BACKGROUND CONTEXT Several studies have analyzed the impact of obesity on severity and specific injury predispositions due to MVA using the Abbreviated Injury Scale (AIS). Although AIS grades individual regions according to severity from minor to maximum, it does not reflect specific description of injury in each region. In the case of cervical spine injury, the type of fracture pattern and spinal cord injury (SCI) cannot be determined from the AIS score. Therefore, the knowledge on impact of obesity on severity of cervical spine injury is limited from prior trauma studies.This information will be useful for providers in the ED to ascertain risk of severe cervical spine injury due to patient's BMI. In addition to risk estimation, fracture pattern, SCI, and patient-specific comorbidities are among important considerations in deciding treatment strategy. PURPOSE The objective of our study was to study the impact of BMI on severity of cervical spine injury after adjusting for injury and patient related variables. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE Patients with traumatic cervical spine fracture presenting to a level I trauma center between January 1, 2010 and December 31, 2014. OUTCOME MEASURES Severity of cervical spine fracture according to AO Spine sub-axial cervical spine fracture classification. METHODS Approval from Institutional Review Board (IRB) was taken before identifying patients for data collection. Review of electronic medical record (EMR) was done to collect patient information. Patients were selected per the following inclusion criteria: (i) traumatic injury that resulted in sub-axial cervical spinal fracture, (ii) patient age 18 to 80 years, (iii) availability of cervical computed tomography (CT) scan, (iv) complete health record of patient clinical and injury characteristics. Patients were excluded if they had isolated atlanto-axial injury or did not have a cervical CT scan. Patients who had suspected pathological fracture were also excluded. CT scans of the cervical spine were assessed by an observer blinded to clinical information.Cervical spine injuries were categorized as severe (S) if they had burst fracture involving both end plates, tension band injuries, and dislocation injuries (Types A4, B0, B1, B2, B3) and/or associated SCI. Injuries with insignificant fractures or single endplate burst morphology (Types A0, A1, A2, A3) and no SCI were categorized as less severe (LS) for our analysis. The association between BMI and severity of cervical spine fracture was studied by multiple-variable logistic regression analysis using a conditional stepwise backward elimination model. The dependent variable was severity of injury with less severe (LS) fracture serving as reference. Independent variable of interest included BMI which was entered as a continuous variable and forced to be in the model at all steps. Other covariates included in the model included age, gender, ethnicity, smoking status, medical comorbidities, mechanism of injury, and other significant organ system injury. All variables were initially entered in the model and backward elimination removal criteria was set at p>.1. RESULTS A total of 751 patients with cervical spine fracture were identified, out of which 291 patients met our inclusion criteria and had adequate records available for analysis. The mean age of included patients was 46.1±19.3 years, and 212 patients (75.8%) were males.Based on morphology of fracture and SCI, 106 (36.4%) were categorized as severe (S) injury. The remaining 185 (63.6%) patients were classified as less severe (LS) injury.%). MVA was the most common injury mechanism (n=177, 60.8%) followed by fall from height (n=85, 29.2%) and random traumatic events (n=29, 10.0%).Our multiple-variable logistic regression model found that increasing BMI was not associated with a likelihood of severe cervical spine injury after adjusting for other clinical and injury parameters (OR 1.03, 95% CI: 0.97–1.08, p=.34). A sub-analysis of MVA cases was done to include side of impact, rollover, protection, and ejection of occupant as covariates in addition to other patient variables. Although trending towards significance, the odds ratio of severe cervical spine injury due to increasing patient BMI was 1.08 (95% CI: 0.99–1.18, p=.06). In this analysis, the presence of rollover was also represented in the final model with OR 2.55 (95% CI: 0.98–6.66, p=.06). CONCLUSIONS In conclusion, our findings indicate that patients with higher BMI may be predisposed to more severe cervical spine fracture and/or SCI after MVA, especially when rollover is present. The same risk may not be present in other common modes of injury such as nonrollover MVA and falls. Further prospective studies with larger sample size, use of clinically relevant outcome parameters (fracture classification, neural deficit), and comprehensive measurement of injury related variables may be helpful to corroborate our findings.
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