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Shaw Chiropractic Neck Injury from Low Velocity Rear Impact Collision During trial preparation as a biomechanics expert I was asked to review the medical records on a patient of a prominent orthopedist. Included in the file was a 20 page "Reconstruction Analysis" report from a well know Northeastern accident reconstruction group. The great majority of the 20 page report had nothing to do with the analysis of the collision. Rather, there were three pages of psudo-collision analysis and seventeen pages of fluff. The three pages of collision analysis did not include one formula or mathematical equation. Instead, the accident reconstructionist (AR) discussed the lack of property damage and the obvious low magnitude impact. The 17 pages of fluff were composed of selected research which has been severely criticized in the scientific community. In his report, the AR made a comment which stood out in my mind. He stated that the magnitude of the impact was not sufficient enough to move the occupants head beyond the normal physiologic range. The assertion is that if the movement of the entire cervical spine is within the "normal" physiologic range there is no way that the occupant could have sustained an injury. In this newsletter, I will discuss this false concept and present the most current theory on this topic. First, what is the "normal" physiologic range of motion? Is it the same for a 20 year old as it is for a 70 year old? Does an arthritic spine have the same mobility as a healthy spine? Do muscular development and conditioning play a role in the "normal" movement? How about genetic and congenital considerations such as anomolies, body type, conformation etc? The answer is obvious, normal is an individual and variable value. It is grossly determined through scientific research on healthy subjects but cannot be applied without consideration of the individual. That being said lets look at how cervical spine injuries really occur. While it is true that movement beyond the individual’s physiologic limits will cause damage one must consider the physiologic limits of the entire spine versus the segmental physiologic limits. Cervical spine movement is composed of the combined movement of the seven cervical vertebra. Loss of movement at one segment may not alter the overall motion but significantly affects injury potential at that level. This is why people who have arthritic changes are particularly vulnerable to injury at the segmental levels of arthritic change. The same would be true of any circumstance affecting segmental mobility. Several months ago I wrote a newsletter discussing the findings of several researchers. The currently accepted mechanism of injury of the cervical spine from whiplash is now understood to be predominantly due to strain/sprain at the segmental level. You may recall that the neck is curved with a C shape (lordotic curve). During a rear impact collision the body moves forward under the neck, first reducing and then reversing the curve one segment at a time until all the segments are in extension. In the process, the normal limits of each segment are challenged. The overall limits of combined segments may not be overcome but segmental limits may be compromised. The researchers found that in a 2.5 to 5 mph impact the entire process takes less than 150 ms. This is far less than the 250-300ms of the entire whiplash phenomenon. High speed fluoroscopic studies (movie x-ray) shows that the neck changes from a C shape to a S shape during this process resulting in greater potential for segmental joint damage. The damage noted by these researchers involves the facet joints as well as the disc integrity. They have seen annular tears, damage to the joint capsule and even disc herniation. Therefore, contrary to the opinion of the AR, a rear impact collision of low velocity can cause significant damage. This is particularly the case when the occupant is unprepared, has head rotation or has complicating conditions such as arthritic changes or concomitant pathology. The point here is that one cannot reasonably take accident research and apply it to real world circumstances. The variables between subjects is so great that each individual occupant must be evaluated for his specific and unique characteristics. You can’t put a square peg in to a round hole. The opinion of the treating doctor is the most important fact to consider. Even more to the point, as an attorney you should never allow an AR to discuss any matter involving occupant injury since it is well beyond their field of expertise. You should make a motion before trial to limit the testimony of the AR. On the other hand, the adequately trained doctor should be disclosed as an expert in biomechanics in addition to his formal training. Of course, this assumes that the physician has had supplement training in trauma biomechanics. Even without the biomechanics background the physician should be competent to explain how the tissues were damaged and the normal course of repair. As always we are available to discuss
these topics further. Please feel free
to contact us at 800-232-6824. |
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