Quantitative analysis of ultrahigh molecular weight polyethylene (UHMWPE) wear debris associated with total knee replacements

The size and morphology of particulate near debris retrieved from tissues a round 18 failed total knee replacements (TKR) were characterized, Interfaci al membranes front nine cemented and nine uncemented TKR mere harvested fro m below the tibial components during revision surgery. Wear debris were ext racted using papain and potassium hydroxide digestion. Ultrahigh molecular weight polyethylene (UHMWPE) particles from around cemented or uncemented T KR were similar in size and morphology, The mean size was 1.7 +/- 0.7 mu m with a range of 0.1-18 mu m. Thirty-sir percent of the particles were less than 1 mu m and 90% were Less than 3 mu m, Morphologically the particles we re predominantly spherical with occasional fibrillar attachments and flakes . Particles from TKR were greater than threefold larger than previously cha racterized particles from total hip replacements, which were 0.5 mu m in me an size, Differences in joint conformity and wear patterns between the hip and knee articulations may explain the disparity in size of the wear debris . Since particle size represents an important variable influencing the magn itude of the biological response, it is possible that in vivo the larger TK R debris results in a diminished mediator release, which in turn may accoun t for the lower incidence of osteolysis and aseptic loosening in some desig ns of TKR, (C) 2000 John Wiley & Sons, Inc.