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Dynamic Chiropractic – June 18, 2007, Vol. 25, Issue 13

Risk Analysis: The Skill Set That Sets You Apart

By Arthur Croft, DC, MS, MPH, FACO

Let me begin this article by pointing out some fairly dismal "facts of life" relative to 21st-century chiropractic practice. (I promise to atone for this by offering rays of hope or perhaps even practice-altering ideas at the end.) Let's face it, most chiropractors have experienced shortfalls in income, owing to the growth of managed care in America and its insidious spread into previously sacrosanct areas, such as automobile insurance.

Adding to this burden are the several statewide shake-ups we've experienced, such as California has encountered with its sweeping workers' compensation law changes, pushing those revenues down for chiropractors by more than 70 percent.

Meanwhile, many states have enacted laws that force plaintiffs in personal-injury cases to pay defense legal fees if the arbitrator's or jurors' award is less than what was offered by defense for settlement of the claim. In California, this is referred to as Code of Civil Procedure 998. The net effect is that the insurer offers a relatively low settlement and then hires an orthopedic surgeon, an accident reconstructionist and a biomechanical engineer as its experts. This immediately drives up the defense's legal costs into the stratosphere. This so-called "slash-and-burn litigation" has had a sobering effect on plaintiffs, who are now more inclined to settle for less, rather than face the prospect of paying the defense's legal bill.

In the meantime, chiropractic still offers the best management solution for injured people. Personal injury is still a very viable part of a well-rounded chiropractic practice, so long as the DCs know how to conduct themselves effectively. So, money is an important factor. Plaintiffs and plaintiff lawyers do not want to have to hire a lot of experts. However, when the defense has hired its gaggle of A-team experts, what is one to do?

First, take comfort in a few simple facts. The reconstruction of these crashes is highly problematic because the reconstructionist is required to make so many assumptions and estimations that the uncertainty can be shown to be very high. This leaves their analysis wide open to attack. In many cases, their testimony may be limited or excluded altogether in the face of a strong motion in limine. The biomechanist, meanwhile, must often rely on the reconstructionist's report and, thus, their theories are likewise subject to attack.

As an accident reconstructionist myself, most of what I do in that area is simply to rebut the conclusions of other reconstructionists. (I don't do the reconstruction precisely, because my argument is that it is not possible to do one with a sufficient degree of reliability.) This abnegation can be done in a variety of ways. For example, if you are a reconstructionist, you can offer direct rebuttal testimony. If you are not a reconstructionist, you can still provide plaintiff's counsel with declarations or assist in the preparation of motions to limit or exclude the reconstructionist's testimony. If you'd like to see some examples of this type of work product, send me an e-mail and I'll send you a few.

More fundamentally important is the fact that neither of these two experts is a physician and thus, cannot examine or interview the plaintiff. They are not licensed to render a diagnosis. Meanwhile, the biomechanics related to motor-vehicle trauma are not terribly complicated and easily can be learned by the chiropractor. One need not have a PhD in the subject to be qualified to discuss it. Consider, for example, Federal Rule of Evidence 702, which deals with the subject of your expert testimony:

If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education may testify thereto in the form of an opinion or otherwise.

Note that one need only be qualified in one of those areas in order to qualify to testify. So, where does that leave you? In pretty good form, actually. You are a physician and can therefore interview, examine and diagnose the patient. You can learn the issues of reconstruction - in particular, its limitations and problems - and can make fairly short work of this. (As I have said many times and will repeat here, in order to deflect the vitriol of my reconstructionist colleagues, accident reconstruction is only limited to a dangerous degree in the special case of low-velocity collisions.)

You should be able to discuss biomechanics when the proper foundation for your testimony is set forth on direct examination. Considering all of this, we now have a situation that is favorable to the plaintiff and the plaintiff's attorney. The treating doctor, who is clearly going to provide the best hope of favorable outcome among the many practitioners available, is also an expert in motor-vehicle collisions and injuries, and can deal with reconstruction and discuss biomechanics eloquently. In many cases, the plaintiff's attorney is no longer faced with the problem of hiring multiple experts.

There is one more very important point to make here. Notwithstanding the potential error rate and uncertainty of reconstruction in low-velocity collisions, about which I have written previously in Dynamic Chiropractic, the entire enterprise of hiring reconstructionists and biomechanical engineers to influence the opinions of arbitrators and jurors is based on a fundamentally flawed premise. This premise holds that knowing crash metrics, such as the change of velocity of the vehicles or their acceleration, we can reliably predict any of three outcome measures: the dichotomous risk for initial injury (i.e., injured or not injured); if injured, the severity of that injury; and whether the injury will resolve or become permanent. In point of fact, there is no evidence to support this premise.

We recently demonstrated that collision damage in these crashes did not correlate with any of these three outcome questions1 (This article should be given to all attorneys you work with and to those claims adjustors who write denial-of-services letters based on the dollar figure of the collision damage). Our meta-analysis clearly demonstrates that that practice, which is referred to as MIST segmentation, is not based on science. In fact, it has been shown to be erroneous. As such, it may very well constitute bad faith.

