“Delta V”: A Poor Predictor of Spinal Trauma from Motor Vehicle Collisions
May 16, 2009
Whenever an individual claims an injury from a motor vehicle collision with low property damage on visual inspection, insurers routinely assert that the impact is too slight to the cervical spine to cause an injury. The auto insurance companies continue to promote ‘junk science’ testimony of high-gun forensic witnesses claiming that “low Delta V” (ΔV)1 cannot cause injuries. This proposition is not only false, but is often accepted by jurors because the testimony is cloaked under the color of “expert testimony.”
Fortunately, experienced attorneys representing those with traumatic injury are making headway with judges to exclude the testimony of witnesses who claim a lower Delta V means that no injury could have been sustained. Also, there continues to be an ever increasing amount of published research which dispels this Delta V myth. A recent study on this issue was published in the medical journal Patient Safety in Surgery 20092, authored by German trauma and orthopedic surgeons. The authors concluded:
This study provides evidence that, in real-life accidents, cervical spine injuries may occur at low ΔV values, while it is possible to escape unscathed from collisions with high ΔV values. In particular, the correlation between ΔV and the occurrence of WADs [whiplash-associated disorders] was very low for any of the collision types. Therefore it is impossible to make meaningful statements about the existence of WAD based solely on assessment of the [property damage] value. This finding might be of importance for the surgeon’s assessment and patient’s safety after a car accident. Diagnostic and therapeutic management should not be based solely on information related to trauma impact.
The study included data from 57 patients who had been the victims of car collisions. Within 48 hours of the collision, data was collected from the patient and from the patient’s car. Visual Analog Scales (VAS) and Neck Disability Index questionnaires were completed to determine the levels of pain and disability experienced by the subjects.
All of the patients who reported neck pain were evaluated with standard orthopaedic and neurologic clinic examination techniques and had radiological imaging done. If physical exam findings so suggested the need, CT scans were done. The severity of the cervical injures were classified in accordance with values set by the Quebec Task Force (QTF).3
Further, the ΔV for each collision was determined by a qualified engineer from direct assessment of the vehicles involved in the collisions, using accepted engineering analysis techniques.
Accepted statistical analysis formula were used to determine the correlation between the pain score (VAS) and the ΔV, the correlation between the NDI and the ΔV, and the correlation between the QTF classification and the ΔV. Careful study of the data obliged the authors to state:
. . . it can be concluded that ΔV is an irrelevant predictive value for cervical spine injury after an MVA . . . The ΔV value as measured in trauma impact does not represent a conclusive predictor for cervical spine injury in real-life motor vehicle accidents. This could be important for surgeons and patients in their medicolegal assessment of WADs.
1. “Delta V” (ΔV) refers to change of velocity, ie. speed. A car is impacted from behind and it velocity is instantaneously increased from its stopped position (or from its current speed) to a higher velocity.
2. “Deceleration during “real life” motor vehicle collisions – a sensitive predictor for the risk of sustaining a cervical injury?”, Martin Ebel, Michael Kramer, Markus Huber-Lang, Erich Hartwig, and Christoph Dehner.
3. The Québec Task Force (QTF) was a task force sponsored by the Société de l’assurance automobile du Québec, the public auto insurer in Quebec, Canada. The QTF submitted a report on whiplash-associated disorders in 1995, which made specific recommendations on prevention, diagnosis and treatment of WAD (whiplash associated disorders.)