The relation between body weight and wear in total hip prosthesis: A finite element study

Abstract

As the current obesity epidemic grows, an increased number of obese patients undergoing Total Hip Arthroplasty (THA) can be expected in the coming years. The National Health Service of the UK (NHS) recommends that an obese patient should undergo weight loss before THA. It is understood that an increased body weight would increase the wear rates on the prostheses, however, the extent of increased wear and the impact on the longevity of the prosthesis is unclear. The NHS found that 45% of THA failures in 2019 were caused by wear which led to a multitude of failures such as infection, aseptic loosening and dislocation such that a revision surgery is then needed. In this study, a finite element model was created to model a walking cycle and a newly developed wear algorithm was used to perform a series of computational wear analyses to investigate the effect of different patient weights on the evolution of wear in THAs up to 5 million cycles. The wear rates shown in this study are closely comparable to previous literature. The XLPE volumetric wear rates were found to be between 15 and 35 mm³/yr (range: 1.5–57 .6mm³/yr) and femoral head taper surface volumetric wear rates were between 0.174 and 0.225 mm³/yr (range: 0.01–3.15 mm³/yr). The results also showed that an increased weight of 140 kg can increase the metallic wear by 26% and polyethylene wear by 30% when compared to 100 kg body weight. As increased wear can lead to a multitude of failure such as aseptic loosening, dislocation and metallosis, from this study, it is recommended that obese patients undergo recommended weight loss and maintain this lesser weight to reduce wear and prolong the life of the THA.