Jul 13 2016
Before 2001, catastrophic craniovertebral junction (CVJ) injuries were the most common cause of death to drivers in the fast-paced sport of professional car racing. That changed with the development and implementation of the HANS® (Head and Neck Support) device and similar restraints.
In their paper, "A revolution in preventing fatal craniovertebral junction injuries: lessons learned from the Head and Neck Support device in professional auto racing" (published online today in the Journal of Neurosurgery: Spine [http://thejns.org/doi/full/10.3171/2015.10.SPINE15337), Anand Kaul and colleagues describe advances in biomechanical engineering that dramatically reduced the incidence of fatal injuries sustained by racecar drivers. The authors recount how Dr. Robert Hubbard, a biomechanical crash engineer, and his brother-in-law, Jim Downing, a racecar driver, joined forces to create a device designed to prevent the occurrence of shear injuries between the head and neck during high-impact crashes. The professional partnership between Hubbard and Downing was forged following the death of their mutual friend, Patrick Jacquemart, a racecar driver who died of such an injury in 1981. It led to the development of a device that would save future drivers from a similar fate.
The craniovertebral junction, or CVJ, is composed of the posterior base of the skull and the uppermost portion of the spine (atlas and axis, the first and second vertebrae) along with connective tendons and ligaments. During a frontal car crash, as the car decelerates, the driver's torso is secured in place by seat belts. The head, however, freely jerks forward (forward flexion), which can produce a distraction or shearing injury to the posterior elements of the vertebrae. Hubbard and Downing designed a device that would anchor the head to the shoulders with the aim of preventing sudden forward flexion.
The predictive thresholds for severe CVJ injuries, established by General Motors, include axial tension greater than 740 lbs and forward neck shear greater than 700 lbs. Kaul et al. recount that while performing crash sled tests without the HANS® device, Hubbard measured 1120-lb neck tension, 1350-lb neck load, and 750-lb neck shear forces. After adding the HANS® device to the test, the neck tension and shear forces were only 210 lbs—evidence that the HANS® device would reduce neck tension and shear forces during a frontal crash to a point well below levels associated with injury. Additional testing found that the HANS® device works in both NASCAR (National Association for Stock Car Auto Racing) and IndyCar/Formula 1 vehicles, despite the fact that the driver seats are set at different angles.
The first-generation HANS® device was created in 1990 and the second-generation device just a few years later, but widespread use lagged for several years. In 2001, racing legend Dale Earnhardt Sr. suffered a fatal CVJ flexion-distraction injury, an event that ultimately spurred implementation of better safety regulations for drivers. Soon after Earnhardt's death, the use of the HANS® device and similar restraints was mandated by NASCAR, CART (Championship Auto Racing Team), and other racing groups.
Since the use of head-and-neck support devices was mandated, there have been no deaths from CVJ injuries in NASCAR or CART professional auto racing.
When asked about this study, Gabriel Smith, MD, the corresponding author, stated, "Utilized almost uniformly in high speed racing today, it is easy to forget the dramatic impact this device has had on safety and injury prevention. The HANS® device epitomizes human innovation, combining engineering with the biomechanical properties of the spine at the craniovertebral junction."
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