Does the overhang of tibial component in fixed bearing medial unicondylar knee arthroplasty affect 1-year results?

Abstract

Aim: Unicondylar knee arthroplasty (UKA) is an effective treatment for single-compartment knee arthrosis. The compatibility of the size of the components with the bone is one of the factors determining patient satisfaction. With this study we aimed to investigate the effect of size concordance of the tibial component and bone in fixed bearing UKA on functional scores and pain.Methods: Demographic data, preoperative and postoperative 1-year visual analog pain scale (VAS) and Oxford Knee Scores (OKS) were collected from 43 patients operated by a single surgeon with a fixed bearing UKA implant (Zimmer UKA, Warsaw USA) for this prospective cohort study. Patients were then grouped according to radiological compliance of the tibial component to the bone as perfect match or overhang, and the groups were compared in terms of pain and functional scores. Results: Among 43 patients included in the study, 9 (20.9%) were males and 34 (79.1%) were females. The mean age of the patients was 62.1 (8.1) years. The median VAS and OKS scores of the patients before surgery were 6 (3-8) and 26 (21-30), respectively. Postoperatively, VAS score decreased to 1 (0-2), while OKS increased to 44 (37-48) (P<0.001 for both). There were only 3 patients with underhang. Twenty-two (52.1%) patients had perfect match and 18 (41.9%) had an overhang from the bone surface. There was no patient with an overhang greater than 3mm. The VAS and OKS scores at post-operative 1-year of 18 patients with overhang and 22 patients without bone overhang were similar (P=0.674 and P=0.873, respectively).Conclusion: The overhang of the tibial component in fixed bearing unicondylar knee arthroplasty is common, however, this does not affect functional results in 1-year follow-up. Nevertheless, the sizing of the component should be checked by adequate means.