Metal or Modularity: Why do Metal Backed Tibias Have Inferior Outcomes to All-Polyethylene Tibial Components in Patients with Osteoarthritis

Background Biomechanical studies have suggested improved stress distribution in metal-backed (MB) compared to all-polyethylene (AP) tibias, but such potential benefits have not been realized clinically. The purpose of this investigation was to analyze the outcomes of AP components in patients with primary osteoarthritis and compare the results to those obtained with MB tibial components in total knee arthroplasty (TKA). Methods We reviewed 11,653 patients undergoing primary TKA for osteoarthritis. There were 9,999 (86%) MB (8,470 modular and 1,529 monoblock) and 1,654 (14%) AP tibial components. All patients had at least 2 years of clinical follow-up with mean follow-up of 8 years (range 2-30 years). Results Mean survivorship for all primary TKA’s at the 5-, 10-, 15-, and 20-year time points was 97%, 92%, 86%, and 78%. AP tibial components were found to have improved survivorship when compared to modular and monoblock MB counterparts (P