A Comparison of Revision Rates for Cemented Versus Cementless Fixation for a Single Prosthesis Posterior-Stabilized Total Knee Arthroplasty: Medium-Term Follow-up of Cases from the UK National Joint Registry, and Radiographic Analysis of a Northern Ireland Cohort.

Background: Cementless total knee arthroplasty (TKA) offers several conceptual benefits over cemented TKA. However, the effect of the cam-post interaction of posterior-stabilized (PS)-TKA on implant osseointegration remains uncertain. Methods: Data were obtained from the UK National Joint Registry (UK NJR), on patients who underwent primary PS-TKA for osteoarthritis using the Stryker Triathlon system between January 1, 2010, and December 31, 2019. Patients were excluded if they had an implausible body mass index (BMI) or where there was use of bone graft, revision implants, or hybrid cementation. A local cohort of patients were similarly identified, with additional postoperative radiographic analysis performed. The primary outcome for both cohorts was all-cause survivorship. Results: There were 18,824 relevant PS-TKA: 1,068 (5.7%) cementless and 17,756 (94.3%) cemented. The cementless group had a higher proportion of men (48.7% vs. 41.9%), a lower median age (70 vs. 71 years), a higher median BMI (31 vs. 30 kg/m2), and shorter median duration of exposure to risk of revision (5.5 vs. 6.9 years, p < 0.01). All-cause revision rates were similar between the cementless and cemented groups (2.4% vs. 2.8%, p = 0.49). The second cohort of 875 patients had no statistical difference in all-cause revision rates for cementless and cemented PS-TKA (2.9% vs. 1.3%, p = 0.22), and radiographic analysis of those with cementless implants revealed that revision was more likely if there was radiographic loosening within the first 30 months postoperatively (33.3% vs. 2.1% if absent). Conclusions: This study, the largest of its kind, reports equivalent revision rates between cementless and cemented fixation of PS-TKA in the medium term, suggesting that either fixation option was reasonable for PS-TKA. This work complements existing NJR reports by providing a comparison not readily available, for the PS design of what is currently the most used TKA system in the United Kingdom. Level of Evidence: Level III. See Instructions for Authors for a complete description of levels of evidence.