EFFECT OF POLYETHYLENE QUALITY ON WEAR IN TOTAL KNEE ARTHROPLASTY

During evaluation of 29 Ortholoc II tibial polyethylene components ret rieved at revision surgery, the authors noticed that components with a lot number prefix of CP (Custom product) consistently had minimal wea r and those with a standard lot number had severe wear, regardless of patient age, weight, gender, and activity level. Non-CP components had earlier and more severe wear than CP components in service for the sa me amount of time. Microscopic evaluation of the polyethylene revealed major differences in the material. Large subsurface cracks, fusion de fects, and intergranular cracks were present in the non-CP components, but these defects were minimal or nonexistent in the CP components. T he components with defects had a significantly greater delamination ra te than those without defects. Gamma irradiation did not seem to accel erate wear or delamination, because irradiated components that had min imal microscopic signs of fusion defects performed as well as nonirrad iated components with a similar microscopic appearance. The manufactur ing details disclosed that different materials and processing methods were used for the 2 groups. The results from this study suggest that i mproved quality control of polyethylene material would greatly decreas e wear and delamination of total knee arthroplasty components.