No difference in patient satisfaction after mobile bearing or fixed bearing medial unicompartmental knee arthroplasty

Purpose Medial unicompartmental knee arthroplasty (UKA) has excellent survival rates using one of the two implant designs: mobile bearing (MB) or fixed bearing (FB). There is a lack of studies comparing patient-reported outcomes (PROs) of both implants. This study aimed to document and compare PROs of MB UKA to FB UKA at 6, 12 and 24 months after surgery. Methods A single high-volume surgeon, retrospective cohort study with prospectively collected data of two groups of UKA patients, with a MB (n = 66) or FB (n = 97) implant. Primary outcome was patient satisfaction (0-10; NRS). Secondary outcomes were pain at rest (NRS), pain during activity (NRS), function (OKS, KOOS-PS), quality of life (EQ-5D-3L), anchor pain, anchor function and anchor recovery. PROs were collected 6, 12 and 24 months postoperatively. The complication rate and revision rate within one year after surgery were recorded. Results For the MB group, the median NRS satisfaction score was 9.0 (8.0-10.0) compared to 9.0 (8.0-9.5) for the FB group at 6 months (p = 0.620). Similar scores were found at 12 and 24 months; both MB 9.0 (8.0-10.0) and FB 9.0 (8.0-10.0) (p = 0.556 and p = 0.522, respectively). There were no statistically significant differences between MB and FB groups in all secondary outcomes postoperatively. Conclusion Medial UKA performed by a high-volume surgeon, using a MB or a FB implant, results in excellent patient satisfaction, pain relief, functional improvement and quality of life improvement at 6, 12 and 24 months after surgery. The recommendation and use of one over the other is not justified based on the outcomes in the current study.