DOS Kongressen 2014 ·
119
Similar polyethylene wear of cementless and
cemented Oxford Partial Knee’s at 2 years follow-up.
A Randomized RSA Study
Maiken Stilling, Anders Odgaard , Claus Fink Jepsen, Kjeld Søballe,
Per Wagner Kristensen, Frank Madsen
Department of Orthopaedic Research, Aarhus University Hospital; Department
of Orthopaedics, Copenhagen University Hospital Gentofte
Background:
Wear of polyethylene is a significant cause of revision surgery in
partial knee replacement. The Oxford Partial Knee has a fully-congruent, mobile,
polyethylene (PE) bearing designed to minimize wear. Well-functioning knees
have low PE wear, but impingement or incongruous articulation may affect the
wear rate. Cementless components are hydroxyapatite coated, which may risk
higher polyethylene wear.
Purpose / Aim of Study:
To compare PE wear of cementless (CL) and cement-
ed (C) Oxford Partial Knee’s at 2 years by radiostereometric analysis (RSA).
Materials and Methods:
80 patients (48 men) were randomly allocated to
surgery with CL hydroxyapatite-coated (n=25) or C (n=55) Oxford Partial
Knee’s (Biomet Inc.) and UHMWPE at 2 hospital sites. Refobacin bone cement
(Biomet Inc.) was used. Evaluations of PE wear (model-based RSA y-translation,
weight bearing set-up) and clinical outcomes (OKS, AKSS) was performed be-
tween baseline and 2 years.
Findings / Results:
At 2 years followup mean PE wear of 0.43 (sd 0.98) mm
in cementless knees was similar (p=0.10) to 0.11 (sd 1.08) mm in cement-
ed knees. The wear rate including creep was 0.21 (sd 0.48) mm in cement-
less knees and 0.06 (sd 0.54) mm in cemented knees (p=0.10). PE wear did
not correlate to age (p=0.45), OKS (p=0.54), pain in general (p=0.61), pain
during work (p=0.50), side instability (p=0.67), knee axis (p=0.96), walking
aids (p=0.50) or patient reported walking distance (p=0.27). At 2 years mean
OKS was 40 (range 21-47) (p=0.53) with similar improvement from baseline
(p=0.11). Satisfaction was high in both groups. No revisions.
Conclusions:
Cementless Oxford Partial Knee’s had a tendency towards higher
PE wear at 2 years followup, and all knees had higher wear rate than reported
for well- functioning partial knees in the literature. Functional results were good
and similar in both groups.
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