DOS 2018

218 · DOS Abstracts Medial unicompartmental knee arthroplasty: do trends in patient characteristics vary with centre volume and usage? A descriptive study of 8.501 cases from the Danish Knee Arthroplasty Registry Cecilie Henkel, Mette Mikkelsen, Alma Bečić Pedersen, Lasse Enkebølle Rasmussen, Kirill Gromov, Andrew Price, Anders Troelsen Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Department of Clinical Epidemiology, Aarhus University Hospital; Department of Orthopaedic Surgery, Vejle Hospital; Department of Orthopaedic Surgery, CopenhagenUniversityHospital Hvidovre; NuffieldDepartment of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, Nuffield Orthopaedic Centre, Oxford Background: The narrow indications for unicompartmental knee arthroplasty (UKA) previously proposed have proven unnecessary, increasing the proportion of patients eligible for UKA to around 50 %. As low surgical volume and UKA- percentage (usage) are associated with higher revision rates, it is of interest whether the changed view on candidacy has affected patient selection for UKA. Purpose / Aim of Study: Therefore, our aim was to explore changes in patient selection for UKA by assessing: 1) time trends in patient characteristics and 2) whether these are associated with centre UKA- volume and -usage. Materials and Methods: We included patients from the Danish Knee Arthroplasty Registry with primary medial UKAs performed for primary osteo- arthritis in 2002-2016 (n=8.501). We explored trends in sex distribution, age, weight, and American Knee Society Score (knee and function scores) as regis- tered preoperatively. Using locally weighted regression, we assessed whether the trends varied with centre volume (< 52 versus ≥ 52 UKAs per year) and usage (UKAs < 20 % versus ≥ 20 % of primary arthroplasties). Findings / Results: Overall, we found a decreasing proportion of females, an increasing trend for age and weight, and a bell-shaped trend for knee and func- tion scores, both decreasing throughout the last 10 years. Patients from low- usage centres were more often female, were younger, weighed less, and had better knee scores; though for age and knee score, the groups were converging since 2011. The corresponding patterns for centre volume were largely analo- gous. Conclusions: Characteristics of UKA-patients have changed in the last 15 years irrespective of centre volume and usage. There were between-group dif- ferences with respect to both volume and usage, though with convergence in trends for age and knee score, suggesting an increasingly uniform approach to patient selection. 159.