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IMPORTANCE: Little is known about variation in outcomes of surgery or about the factors associated with such variation. OBJECTIVES: To evaluate variation in patient outcomes and costs for primary hip and knee replacement across health areas in England and to identify whether patient, surgical, or hospital factors are associated with such variation. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from the National Joint Registry, linked to English Hospital Episode Statistics and Patient Reported Outcome Measures data sets, for 383 382 adult patients who underwent primary total hip replacement (THR) or primary total and unicompartmental knee replacement (TKR) surgical procedures from January 2014 to December 2016. Geographical Information Systems were used to display maps describing adjusted estimates of variation in outcomes across health areas. Data analysis took place from January 2018 to August 2019. EXPOSURES: Patient characteristics (eg, age, sex, body mass index [BMI], and socioeconomic deprivation), surgical factors (eg, surgeon volume and grade), and hospital organizational factors (eg, number of operating theaters, number of specialist consultants, and hospital volume). MAIN OUTCOMES AND MEASURES: Length of stay (LOS), bed-day costs, change in Oxford hip or knee scores 6 months after surgery, and complications 6 months after surgery. RESULTS: A total of 173 107 patients (mean [SD] age, 69.3 [10.7] years; mean [SD] BMI, 28.9 [5.2]) underwent primary THR and 210 275 patients (mean [SD] age 69.7 [9.4] years; mean [SD] BMI, 31.1 [5.5]) underwent primary TKR, nested in 207 health areas. A number of factors were associated with longer LOS, higher bed-day costs, smaller changes in Oxford hip or knee scores, and a higher percentage of complications, including a workforce with a higher number of less experienced physicians (eg, LOS for less experienced surgeons, THR: regression coefficient, 0.02; 95% CI, 0.01 to 0.03; P 150 surgical procedures per year, THR: regression coefficient, -1.03; 95% CI, -1.47 to -0.58; P 

Original publication




Journal article


Jama netw open

Publication Date





Aged, Arthroplasty, Replacement, Hip, Arthroplasty, Replacement, Knee, England, Female, Geographic Information Systems, Humans, Male, Outcome Assessment, Health Care, Patient Reported Outcome Measures, Registries