Incidence and mechanism of neurological deficit after thoracolumbar fractures sustained in motor vehicle collisions
Authors: Mukherjee Sourabh , Beck Chad , Yoganandan Narayan , Rao Raj D. 
Published: October 2015

OBJECT
To determine the incidence of and assess the risk factors associated with neurological injury in motor vehicle occupants who sustain fractures of the thoracolumbar spine.

METHODS
In this study, the authors queried medical, vehicle, and crash data elements from the Crash Injury Research and Engineering Network (CIREN), a prospectively gathered multicenter database compiled from Level I trauma centers. Subjects had fractures involving the T1–L5 vertebral segments, an Abbreviated Injury Scale (AIS) score of ≥ 3, or injury to 2 body regions with an AIS score of ≥ 2 in each region. Demographic parameters obtained for all subjects included age, sex, height, body weight, and body mass index. Clinical parameters obtained included the level of the injured vertebra and the level and type of spinal cord injury. Vehicular crash data included vehicle make, seatbelt type, and usage and appropriate use of the seatbelt. Crash data parameters included the principal direction of force, change in velocity on impact (ΔV), airbag deployment, and vehicle rollover. The authors performed a univariate analysis of the incidence and the odds of sustaining spinal neurological injury associated with major thoracolumbar fractures with respect to the demographic, clinical, and crash parameters.

RESULTS
Neurological deficit associated with thoracolumbar fracture was most frequent at extremes of age; the highest rates were in the 0- to 10-year (26.7% [4 of 15]) and 70- to 80-year (18.4% [7 of 38]) age groups. Underweight occupants (OR 3.52 [CI 1.055–11.7]) and obese occupants (OR 3.27 [CI 1.28–8.31]) both had higher odds of sustaining spinal cord injury than occupants with a normal body mass index. The highest risk of neurological injury existed in crashes in which airbags deployed and the occupant was not restrained by a seatbelt (OR 2.35 [CI 0.087–1.62]). Reduction in the risk of neurological injuries occurred when 3-point seatbelts were used correctly in conjunction with the deployment of airbags (OR 0.34 [CI 1.3–6.6]) compared with the occupants who were not restrained by a seatbelt and for whom airbags were not deployed. Crashes with a ΔV greater than 50 km/hour had a significantly higher risk of spinal cord injury (OR 3.45 [CI 0.136–0.617]) than those at lower ΔV values.

CONCLUSIONS
Deployment of airbags was protective against neurological injury only when used in conjunction with 3-point seatbelts. Vehicle occupants who were either obese or underweight, very young or elderly, and those in crashes with a ΔV greater than 50 km/hour were at higher risk of thoracolumbar neurological injury. Neurological injury at thoracic and lumbar levels was associated with multiple factors, including the incidence of fatality, occupant factors such as age and body habitus, energy at impact, and direction of impact. Current vehicle safety technologies are geared toward a normative body morphology and need to be reevaluated for various body morphologies and torso compliances to lower the risk of neurological injury resulting from thoracolumbar fractures.