Hip fracture time-to-surgery and mortality revisited: mitigating comorbidity confounding by effect of holidays on surgical timing.

Abstract

The association between delayed hip fracture surgery and mortality remains elusive because of strong confounding by comorbidity factors. We designed a study to investigate the effect of small delays in surgery due to holidays. Consecutive hip fractures operated in a high-income, publicly funded healthcare system between 2006 and 2013 were analysed. Age <65 years, pathological fractures, history of previous hip operation and time to surgery >sevendays were excluded. Patients were grouped according to number of holidays following admission (HFA) as a surrogate for time to surgery, with difference in mean time to surgery tested for statistical significance and baseline characteristics including age, sex, Charlson comorbidity index (CCI) and fracture and operation types assessed. Survival up to twoyears was compared. Thirty-one thousand five hundred and ninety-two patients were included. Patient groups with zero, one, two or three HFA had significantly different mean time to operation of 2.25, 2.47, 2.67 and 2.84days, respectively (Kruskal-Wallis test p < 0.0001), but baseline characteristics were similar. There was no difference in mortality at sixmonths (p = 0.431) and twoyears (p = 0.785). Cox's regression analysis identified age, gender and CCI as independent predictors of mortality but not HFA, and the adjusted hazards ratio for each HFA increment was 1.026 [95% confidence interval (CI) 0.999-1.025; p = 0.056] which was not statistically significant. We observed no increase in mortality rate in patients having small delays in surgery because of holidays.