Is elevated body mass index protective against cervical spine injury in adults?

Correlate body mass index (BMI) with incidence and type of cervical spine injury seen on CT in adult patients presenting with blunt trauma.

Retrospective chart review of all adult blunt trauma patients who had a cervical spine CT performed at our level 1 trauma center during an approximately 3-year period.

A statistically significant (p = 0.01) difference in cervical spine injury incidence was present between different BMI groups. Cervical spine injury incidence was 7.7% for underweight (BMI ≤ 18) patients, 7.1% for normal weight (BMI 18-25) patients, 6.2% for overweight/obese (BMI 25-35) patients, and 4.7% for morbidly obese (BMI > 35) patients. Using BMI > 18-25 as a reference group, females with BMI > 25-35 had an adjusted odds ratio (aOR) of 0.56 (CI 0.41-0.75) and females with BMI > 35 had an aOR of 0.42 (CI 0.26-0.70). Males with a BMI ≤ 18 had an aOR of 2.20 (CI 1.12-4.32) and males with BMI > 35 had an aOR of 0.66 (CI 0.46-0.95). A particularly low incidence of cervical spine injury was observed in patients older than 65 in the obese group with a cervical spine injury rate of only 1.4% in this patient population. No statistical significant difference was seen in injury morphology across the BMI groups.

An inverse relationship exists between BMI and the overall incidence of cervical spine injury. This protective effect appears to be influenced by gender with elevated BMI having lower relative odds of cervical spine injury in women than in men. A particularly low rate of cervical spine injury was identified in obese patients over the age of 65. Routine imaging of all elderly, obese trauma patients with low energy mechanism of injury may not be warranted.