Abstract
Background and purpose — Differences in stress distribution in a mobile-bearing and fixed-bearing unicompartmental knee arthroplasty (UKA) design might lead to a difference in fixation of the tibial component. We compared tibial component migration of a mobile-bearing (MB) UKA and a fixed-bearing (FB) UKA using radiostereometric analysis.Patients and methods — In a randomized, patient-blinded clinical trial 62 patients received either the MB Oxford UKA or the FB Sigma UKA. The patients were followed for 24 months with radiostereometric analysis. Clinical outcome was assessed with Oxford Knee Score (OKS), RAND-36 and leg extension power.Results — Migration of the tibial components was similar between groups throughout follow-up. At 12 months, MTPM of the tibial component was 0.44 mm (95% CI 0.34–0.55) for the MB group and 0.40 mm (CI 0.31–0.50) for the FB group. Between 12 and 24 months, the tibial components migrated with a median MTPM increase of 0.03 mm (CI –0.02 to 0.08) in the MB group and 0.03 mm (CI –0.02 to 0.07) in the FB group. Continuous migration of the tibial component was found for 1 MB UKA and 2 FB UKAs. Both groups showed similar and clinically relevant improvement in clinical outcome.Interpretation — MB and FB tibial components had similar good fixation and clinical improvement until 2 years. Based on this study, a low 5- to 10-year revision rate can be expected for both implants.Trial registration: ClinicalTrials.gov identifier: NCT03434600.
Highlights
Patients and methods — In a randomized, patientblinded clinical trial 62 patients received either the MB Oxford unicompartmental knee arthroplasty (UKA) or the FB Sigma UKA
Between 12 and 24 months, the tibial components migrated with a median Maximal total point motion (MTPM) increase of 0.03 mm (CI –0.02 to 0.08) in the MB group and 0.03 mm (CI –0.02 to 0.07) in the FB group
Primary outcome—radiostereometric analysis (RSA) Tibial component Migration of the tibial components was similar between groups throughout follow-up, both groups showed
Summary
The FB Sigma medial UKA consists of a 2-pegged femoral component with a large posterior condyle radius, a concave fixed bearing, and a tibial component with a keel and a peg at Excluded from analysis due to < 3 visible tantalum beads: Femur Tibia. 4 months visible tantalum beads: 24 months the non-articulating surface Both UKAs were implanted with Palacos bone cement (Heraeus Holding GmbH, Hanau, Germany). Patient satisfaction and knee inserted in the periprosthetic femoral and tibial bone in order function are important clinical outcomes after knee surgery. Patients were randomized to receive the Oxford UKA (MB analysis was not possible due to occluded markers or primary group) or the Sigma UKA (FB group). Pooled data were comparable to precision data from the literature (Tables 1 and 2, see Supplementary data) (Stilling et al 2011, Molt et al 2012, Pijls et al 2012a, Koppens et al 2018)
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