Spine and spinal cord injury in motor vehicle crashes: a function of change in velocity and energy dissipation on impact with respect to the direction of crash.
OBJECTIVE
To examine the effect of change in velocity (DeltaV) and energy dissipation (IE) on impact, above and below the test levels for Federal MVC Safety Standards, on the incidence of spine fractures (SF), spinal cord injury (SCI)), SF mortality and the associated injury patterns in Frontal (F) and Lateral (L) MVCs. Comparison of 214 patients with SF or SCI with 938 patients who did not have SF or SCI.


METHODS
1152 MVC adult drivers or front-seat passengers (701 F & 451 L) evaluated at 10 Level I CIREN study Trauma Centers together with vehicle and crash scene engineering reconstruction. Patient seat belt (SB) and/or airbag (AB) use correlated with clinical, or autopsy findings.


RESULTS
The relationship between DeltaV and IE rose exponentially as DeltaV increased. Of the 1152 patients, all with AIS> or =3 injuries, there were 214 patients with spine fractures of AIS > or =2. In FMVCs there were more SF patients with Cervical SF than in LMVCs (68F versus 64 L) and more Thoracic (35F versus 21L) and Lumbar (39F versus 16L) SF. However, the incidence of spinal cord injury was greatest in the Cervical SF (33%), compared with the Thoracic SF (18%), or Lumbar SF (2%). Most important, in FMVCs 49% of SF, 47% of SCI and 71% of the SF deaths (p < 0.05) occurred at > mean of 47.4 kph. In contrast, in LMVCs 51% of SF, 52% of SCI and 67% of the SF deaths occurred at DeltaV > mean of 35.3 kph. However, 80% of all deaths in SCI occurred in Cervical SF cases, in these 74% also had a brain injury. In contrast, the deaths in Thoracic SF were due to combinations of brain (45%), thorax (95%) or associated pelvic fracture injuries (50%). Airbag (AB), or Seat belt (SB) restraints appeared to protect FMVC SF patients from SCI at lower DeltaV, but 84% of Cervical SCI patients at DeltaV > 47 kph had AB protection and in a few cases the AB appeared responsible for the SCI. In contrast, 82% of Lumbar SF patients had SB, but in FMVCs where jackknifing due to backloading occurred, improper SB positioning may have contributed to the SF.


CONCLUSIONS
The implication for SCI in both front seat drivers and passengers in either FMVC or LMVC crashes above their respective DeltaV means is that improved spine fracture protection is necessary at higher DeltaV levels. More effective safety systems to prevent Cervical SCIs should be developed using two-level frontal and side AB & SB+pretensioner devices, which protect against SF at DeltaV both at and 1SD above the FMVC (47 & 72 kph = 30 & 45 mph) and LMVC (35 & 54 kph =22 & 34 mph) means.
Smith
Joyce A
JA
New Jersey Crash Injury Research Engineering Network Center, New Jersey Medical School, Newark, NJ 07107, USA.
Siegel
John H
JH
Siddiqi
Shabana Q
SQ
D000054:Acceleration; D000063:Accidents, Traffic / Q000401:mortality*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017278:Air Bags / Q000009:adverse effects / Q000706:statistics & numerical data; D000704:Analysis of Variance; D001334:Automobile Driving; D001336:Automobiles; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D015601:Injury Severity Score; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009515:New Jersey / Q000453:epidemiology; D012622:Seat Belts / Q000009:adverse effects / Q000706:statistics & numerical data; D013119:Spinal Cord Injuries / Q000209:etiology / Q000401:mortality*; D016103:Spinal Fractures / Q000209:etiology / Q000401:mortality*