Fixed-Bearing versus Mobile-Bearing Unicondylar Knee Arthroplasty: Comparison of Patients with Similar Component and Mechanical Axis Alignment

Aim: Unicondylar knee arthroplasty (UKA) is among the treatment options for patients with arthritis limited to one compartment of the knee. Fixed-bearing (FB) and mobile-bearing (MB) inserts are present. This study aimed to compare functional and clinical outcomes and revision rates of patients operated with FB-UKA and MB-UKA.
Material and Methods: A total of 131 knees of 118 patients underwent cemented UKA, with a mean follow-up period of 80.58±31.31 months for FB-UKA and 97.66±29.24 months for MB-UKA. Clinical and functional evaluation was performed by the Knee Society Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, at the last follow-up visit. The factors affecting the radiological and functional results, complication, and revision rates were examined under three main titles; i) surgeon-related, ii) patient-related, and iii) component alignment-related factors.
Results: There was no significant difference between the groups in terms of age, gender, body mass index, and side. Regarding the KSS scores, 9 (6.87%) knees were within acceptable limits, 62 (47.32%) knees were found to be good, and 60 (45.80%) knees were found to be excellent. No statistically significant difference was found between groups (p=0.497). Regarding the WOMAC scores, the MB-UKA group had significantly lower pain (p=0.049) and stiffness (p=0.014), but similar functional (p=0.591) scores. There was no statistically significant difference regarding revision rates (p=0.931).
Conclusion: Similar clinical, functional, and radiological results and low revision rates were found. In terms of pain and joint stiffness, a significant difference was found between groups, in favor of MB-UKA.