Background

ARCCA Inc. has investigated thousands of low-speed, multi-vehicle rear-end impacts with discernibly little vehicle damage and pronounced claims of lumbar, thoracic, cervical or head injuries. Determination of a causal relationship between claimed injuries and a low-speed rear-end impact requires thorough analyses of the subject incident and knowledge of the unique tolerance level of the individual in question. Unfortunately, this task is often incorrectly given to a treating physician who may be ill-equipped to properly analyze the subject incident. Evaluations of incident severity, including the principal direction of force and delta-V, as well as the associated vehicle and occupant kinematics and kinetics are required to properly assess both the magnitude and direction of force that an occupant sustains in a low-speed rear-end impact. Therefore, a biomedical engineer who is trained in the application of the concepts and methods of mechanical engineering and the physical sciences to medicine and the human body is needed to correlate mechanisms of the claimed injuries with the mode and intensity of the energy transfer associated with the subject incident.

Historically, low-speed rear impacts have been associated with claims of whiplash injuries and it has recently been estimated that in the United States over 805,000 whiplash injuries are claimed annually, costing an estimated $5.2 billion.1 Throughout ARCCA's experience and research it has been observed that claimed cervical spine injuries are often associated with concurrent claims of lumbar spine injuries, such as lumbar sprains/strains, disc herniations, spondylolysis and spondylolisthesis. For example, it has been estimated that clinical and epidemiological literature demonstrates the existence of low back complaints in approximately 45 percent of cases that include claims of whiplash. Reports of the contemporaneous complaints of low back pain appear in the literature as far back as the mid-1950s and continue through the present, with most authors reporting an incidence of low back pain of 35 to over 50 percent in cases of claimed whiplash injury.2,3,4,5,6,7,8

While previous research has been conducted on the response of occupants to low-speed rear impacts, there have been no published data regarding kinetics of the lumbar spine during these incidents. For example, several studies have subjected human volunteers of various ages to multiple low-speed rear-end impacts to evaluate the injury thresholds for cervical strains and other associated injuries.9,10,11 These studies have provided valuable insight into the tolerance levels of the human cervical spine during low-speed rear impacts and have enabled researchers and clinicians to better understand the often improbable existence of a causal relationship between an individual's claimed cervical injuries and a specific subject incident. In addition, despite the inclusion of volunteers with various degrees of lumbar spinal degeneration, previous studies have reported a lack of relative motion in the lumbar spine and therefore a decreased likelihood of significant low back injuries in low-speed rear impacts.12,13

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