Background: Adoption of cross-linked polyethylene in Total Knee Arthroplasty (TKA) has been tentative, however, this study examined the 10-year survivorship of a fixed bearing knee replacement system featuring a Moderately CrossLinked Polyethylene (MXLK) bearing, a cobalt chrome (CoCr) tibial tray with a highly polished top surface, and a new polyethylene-to-tray locking mechanism. 

Materials & Methods: From November 2005 to June 2008, 537 PFC Sigma TKAs were prospectively entered into this non-comparative, multicenter, multinational study. Average age at time of surgery was 66.7 years, 57% were female, average body mass index was 30.5 kg/m2, and the dominant diagnosis was osteoarthritis (96.6%). Kaplan-Meier (KM) survivorship was the primary endpoint with primary event definition being removal of any component for any reason. Additional endpoints included: American Knee Society scores (1993 version: knee and function), Oxford Knee score (0- 48 scale); radiographically assessed rates of progressive Radiolucent Lines (RLL’s) greater than 2mm. 

Results: The primary endpoint 10-year KM survivorship estimate was 95.4% (95% C.I.: 93.1% - 97.0%). There were 22 revisions reported through 10 years, and another 1 thereafter. The mean 10-year AKS score was 88.1 points (mean change from baseline (MCFB) 48.6). The mean 10-year Oxford Knee score was 36.3 points (MCFB 15.9). Percent of subjects with progressive RLL’s greater than 2mm on the AP Tibia was 4.4% (12/274) at 1 year and 2.0% (5/256) at 10 years. For the Lateral Tibia, Femoral and patellofemoral radiographic views progressive RLL’s greater than 2mm never exceeded 2.0%. There were 9 device related SAEs in 537 subjects (1.7%). 

Conclusion: Manufacturing and design changes have been made to increase longevity of knee replacement systems as a result of concerns of polyethylene wear after TKA. Results of the current study demonstrate excellent 10-year survivorship for the PFC Sigma knee system.

Ivan J. Brenkel is a retired Consultant Trauma and Orthopaedic Surgeon who practiced at the Queen Margaret Hospital in Dunfermline, Scotland. He is widely recognized for his clinical research, particularly in lower limb arthroplasty (hip and knee replacements) and the management of hip fractures. He specialized in trauma, hip and knee arthroplasties (joint replacements), and conducted extensive clinical research, including notable studies on post-surgery outcomes in younger patients.