Risk of Hip Arthroplasty After Open Reduction Internal Fixation of a Fracture of the Acetabulum: A Matched Cohort Study

Objectives:To determine what proportion of operatively treated acetabular fracture patients proceeded to total hip arthroplasty (THA), over what time period, and quantify the influence of patient, provider, and surgical factors on rates of THA. Design:Retrospective matched cohort prognostic study using administrative data. Setting:This study used the large population database of Ontario (population 13,125,000 in 2010), Canada. Participants:Patients who underwent open reduction internal fixation (ORIF) of an acetabulum fracture between 1996 and 2010 in the province of Ontario were identified from administrative health databases. Method:Each patient was matched to 4 individuals from the general population according to age, sex, income, and urban/rural residence. The rates of THA at 2, 5, and 10 years were compared using time-to-event analysis. The influence of patient, provider, and surgical factors on the risk of eventual THA was examined using a Cox model. Intervention:The primary intervention was ORIF of the acetabulum. Main Outcome Measurement:The primary outcome measurement was THA. Results:A total of 1725 eligible patients were identified and were matched to 6900 controls. Among cases, there was a 13.9% (N = 240) rate of hip arthroplasty after a median of 6.25 (interquartile range 3.5-10.1) years, compared with 0.6% (N = 38) among matched controls (relative risk = 25.26). The greatest difference in risk of eventually undergoing a THA was in the first 10 years, after which time the risk in the group that had undergone ORIF acetabulum trended down toward that of the control group. Among surgical patients, risk factors for eventual hip arthroplasty included older age [hazard ratio (HR) 1.035 (1.027, 1.044); P < 0.0001]; female sex [HR 1.65 (1.257, 2.165); P = 0.0003]. Higher surgeon volume revealed a 2.6% decreased risk of arthroplasty for each acetabulum ORIF performed above 10 per year [HR 0.974 (0.960, 0.989); P = 0.0007]. Conclusion:Patients who underwent acetabulum fracture ORIF had a 25 times higher prevalence of hip arthroplasty compared with matched controls. THA rate was greater in women, older patients, and patients whom had ORIF performed by low-volume surgeons.