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Shaw Chiropractic
A Medical-Legal Newsletter for Personal Injury Attorneys
by Dr. Steven W. Shaw

Research on Rear Impacts Collisions Demonstrates Greater Injury Potential

Many of you have heard of Dr. Arthur Croft of the Spine Research Institute of San Diego (SRISD) from his text on Whiplash Associated Disorders. Dr Croft and his associates recently presented a paper at the International Research Council on the Biomechanics of Impact. The paper titled Differential occupant kinematics and forces between frontal and rear automobile impacts at low speed evidence for a differential injury risk was presented by authors Croft AC, Haneline MT, Freeman MD:. International IRCOBI Conference on the Biomechanics of Impact, Munich, Germany, September 18-20, 2002, 365-366.
Key words: Accelerations, biomechanics, kinematics, neck, occupants, rear impacts

Abstract: Numerous factors are believed to influence the risk for injury to the cervical spine in low speed automobile crashes. These include occupant stature, gender, position, age, pre-exiting health status, and awareness of impending crash. Factors extrinsic to the occupant that are thought to influence the risk for injury include seat back characteristics, head restraint geometry, type of restraint system used, crash speed, relative vehicle mass, and the direction of impact. Several studies have indicated that rear impact crashes are associated with greater risk for injury and, in some cases, a worse prognosis. Epidemiological studies have identified many risk factors, but the retrospective study design and wide ranging variables of real life crash scenarios has not allowed careful comparison of specific variables. The researchers sought to answer the question concerning the possible reasons for the disparity in risk between front vector crashes and rear vector crashes using human subject crash testing.

Conclusions
The findings of this study shed some light on possible reasons for the observed difference in injury risk between frontal and rear impact crash injuries reported in clinical and epidemiological literature and will likely have medicolegal implications as well. The results suggest that more attention should be given to crashworthiness in the rear impact crash vector. As in all human subject crash tests, subjects can be made to be unaware, but not necessarily unprepared. Reactions times are likely to be more brisk for volunteers than for real world occupants. The small study size does not allow a high level of confidence in differential forces and resulting kinematics, but the results were always consistent and the differences were large. Differential risk assignment for real world occupants will require a more comprehensive epidemiological review. This is the first study to look specifically at differential effects of rear vs. frontal crashes at low speeds, holding all other variables constant.

This information is valuable in assessing your clients case as it relates to the potential for injury. The factors which influence injury potential are numerous and rarely considered by non-physicians. This paper demonstrates that of all the factors to consider the direction of impact and the state of preparedness are essential to consider when determining the potential adverse affects to the occupant.