– By Patrick Sundby, Accident Investigator;
Mark Studin DC, FASBE(C), DAAPM, DAAMLP;
and Kenneth M. Bahoora, DC
In this month’s medico-legal feature, VLM brings you the voices of three professionals in their fields who are experienced in spinal biomechanics, and low-speed and catastrophic crashes. Below, they share answers and insights about some common questions they’re asked, including the topics of bodily injuries, crash dynamics and accident reconstruction.
1. “How do airbags work and why do they deploy in some cases and not others?”
Almost all airbag-equipped vehicles contain an airbag control module. The module monitors various vehicle systems and has a predetermined threshold for deployment. (In simpler terms, this means the collision has to meet certain settings to deploy an airbag.)
While each car brand’s system is different from the next, the concept is the same: The module constantly monitors a vehicle’s speed, and when a collision occurs, the module can tell the change in speed is happening faster than if the car was slowing by brakes alone. IF the collision, as calculated by the module, is extreme enough, it will deploy the appropriate airbag(s). (Note: The module having the final say in why an airbag is deployed is truly vehicle-specific, as well as module software and hardware dependent.)
The module can know changes in the vehicle’s direction and speed via onboard accelerometers. The module constantly calculates these changes and when it “sees” a change beyond preset thresholds, it begins to monitor the changes very closely (this is called “algorithm enablement”). If the module determines the changes meet the criteria for airbag deployment, it will deploy the appropriate airbag(s).
Many vehicles also have failsafe sensors mounted in the vehicle that are designed as a secondary mechanical and/or electrical triggering system. These sensors are mounted on the front of the vehicle, usually under the radiator. When crushed or damaged, they force an airbag deployment.
Occasionally, someone will ask how a vehicle knows that a seat is occupied. (The driver’s seat is obvious, but beyond this, the front passenger seat has a pressure sensor that can tell when a predetermined amount of weight is on it, and in most vehicles, the rest of the seats use the seatbelt latch.) When you are driving, the module also monitors the status of seatbelts and the pressure sensors, and uses that data to make the best decision possible about which airbags to deploy and when.
2. “I got this collision expert’s report but there doesn’t appear to be any explanation for his findings. Is this normal?”
We are often asked about a specialist’s report, but the most common subset questions are about the lack of support for findings in the report. So we have chosen to address this question because it’s of personal and professional interest to us.
The answer to the above is both yes and no: Yes, it happens; and no, it’s not acceptable standard.
One of the reasons I (Patrick Sundby) have chosen to work with Dr. Bahoora and Dr. Studin is because of their tenacious commitment to research. If you have seen these doctors present, you know they have scholarly research to back up their points. Working with doctors that have been through accredited and standardized training based on a lot of scholarly research is imperative. All professional fields of post-primary education are based in accredited and scholarly formal standards. Collision reconstruction specialists are no different. While not necessarily part of an undergraduate or graduate program, the training and education they have is based on the same accredited and scholarly formal training and education. And because of this correlation, the same standard should be applied to collision reconstruction specialists.
Scholarly research is based on objective methods of testing and investigation, peer review, and rigorous scrutiny before being accepted. When an expert offers an opinion without citing supporting scholarly documentation, it’s not worthless, but rather it stands alone as opinion. Conversely, when an expert offers an opinion with appropriate supporting scholarly documentation, an opinion is accompanied by work, expertise, and research.
3. “Is the listed cost on the appraisal an accurate reflection of damage?”
An appraisal for repairs is often used to justify “low speed” in a low-speed crash by citing minimal costs; but there are a few points regarding them to consider.
Regarding the above, the short and easy answer is “no,” and the long answer starts with understanding who did the appraisal, and the background of the appraiser. Usually, appraisers are trained by the insurance company for whom they work. As such, minimizing the costs and expenses of repair is in the insurance company’s interest. Second, most appraisers do not disassemble a vehicle to determine if there is any hidden damage, particularly in low-speed collisions.
The next problem is that when replacement parts are needed, where should they come from? Original equipment manufacturer (OEM) parts cost substantially more than equal- or like-quality (ELQ) parts, which makes ELQ parts the preferred choice of insurance companies.
Along this same line, the quality of paint also varies. Paint manufacturers offer paint systems to meet OEM specifications and are very durable paints; however, they also offer more economically friendly paint that is not as durable or as closely color matched to the original. And as expected, it costs less.
