Low Speed Crashes Can Cause Serious Injuries – Debunking the MIST Defence

Anyone who has been injured in a low speed collision can expect the insurance company to raise the so-called MIST defence.

MIST stands for Minor Impact Soft Tissue defence. The argument is that the forces involved in low speed colisions are so insignificant that it isn’t possible for drivers or passengers to be injured. The strategy is sometimes called the No Crash – No Cash defence. This myth is based on faulty science and propaganda propounded by the insurance industry.

Fortunately, our understanding of the biomechanics surrounding aceleration – deceleration injuries (commonly called whiplash) has grown significantly since the first detailed analysis of the mechanics of the spine were done.

Countless studies and research have established that the violent and abnormal movements of the neck during a rear end collision can cause significant damage to the joints of the spine.

For example one recent study examined the effect of “whiplash” on the anterior ligament (ALL) of the spine. The anterior longitudinal ligament runs along the front of the human neck, it provides stability to the vertebrae of the spine. In a rear-end collision, this ligament can become sprained resulting in pain and in some cases chronic degeneration of the spine.

In the research study, an anatomical model of the human spine was subjected to three different collision speeds: 8.4 km/hr, 10.7 km/hr and 12.8 km / hr. The displacement or movement at each vertebral segment was then calculated and analyzed.

The researchers found that as the speed of impact increases, the extent of the strain placed on the ligament increased. This is not surprising.  But the interesting finding was that the maximum strain or displacement happened early in the aceleration – deceleration (whiplash) movement.

The authors report some observations that are relevant to those working in whiplash cases:

• The anterior longitudinal ligament was stretched close to the failure rate of the ligament, at collision speeds of just 12 kilometers per hour (which is roughly the speed of a fast walk).

• Injuries that do not result in failure of the lugament can be difficult to diagnose because they are almost invisible on X-rays.

• The anterior ligament of the spine have pain receptors. Sprains or tears of the anterior longitudinal ligament can cause pain that may affect other areas the spine.

The authors summarized some of the potentially serious, chronic problems that can result from ligament injuries in the neck:

“A possible clinical implication associated with ALL injury is cervical instability. Catastrophic injury of the ALL can result in acute disability while sub-catastrophic injury may lead to chronic pathology. Injuries to the ALL had the highest correlation to extension instability. However, that study also indicated high correlation of ALL injury to axial rotation instability and anterior column injury to lateral bending instability. Injuries produced experimentally in that study were similar to clinically observed injuries. Anterior cervical injuries sustained in whiplash are typically distractive extension stage 1 injuries resulting in an absence of neurologic abnormalities. These injuries are not visible using conventional radiography and result in cervical instability. The ALL is intimately connected to the annular fibers of the intervertebral disc. Presuming all sub-components of the intervertebral motion segment are normal prior to injury, subcatastrophic failure of the ALL (stretch) will likely result in chronic changes within the disc as a result of decreased extension stability. The added hypermobility may lead to spinal disorders such as early degeneration of the connected intervertebral disc or vertebrae. In addition, segmental hypermobility leads to long-term instability. Catastrophic failure of the ALL in a whiplash injury will almost inevitably result in simultaneous injury to the intervertebral disc, and is likely to require surgical intervention.”

This research proves that even in relatively low speed collisions, the anterior ligament of the spine can experience forces and injuries that can lead to long-term disability.

If you have been in a rear-end collision, it is important to get a thorough examination and diagnosis to determine your cervical instability and the potential for spinal degeneration in the future.

Stemper BD, Yoganandan N, Pintar FA, Rao RD. Anterior longitudinal ligament injuries in whiplash may lead to cervical instability. Medical Engineering & Physics 2006;28:515-524.