A study of polyethylene and modularity issues in >1,000 posterior cruciate-retaining knees at 5 to 11 years

Polyethylene quality and production technique and monoblock versus modular design of tibial components affect the polyethylene wear of total knee arthroplasties (TKAs). We reviewed > 1,000 TKAs performed with the AGC prosthesis (Biomet, Warsaw, IN) using a uniform surgical technique with a 5- to 11-year follow-up. Of tibial components, 698 were of compression-molded monoblock design and 353 were of ram-extruded modular assembly design. The effect of the differences in tibial component design on the 5- to 11-year clinical and radiologic outcomes was studied. Higher rates of osteolysis, radiolucent lines, and revision were found with the ram-extruded modular design. This modular design is similar to most tibial component designs currently used in TKA, yet osteolysis in completely cemented components is described rarely. The TKAs done with a compression-molded monoblock design gave better clinical and radiologic results. The improved results may be due to polyethylene quality, assembly design, or a combination of these factors.