New study examines whiplash injuries

Nov 23 2004

If you happen to be looking left or right when your car is rear-ended, you could be lucky enough to avoid the headache of whiplash.

A new study at the University of Alberta shows that whiplash injuries in low-speed accidents are much less likely if the victim's head happens to be turned to either side instead of facing front when the vehicle is struck.

The research involving neck muscles is giving a solid scientific definition to whiplash that may help identify and establish soft tissue injuries--if any are actually suffered in the course of an accident.

Results from the study appear in the November, 2004 issue of Clinical Biomechanics. The findings, based on research begun at the university in 1999, will help clear up the murky definition of whiplash--injuries to the head and neck most commonly suffered in rear-end vehicle collisions, said Dr. Shrawan Kumar, a professor of physical therapy and neuroscience at the University of Alberta.

"Having a scientific framework for whiplash injects a great deal of objectivity into a subjective realm where there are a lot of legal claims and counter-claims. It clears up some of the mystery surrounding the condition," said Dr.Kumar, lead author on the paper.

Using 20 healthy volunteers and a special sled equipped with a rotating chair (complete with a seatbelt) and a pneumatic piston, the researchers measured the response of six different neck muscles to gradually increased low-velocity impacts from eight different directions. The muscle responses were measured using surface electrodes.

Each volunteer was fitted at the forehead and top of the back with accelerometers--devices which measured the effect of impact on the head-neck motion. The acceleration of the chair was also recorded.

The tests revealed that there was less risk of injury when the subjects had their heads turned either to the right or to the left at the time of low-velocity impact (up to 10 km/h). "The act of turning the head tenses the muscles, which prevents movement of the neck and decreases the chances of soft tissue injury," Dr. Kumar said.

Low-velocity whiplash is one of the most contentious injuries in the legal arena. The effects of low-speed, rear-end collisions have not previously been extensively researched, and that has left a gray area in diagnosing soft-tissue injuries, Dr. Kumar said. The muscles and ligaments of the neck--not the bones--are more at risk in low-speed accidents, he noted.

The findings will indirectly benefit people who claim questionable whiplash injuries, he added. "This should prevent a person, if rear-ended, from assuming a 'sick role', disabling oneself psychologically and socially, hoping to gain something."

The information gathered from the research can also be used in developing safety features to protect drivers even in low-velocity collisions.

This study is the latest in a series conducted on whiplash since 1999 by Dr. Kumar and his fellow researchers, Dr. Robert Ferrari and Yogesh Narayan.

In an earlier research project using similar test methods, Dr. Kumar and his colleagues determined that in a low-speed rear-end collision, it is the front ligatures of the neck, not the back ones, that are at greater risk of injury, and that the opposite is true for front-end collisions. This contradicts a common assumption that a rear-end collision will do the most damage to the back of the head and neck, Dr. Kumar said.

They also found that mere awareness of an impending impact reduces the head-neck acceleration by 40 per cent, mitigating the risk of injury.

"Based on scientific evidence, we can now show there is a certain degree of safety built into the human system which needs to be exceeded before injury can be precipitated."