Postoperative mortality in hip fracture patients stratified by the Revised Cardiac Risk Index: a Swedish nationwide retrospective cohort study

OBJECTIVES: The Revised Cardiac Risk Index (RCRI) is a tool that can be used to evaluate the 30-day risk of postoperative myocardial infarction, cardiac arrest and mortality. This study aims to confirm its association with postoperative mortality in patients who underwent hip fracture surgery. METHODS: All adults who underwent primary emergency hip fracture surgery in Sweden between January 1, 2008 and December 31, 2017 were included in this study. The database was retrieved by cross-referencing the Swedish National Quality Register for hip fractures with the Swedish National Board of Health and Welfare registers. The outcomes of interest were the association between the RCRI score and mortality at 30 days, 90 days and 1 year postoperatively. RESULTS: 134 915 cases were included in the current study. There was a statistically significant linear trend in postoperative mortality with increasing RCRI scores at 30 days, 90 days and 1 year. An RCRI score ≥4 was associated with a 3.1 times greater risk of 30-day postoperative mortality (adjusted incidence rate ratio (IRR) 3.13, p<0.001), a 2.5 times greater risk of 90-day postoperative mortality (adjusted IRR 2.54, p<0.001) and a 2.8 times greater risk of 1-year postoperative mortality (adjusted HR 2.81, p<0.001) compared with that observed with an RCRI score of 0. CONCLUSION: An increasing RCRI score is strongly associated with an elevated risk 30-day, 90-day and 1-year postoperative mortality after primary hip fracture surgery. The objective and easily retrievable nature of the variables included in the RCRI calculation makes it an appealing choice for risk stratification in the clinical setting. LEVELS OF EVIDENCE: Level III.