Neck Ligaments Are Weakened After Auto Collisions

This study is important, because it shows that the ligaments of the cervical spine are weakened after even a “minor” auto collision. This weakening of the integrity of the cervical spine can result in abnormal motion of the spine, pain, and premature degeneration of the vertebral joints – more commonly known as osteoarthritis.

After years of study, it is clear that the spinal ligaments can be stretched or torn during an auto collision. Previous studies have shown that the anterior longitudinal ligaments, the transverse ligaments, and the facet capsules can be damaged, even in “minor” crashes.

The scientific consensus is this: during an auto collision, the individual vertebrae of the spine move so rapidly and so extremely, the ligaments that hold the spine together are sprained.

A new study from Yale University has taken an important new step in understanding the exact nature of these injuries. First, the researchers started with six cadaver spines that they had previously exposed to simulated rear end collisions. They took these spines apart and tested the failure point of each of the individual ligaments. They then compared the failure rate of the whiplash spinal ligaments to previously collected data on normal, non-injured spines.

The authors studied four different characteristics of the ligaments: failure force, elongation, energy absorbed, and stiffness. The data from the whiplash-exposed ligaments was then compared to the control ligaments.

The authors found that the whiplash ligaments were significantly weaker than the control specimens:

“The present study determined the dynamic failure properties of whiplash-exposed human cervical spine ligaments and compared the results with previously reported control data. Significant decreases in ligament strength were observed following whiplash, supporting the ligament-injury hypothesis of whiplash syndrome. Clinical studies, which have documented pain relief in whiplash patients following nerve block and radiofrequency ablation of facet joint afferents provide support for the present results which indicate whiplash loading causes decreased ligament strength.”

The study provides a suggested sequence of events that may occur after injury to the ligaments that can cause chronic pain and disability after a collision:

1. The violent stretching of the ligaments causes subfailure injuries to the ligaments and nerve receptors in the ligaments.
2. This weakening of the ligaments may lead to altered joint motion and loading patterns, compressing the joint tissues.
3. This compression can result in inflammation, pain, and accelerated degeneration of the joint tissue, resulting in osteoarthritis of the neck.

This study is the first to show that the individual ligaments of the spine are weakened after a whiplash-type motion. Clinically, it is important to carefully measure range of motion and to use flexion/extension radiographs in these patients to help pinpoint those areas of the spine that have been injured.

Tominaga Y, Ndu AB, Coe MP, et al. Neck ligament strength is decreased following whiplash trauma. BMC Musculoskeletal Disorders 2006;7:103.

Who's at Risk of Developing Chronic 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 studies (4) 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 Papeet 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 Sterling (3) and Berglund (4) 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. Berglund(4) 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.