The last problem to discuss is job downtime. The longer a vehicle is in for repairs, the more it costs the insurance company in rental fees. While a shop can, and will, have a minimum amount of time to fix the vehicle, the insurance company is going to keep it on a timeframe and constantly press for the vehicle to be completed. Sometimes that can create an environment where the repair facility will sacrifice quality of workmanship to complete the job faster for a better profit margin.
The above variables greatly dictate the final number, making it too subjective for a reliable point to support the threshold of injury. In other words, the use of “low cost” as a justification for no injury is not appropriate, as no causality relationship exists. If a breakdown of the repair bill is provided, you could objectively price the repair parts and effectively show the bias toward reducing the cost of the repair.
4. It is a common finding that whiplash patients suffer injury to their discs.Determining whether the pathologic disc is causally related to the whiplash becomes a concern in the medico-legal arena…which means that a common question we receive is, “How can you tell if the pathological disc found on MR imaging is directly related to the whiplash?”
Initially, the first step in determining the relationship between causality and bodily injury is to be certain that patients have a complete history taken, and that an examination is performed by a qualified health care provider that is trained in trauma care. Many practitioners are licensed to treat the trauma case, but many are ill equipped in training and experience and don’t have the credentials to ensure an accurate diagnosis as to determine proper relationship to causality.
Beyond radiating symptomatology—as Del Grande, Maus and Carrino (2012) have reported as an accepted parameter for determining herniation causality—it is important to realize that radiating clinical symptoms arising out of injury to an intervertebral disc are dependent on the anatomical positioning of the injured and inflamed disc material. It is only when the disc herniation is of a lateralized nature that the segmental nerve root is compressed or inflamed, producing radiation of axial symptoms to the corresponding upper or lower extremity.
To discuss radiation as a primary indicator of acute traumatic injury to the intervertebral disc omits central disc herniations, which alone do not typically produce extremity symptomology. When it comes to acute injury in the absence of radiating symptoms, local symptomatology should also be considered in approaching a mechanism and timing of the injury. Furthermore, one must also look at the morphology or architecture of the individual vertebrae as demonstrative evidence to age-date disc pathology inclusive of both herniations and traumatically induced directional, non-diffuse bulges as described by Fardon et al (2014).
Wolf’s Law, as described by Isaacson and Bloebaum (2010), is that “physical forces exerted on a bone alter bone architecture and is a well-established principle…” (p. 1271). This has been understood and accepted as a general principle since the late 1800s, and has been verified through the past century’s research inclusive of contemporary research. Simply put, if a bone has abnormal stresses, it will change morphology or shape within expected parameters. Since these changes are “expected,” the question becomes, “how does Wolf’s Law apply to traumatic external forces and acute disc injury, and how does this relate to causality?”
In order to fully understand the process, it is critical to understand the biochemical reaction (or functional adaptation) that occurs with abnormal stresses on bone…that centers on bioelectric changes that occur at the cellular level.
According to Issacson and Bloebaum (2010), when tissue is damaged, the injury potential creates steady local electric fields that result from ion flux—positive and negative charges moving through local cellar membranes—which is an integral part in the regeneration/remodeling of bony tissue. Bone remodeling is a tightly coupled functional system and is strongly influenced by age, activity level and mechanical loading. This functional adaptation of bone demonstrates the unique ability of bone to alter its trabecular (structural bone tissue) orientation as a result of loading conditions. According to Frost (1994), bone remodeling is a direct response to mechanical influences and strains on the osseous system. This can occur as a normal process to strengthen bone, or as a response to altered anatomy, biomechanics or direct traumatic injury. Since this is a predicable scenario, we can identify specific factors that will help us to determine whether the response was present over time or is at the beginning phase of remodeling. That is the fundamental basis for putting a causally related date to the injury.
5. Individuals suffer significant injury in crashes where there is low car damage. In such cases, it is common for MR imaging to detect significant disc pathology following these low-damage crash scenarios. A question for us then becomes: “How do low-damage crashes cause disc injury?”
Gathering a proper medical and crash-mechanism history is the initial step. In addition, forming a risk and causation analysis is essential in determining causality relative to bodily injury. This will also assist in determining the threshold some individuals hold for being injured with less trauma.
