Submicron sized ultra-high molecular weight polyethylene wear particle analysis from revised SB Charite III total disc replacements

Submicron sized particles are frequently observed in retrieved total hip and knee periprosthetic tissues and appear to be critical in the activation of the phagocytic inflammatory response. In this paper the concentration, size and shape of ultra-high molecular weight polyethylene (UHMWPE) wear particles between 0.05 and 2.00 mu m were determined after isolation from periprosthetic tissues from retrieved lumbar SB Charite III total disc replacements (TDR) using scanning electron microscopy (SEM). For comparison, UHMWPE wear particles were isolated from gamma-radiation-air sterilized total hip arthroplasty (THA) revision tissues. The mean concentration of UHMWPE particles in TDR tissues was 1.6 x 10(9) g(-1) tissue (range 1.3-2.0), which was significantly lower than the concentration of 2.3 x 10(9) g(-1) THA revision tissue (range 1.8-3.2) (P = 0.03). The mean particle size (equivalent circular diameter: TDR, 0.46 mu m; THA 0.53 mu m, P = 0.60) and mean shape were comparable between TDR and THA (aspect ratio: TDR, 1.89; THA, 1.99, P = 0.35; roundness: TDR, 0.58; THA, 0.56, P = 0.35). However, the TDR particles tended to be smaller and more round. Although no correlations were found between visible damage to the UHMWPE core and the concentration or shape of the UHMWPE particles, a positive correlation was found between increasing particle size and increasing rim penetration of the TDR core (P = 0.04). The presence of UHMWPE particles of similar size and shape in TDR tissue, albeit lower in concentration, might explain why, unlike THA, pain rather than osteolysis is the major reason for revision surgery.