While our study looked at crash damage, it did not specifically deal with collision velocity or acceleration, although there is obviously a relationship between them. That leaves the door open to ask whether there might actually be a relationship between velocity or acceleration and injury risk, as some contend. Here is where epidemiological evidence tells us there is not. In one of the best studies to date, the authors used a paired-comparison method to explore risk factors in whiplash injury. The traditional approach in outcome studies of motor vehicle collision injuries has been to enroll a series of subjects presenting to an emergency department. The chief limitation to this method is that it is impossible to know whether the various collisions of all these subjects produced comparable forces. The potential variability is huge.

In a paired-comparison method, we take two or more subjects from one vehicle and then compare them across the various risk factors, thus eliminating the crash severity variable as a potential confounder. The most interesting finding in this study was that, as we have all seen many times in clinical practice, one person is often injured while another is not, or one person's injuries are minor while another's are more severe. They found, in other words, that human risk factors were more deterministic vis-à-vis risks than were crash metrics themselves. In case the profundity of this finding is missed, it means the entire enterprise of hiring reconstructionists and biomechanical engineers to analyze low-velocity collisions in order to determine risk for injury is flawed. Then why do it, you ask? Simple: The mystery of mathematics and physics is both terrible and compelling to a jury. If it isn't demystified, it usually will win the day. Believe me, auto insurers know this all too well.

Risk Analysis

If all this is true, what then would constitute the most realistic and valid, the most scientific and reliable, and the most practical way to analyze risk? It is the conducting of your own risk analysis based on published real-world outcome studies. And this is something reconstructionists and (most) biomechanists not only are not capable of doing, but are, in most cases, barred from doing. Here is the real value of your presence in the case outside of your treatment capacity. Here's how to do it.

I split this risk analysis into two risks: one, the risk for acute injury; and two, the risk for poor outcome (i.e., long-term symptoms). If your patient recovers, the only set of risk factors that are even relevant is the former. However, should the patient be left with permanent residual symptoms, then the relevant set of risk factors is the latter. The following lists each have a good many references to the biomedical literature in support of them, but space limitations prevents my listing them all. If you are interested in this supporting literature, please e-mail me.

Risk for Acute Injury

  • female sex
  • females weighing less than 130 pounds in frontal crashes
  • history of neck injury
  • head restraint below head's center of gravity (males and females); large topset
  • history of CAD injury
  • poor head restraint geometry/tall occupant (e.g., >80th percentile male)
  • rear vs. other vector impacts
  • use of seat belts/shoulder harness (standard three-point restraints)*
  • body mass index/head neck index (decreased risk with increasing mass and neck size)
  • out-of-position occupant (e.g., leaning forward/slumped)
  • non-failure of seat back
  • having the head turned at impact
  • non-awareness of impending impact
  • increasing age (middle age and beyond)
  • front vs. rear seat position
  • impact by vehicle of greater mass (>25% greater)
  • crash speed under 10 mph
  • rear-struck occupant when the bullet vehicle has a longitudinally mounted motor
  • driver vs. front seat passenger

Risk for Late Whiplash

  • female sex
  • rear vector impact vs. other vectors
  • body mass index in females only
  • immediate/early onset of symptoms (within 12 hours) and/or more severe initial symptoms
  • ligamentous instability
  • initial back pain
  • initial decreased cervical spine ROM (females only)
  • initial upper back pain
  • initial upper-extremity numbness or weakness or pain
  • greater subjective cognitive impairment
  • greater number of initial symptoms
  • greater severity or frequency of initial symptoms
  • high initial pain intensity
  • use of seat belt shoulder harness* [For neck (not back) pain, nonuse had a protective effect]
  • initial physical findings of limited range of motion
  • neck pain on palpation
  • muscle pain
  • disturbed vision
  • initial sleep disturbance or fatigue
  • initial neurological symptoms; radiating pain into upper extremities
  • past history of neck pain or headache
  • headache
  • initial degenerative changes seen on radiographs
  • foraminal stenosis (cervical)
  • loss or reversal of cervical lordosis
  • increasing age (middle age and beyond)
  • front seat position; driver seat vs. passenger seat for females
  • rear seat position
  • occupants of vehicles manufactured in the late 1980s to early 1990s (OR=2.7 vs. those in early 1980s vehicles); relevant for rear impact crashes only (Other data suggest this relationship holds for all 1990s vehicles)
  • initial generalized sensory hyperalgesia
  • head rotation at impact; both frontal and rear

*Always wear your seat belt. It can save your life.

This wide outcome-literature-based risk analysis will provide an infinitely more reliable, valid and scientific assessment of risk than can ever be provided by reconstructionists or engineers, based on crash analysis alone. Including this referenced risk analysis in your reports will allow attorneys to better understand the case and will allow the insurer to set more realistic reserves, which is actually of benefit to all parties.

If I were a plaintiff attorney, I know I'd have the best all-around expert and treating doctor and a DC, who is knowledgeable not only in the latest clinical approaches to treatment, but also in traumatology and risk analysis. In a lot of cases, he or she would be all I needed to handle the routine personal-injury claim more effectively. And that, good doctors, is your chief selling point. Remember, there are 3 million of these injuries every year in the U.S., and presently, only 36 percent are treated by chiropractors. This is probably one of the reasons the outcome statistics for this kind of injury are not particularly sanguine.


  1. Croft AC, Freeman MD. Correlating crash severity with injury risk, injury severity, and long-term symptoms in low velocity motor vehicle collisions. Medical Science Monitor, 2005;11:RA316-21.

Click here for previous articles by Arthur Croft, DC, MS, MPH, FACO.

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