Mortality following benign sacral insufficiency fracture and associated risk factors

Summary This study demonstrated increased mortality following sacral insufficiency fractures as with other major osteoporotic fractures. The 6-month mortality rate was 9.8%, the 1-year mortality rate was 17.5%, and the 3-year mortality rate was 25.5%. Sex- and age-adjusted standardized mortality ratio increased after fractures. Introduction There are no data about mortality after sacral insufficiency fractures. The purposes of this study were to investigate the mortality rate among sacral insufficiency fracture patients and to identify risk factors associated with mortality. Methods This is a retrospective cohort study of patients diagnosed with sacral insufficiency fracture via radiological exam in a single institute from 2001 to 2014, excluding patients with pathological sacral fracture due to metastasis or primary tumor. Mortality and its predisposing factors were analyzed based on a review of electronic medical records and mortality data provided by the Korean Statistical Information Service. Kaplan–Meier survival analysis and Cox regression analysis were used for statistical analysis. Results A total of 325 patients were included (275 women and 50 men). The mean age at the time of diagnosis was 69.4 years. One hundred and forty patients (43.1%) had a history of malignancy, and 71 patients (21.8%) had undergone pelvic radiation therapy before fracture diagnosis. Twenty-one patients (6.5%) underwent sacroplasty, and the others underwent conservative management after fracture diagnosis. The mean follow-up was 51.5 months, and a total of 101 patients died at the final follow-up. The 6-month mortality rate was 9.8%, the 1-year mortality rate was 17.5%, and the 3-year mortality rate was 25.5%. Sex- and age-adjusted standardized mortality ratio (SMR) increased after fractures. The overall SMR is 8.9 at 3 months decreasing to 4.5 at 2 years. Multivariable Cox regression analysis showed that significant factors associated with increased mortality were male gender, malignancy history, lumbosacral fusion with distal fusion level S1, stroke history, low total femur bone mineral density score, and low body mass index. Conclusions Like other types of osteoporotic fractures, sacral insufficiency fractures are associated with increased mortality.