INTRODUCTION

Loosening is concerned to be the major cause of revision in the artificial prosthesis. Wear debris of UHMWPE dispersed into the implant-bone interface are phagocytosed by macrophages releasing inflammatory cytokines such as TNF-α which leads to osteolysis and loosening eventually. It is known that the size and structure [1] as well as attached substances on particle surface such as endotoxin could affect the amount of cytokines released [2]. An in vivo study using rat femurs showed that the presence of polyethylene particles around implants could result in accumulation of lipopolysaccharide (LPS) from exogenous sources that may affect bone remodeling around implants [3]. It is also reported that LPS is transported throughout the body with lipoproteins or LPS binding proteins [4] and Circulating LPS may originate from local sites of infection or via bloodborne bacteria [5]. In this study, we evaluated the effects of LPS that attached to UHMWPE particle surface by measuring TNF-α released from macrophages.