Whiplash Injuries - Monach University Accident Research Center

Medical reports refer to whiplash as "railway spine". This term was used in the 19th century to describe the persistent pain and other "subjective symptoms" reported by railway passengers and personnel due to minor railway crashes. Similar injuries can result from all types of motor vehicle crashes, but the typical mechanism involves rear-end collisions. During a typical rear-end collision, the struck vehicle is subjected to a forceful forward acceleration. The occupant is pushed forward by the seat back and the head lags behind due to its inertia. The head is subjected to a swift rearward translational motion followed by an extension motion. At a later stage, the head and torso will be rebound forward and hit the seat belt, flexing the neck .

The literature suggests that the most common injuries due to whiplash involve the zygapophyseal joints, the intervertebral discs, and the upper cervical ligaments. Other injuries may occur for example nerve damage and muscle injuries. In this respect, headache and neck pain are the dominating symptoms followed by pain in the shoulder girdle. The third most common symptom is paresthesia and weakness in the upper limbs. It is time to implement the knowledge about what causes whiplash injuries. During the recent years, substantial knowledge has been gained and possible solutions to reduce the problem have been installed in some vehicles.

Some important facts to know about Whiplash Injuries:

• Whiplash injuries usually occur within 24 hours of the impact. The most common symptoms are a headache and neck pain followed by pain in the shoulder girdle. Thereafter come paraesthesia and weakness in the arms.
• Based on data provided by NSW Compulsory Third Party (CTP) insurers to the MAA’s Claims Register to the end of June 1998, whiplash is the single most frequently recorded crash injury. Whiplash was involved in 38.9% (49,344) of the total 126,923 CTP claims reported and accounted for 25% ($1466.3M) of the total incurred the cost.
• Many people with whiplash injury also report pain elsewhere due to the crash.
• About 10% of all whiplash injuries become long-term injuries in rear crashes and about 5% in frontal crashes.
• Frontal crash airbags in combination with pretensioners and load limiters are thought to be strong factors in reducing whiplash injuries in frontal crashes.
• In frontal crashes, it is well known that wearing a seat belt increases the risk of whiplash injuries. But it is hard to find clear-cut evidence that wearing a seat belt in low severity rear-end crashes increase the risk of neck injuries.
• In frontal crashes, the deceleration of the vehicle directly after the occupant’s seat belt contact seems to explain the risk of sustaining long-term whiplash injuries.
• To reduce the injuries to the neck and the rest of the spine in rear crashes the vehicle seat and head restraint must be seen as one unit.
• A seatback with controlled deformation energy absorption offers better protection for out of position occupants in rear-end crashes.
• Stiffer seatbacks tend to increase loadings on the cervical, thoracic and lumbar spine in rear-end crashes.
• For lower severity rear crashes factors like the head restraint and seat back geometry and cushion properties are more important; at higher severity, rear-end crashes the seat force-deflection characteristics are more important.
• A head restraint should prevent extreme hyperextension of the neck and minimize the relative motion between the head and torso. Head restraints alone are not enough to prevent all whiplash injuries.
• A towbar adds structure to the end of the vehicle. Statistics from Sweden shows that a vehicle with a towbar has around 20% higher long-term whiplash injury risk if it is hit in a rear-end crash.
• There are at least three different anti-whiplash seats on the market. There are two general principles that apply; one propels the head restraint forward to meet the head and thereby reduces the relative head torso movement; the second principle allows the occupant to move backward until both the head and the spine are supported from the seat closer in time. Thereafter if the forces are high, the seat reclines and thereby reduces the acceleration.
• There is much evidence suggesting that the zygapophyseal joints are damaged during a whiplash event.
• Violent pressure gradients in the spinal canal during the whiplash movement can occur and probably cause nerve damage.
• In rear crashes, a low NIC value most probably reduces the risk of muscle strain, upper neck lesion, zygapophyseal joint pinching as well as harmful pressure transients.
• A rear-impact dummy has been developed to measure the risk of whiplash injuries, in low-speed rear-end crashes. This dummy, the BioRID has been designed especially to study the relative motion of the head and torso. For tests representing crashes in which a vehicle is struck in the rear, BioRID can help researchers learn more about how seatbacks, head restraints, and other vehicle characteristics influence the likelihood of whiplash injury.
• To evaluate the whiplash injury risk in frontal crashes it seems possible to use both the NICprotraction value and the My flexion value and NIJ.