Purpose: To determine survivorship and functional outcomes of fixed and mobile-bearing designs in lateral unicompartmental knee arthroplasties (UKA).
Methods: Medline, EMBASE and Cochrane databases were searched. Annual revision rate and functional outcomes were assessed for both fixed and mobile-bearing designs.
Results: A total of 28 studies, of which 19 fixed-bearing and 9 mobile-bearing, representing 2265 lateral UKAs were included for survivorship and functional outcome analyses. The mean follow-up of fixed and mobile-bearing studies was 7.5 and 3.9 years, respectively. Annual revision rate of fixed-bearing designs was 0.94 (95% CI 0.66-1.33) compared to 2.16 (95% CI 1.54-3.04) for mobile-bearing. A subgroup analysis of the domed shaped mobile-bearing design noted an annual revision rate of 1.81 (95% CI 0.98-3.34). Good-to-excellent functional outcomes were observed following fixed and mobile-bearing lateral UKAs; no significant differences were found.
Conclusion: Mobile-bearing lateral UKAs have a higher rate of revision compared to fixed-bearing lateral UKAs with regard to short- to mid-term survivorship; however, the clinical outcomes are similar. Despite the introduction of the domed shaped mobile-bearing design, findings of this study suggest fixed-bearing implant design is preferable in the setting of isolated lateral osteoarthritis (OA). This systematic review was based on low to moderate evidence, therefore, future registry data are needed to confirm these findings. However, this study included a large number of patients, and could provide information regarding risk of revision and functional outcomes of mobile and fixed-bearing type lateral UKA.
Level of evidence: IV.
Keywords: Annual revision rate; Bearing design; Lateral UKA; Lateral unicompartmental knee arthroplasty.