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

Abstract

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. 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. 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). 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 II.