Similar polyethylene wear between cemented and cementless Oxford medial UKA: a 5-year follow-up randomized controlled trial on 79 patients using radiostereometry

• Published in: Acta orthopaedica 2019-01, Vol.90 (1), p.67-73
• Main Authors: Horsager, Kristian, Madsen, Frank, Odgaard, Anders, Fink Jepsen, Claus, Rømer, Lone, Kristensen, Per Wagner, Kaptein, Bart L, Søballe, Kjeld, Stilling, Maiken
• Format: Article
• Language: English
• Subjects: Arthroplasty, Replacement, Knee - adverse effects; Arthroplasty, Replacement, Knee - instrumentation; Arthroplasty, Replacement, Knee - methods; Bone Cements - therapeutic use; Cementation - methods; Coated Materials, Biocompatible - therapeutic use; Female; Follow-Up Studies; Humans; Knee Prosthesis - adverse effects; Male; Middle Aged; Osteoarthritis, Knee - surgery; Polyethylene - therapeutic use; Prosthesis Design; Prosthesis Failure; Radiostereometric Analysis; Treatment Outcome
• ISSN: 1745-3674; 1745-3682; 1745-3682
• DOI: 10.1080/17453674.2018.1543757

Background and purpose - Hydroxyapatite (HA)-coated implants have been associated with high polyethylene wear in hip arthroplasties. HA coating as a promoter of wear in knee arthroplasties has not been investigated. We compared the wear-rate of the polyethylene bearing for cemented and cementless HA-coated Oxford medial unicondylar knee arthroplasties (UKA). Secondarily, we investigated whether wear-rates were influenced by overhang or impingement of the bearing. Patients and methods - 80 patients (mean age 64 years), treatment-blinded, were randomized to 1 of 3 Oxford medial UKA versions: cemented with double-pegged or single-pegged femoral component or cementless HA-coated with double-pegged femoral component (ratios 1:1:1). We compared wear between the cemented (n = 55) and cementless group (n = 25) (ratio 2:1). Wear, impingement, and overhang were quantified between surgery and 5-year follow-up using radiostereometry. Clinical outcome was evaluated with the Oxford Knee Score. Results - The mean wear-rate for patients without bearing overhang was 0.04 mm/year (95% CI 0.02-0.07) for the cemented group and 0.05 mm/year (CI 0.02-0.08) for the cementless group. The mean difference in wear was 0.008 mm/year (CI -0.04 to 0.03). No impingement was identified. Half of the patients had medial bearing overhang, mean 2.5 mm (1-5). Wear increased by 0.014 mm/year for each mm increment in overhang. The mean Oxford Knee Score was 39 for the cementless group and 38 for the cemented group at the 5-year follow-up. Interpretation - The wear-rates were similar for the 2 fixation methods, which supports further use of the cementless Oxford medial UKA. However, a caveat is a relatively large 95% CI of the mean difference in wear-rate. Component size and position is important as half of the patients presented with an additional increase in wear-rate due to medial bearing overhang. Trial registration: ClinicalTrials.gov identifier: NCT00679120.