Aims. The metabolic equivalent of task (MET) score examines patient performance in relation to energy expenditure before and after knee arthroplasty. This study assesses its use in a knee arthroplasty population in comparison with the widely used Oxford Knee Score (OKS) and EuroQol five-dimension index (EQ-5D), which are reported to be limited by ceiling effects. Methods. A total of 116 patients with OKS, EQ-5D, and MET scores before, and at least six months following, unilateral primary knee arthroplasty were identified from a database. Procedures were performed by a single surgeon between 2014 and 2019 consecutively. Scores were analyzed for normality, skewness, kurtosis, and the presence of ceiling/floor effects. Concurrent validity between the MET score, OKS, and EQ-5D was assessed using Spearman’s rank. Results. Postoperatively the OKS and EQ-5D demonstrated negative skews in distribution, with high kurtosis at six months and one year. The OKS demonstrated a ceiling effect at one year (15.7%) postoperatively. The EQ-5D demonstrated a ceiling effect at six months (30.2%) and one year (39.8%) postoperatively. The MET score did not demonstrate a skewed distribution or ceiling effect either at six months or one year postoperatively. Weak-moderate correlations were noted between the MET score and conventional scores at six months and one year postoperatively. Conclusion. In contrast to the OKS and EQ-5D, the MET score was normally distributed postoperatively with no ceiling effect. It is worth consideration as an arthroplasty outcome measure, particularly for patients with high expectations. Cite this article: Bone Jt Open 2023;4(3):129–137

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 outcome measures. Methods. From our electronic database of 751 hip arthroplasty procedures, 221 patients were included. Patients were excluded if they had revision surgery, an alternative hip procedure, or incomplete data either preoperatively or at one-year follow-up. Included patients had a mean age of 59.4 years (SD 11.3) and 54.3% were male, incorporating 117 primary total hip and 104 hip resurfacing arthroplasty operations. Oxford Hip Score (OHS), EuroQol five-dimension questionnaire (EQ-5D), and the MET were recorded preoperatively and at one-year follow-up. The distribution was examined reporting the presence of ceiling and floor effects. Validity was assessed correlating the MET with the other scores using Spearman’s rank correlation coefficient and determining responsiveness. A subgroup of 93 patients scoring 48/48 on the OHS were analyzed by age, sex, BMI, and preoperative MET using the other metrics to determine if differences could be established despite scoring identically on the OHS. Results. Postoperatively the OHS and EQ-5D demonstrate considerable negatively skewed distributions with ceiling effects of 41.6% and 53.8%, respectively. The MET was normally distributed postoperatively with no relevant ceiling effect. Weak-to-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 mean MET scores were demonstrated for patients aged < 60 years (12.7 (SD 4.7) vs 10.6 (SD 2.4), p = 0.008), male patients (12.5 (SD 4.5) vs 10.8 (SD 2.8), p = 0.024), and those with preoperative MET scores > 6 (12.6 (SD 4.2) vs 11.0 (SD 3.3), p = 0.040). Conclusion. The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS. Cite this article: Bone Joint Res 2022;11(5):317–326

This study investigates the use of the Metabolic Equivalent of Task (MET) score in a hip arthroplasty population and its ability to capture additional benefit beyond the maximum Oxford Hip Score (OHS). OHS, EuroQol-5D index (EQ-5D), and the MET were prospectively 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 using the standardised response mean (SRM). A subgroup of 93 patients scoring 48/48 on the OHS were analysed by age group, sex, BMI and pre-operative MET using the other two metrics to determine if differences could be established despite all scoring identically on the OHS. 117 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 but statistically significant correlations were found between the MET and the other two metrics both pre & post-operatively. Responsiveness was excellent, SRM for OHS: 2.01, EQ-5D: 1.06 and MET: 1.17. In the 48/48 scoring 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). The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS. As a simple, valid activity metric, it should be considered in addition to conventional PROMs in order to capture the entire benefit experienced following hip arthroplasty

