Objectives—In Lithuania, there is little awareness of the notion that chronic symptoms may result from rear end collisions via the so-called whiplash injury. After most such collisions no contact with the health service is established. An opportunity therefore exists to study posttraumatic pain without the confounding factors present in western societies. Methods—In a prospective, controlled inception cohort study, 210 victims of a rear end collision were consecutively identified from the daily records of the Kaunas traffic police. Neck pain and headache were evaluated by mailed questionnaires shortly after the accident, after 2 months, and after 1 year. As controls, 210 sex and age matched subjects were randomly taken from the population register of the same geographical area and evaluated for the same symptoms immediately after their identification and after 1 year. Results—Initial pain was reported by 47% of accident victims; 10% had neck pain alone, 18% had neck pain together with headache, and 19% had headache alone. The median duration of the initial neck pain was 3 days and maximal duration 17 days. The median duration of headache was 4.5 hours and the maximum duration was 20 days. After 1 year, there were no significant diVerences between the accident victims and the control group concerning frequency and intensity of these symptoms. Conclusions—In a country were there is no preconceived notion of chronic pain arising from rear end collisions, and thus no fear of long term disability, and usually no involvement of the therapeutic community, insurance companies, or litigation, symptoms after an acute whiplash injury are self limiting, brief, and do not seem to evolve to the so-called late whiplash syndrome. (J Neurol Neurosurg Psychiatry 1999;66:279‐283)

https://jnnp.bmj.com/content/jnnp/66/3/279.full.pdf

Pain after whiplash: a prospective controlled inception cohort study.

A study was conducted to find out whether in a rear-impact motor vehicle accident, velocity changes in the impact vehicle of between 10 and 15 km/h can cause so-called “whiplash injuries”. An assessment of the actual injury mechanism of such whiplash injuries and comparison of vehicle rear-end collisions with amusement park bumper car collisions was also carried out. The study was based on experimental biochemical, kinematic, and clinical analysis with volunteers. In Europe between DM 10 and 20 billion each year is paid out by insurance companies alone for whiplash injuries, although various studies show that the biodynamic stresses arising in the case of slight to moderate vehicle damage may not be high enough to cause such injuries. Most of these experimental studies with cadavers, dummies, and some with volunteers were performed with velocity changes below 10 km/h. About 65% of the insurance claims, however, take place in cases with velocity changes of up to 15 km/h. Fourteen male volunteers (aged 28–47 years; average 33.2 years) and five female volunteers (aged 26–37 years; average 32.8 years) participated in 17 vehicle rear-end collisions and 3 bumper car collisions. All cars were fitted with normal European bumper systems. Before, 1 day after and 4–5 weeks after each vehicle crash test and in two of the three bumper car crash tests a clinical examination, a computerized motion analysis, and an MRI examination with Gd-DTPA of the cervical spine of the test persons were performed. During each crash test, in which the test persons were completely screened-off visually and acoustically, the muscle tension of various neck muscles was recorded by surface eletromyography (EMG). The kinematic responses of the test persons and the forces occurring were measured by accelerometers. The kinematic analyses were performed with movement markers and a screening frequency of 700 Hz. To record the acceleration effects of the target vehicle and the bullet vehicle, vehicle accident data recorders were installed in both. The contact phase of the vehicle structures and the kinematics of the test persons were also recorded using high-speed cameras. The results showed that the range of velocity change (vehicle collisions) was 8.7–14.2 km/h (average 11.4 km/h) and the range of mean acceleration of the target vehicle was 2.1–3.6 g (average 2.7 g). The range of velocity change (bumper car collisions) was 8.3–10.6 km/h (average 9.9 km/h) and the range of mean acceleration of the target bumper car was 1.8–2.6 g (average 2.2 g). No injury signs were found at the physical examinations, computerized motion analyses, or at the MRI examinations. Only one of the male volunteers suffered a reduction of rotation of the cervical spine to the left of 10° for 10 weeks. The kinematic analysis very clearly showed that the whiplash mechanism consists of translation/extension (high energy) of the cervical spine with consecutive flexion (low energy) of the cervical spine: hyperextension of the cervical spine during the vehicle crashes was not observed. All the tests showed that the EMG signal of the neck muscles starts before the head movement takes place. The stresses recorded in the vehicle collisions were in the same range as those recorded in the bumper car crashes. From the extent of the damage to the vehicles after a collision it is possible to determine the level of the velocity change. The study concluded that, the “limit of harmlessness” for stresses arising from rear-end impacts with regard to the velocity changes lies between 10 and 15 km/h. For everyday practice, photographs of the damage to cars involved in a rear-end impact are essential to determine this velocity change. The stress occurring in vehicle rear-end collisions can be compared to the stress in bumper car collisions.

Do "whiplash injuries" occur in low-speed rear impacts?

The validity of whiplash syndrome has been a source of debate in the medical literature for many years. Some authors have published articles suggesting that whiplash injuries are impossible at certain collision speeds; others have stated that the problem is psychological, or is feigned as a means to obtain secondary financial gain. These articles contradict the majority of the literature, which shows that whiplash injuries and their sequelae are a highly prevalent problem that affects a significant proportion of the population. The authors of the current literature critique reviewed the biomedical and engineering literature relating to whiplash syndrome, searching for articles that refuted the validity of whiplash injuries. Twenty articles containing nine distinct statements refuting the validity of whiplash syndrome were found that fit the inclusion criteria. The methodology described in these articles was evaluated critically to determine if the authors' observations regarding the validity of whiplash syndrome were scientifically sound. The authors of the current critique found that all of the articles contained significant methodologic flaws with regard to their respective authors' statements refuting the validity of whiplash syndrome. The most frequently found flaws were inadequate study size, nonrepresentative study sample, nonrepresentative crash conditions (for crash tests), and inappropriate study design. As a result of the current literature review, it was determined that there is no epidemiologic or scientific basis in the literature for the following statements: whiplash injuries do not lead to chronic pain, rear impact collisions that do not result in vehicle damage are unlikely to cause injury, and whiplash trauma is biomechanically comparable with common movements of daily living. Language: en

A review and methodologic critique of the literature refuting whiplash syndrome.

This study enhances the existing database of human subject test exposures with an emphasis on electromyographic activity before, during, and after low speed rear impact. Ten nominal 16 km/h closing speed car-to-car impacts were conducted using instrumented male and female subjects aged 22-54 years, with struck vehicle velocity changes of up to 10 km/h. Two head restraint conditions were studied. One condition was a standard seat integrated head restraint. For the second condition the integrated head restraint was modified by adding 2 padding inches to the existing head restraint. No injuries were sustained by any occupant. In all cases, the subjects exhibited pre-impact muscle activity commensurate with that of a relaxed seated posture. Initial muscle activity typically occurred during the initial impact phase as the occupant's cervical spine was extending. Full muscle tension likely did not develop until the cervical spine was flexing. Initial muscle activity was consistent with being triggered by lumbar spine acceleration, and occurred approximately 90-120 milliseconds after onset of lumbar spine acceleration. No significant differences were noted between muscle response times for the two head restraint conditions. Decreases in rearward head displacement, cervical spine extension, and head acceleration were found for the modified head restraint. For the covering abstract of the conference see IRRD 891635.

G T K Harper

Papers

Low speed rear-end collision testing using human subjects