National Trends in Unicompartmental Knee Arthroplasty During a Period of Major Survivorship Improvements: Insights From the Dutch Arthroplasty Register

Background The rising use of unicompartmental knee arthroplasty (UKA) among various Western countries raises questions regarding the multifaceted determinants driving this trend. Therefore, this study aimed to examine trends and their associations with 3-year survivorship, focusing on patient, implant, hospital, and revision-related factors. Methods All primary medial UKAs for osteoarthritis registered in the Dutch Arthroplasty Register from 2014 to 2021 were included. Age, sex, BMI, prior ipsilateral knee surgery, implant type (cemented and uncemented mobile-bearing; cemented fixed-bearing), hospital practice (annual volume and usage), reasons for revision, and revision type were analyzed across four consecutive 2-year intervals. The 3-year survivorship was evaluated, and factors associated with revision risk were identified across these intervals. Results A total of 27,234 medial UKAs were analyzed, revealing an increased patient age, a higher proportion of men, and fewer prior ipsilateral knee surgeries over time ( P < 0.001). A profound increase occurred in uncemented mobile-bearing use and high-volume and usage hospitals ( P < 0.001). The 3-year survivorship increased from 93.9 to 96.2% ( P < 0.001). Higher hospital volume and usage, older patient age, and fewer prior ipsilateral knee surgeries were associated with reduced 3-year revision risk ( P < 0.001) across various time intervals; body mass index and sex were not ( P > 0.05). The reasons for revision shifted over time, with increases in infection, pain, and periprosthetic fractures, while femoral loosening decreased ( P < 0.001). Although most revisions were conversions to total knee arthroplasty, this decreased as bearing exchanges became more common ( P < 0.001). Conclusions This nationwide registry study demonstrated significant changes in patient, implant, and hospital factors for medial UKA, alongside improved 3-year survivorship. Associations between these factors and revision risk suggest these changes may have contributed to better survivorship. Changing patterns in revision reasons and types reflect evolving challenges in UKA management. These findings provide evidence to inform strategies for improving survivorship and understanding revision patterns in medial UKA.