Uncemented Oxford mobile-bearing unicompartmental knee arthroplasty demonstrates superior long-term implant survival compared to cemented fixation in patients under 60 years

Abstract

Purpose: More patients are undergoing unicompartmental knee arthroplasty (UKA) at a younger age, and uncemented fixation has been introduced relatively recently. This study aimed to assess the effect of age and fixation type on outcomes following Oxford medial UKA. Methods: This retrospective multicentre study compared survivorship, revision indications and Oxford knee score (OKS) between cemented and uncemented mobile-bearing UKAs across three age groups (<60, 60–69 and ≥70 years). A total of 1401 primary medial Oxford UKAs were included, with mean follow-up of 7.2 ± 3.6 years. Results: Overall, implant survivorship was 93.9%. For patients <60 years, revision-free implant survivorship was higher with uncemented versus cemented fixation 10 years: (91.0% vs. 81.8%, p = 0.014) and 15 years (88.2% vs. 78.8%, p = 0.02). The unadjusted hazard ratio (HR) indicated an approximately threefold higher revision risk with cemented implants (HR 2.90, 95% confidence interval [CI]: 1.18–7.11; p = 0.02). There was no difference in revision-free implant survivorship in older patients (60–69 years: 10-years: 94.8% vs. 91.6%, p = 0.131; 15 years: 91.7% vs. 80.6%, HR: 1.98, 95% CI: 0.91–4.31, p = 0.087; ≥70 years: 10 years: 93.4% vs. 95.6%, p = 0.446; 15 years: 91.6% vs. 91.6%, HR: 0.83, 95% CI: 0.37–1.90, p = 0.67). Bearing dislocation was the most common reason for revision in uncemented implants among younger patients (50.0% and 40.0% of all revisions, respectively), whereas for the cemented group it was osteoarthritis progression (41.7% and 50.0%, respectively). OKS did not differ by fixation type, except for a small early advantage in the 60–69 group at 6 months (38.5 ± 8.1 vs. 40.5 ± 7.2; p = 0.03). Conclusion: Uncemented mobile-bearing Oxford UKA had superior long-term survivorship in patients <60 years of age. There was no difference for patients ≥60 years. These findings suggest that uncemented UKA should be considered for patients <60 years, whereas either cemented or uncemented UKA is suitable for patients >60 years. Level of Evidence: Level II.