DOS 2020

DOS Kongressen 2020 · 185 Categorization of changes in the Oxford Knee Score after Total Knee Replacement: An interpretive tool developed from a data set of 46,094 replacements. Mette Mikkelsen, Anqi Gao, Lina Holm Ingelsrud, David Beard, Anders Troelsen, Andrew Price Dept. of Orthopedic Surgery, Clinical Orthopedic Research Hvidovre (CORH), Copenhagen University Hospital Hvidovre; Nuffield Dept. of Orthopaedics, Rheumatology and Musculoskeletal Science, University of Oxford; Dept. of Orthopaedics, Rheumatology and Musculoskeletal Science, University of Oxford Background: With the increase in use of Patient Reported Outcome Measurements in orthopedics, including the introduction into registries, there is a need for interpretative tools to contextualize our outcome. Purpose / Aim of Study: The aim of this study was to create an interpre- tive classification for the transition in the Oxford Knee Score (OKS) from pre- operative to 6-months follow- up (the change score) using the anchor-based method. Materials and Methods: Registry data from 46094 total knee replacements from the year 2014/15, accessed via the Health and Social Care Information Centre (HSCIC) official website. Data included pre-operative and 6-month follow-up OKS and response to the transition anchor question: “How are the problems now in the operated knee compared to pre-operation?” Please select one of the following: “much better”, “a little better”, “about the same”, “a little worse” and “much worse”. Categories were determined using Gaussian approxi- mation probability and k-fold cross-validation. Findings / Results: 4 categories were identified with the corresponding change score intervals; “1. Much Better” (≥ 16), “2. A Little Better” (7-15), “3. About the Same” (1-6) and “4. Much Worse” (≤ 0) based on the anchor questions’ original 5 categories. The mean 10-fold cross-validation error was 0.349 OKS points (95 % confidence interval 0.511 to 0.632). Sensitivity ranged from 0.34 to 0.68, specificity raged from 0.74 to 0.95. Conclusions: We have categorized the change score into a clinically meaningful classification. We argue it should be an addition to the continuous OKS outcome to contextualize the outcomes and aid in interpretation of research results. 164.