Associations Between Time to Reduction and Complications in Patients With First-Time Total Hip Arthroplasty Dislocation: A Retrospective Cohort Study

BACKGROUND: Total hip arthroplasty (THA) is one of the most frequently performed surgeries worldwide. Approximately 1% to 10% of patients experience one or multiple dislocations of their THA, a painful condition requiring urgent treatment. In Denmark, the usual treatment is closed reduction, typically performed in the operating theater under general anesthesia. However, logistical and clinical challenges can delay treatment in an often frail, elderly population. This study investigated whether time to reduction and type of anesthetics were associated with post-reduction length of stay (LOS) and complications in patients with THA dislocation. We hypothesized that longer time to reduction would be associated with increased post-reduction LOS and complications. METHODS: This retrospective observational cohort study included adults (≥18 years) with a first-time THA dislocation who underwent closed reduction in the operating theater, from 1 January 2017 to 31 January 2025 in the Capital and Zealand Regions of Denmark. Data were extracted from the Electronic Health Record "Sundhedsplatformen." The primary outcome was post-reduction LOS, assessed using linear regression adjusted for predefined confounders. Secondary outcomes were 90-day all-cause mortality, delirium, readmission, intensive care unit admission, infections, acute kidney injury, and cardiovascular complications. RESULTS: A total of 3494 reductions were included; 86.7% were performed within 12 hours of admission. Increasing time to reduction was associated with longer post-reduction LOS. In the reference group (<3 hours), median post-reduction LOS was 15.4 hours (IQR 10.5-23.4). Compared with this group, post-reduction LOS increased by 50.6 hours for reductions at 12-18 hours (95% CI 30.4-71.5¸P < .001), 197 hours at 18-24 hours (95% CI 146-249; P < .001), and 137 hours beyond 24 hours (95% CI 119-154; P < .001). Post-reduction LOS beyond 24 hours was also statistically significantly associated with increased mortality, delirium, and infection. CONCLUSIONS: Most patients underwent closed reduction within 12 hours, without increased risk of complications. Reductions exceeding 12 hours of waiting time were associated with longer post-reduction LOS, even when adjusting for known confounders. Further delays were associated with increased odds of mortality, delirium, and infections. Whether these associations were driven by system delays or patient-related factors remains unclear.