In 1948, G. Q. Chance, a 20th-century English radiologist, described three cases involving a rare fracture in the thoracolumbar spine that now bears his name.* These Chance fractures resulted from extreme flexion, causing a “horizontal splitting of the spine and neural arch, ending in an upward curve which usually reached the upper surface of the body just in front of the neural foramen.”† With the introduction of automobile lap-type seat belts in the 1950s and their increased use by the 1960s, there was an upsurge in frequency of these fractures that resulted from the jackknife-like restraint forces applied to the spine during a collision, especially when the belts were improperly worn.
Lap belts and Chance fractures
A typical hyperflexion fracture of the thoracolumbar spine results from forces on the anterior half of the vertebral body and would normally result in a wedge or compression fracture, most commonly in the 12th thoracic vertebra or the first lumbar vertebra. Wearing a lap belt shifts the fulcrum of the forces from the anterior portion of the vertebral body far forward to the area where the lap belt actually contacts the anterior abdominal wall. The spine is now posterior to this flexion axis, and the entire spine then becomes subject to these stress forces. This can result in posterior ligamentous injury or posterior element fracture with or without vertebral body fracture.‡ These transverse fractures are more commonly found in the first, second, or third lumbar vertebrae. Chance fractures can also result from falls or injuries where the patient was thrown forward, and the anterior abdominal wall came in contact with some fixed object (tree limb, bannister, fence railing, ledge, and so on) that acted as a fulcrum resulting in forces that put the torso into acute flexion.
To examine the occurrence of motor vehicle-related injuries that would include Chance fractures in the National Trauma Data Bank® (NTDB®) research dataset for 2013, admissions medical records were searched using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnoses codes. Specifically searched were records for motor vehicle passengers containing an external cause of injury code (E-code) E810–E816 (motor vehicle traffic crashes) with a post decimal value of 0.1 for passenger, or E819 (motor vehicle crash unspecified) with a post decimal value of 0.1 for passenger and either a diagnosis code of 805.4 (lumbar fracture closed) or 806.4 (lumbar fracture closed with spinal cord injury). These records were then searched for a protective device field choice = 2 (lap belt). A total of 1,923 records were found, 1,821 of which contained a discharge status, including 1,187 patients discharged to home, 334 to acute care/rehab, and 229 to skilled nursing facilities; 71 died. These patients were 66 percent female, on average 23.8 years of age, had an average hospital length of stay of 10.4 days, an intensive care unit length of stay of 8.8 days, an average injury severity score of 11.4, and were on the ventilator for an average of 10.8 days. Of the 1,020 tested for alcohol more than one-fifth (219) were positive. (See figure.)
Even though seat belt use is legislated at the state level, on January 1, 1968, Title 49 of the U.S. Code, Chapter 208, Motor Vehicle Safety Standard, took effect, requiring all vehicles (except buses) to be fitted with seat belts in all designated seating positions.‡ Subsequently, the law has been modified to include three-point restraints in outboard seating positions, and finally three-point restraints in all seating positions. With the overwhelming majority of seat belts in use being three-point restraints, the risk of a hyperflexion lap-belt type injury is greatly reduced. Seat belts save lives. Don’t chance it; buckle up.
Throughout the year, we will be highlighting these data through brief reports in the Bulletin. The National Trauma Data Bank 2013 Annual Report is available on the ACS website as a PDF file at www.ntdb.org. In addition, information about how to obtain NTDB data for more detailed study is available on the website. To learn more about submitting your trauma center’s data, contact Melanie L. Neal, Manager, NTDB, at firstname.lastname@example.org.
Statistical support for this article has been provided by Crystal Caden-Price, Data Analyst, and Alice Rollins, NTDB Coordinator.
*Dhall SS, Tumialán LM, Mummaneni PV. Chance fracture of the second thoracic vertebra: Case illustration. J Trauma. 2006;60(4):922.
†Rogers LF. The roentgenographic appearance of transverse or chance fractures of the spine: The seat belt fracture. Am J Roentgenology. April 1971. Available at: http://www.ajronline.org.proxy.cc.uic.edu/doi/pdf/10.2214/ajr.111.4.844. Accessed July 18, 2014.
‡National Highway Traffic Safety Administration. Federal Motor Vehicle Safety Standards and Regulations. U.S. Department of Transportation. Available at: http://www.nhtsa.gov/cars/rules/import/FMVSS/#SN208. Accessed June 30, 2014.