Social inequalities in patient outcomes after total hip replacement surgery for osteoarthritis in England: A population-based cohort study of the National Joint Registry

BACKGROUND: Reducing health inequalities is of national importance. Total hip replacement (THR) is a commonly used elective surgical procedure. Few studies have examined area-level inequalities for a wide range of outcomes following THR. The aim of this study is to compare area-level socioeconomic differences in outcomes following primary THR surgery for osteoarthritis in England. METHODS AND FINDINGS: This is a population-based prospective cohort study of the National Joint Registry (NJR). Data from the NJR were linked to national mortality, Hospital Episode Statistics and Patient Reported Outcome Measures (PROMs) databases for England from 2007 to 2017 with follow-up to 2023 for outcomes, for patients aged 50 years and over with osteoarthritis. Outcomes of 90-day mortality; 5-year revision rate; 6-month health complications; 1-year rehospitalisation and reoperation for orthopaedic indications; and patient-reported Oxford Hip Score (OHS), post-THR surgery were examined by area-level Index of Multiple Deprivation quintiles. Modified Poisson regression was adjusted for patient age, sex, body mass index, pre-operative physical state and comorbidity. Among 448,184 patients with primary THR, mean age was 70 years (standard deviation: 9 years) and 61% were women. Patients from the most deprived group were more likely to die within 90 days of the operation compared to the least deprived group (adjusted rate ratio, RR: 1.25 (95% confidence interval (CI) [1.07, 1.46]); adjusted risk difference, RD: 9 (95% CI [2, 16]) per 10,000. Similarly, those from the most deprived group were more likely to experience complications (RR: 1.26 (95% CI [1.21, 1.32]); RD: 1.14% (95% CI [0.92, 1.36])); be rehospitalised (RR: 1.16 (95% CI [1.14, 1.19]; RD: 2.78% (95% CI [2.39, 3.17])) or reoperated (RR: 1.23 (95% CI [1.13, 1.33]); RD: 0.31% (95% CI [0.19, 0.44])) and report poorer OHS (adjusted score: -2.97 (95% CI [-3.10, -2.84]) N = 200,522). There was no variation by deprivation level for THR revision rates at 5 years (RR: 1.02 (95% CI [0.94, 1.10]); RD: 0.02% (95% CI [-0.10, 0.15])). The main study limitations are the lack of complete PROMs data, and the exclusion of self-funded patients or those with private insurance for THR procedures in independent hospitals. CONCLUSIONS: Inequalities in several outcomes after THR are present in England by area-level deprivation. These findings are useful to inform shared decision-making for patients deciding whether to undergo hip replacement and to benchmark the effectiveness of policies which aim to reduce health inequalities following THR.