Whiplash-caused neck injuries are some of the most highly contested personal injury claims. Properly understood, 'whiplash' is used to describe the mechanism of injury to the occipital region of the head and the cervical region of the spine that occurs to a seated occupant of a motor vehicle that is struck from behind by another motor vehicle. Whiplash does not occur in front-end collisions and does not describe low back or other injuries that also may occur in rear end collisions. Whiplash-caused neck injuries are highly contested because the resulting injuries often do not show up on standard diagnostic imaging tests. In addition, whiplash injuries often occur in low speed collisions where the involved vehicles are undamaged or minimally damaged. For this reason, claims professionals and defense attorneys view these claims with almost universal skepticism. On the plaintiffs' side, the lack of objective imaging studies and the [often] low speeds involved can make convincing juries to award even nominal damages difficult.Unfortunately, science has not reached common consensus regarding how whiplash causes injury or what precise forces are necessary to cause whiplash neck injuries in low speed collisions. However, researchers have come to a consensus on how the body reacts in rear-end collision which is important to understand when prosecuting or defending whiplash claims.When a rear end collision occurs, the head, neck, lower torso/pelvis, and upper torso actually act independently of one another. When the collision first occurs, the lower torso and pelvis are pushed forward relative to the upper torso, neck, and head. This motion causes "an initial flexion of the neck, even though the head is still effectively stationary…" Then the upper torso accelerates forward before the head begins moving. This is called "retraction" and "causes the lower vertebrae of the cervical spine to extend." At this point, the cervical spine and its musculature is not sufficiently strong to overcome the forces of the lower and upper torso movement so the upper cervical spine segments flex. The flexion and extension of the cervical spine allows it "to support the horizontal forces, and these forces both accelerate the base of the skull forward and set up a rearward rotation (extension) of the head." Interestingly, when the lower torso moves forward, the "upward thrust of the trunk compresses the cervical spine." Also noteworthy is that peak strains on the neck occur before the human body is able to activate the neck muscles in response.The manner in which the human body moves during a rear-end traffic accident is significant for a number of reasons. First, the forces generated on the cervical spine and occipital regions happen before the human body reacts to them. This means that a person who is in a rear-end collision cannot accurately describe what happened to their body during the collision. To occupants, it will feel like their head snapped forward and then back when in effect, the head remained stationary relative to the forward translation of the body. The difference in acceleration between upper and lower torso causes the upper and lower cervical spine to react by flexing and extending before the person is aware that anything is happening. In addition to horizontal shearing (forward motion of the torso vis-à-vis the stationary head), the upward motion of the torso also compresses the anterior portion of the cervical vertebrae (against which "the facet joints offer little or no protection") before the human body is capable of being aware of the motion. No claimant will be able to describe the mechanics accurately because sense data are generated and processed in the brain slower than the body's actual physical response. What a person in a rear-end collision feels is markedly different than what actually happens to the body.Second, the motion of the head and neck during a rear-end collision will more than likely be within the normal range of tolerance for the human neck if the occupant is belted with a normal and operable shoulder/lap belt combination. Hence, evidence of tissue disruption is unlikely to appear on diagnostic imaging studies. For claim handlers and attorneys (on both sides), the lack of objective imaging evidence creates enormous difficulties. Although the lack of objective evidence seems to favor the defense, the commonplace nature of whiplash injuries (and the fact that large portions of the medical and scientific communities accept that whiplash is a mechanism that can legitimately cause injury) would seem to favor the plaintiff. The bottom line is that these cases end up in a medico-legal morass because of the seemingly contradictory nature of the evidence which does not necessarily favor one side or the other.A key to managing whiplash claims successfully is understanding the biomechanics involved. For example, there is general consensus that gender matters in whiplash accidents: female gender increases the likelihood of injury. In addition, height is predictive of injury. Taller persons are likelier to be injured than shorter persons of the same gender because taller persons are less likely to have the headrest set at the proper height. Many other factors such as body positioning and pre-impact awareness influence the likelihood of neck injury in whiplash accidents. It behooves the parties to understand how the facts of the claim fit into the biomechanics.Stay tuned as we will address strategies for using biomechanics to your advantage in whiplash claims in our next whiplash post. [Attention: shameless plug warning!] Also, two internationally renowned experts in the biomechanical analysis of whiplash, Raj Rao, M.D., Ph.D and Brian Stemper, Ph.D. (who happen to be located at the Medical College of Wisconsin right in our backyard) will be speaking at the upcoming Medical Systemspersonal injury conference. Anyone interested in a detailed analysis of factors that influence injury in automotive rear impacts and the medical aspects of whiplash syndrome should consider attending.
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