molecular weight polyethylene (UHMWPE).1–2 As a bearing material operating under mixed lubrication regimes, UHMWPE is subject to wear. Wear particles cause an adverse tissue reaction eventually resulting in loosening of the prosthesis. The modulus of elasticity of the UHMWPE does not allow sufficient deformation of asperities which would increase the film thickness between the bearing surfaces and prevent wear. Elastomers, however, can deform under pressure and enhance lubrication by the formation of a fluid film through elastohydrodynamic and micro-elastohydrodynamic lubrication.3 However, elastomeric coatings are subject to fatigue and debonding from their rigid substrates. To promote fluid film lubrication and prevent failure associated with the use of soft elastomeric bearings, a “true cushion” bearing was designed consisting of a soft elastomer sandwiched between a thin rigid coating and a thick rigid substrate of similar chemistry. This study was aimed at characterizing the frictional behavior of this construct in a lubricated environment as compared to UHMWPE and a non-coated soft elastomeric bearing.