The metabolic equivalent of task score: a useful metric for comparing high functioning hip arthroplasty patients

Abstract

Aims: This study investigates the use of the Metabolic Equivalent of Task (MET) score in a young hip arthroplasty population and its ability to capture additional benefit beyond the ceiling effect of conventional patient reported outcomes. Patients & Method: Oxford Hip Score (OHS), EuroQol-5D index (EQ-5D), and the MET were recorded in 221 primary hip arthroplasty procedures pre-operatively and at 1-year. The distribution was examined reporting the presence of ceiling & floor effects. Validity was assessed correlating the MET with the other scores using Spearman’s rank and determining responsiveness. A subgroup of 93 patients scoring 48/48 on the OHS were analysed by age, sex, BMI and pre-operative MET using the other metrics to determine if differences could be established despite scoring identically on the OHS. Results: From our electronic database of 751 hip arthroplasty procedures, 117 primary total hip and 104 hip resurfacing arthroplasty operations were included. Mean age was 59.4 ± 11.3. Post-operatively the OHS and EQ-5D demonstrate significant negatively skewed distributions with ceiling effects of 41% and 53%, respectively. The MET was normally distributed post-operatively with no ceiling effect. Weak-moderate significant correlations were found between the MET and the other two metrics. In the 48/48 subgroup, no differences were found comparing groups with the EQ-5D, however significantly higher MET scores were demonstrated for patients aged <60 (12.7 vs 10.6, p=0.008), male patients (12.5 vs 10.8, p=0.024) and those with pre-operative MET scores >6 (12.6 vs 11.0, p=0.040). Conclusion: The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS.