All-polyethylene tibial components are not inferior to metal-backed tibial components in long-term follow-up of knee arthroplasties

Background: All-polyethylene tibias (APT) are under-utilized in most of the Western countries, due to a shift from the original all-polyethylene design to metal-backed tibia (MBT) components. Only few total knee prostheses allow direct comparison between APT and MBT components, due to different geometric designs in many systems. The Depuy PFC Sigma prostheses have a similar geometric design in both the MBT and the APT, and with the same corresponding femoral component, thus allowing an assessment and comparison between APT and MBT components. Methods: This is a retrospective analysis of a consecutive series of osteoarthritic patients who underwent total knee arthroplasties with at least 10-year follow-up comparing a modern congruent APT component to a modular MBT component of the same design. Results: Seventy-three patients (81 knees, mean age 73 years) were available for assessment. Among the cohort, three patients had revision surgery (one from the APT group). In total, 73 patients were available for follow-up (59 MBT prostheses and 22 APT prostheses). There were no differences in knee function (Knee Society score, range of motion, stability) or radiographic parameters between the groups. Of the three revisions due to tibial tray loosening, only one was performed in the APT group and two were performed in the MBT group; another revision in the MBT group was due to loosening of both components; none of the revisions were due to septic complications. Ten-year survivorship of both designs was 92 %. Conclusions: While function of both designs appears similar, the APT design shows a trend toward requiring fewer revisions and is more cost-effective.