Risk Factors of Whiplash

Auto injuries are a common problem seen in clinical practice. Most of the time, a patient will have some temporary discomfort that will resolve within a few weeks. A significant percentage of patients – around 20 to 30% – will develop some kind of chronic pain or disability from their injury. Four recent studies have looked at the issue of chronic pain to see if there are any predictive factors that can help us determine who is at risk of developing long-term problems.

The following is a list of documented risk factors found in these studies:

Gender. One of the four studies4 found that women were more likely than men to be injured in general, which confirms previous studies. Researchers speculate that the lower muscle mass in female necks may increase the risk of injury.

Turned head. Two recent studies have been done on this issue, and they both have found that when the occupant’s head is turned at the moment of impact, the spine is exposed to motion that exceeds the normal physiological range. This can result in ligament tears or damage to the spinal nerve roots.2

Direction of impact. It has been known for years that a rear-end collision is more likely to result in injury than is a frontal collision. Pape et al.1 found in their study that rear-end collisions were a greater risk factor than frontal impacts.

Previous injuries. It’s not surprising that a pre-existing injury to the neck or shoulder could be worsened after an auto collision, and that’s what Pape et al.1 found. In fact, patients with a history of neck and/or shoulder pain were more than twice as likely to have chronic problems three years after the collision.

Muscular tension immediately after the crash. Pape et al.1 found that patients with increased muscular tension soon after the crash were 3.43 times as likely to develop long-term symptoms.

Reduced range of motion. Sterling et al.3 found, as have other studies, that reduced ROM predicts symptoms two to three years after the injury.

Immediate pain and/or numbness. Both Sterling3 and Berglund4 found that patients who reported symptoms immediately after the crash were more likely to develop chronic pain. Immediate numbness indicates that the patient suffered some kind of nerve injury in the collision, and unless these types of injuries are diagnosed and treated quickly, they could easily develop into chronic pain. Berglund4 found that these patients were 6.5 times as likely to develop long-term problems.

The issues of reduced ROM and increased muscular tension are related, and understanding this issue is critical in treating auto injury patients. Upon injury to the disk or ligaments of the spine, an immediate reflex reaction is instigated – causing surrounding muscles to contract. This muscular guarding can be palpated as tension or inflammation. The increased muscular activity has the result of restricting ROM. How do these symptoms predict chronic pain? If the underlying tissue damage – ligament or disk – does not heal properly, long-term pain and restricted motion can result.

These studies help us treat auto injury cases in two ways: first, they demonstrate the need to take a careful and thorough history of the collision. For instance, asking the patient if his or her head was turned at the moment of impact can help us diagnose the injury. Second, by being aware of risk factors, we can focus our attention on those patients more likely to suffer long-term consequences of their injury.

  1. Pape E, Brox JI, Hagen KB, et al. Prognostic factors for chronic neck pain in persons with minor or moderate injuries in traffic accidents. Accident Analysis and Prevention 2007 Jan;39(1):135-46.
  2. Panjabi MM, Ivancic PC, Maak TG, et al. Multiplanar cervical spine injury due to head-turned rear impact. Spine 2006;31(4):420-429.
  3. Sterling M, Jull G, Kenardy J. Physical and psychological factors maintain long-term predictive capacity post-whiplash injury. Pain 2006;122:102-108.
  4. Berglund A, Bodin L, Jensen I, et al. The influence of prognostic factors on neck pain intensity, disability, anxiety and depression over a 2-year period in subjects with acute whiplash injury. Pain 2006;125(3):244-56.
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