The Mark Coventry Award: Five-Year Outcomes of a Randomized Controlled Trial on Cemented versus Uncemented Total Knee Arthroplasty: The KneeFix Trial

INTRODUCTION: Uncemented total knee arthroplasty (TKA) components were developed to improve fixation relative to cemented implants. While uncemented femoral components have yielded favorable results, outcomes for earlier uncemented tibial and patellar designs have been inconsistent. Contemporary trabecular-metal implants aim to enhance biological fixation by optimizing osseointegration, yet randomized data comparing fully uncemented constructs including the patella, are limited. We conducted a prospective, single-blinded randomized controlled trial (RCT) comparing 5-year radiological, clinical, and patient-reported outcomes of fully-cemented and fully uncemented trabecular-metal TKA with patella resurfacing. METHODS: Between 2017 and 2020, 316 knees (280 patients) were randomized 1:1 to fully-cemented (n = 158) or fully-uncemented (n = 158) TKA with patella resurfacing. There were 15 patients randomized to the uncemented group who required cementation of at least one component. The primary outcome was implant fixation at five years, assessed on standardized radiographs for progressive and non-progressive radiolucent lines. The secondary outcomes included revisions, other reoperations, and patient-reported outcome measures (PROMs) at five years. Risk ratios, t-tests, and Chi-square tests were performed using a modified intention-to-treat approach. RESULTS: Follow up was 97% at five years. Uncemented TKA had fewer non-progressive radiolucent lines than cemented TKA (two versus 27 cases, relative risk (RR): 0.50, 95% confidence interval (CI): 0.42 to 0.59, P < 0.001). There was one progressive radiolucency that occurred in the cemented group. There were no differences between the groups for revisions (one cemented versus two uncemented, RR 1.52, CI: 0.31 to 7.56, P = 0.55), other reoperations (10 cemented versus eight uncemented, RR: 0.90, CI 0.59 to 1.39, P = 0.66), or PROMs (Oxford Knee Score, EuroQol-5 Dimensions, International Knee Society Score, Pain Visual Analog Scale, Forgotten Joint Score, and Satisfaction). CONCLUSIONS: At five years, fully-uncemented TKA utilizing trabecular metal with patella resurfacing demonstrated equivalent clinical and patient-reported outcomes and similar revision/reoperation rates to fully-cemented TKA, with fewer non-progressive radiolucent lines. Longer-term follow-up is required to determine whether radiographic differences affect implant survivorship and longevity overall.