Patients may be able to return to higher level activities following hip arthroplasty with modern techniques and prostheses, but the Oxford hip score, the standard PROM used by the NJS exhibits severe skew and kurtosis. The commonest score is 48/48. Most patients score above 40 preventing any discrimination between approaches or prostheses. We therefore sought both subjective and objective metrics which were relevant and valid without skew or high kurtosis in postoperative patients. The Metabolic Equivalent of Task (MET) reports energy usage in kcal/min burnt across a range of activities, condensed into a score of 0–25. A MET over 8 is considered ‘conditioning exercise’ tethered to life expectancy. A 2 point difference in average MET is considered a clinically relevant difference. Walking speed is a simple valid metric tethered to life expectancy, with a 0.1m/sec difference in walking speed equates to a clinically important difference. Oxford Hip Score (OHS), and the MET were prospectively recorded in 221 primary hip arthroplasty procedures pre-operatively and at 1-year using a web based application. Pre and postoperative Gait analysis was undertaken on a subgroup of 34 patients, in comparison with age and sex matched controls. Post-operatively, the OHS demonstrated significant skewed distributions with ceiling effects of 41% scoring 48/48. The MET was normally distributed around a mean of 10.3, with a standard deviation of 3.8 and no ceiling effect. Walking speed was normally distributed around a mean of 1.8m/sec, with a standard deviation was 0.15 m/sec. The MET is a simple patient reported score, which is normally distributed in patients following hip arthroplasty, around a mean of 10.3 with a standard deviation of 3.8. This valid activity metric correlates well with fast walking speed. This is also normally distributed with a standard deviation of over 0.1m/sec confirming low kurtosis. These simple measures have face validity: undertaking less active pastimes and being unable to keep up with other walkers are obviously inadvisable. The normal kurtosis of these metrics suggest that they may able to detect clinically relevant differences in outcome which are undetectable with commonly used PROMs. For surgeons developing less invasive approaches or using novel stems, these measures may detect clinically important improvements undetectable by the Oxford Hip Score

Patients undergoing hip resurfacing arthroplasty (HRA) is typically reserved for highly active patients. Patient Reported Outcome Measures (PROMs) such as the Oxford Hip Score (OHS) are reported to have ceiling effects, which may limit physicians' ability to measure health gain in these patients. The Metabolic Equivalent of Task (MET) index is a validated compendium assigning energy expenditure to a wide range of activities; for example, a slow walk expends 2.9 kcal/kg/hour, golf expends 4.0 kcal/kg/hour, while moderate lacrosse typically expends 8.1 kcal/kg/hour. We hypothesized that for patients with high OHS (47–48) after HRA, the MET index could better discriminate between high-performing individuals. We evaluated 97 consecutive HRA patients performed by a single surgeon. They prospectively completed an online Oxford Hip Score. They also listed three activities which they had performed independently in the preceding 2 weeks with a Likert-scale slider denoting intensity of effort. Matched data-sets were obtained from 51 patients, from which 23 had OHS of 47–48 at 6-months. Their activity with the highest MET index was selected for analysis. The 23 patients' OHS improved from 29.3 ± 7.0 preoperatively to 47.6 ± 0.5 after 6-months, while their MET indices improved from 8.5 ± 3.7 to 12.9 ± 3.5 kcal/kg/hr. The activities performed by these high-performance individuals ranged from the lowest, pilates (8.05 kcal/kg/hour), to highest, running at 22km/hr (23 kcal/kg/hour). 45% of patients undergoing HRA in this cohort had OHS of 47 and 48 at 6-months after surgery. Unlike the OHS, the MET index described variation in physical activity in these high-performance individuals, and did so on an objective measurable scale

Any arthroplasty that offers superior function needs to be assessed using metrics that are capable of detecting those functions. The Oxford Hip Score (OHS), the Harris Hip Score (HHS) and WOMAC are patient reported outcome measures (PROMs) with well documented ceiling effects: following hip arthroplasty, many patients are clustered close to full marks following surgery. Two recent well conducted randomised clinical trials made exactly this error, by using OHS and WOMAC to detect a differences in outcome between hip resurfacing and hip arthroplasty despite published data already showing in single arm studies that these two procedures score close to full marks using either of these PROMS. We have already reported that patients with hip resurfacing arthroplasty (HRA) were able to walk faster and with more normal stride length than patients with well performing hip replacements. In an attempt to relate this functional superiority to an outcome measure that does not rely upon the use of expensive machinery, we developed a patient centred outcome measure (PCOM) based upon a method developed by Philip Noble's group, and the University of Arizona's Metabolic Equivalent of Task Index (MET). This PCOM allows patients to select the functions that matter to them personally against which the success of their own operation will be measured, with greater sensitivity to intensity than is achieved by the UCLA. Our null hypothesis was that this PCOM would be no more successful than the PROMs in routine use in discriminating between types of hip arthroplasty, and that there would be no difference in gait between patients following these procedures. From our database of over 800 patients whose gait has been assessed in the lab, we identified 22 patients with a well performing conventional THAs, and matched them for age, sex, BMI, height, preop diagnosis with 22 patients with a well performing conventional THA. Both were compared with healthy controls using the novel PCOM and in a gait lab. Results. PROMs for the two groups were almost identical, while HRA scored higher in the PCOM. The 9% difference was significant (p<0.05). At top walking speed, HRA were 10% faster, with a 9% longer stride length, both of these metrics also reached significance. Discussion. Function following hip replacement is very good, with high satisfaction rates, but the use of a PCOM, and objective measures of function reveal substantial inferiority of THA over THR in two well matched groups. This 9% difference is well over the 5% difference that is considered ‘clinically relevant’. When coupled with the very strong data regarding life expectancy and infection, this functional data makes a compelling case for the use of resurfacing in active adults