A Randomized Controlled Trial Comparing “High-Flex” vs “Standard” Posterior Cruciate Substituting Polyethylene Tibial Inserts in Total Knee Arthroplasty

The purpose of this study is to compare the range of motion and clinical outcomes of a standard posterior-stabilized (PS) vs the high-flex (HF) polyethylene tibial insert of a posterior cruciate substituting total knee arthroplasty system. One hundred patients were entered into a prospective, blinded, randomized clinical trial in which 50 patients received a Genesis II PS insert and 50 patients received a Genesis II HF insert (Smith & Nephew, Memphis, TN). At an average follow-up of 2.7 years (range, 2.3-3.1 years), there were no differences in any outcome measures (Western Ontario and McMaster Universities osteoarthritis index, Short-Form 12, Knee Society clinical rating scores, anterior knee pain). There were no differences (P = .811) in average knee flexion at 2 years (standard, 123° ± 7°; HF, 124° ± 7°). In summary, this prospective blinded randomized clinical trial demonstrated no differences between a PS and HF polyethylene design. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.