Epidemiology of cervical spine fractures in the US military.

BACKGROUND CONTEXT The epidemiology of cervical spine fractures and associated spinal cord injury (SCI) has not previously been estimated within the American population. PURPOSE To determine the incidence of cervical spine fractures and associated SCI and identify potential risk factors for these injuries in a large multicultural military population. STUDY DESIGN Query of a prospectively collected military database. PATIENT SAMPLE The 13,813,333 military servicemembers serving in the US Armed Forces between 2000 and 2009. OUTCOME MEASURES The Defense Medical Epidemiology Database (DMED) was queried to identify all servicemembers diagnosed with cervical spine fractures with and without SCI during the time period under investigation. Data were used to determine the incidence of cervical spine fractures and SCI as well as identify risk factors for their development. METHODS The DMED was queried for the years 2000 to 2009 using the International Classification of Diseases, Ninth Revision, Clinical Modification code for cervical spine fractures with and without SCI (805.0, 805.1, 806.0, and 806.1). The database was also used to determine the total number of servicemembers within the military during the same period. The incidence of cervical spine fractures and fractures associated with SCI was determined, and unadjusted incidence rates were calculated for the demographic characteristics of sex, race, military rank, branch of service, and age. Adjusted incidence rate ratios were then determined using multivariate Poisson regression analysis to control for other factors in the model and identify significant risk factors for cervical spine fractures and cervical injuries associated with SCI. RESULTS From 2000 to 2009, there were 4,048 cervical spine fractures in a population at risk of 13,813,333 servicemembers. The overall incidence of cervical spine fractures was 0.29 per 1,000 person-years, and the incidence of fracture associated SCI was 70 per 1,000,000. The cohorts at highest risk of cervical spine fracture were males, whites, Enlisted personnel, those serving in the Army, Navy, or Marine Corps, and servicemembers aged 20 to 29. Risk of fracture-associated SCI was significantly increased in males, Enlisted personnel, servicemembers in the Army, Navy, or Marines, and those aged 20 to 29. CONCLUSIONS This study is the largest population-based investigation to be conducted within the United States regarding the incidence of SCI and the only study addressing incidence and risk factors for cervical spine fractures. Male sex, white race, Enlisted military rank, service in the Army, Navy, or Marine Corps, and ages 20 to 29 were found to significantly increase the risk for cervical fractures and/or fracture associated SCI. Our findings support previously published data but also represent best available evidence based on the size and diversity of the population under study. LEVEL OF EVIDENCE Prognostic; Level II.