Abstract
ObjectivesTo create estimates for clinically meaningful changes and differences in pain and joint function for the Oxford Hip and Knee Scores (OHS/OKS) in primary and revision joint replacement. Study Design and Setting694,487 primary and revision joint replacement procedures were analyzed from the NHS PROMs dataset between 2012-2020. Minimal important changes (MIC) and differences (MID) were calculated using distribution and anchor-based methods (including receiver-operating characteristic (ROC) curve and predictive-modelling techniques). ResultsFor comparison of two or more groups (such as in a clinic trial), MID estimates were ∼5 points. For cohort studies investigating changes over time in a single group of patients, MICgroup estimates were 12.4 points (primary hip replacement), 8.6 points (revision hip replacement), 10.5 points (primary knee replacement) and 9.4 points (revision knee replacement). For studies investigating changes over time at the individual patient level, MICadjusted estimates were ∼8 points, ∼6 points, ∼7 points and ∼6 points respectively. ConclusionThis study has calculated contemporary estimates of clinically important changes and differences for the OHS/OKS for primary and revision hip and knee replacement. These estimates can be used to inform sample size calculations and to interpret changes in joint function over time and differences between groups.
Highlights
Patient-reported outcome measures (PROMs) have established roles in the measurement of outcome in randomised controlled trials [2,3] and observational studies [4], as well as more contemporary roles comparing healthcare delivery between providers [5] and supporting patient decision-making [6]
The instruments are valid for use in revision hip and knee joint replacement procedures where the goal of surgery is the alleviation of pain or improvement in joint function [12,13]
This concept is useful when judging the efficacy of joint replacement, where one needs to be able to decide whether changes or differences in a PROM score are clinically meaningful [15]
Summary
Patient-reported outcome measures (PROMs) have established roles in the measurement of outcome in randomised controlled trials [2,3] and observational studies [4], as well as more contemporary roles comparing healthcare delivery between providers [5] and supporting patient decision-making [6]. In the UK, the collection of PROMs before and after hip and knee replacement surgery has been mandated since 2009 as part of a national audit [5] This programme uses two well-established PROM instruments, the Oxford Hip Score (OHS) and the Oxford Knee Score (OKS) [7,8], to evaluate pain and joint function during activities of daily living [9,10]. Both instruments have been found to have good measurement properties and evidence to support their use in primary joint replacement [11]. For comparative studies (such as randomized controlled trials), the concept of the minimal important difference (MID) is defined as the smallest difference in score between two or more groups at the time of outcome assessment that is considered to be clinically meaningful [15]
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