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Shaw Chiropractic How Important are Biomechanics? While I sit here in my office preparing to leave for my biomechanical trauma masters degree program I review an article on low speed collisions. It discusses a recent study on predicting symptoms from vehicular collisions between 2.5 and 5 mph. The authors find that even at these low speed collisions 31% of the 75 healthy test subjects had immediate onset of symptoms. The authors carefully analyzed the test data and found that there was no simple model to predict whiplash symptoms following rear-end impacts. The most reliable predictive method consisted of 16 different factors and even with the 16 variables the model was only 80% sensitive for accuracy. The authors admit that the clinical usefulness of the model is lost in it’s complexity but identify several significant points. They point out that the physics and biomechanics of the collision are not as important as the occupant factors. They point out that the injury tolerance of biological tissues is variable. They also point out that pain perception may also play a role in injury causation and symptom production. What factors may lead to greater injury? Many pre-morbid illness affect tissue viscoelasticity. Several examples include Rhumatoid arthritis, Systemic Lupus Erythematosis, Osteoarthritis all of which reduce the threshold for injury. What about a more common disease like diabetes? Diabetics have prolonged healing times and heal with poor quality fibrotic tissues. How about other occupant factors like gender, physical conditioning, body composition and age? You should know that injury threshold research is performed on healthy subjects to eliminate as many variables as possible. To my knowledge there has never been a study comparing similar collisions on subjects of different pre-morbid illness. Besides, how ethical would it be to use 70 year old diabetic Rhumatoid arthritic obese female subjects and compare them to similar rear impact collisions on healthy individuals to see how they differ? I don’t believe we will ever see this type of research but we can extrapolate from what we know about these pathological processes and biological tissue responses to forces from laboratory settings. The authors conclude that making assumptions about injury threshold based solely upon collision factors is risky business. It would be foolish to completely discount the collision dynamics. However, attorneys, doctors and insurance adjusters should be aware of the relatively low importance collision dynamics play in the injury potential threshold when compared to the more important occupant factors. These occupant factors cannot be assessed quantitatively but do have qualitative considerations which in combination with other factors lead the physician (or attorney) towards a reasonable deduction regarding injury potential regardless of collision dynamics. The authors state that the results of their study "indicate that the practice of predicting injury from a single peak kinematic response variable can lead to erroneous conclusions." The authors were specifically relating their opinion to the Murray Allen study which described events such as "Plopping down in a chair" or "Steeping off a curb". To make this practical you should make
sure your treating doctors are addressing
all these occupant issue in the reports.
It starts with a good medical history
and systems review. The doctor should
identify and elaborate on any pre-morbid
consideration and discuss how it will
adversely affect your clients capacity
to withstand even a small impact or how
it will interfere with the healing process.
Once you have been given this information
you can use it in your settlement negotiations
or at trial to demonstrate the life influencing
consequences of your client’s injuries. |
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