“…We classified potential factors as patient, surgical, or hospital organizational factors (eTable 1 in the Supplement). Patient factors included calendar year of THR or TKR; age; sex; body mass index, calculated as weight in kilograms divided by height in meters squared 10 ; American Society of Anesthesiologists (ASA) grade 11 ; area-level socioeconomic deprivation using the Index of Multiple Deprivation, based on patient residential post code; rural vs urban indicator; primary indication; Charlson Comorbidity Index (CCI) score; baseline OHS or OKS score; and the baseline European Quality of Life-Five Domain (EQ-5D-3L) score. Surgical factors included lead surgeon experience, surgical volume per lead surgeon and year, surgical volume per unit and year, minimally invasive surgery (yes or no), thromboprophylaxis, mechanical prophylaxis, anesthetic type, and type of approach.…”