Revisiting minimally important changes for the Oxford Hip and Knee scores

PurposeA number of metrics and thresholds have been proposed to evaluate minimally meaningful change in the Oxford Hip and Oxford Knee scores (OHS and OKS). The study aim was to evaluate the impact of baseline scores on these metrics, and whether treatment success could be evaluated beyond these single metrics. Patients & MethodsThe data were collated from the National Health Service in England including the OHS, OKS and a global transition item (GTI). Minimally important change (MIC) scores were derived and categorised by the GTI, baseline and post-operative score categories. These metrics were also evaluated against standard error of measurement (SEM). ResultsA total of 387,524 records were extracted. Although the overall MIC were in-line with previous research, the results showed these measures varied by pre-operative scores. Few MIC estimates exceeded measurement error thresholds. Those that did were fell in the category of post-operative scores [≥] 30 for both instruments. ConclusionsThe MIC for both the OHS and OKS are potentially unreliable single metrics for evaluating meaningful change. A combination of baseline, post-intervention and change scores may provide more a robust measure for the evaluation of patient outcomes and healthcare services.