Additionally, human risk factors for injury—which are quite extrinsic to the crash metrics—can often be more important predictors of occupant injury than the crash metrics themselves. It is not uncommon for one person in a crash to be injured and another person in the same vehicle to walk away unscathed. Clearly, both were exposed to the same crash metrics in terms of the vehicle’s speed change, impact, etc. But those factors by themselves are not sufficient to predict occupant risk. What we question in order to reasonably assess risk in a crash is position in the vehicle, the use of restraints, the role of awareness, age, sex, physical strength, size, health, prior injuries, and other factors. Analyzing risk in all cases is imperative, as it can confirm why significant injury can occur with fewer traumas.
With respect to causation and its relationship to disc injury with minor damage car crashes, a crash-related injury causation analysis for a specific individual should also be performed by assessing the risk of injury from the collision and comparing it to the probability that the injuries or conditions would have been present at the same point in time if the collision had not occurred. This is called a relative or comparative risk analysis—also known as a “differential etiology” approach to causation—in which the most probable cause is selected among all competing causes. The analysis is accomplished via the application of crash reconstruction, biomechanical, medical, and epidemiologic (risk assessment) principles. The methodology for assessing causation of disc injury following low damage traffic crashes used here has been described in peer-reviewed literature, and has been deemed generally accepted by U.S. courts.
The three fundamental elements of an injury causation analysis are as follows:
1. Whether the injury mechanism had the potential to cause the injury in question;
2. The degree of temporal proximity between the injury mechanism and the onset of the symptoms reasonably indicating the presence of the injury; and
3. Whether there is a more likely alternative explanation for the occurrence of the symptoms at the same point in time.
Michael D. Freeman, Ph.D., MPH DC, a forensic epidemiologist, has documented that spinal disk injuries have been described in peer-reviewed literature as occurring at load levels similar to 3-4 mph rear impact collisions. (15,16) He goes on to state that studies of real-world (epidemiologic) crashes compared with medical findings indicate that at a 5-7 mph delta V (change in velocity); 35-47 percent of occupants will receive some degree of injury; 3.5-6.4 percent will develop long lasting (as in greater than 6 months) symptoms; and 2.5 -3.7 percent—or between 1 in 27 or 1 in 40— will demonstrate symptoms of a cervical spine disk derangement. (14)
An assumption is that insurance carriers simply don’t understand the concept of risk and causation, and will assume that an individual involved in a low-damage crash scenario simply can’t endure a spinal disc injury. The above-mentioned concepts confirm that this couldn’t be further from the truth.
We answer questions like the above every day and are available for your questions at any time. Our contact information can be accessed below.
Dr. Kenneth Bahoora has been a treating physician in Nevada for 18 years. He graduated from Life University in Atlanta, Geo., where he received his diploma as a doctor of chiropractic. He has received specialized knowledge with post graduate education in accident reconstruction, spinal biomechanical engineering, spinal MRI interpretation, MRI physics, providing impairment ratings utilizing AMA Guides 5th & 6th Edition, examining, and triaging the trauma patient, and neurodiagnostic interpretation protocols. He lectures to doctors and the legal community on subjects including but not limited to trauma and injury protocols and crash dynamics and the trauma victim. He can be reached for further explanation at email@example.com or 702.204.4240.
Patrick Sundby has decades of experience in the automotive industry including several years in law enforcement collision investigation. He has also been a driver training and firearms instructor in law enforcement, and a police officer for 9 years before specializing in accident investigations. He has had the privilege of participating in both learning and teaching at Prince William County Criminal Justice Training Academy in Virginia and studied at the Federal Law Enforcement Training Center in Georgia. His specialty is low-speed and catastrophic crashes and has testified over 500 times at various levels. He can be reached at 571.265.8076 or firstname.lastname@example.org
Dr. Mark Studin teaches at the doctoral level as an adjunct assistant professor of Chiropractic at the University of Bridgeport, College of Chiropractic, and an adjunct assistant professor of Clinical Sciences at Texas Chiropractic College. He also teaches at the graduate medical level as a clinical presenter credentialed by the Accreditation Council for Continuing Medical Education in Joint Sponsorship with the State University of New York at Buffalo, School of Medicine and Biomedical Sciences, along with being credentialed nationally for chiropractic post-doctoral education in a broad range of clinical subjects.
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17. Reliability is a metric based on epidemiologic study, from which the true and false positive rate of a test is derived.
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