Socioeconomic inequalities in patient-reported outcome measures among total hip and knee arthroplasty patients: a comprehensive analysis of instruments and domains.

Background: Prior to total hip and knee arthroplasty (THA/TKA), patients with low socioeconomic status (SES) report worse Patient-Reported Outcome Measures (PROMs), persisting postoperatively. This study explores which self-reported PROMs and their specific domains are most involved.

Methods: We obtained data from the Dutch Arthroplasty Registry (2014-2022), including over 100,000 THA/TKA patients with complete preoperative and 12-month follow-up PROMs. The EQ-5D-3L and EQ-5D-5L, EQ Visual Analogue Scale (VAS), Oxford Hip and Oxford Knee Score (OHS/OKS), and Numerical Rating Scales (NRS) for pain and satisfaction (TKA only, at 12-month follow-up) were obtained. The PROMs were transformed to a 0-100 scale for direct comparison. A SES-indicator based on neighborhood income, unemployment rate, and education level was divided into quintiles, which are equal groups representing 20% of the Dutch population, and was ranked from least to most deprived. Through linear regression we contrasted the most and least deprived groups, adjusting for patient and surgical characteristics. The contribution (percentage) of each domain to the overall health inequalities was estimated for the EQ-5D's and the OHS/OKS.

Results: In TKA patients, the most compared to the least deprived group had a lower preoperative EQ-5D-3L score: -2.1 [95% confidence interval - 2.6, -1.6], p < 0.001. At 12-month follow-up, the difference was smaller: EQ-5D-3L 1.3 [-1.9, -0.7], p < 0.001. A larger difference between the most and least deprived was present in OKS (preoperatively: -4.3 [-5.3, -3.4], p < 0.001; 12-month: -1.8 [-2.5, -1.2], p < 0.001). The difference in EQ VAS was smaller (preoperatively: -0.8 [-1.5, -0.1], p = 0.024; 12-month: -0.5 [-1.2, 0.1], p = 0.108). The difference in NRS pain (in rest) was comparable to those in EQ-5D-3L and OKS (preoperatively: -4.5 [-5.4, -3.5], p < 0.001; 12-month: -2.7 [-3.5, -1.9], p < 0.001), while no difference between the most and least deprived in NRS satisfaction was observed at 12 months. For EQ-5D-3L, the domain usual activities accounted for up to 46% of the difference between SES groups, while anxiety/depression played a limited role (up to 17%). For OHS/OKS, functioning contributed most in THA (up to 61%) and pain contributed most in TKA (up to 68%). Differences in PROM scores between SES groups, and how these differences compared across PROMs, were similar in THA patients. Overall, the EQ-5D-5L produced similar patterns compared to the EQ-5D-3L.

Conclusions: Deprived THA/TKA patients have poorer pre- and postoperative health, which was primarily related to worse functioning and pain; the clinical relevance of these differences remain uncertain. These differences did not translate into worse overall health (EQ VAS) or into higher dissatisfaction among deprived patients. Future research should investigate whether the EQ VAS and satisfaction measure reflected health differences between SES groups or were biased by reporting heterogeneity, where respondents interpreted the wording differently.