In Vivo Wear Particles of Remelted Highly Cross-Linked Polyethylene in Total Hip Arthropalsty

INTRODUCTION: Polyethylene wear particles induce cytokine release by macrophage, which leads to osteolysis and aseptic loosening in total joint arthroplasties. Generation of polyethylene wear particles is one of the most important factors that affecting mid-term and long-term results of total hip arthroplasty (THA). Therefore, to reduce wear generation and to achieve better long-term results of THA, highly cross-linked polyethylene (HXLPE) was recently introduced and coming into wide use. Wear reduction in hip simulator and excellent mid-term clinical results were reported. However, there have been only a few reports on the in vivo analysis of HXLPE wear particles. Number, size, and shape were the features of polyethylene wear particles which had very important effects on macrophage response and the prevalence of osteolysis. Increased number, submicron size, and elongated shape of polyethylene wear particles induced stronger macrophage responses and increased the likelihood of osteolysis. In vitro study showed that HXLPE generated less, smaller, and rounder particles. If HXLPE generates smaller particles in vivo, reduction of volumetric wear does not result in reduction of the number and the biological activity of wear particles. Therefore, in vivo HXLPE wear particle analysis is very important. However, there has been no report on in vivo wear particle analysis of remelted HXLPE. In the current study, remelted HXLPE wear particles from revision THAs were analyzed and compared to our previous reports on conventional PE, 100 Mrad cross-linked PE, and annealed HXLPE.