Whiplash is a slang term for an injury to the neck that’s typically associated with a motor vehicle collision (MVC). A better term for “whiplash” is “whiplash associated disorder” (WAD) as it includes specific history and exam findings. There are usually two phases to an MVC: 1) an acceleration phase that is followed by 2) a deceleration phase. Injury can arise during either phase depending on the following: 1) The direction or angle of the collision (head-on, rear-end, T-bone, etc.); 2) The size of the bullet vs. target vehicle; 3) The speed the vehicles are traveling; 4) The size of the injured person’s neck (short/stocky vs. long/thin), 5) Head rotation at impact; 6) Position of the headrest (ideally ≤1 inch from the back of the head and raised up to bottom of the ears); 7) The angle and “springiness” of the seatback; 8) Seat belt use and position; 9) Collision anticipation, 10) Condition of the road (dry vs. wet/slippery), and more!
Anatomically, injury can occur to muscles and/or their tendon attachments, the ligaments that firmly hold bone to bone, the fascia (or the covering of the muscles), the bones, the joints, the skin, the nerves, and/or blood vessels. It all boils down to the ten or more factors listed above, and as discussed in last month’s topic on PTSD, depending on whether concussion occurs and how well the injured person reacts or copes with the injury (the psychosocial part). Obviously, A LOT of factors drive the outcome of a whiplash injury!
One of the more vulnerable parts of the neck that is frequently injured are the small facet joints and/or their coverings (called joint capsules). This is referred to as a WAD II injury. Picture a vertebrae as a bony tripod with one leg being big and wide representing the vertebral body and shock absorbing disk. This large leg is the main weight-bearing part of the tripod supporting up to 80% of the weight. The other two legs represent the facet joints that lie in the back of the vertebrae that open and close as we look down (opens) and look up (closes). When we turn our head, the movement primarily occurs in the first two vertebrae high up in the neck. Injury here most commonly occurs when the head twists or rotates, which can result from either the angle the chest portion of the seat belt lays against and/or if the head is rotated upon impact, such as looking in the rear view mirror. In other words, it’s probable that head rotation occurs in MOST motor vehicle collisions due to the seat belt’s angled position as it crosses the chest. When this twisting / rotation movement of the head occurs suddenly, it can result in brain injury or concussion, as studies show that delicate axons and nerve fibers can literally twist and tear due to this rotational component of the injury. Also, it’s WELL ESTABLISHED that the head DOES NOT have to hit anything to cause a concussion injury, as simply the force of the brain hitting the inside walls of the skull is enough to do this!
Another slightly less common WAD injury involves the pinching of the nerve root as it exits the spine (referred to as a WAD III injury). Think of the nerves as wires between a switch and a light, each having a specific area that they “run” (innervate). For example, if tingling/numbness occurs in the thumb and index finger, it can mean the C6 nerve could be interfered with at some point in between the spine and the fingers. We also test specific muscles for weakness associated with each individual nerve to identify the main culprit! When a nerve gets pinched, sensory and/or motor deficits can occur, which is validated by the neurological examination. The disk is basically like a “jelly donut” where the jelly is located in the central part of the disk and held in place by a tough fibroelastic tissue (called the annulus fibrosis). When this “jelly-like” substance (called nucleus pulposis) breaks through the tough, outer “annulus” and pushes against the nerve, loss of sensation and/or specific muscle weakness can occur. As chiropractors, we will carefully examine you and render many highly effective treatment methods!