Predictors of total hip replacement in community based older adults: a cohort study

Abstract Background: Hip osteoarthritis (OA) commonly affects older adults and leads to high morbidity. There is no preventative treatment available and total hip replacement (THR) is offered for end stage disease. Known predictors of THR include pain and radiographic OA. Hip structure has also been shown to worsen hip OA and predict THR. A better understanding of predictors of THR can aid in triaging patients and researching preventative strategies. The purpose of this study is to describe predictors of THR in community dwelling older adults. Methods: At baseline, participants had assessment of radiographic OA and cam morphology (from pelvic radiographs), shape mode scores (from dual energy X-ray absorptiometry (DXA)) and hip bone mineral density (BMD) (from DXA). After 2.6 and 5 years, participants reported hip pain using WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), and had hip structural changes assessed using magnetic resonance imaging (MRI). Risk of THR was analysed using mixed-effect Poisson regression. Results: Incidence of THR for OA over 14 years was 5.0% (40 / 802). As expected, WOMAC hip pain and hip radiographic OA both predicted risk of THR. Additionally, shape mode 2 score (decreasing acetabular coverage) (RR 1.57 per SD; 95% CI 1.01-2.46), shape mode 4 score (non-spherical femoral head) (RR 0.65/SD; 95% CI 0.44-0.97), cam morphology (α >60°) (RR 2.66/SD; 95% CI 1.38-5.13), neck of femur BMD (RR 1.85/SD, 95% CI 1.4-2.44) and bone marrow lesions (BMLs) increased risk of THR (RR 5.62/unit; 95% CI 1.1 – 28.81). Conclusion: In addition to hip pain and radiographic hip OA, measures of hip shape, cam morphology, BMD and BMLs independently predict risk of THR. This supports the role of hip bone geometry and structure in the pathogenesis of end stage hip OA and has identified factors that can be used to improve prediction models for THR.