title: Meaningful changes for the Oxford hip and knee scores after joint replacement surgery.
abstract: OBJECTIVE
  To present estimates of clinically meaningful or minimal important changes for the Oxford Hip Score (OHS) and the Oxford Knee Score (OKS) after joint replacement surgery.
  
  
  METHODS
  Secondary data analysis of the NHS patient-reported outcome measures data set that included 82,415 patients listed for hip replacement surgery and 94,015 patients listed for knee replacement surgery was performed.
  
  
  RESULTS
  Anchor-based methods revealed that meaningful change indices at the group level [minimal important change (MIC)], for example in cohort studies, were ∼ 11 points for the OHS and ∼ 9 points for the OKS. For assessment of individual patients, receiver operating characteristic analysis produced MICs of 8 and 7 points for OHS and OKS, respectively. Additionally, the between group minimal important difference (MID), which allows the estimation of a clinically relevant difference in change scores from baseline when comparing two groups, that is, for clinical trials, was estimated to be ∼ 5 points for both the OKS and the OHS. The distribution-based minimal detectable change (MDC90) estimates for the OKS and OHS were 4 and 5 points, respectively.
  
  
  CONCLUSIONS
  This study has produced and discussed estimates of minimal important change/difference for the OKS/OHS. These estimates should be used in the power calculations and the interpretation of studies using the OKS and OHS. The MDC90 (∼ 4 points OKS and ∼ 5 points OHS) represents the smallest possible detectable change for each of these instruments, thus indicating that any lower value would fall within measurement error.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Headington, Oxford OX3 7LD, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beard
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Headington, Oxford OX3 7LD, UK. Electronic address: kristina.harris@ndorms.ox.ac.uk.
authors.forename: Kristina
authors.initials: K
authors.lastname: Harris
authors.affiliation: Department of Public Health, University of Oxford, Rosemary Rue Building, Old Road Campus, Headington, Oxford OX3 7LF, UK.
authors.forename: Jill
authors.initials: J
authors.lastname: Dawson
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Doll
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Headington, Oxford OX3 7LD, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Murray
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Headington, Oxford OX3 7LD, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Carr
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Botnar Research Centre, University of Oxford, Headington, Oxford OX3 7LD, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Price
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D015331:Cohort Studies; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D016896:Treatment Outcome
keywords: Hip replacement; Knee replacement; Minimal important change; Minimal important difference; Responder definition; Study designs