Interpretation threshold values for the Oxford Knee Score in patients undergoing unicompartmental knee arthroplasty

Lasse K Harris; Anders Troelsen; Berend Terluin; Kirill Gromov; Andrew Price; Lina H Ingelsrud

doi:10.2340/17453674.2022.3909

Authors

Lasse K Harris Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen Denmark https://orcid.org/0000-0002-2732-4342
Anders Troelsen Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen Denmark https://orcid.org/0000-0003-0132-8182
Berend Terluin Department of General Practice, Amsterdam Public Health Research Institute, Amsterdam UMC, Amsterdam, The Netherlands https://orcid.org/0000-0002-8944-5238
Kirill Gromov Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen Denmark https://orcid.org/0000-0002-8114-5193
Andrew Price Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, UK
Lina H Ingelsrud Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Copenhagen Denmark https://orcid.org/0000-0003-2261-7709

DOI:

https://doi.org/10.2340/17453674.2022.3909

Keywords:

Interpretation threshold values, Oxford Knee Score, Unicompartmental Knee Arthroplasty

Abstract

Background and purpose: Developing meaningful thresholds for the Oxford Knee Score (OKS) advances its clinical use. We determined the minimal important change (MIC), patient acceptable symptom state (PASS), and treatment failure (TF) values as meaningful thresholds for the OKS at 3-, 12-, and 24-month follow-up in patients undergoing unicompartmental knee arthroplasty (UKA).
Patients and methods: This is a cohort study with data from patients undergoing UKA collected at a hospital in Denmark between February 2016 and September 2021. The OKS was completed preoperatively and at 3, 12, and 24 months postoperatively. Interpretation threshold values were calculated with the anchor-based adjusted predictive modeling method. Non-parametric bootstrapping was used to derive 95% confidence intervals (CI).
Results: Complete 3-, 12-, and 24-month postoperative data was obtained for 331 of 423 (78%), 340 of 479 (71%), and 235 of 338 (70%) patients, median age of 68–69 years (58–59% females). Adjusted OKS MIC values were 4.7 (CI 3.3–6.0), 7.1 (CI 5.2–8.6), and 5.4 (CI 3.4– 7.3), adjusted OKS PASS values were 28.9 (CI 27.6–30.3), 32.7 (CI 31.5–33.9), and 31.3 (CI 29.1–33.3), and adjusted OKS TF values were 24.4 (CI 20.7–27.4), 29.3 (CI 27.3–31.1), and 28.5 (CI 26.0–30.5) at 3, 12, and 24 months postoperatively, respectively. All values statistically significantly increased from 3 to 12 months but not from 12 to 24 months.
Interpretation: The UKA-specific measurement properties and clinical thresholds for the OKS can improve the interpretation of UKA outcome and assist quality assessment in institutional and national registries.