One of the leading researchers on the study of whiplash pain is Dr. Nikolai Bogduk of the University of Newcastle, Australia. At his keynote speech at the World Congress on Whiplash-Associated Disorders, he had this to say about the current state of affairs:

"The typical and most common symptoms of whiplash injury are: neck pain, headache, dizziness, visual disturbance, impaired concentration, and sensory disturbances of the upper limb. The cause of these symptoms cannot be determined by conventional history and physical examination, or by conventional medical imaging. However, and most critically, their cause cannot be argued by fantasy and imagination. Failure to find a cause by conventional means is not a pretext for stating that there is nothing wrong with the patient. [Emphasis added.] Such negative proclamations ignore the lack of reliability and lack of validity of conventional medical practices. Just as no one can make a diagnosis from history and examination, no one can refute a diagnosis by the same means. Such negative and pejorative opinions as have traditionally been cast on patients with whiplash disorders reflect the biases, prejudices and lack of knowledge of the so-called experts. Negative views arise when experts do not know what could be wrong and do not know how, or bother, to investigate the patient properly. It is more convenient to proclaim that there is nothing wrong."1

"Modern biomechanics research has provided detailed models of what can happen in a whiplash injury. Japanese studies of normal volunteers have demonstrated how the anterior elements of the neck can be torn and how posterior elements can be crushed. Post-mortem studies have shown the spectrum of lesions that might, and can, befall a patient. These include contusions and fractures of the zygapophysial joints, and tears of the cervical discs—the very lesions predicted from the Japanese studies."1

Over the last year, a great deal has been written about the role of facet joints and whiplash injury. Indeed, it is becoming one of the leading areas of research on whiplash. Bogduk's own research, and a paper presented by Harrison,2 show that approximately 50% of whiplash pain is due to the facet joints. Some additional material was published on cervical mechanics during the World Congress on Whiplash-Associated Disorders that further demonstrates how facet joints may be injured in rear-end collisions.

The S-Shaped Curve

A growing body of literature indicates that the motion of the spine during a whiplash accident is very different from the normal motion of the spine. Extension, or backward rotation of the head, is normally achieved by each vertebrae in the spine contributing a roughly equal amount of motion.

New research by Kaneoka et al,3,4 builds upon their earlier research, and again, they find that at approximately 100 milliseconds into the collision, the cervical spine undergoes an S-shaped curve, where the upper spine experiences flexion and the lower cervical spine undergoes extension. This S-shaped curve is caused by the simultaneous compression of the spine when the occupant's body moves up the seat back, and the forward motion of the torso when the car seat pushes into the occupant.

This motion was determined by high-speed x-ray video of the whiplash motion in a test subject at approximately 5-mph. Unfortunately, while this experimental setup permits an overview of what happens to the spine during a collision, more detailed information about individual vertebral segments is more difficult to observe.

Yoganandan et al5 undertook this challenge by analyzing the whiplash motion in a human cadaver specimen of the head and neck. The head/neck complex was carefully prepared with reflective targets, and then subjected to whiplash-type impacts on a specially built sled. The specimen was filmed at high speed and at high resolution, and careful measurements were taken of the motion of the individual vertebrae.

Yoganandan et al confirmed what the other researchers have found—that there is indeed an S-shaped curve that occurs at approximately 100 milliseconds into the collision. Futhermore, Yoganandan et al were able to show the detailed motion between the 5th and 6th cervical vertebrae. They write, "...the lower cervical spine facet joint kinematics demonstrate varying local compression and sliding. While both the anterior- and posterior-most regions of the facet joint slide, the posterior-most region of the joint compresses more than the anterior-most region. These varying kinematics at the two ends of the facet joint result in a pinching mechanism."5

"The two most common [whiplash] complaints are headache and neck pain. It is widely known that these complaints are soft tissue related. These patients do not demonstrate radiographic damage, and computed tomography and magnetic resonance images are also normal considering the age of the patient. This lack of abnormal anatomic correlation has eluded clinicians from making a fully objective diagnosis of relating the structural components to the specific pattern of WAD. The transient reverse curvature kinematics observed may offer an explanation to the presence of these headaches. The temporal local flexion of the occipito-atlanto-axial complex distracts the posterior structures with a concomitant compression of the anterior structures of the upper cervical spine. This local distraction may overstretch the dorsal region with includes the upper cervical musculature and ligament complexes. The stretching of these innervated soft tissue structures may induce pain to connective regions...The pinching action [seen in the lower cervical spine] as demonstrated by the sliding motion and compressive action of the joint represented by the accentuated motions in the posterior-most regions (compared to the anterior region), may compromise the integrity of the synovium, thus eliciting neck pain."

    1. Bogduk N. There can be a lesion; you just have to look. Verbal presentation and abstract, Keynote speech, 2/9/99, World Congress on Whiplash-Associated Disorders 1999;100-101.
    2. Harrison P. The prevalence of zygapophysial joint disease as a cause of chronic neck pain/headache. World Congress on Whiplash-Associated Disorders 1999;120.
    3. Kaneoka K, Ono K, Inami S, Hayashi K. Motion analysis of cervical vertebrae during simulated whiplash loading. Compendium of papers presented at the Traffic Safety and Auto Engineering Stream, World Congress on Whiplash-Associated Disorders 1999;151-160.
    4. Watanabe Y, Ichikawa H, Kayama O, Ono K, et al. Influence of seat characteristics on occupant motion in low speed rear impacts. Compendium of papers presented at the Traffic Safety and Auto Engineering Stream, World Congress on Whiplash-Associated Disorders 1999;297-324.
    5. Yoganandan N, Pintar FA, Cusick JF. Biomechanical analyses of whiplash injuries using experimental model. Compendium of papers presented at the Traffic Safety and Auto Engineering Stream, World Congress on Whiplash-Associated Disorders 1999;325-343.