Assessment of Fixed Bearing and Rotating Platform Total Knee Arthroplasty Designs Using the Patient Knee Implant Performance Scoring System: Post-hoc Pooled Analysis of Data From Two Prospective, International, Multi-centre, Non-randomised Studies.

Background The optimal choice of polyethylene insert in total knee arthroplasty (TKA) continues to cause contention. Rotating platform bearings (RP) have theoretical advantages but have failed to demonstrate a functional difference compared to fixed bearings (FB) in clinical studies. No studies have analysed the effect of body mass index (BMI) on functional scores between RP and FB TKA. No studies have investigated RP and FB TKA using the new Patient Knee Implant Performance (PKIP) patient-reported outcome measure (PROM). Methods This was a post-hoc analysis of the data from two prospective, non-randomised, multi-centre studies conducted across centres in Australia, the United Kingdom, and the United States by DePuy Synthes (West Chester, Pennsylvania, United States). Functional outcomes between RP TKA and FB TKA were compared. Baseline and two-year follow-up data were compared across multiple PROMs in both groups, including PKIP. The analysis included adjustment for BMI between groups. Results A total of 1,718 patients across 27 centres were included in the study. Of this, 959 participants underwent FB TKA and 759 participants underwent RP TKA. No significant difference was found between RP and FB in the change from baseline at two years across any parameter in all PROMs. When adjusted for BMI, statistical differences were seen between RP TKA and FB TKA at two years in several PROMs. Conclusion Both FB and RB showed excellent results at two years. Our data does not demonstrate a significant difference in RP TKA over FB TKA at two years in any PROM. Advantages were seen in some PROMs for RP when adjusted for BMI alone at two years.