The causal effect of hospital volume on health gains from hip replacement surgery

This study investigates the causal effect of hospital volume on health gains from hip replacement surgery in the English National Health Service. We exploit a unique dataset, which links routine hospital records and patient-reported outcome measures (PROMs) for all public hospitals in England. PROMs assess patients’ health along key dimensions of pain and mobility shortly before and six months after the surgery. We investigate whether higher hospital volume increases patient health six months post-surgery, conditioning on pre-surgery health and other patient medical and socioeconomic indicators. We address possible reverse-causality bias due to hospital demand being responsive to quality by constructing a measure of predicted hospital volumes based on a patient choice model. The results suggest that the observed volume-outcome effect in hip replacement surgery is clinically small and no longer statistically significant once we account for the endogeneity of volume.