In vitro macrophage response to polyethylene and polycarbonate-urethane particles

This study was undertaken to compare macrophage response to polycarbonate-urethane (PCU), a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty to cross-linked ultra-high molecular weight polyethylene (xUHMWPE) in the presence or absence of endotoxin. Polyethylene wear debris that is generated by total hip and knee replacements has been linked to osteolysis and limiting the lifespan of the implant. We added both lipopolysaccharide (LPS)-free and endotoxin-associated xUHMWPE and PCU particles to a human monocyte cell line (TH1) in culture and measured cell viability and tumor necrosis factor (TNF)alpha, interleukin (IL)-1beta, and prostaglandin E(2) (PGE(2)) in the medium after 24 h. Results indicate that particles (both xUHMWPE and PCU) free of endotoxin did not significantly induce secretion of TNFalpha, IL-1beta, or PGE(2) above basal levels. However, endotoxin-exposed PCU particles induced significantly less TNFalpha and IL-1beta than endotoxin-exposed xUHMWPE particles. This indicates that if endotoxin is available for binding to particles in vivo, then xUHMWPE may be more inflammatory to periprosthetic tissue and bone in part because of its affinity/reactivity with endotoxin when compared with PCU.