Study authors Raj Rao (Department of Orthopaedic Surgery, Medical College of Wisconsin, Milwaukee, USA) and others write in The Spine Journal that although analyses of mechanisms of car crashes have resulted in improved car safety, “little effort” has been made to characterise the mechanisms of injury in car crashes that specifically result in thoracic and lumbar fractures. They add that they used a large multicentre database—the Crash Injury Research and Engineering Network (CIREN) database—to determine: “the types of injuries sustained to the thoracic and lumbar spine in motor vehicle crash occupants and to study the associated morbidity incurred by occupants with these factures of the spine.”
Of the 4,572 cases reported in the database, Rao et al identified that 631 occupants sustained thoracic and lumbar spine injuries. Of these, 299 had major injuries and 332 had minor injuries. Data available showed that 41.3% of all occupants used a three-point seat belt appropriately, 54.4% did not wear a seat belt, and 4.3% wore a two-point seatbelt or wore a seatbelt inappropriately. The authors comment: “Paradoxically, the appropriate use of three-point seatbelts did not appear to have a protective effect against thoracic and lumbar spine injury, with 35.5% of appropriately belted individuals in the CIREN database sustaining thoracic and lumbar spine injuries, while 11.6% of unbelted occupants sustained thoracic and lumbar spine injuries.” Furthermore, belted individuals sustained major thoracic and lumbar injuries more frequently than unbelted individuals—18.4% of 1,033 occupants overall vs. 5.6% of 1,360 occupants overall, respectively.
However, unbelted individuals who sustained a thoracic or lumbar spine injury had a higher average injury severity score and higher fatality rate compared with individuals who a three-point seat belt and sustained such injuries: 29.7 and 16.5% of 158 occupants injured vs. 25 and 9% of 365 occupants injured.
Although appropriate use of a three-point seat belt was not associated with a protective effect, airbag deployment was (overall, 1,523 occupants from the whole database had airbag deployment compared with 1,101 occupants). Rao et al comment: “Major thoracic and lumbar spine injuries were more frequent in occupants without airbag deployment (81% of 21 occupants injured) than when airbags were deployed (63% of 243 occupants injured).” They add that airbag deployment among occupants wearing a three-point seat belt appeared to have a protective effect with a lower severity score and fatality rate.
The authors conclude: “While seatbelt usage does appear to confer some protective effect against fatality and severity of injury, this does not necessarily transfer to protective effect against thoracic and lumbar spine injury.” They add that future advancements in car safety and engineering should “address the need to reduce thoracic and lumbar spine injuries in belted occupants”.