Minimal important changes and differences were estimated for Oxford hip and knee scores following primary and revision arthroplasty.

OBJECTIVES

To 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 SETTING

694,487 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).

RESULTS

For 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, MIC 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, MIC estimates were ∼8 points, ∼6 points, ∼7 points and ∼6 points respectively.

CONCLUSION

This 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.