Does obesity lead to lower rates of clinically meaningful improvement or satisfaction after total hip arthroplasty? A propensity score-matched study

Background: Current literature lacks consensus regarding the impact of obesity on clinical outcomes of total hip arthroplasty (THA). The variability of results may reflect the lack of minimal clinically important difference (MCID) analysis, which helps to standardise the interpretation of patient-reported outcome measures (PROMs). We compared the PROMs, patient satisfaction and survivorship between obese and non-obese patients after THA. Methods: Prospectively collected registry data of 192 obese patients and 192 propensity score-matched controls who underwent primary THA at a single institution were reviewed. Clinical outcomes and satisfaction rates were assessed at 6 months and 2 years. Reoperations for surgical complications and revision rates were analysed. Results: Obese patients had a significantly poorer Oxford Hip Score (OHS) at 6 months and WOMAC-Function at 2 years. However, there was no difference in overall WOMAC, WOMAC-Pain, WOMAC-stiffness, SF-36 mental and physical component summary (PCS). A similar proportion of patients in each group achieved the MCID for OHS, WOMAC and SF-36 PCS. At 2 years, 90.3% of obese patients and 91.7% of controls were satisfied (p = 0.755). At a mean follow-up of 9 years, there were 5 reoperations (2.6%) for surgical complications in the obese group and 1 (0.5%) in the control group; whereas 12 revisions (6.3%) were recorded in the obese group and 3 (1.6%) in the control group (p = 0.021). Conclusions: Despite a higher revision rate, obese patients undergoing THA may experience a similar level of clinical meaningful improvement and satisfaction as their non-obese counterparts. This study provides valuable prognostic information for obese patients and guides preoperative counselling.