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In our spring 1995 issue of the Leading Edge, we investigated "The Enigma of Whiplash". Since the writing of that article, more recent publications have explored this area further, although the enigma remains.

Human Head and Neck Kinematics After Low Velocity Rear-end Impacts - Understanding "Whiplash", McConnell et al, SAE 952724, is an engineering study utilizing instrumented volunteers. In these tests, seven subjects were exposed to staged rear impacts up to a speed change magnitude of 10.9 kph. Although symptoms of injuries (neck pain) were reported for up to 3 days after the test, none of the test subjects reported lasting injury. The test analysis, using high speed film, unveiled a number of interesting findings:

The upper torso does not ramp up the seatback but remains essentially level, while the seatback/headrest move slightly lower due to rearward deflection; the early head motion was mostly rotational, with the proposed analogy of a "ball and chain" used to describe the resulting motion. Subjects reported symptoms of injury even though their rearward head rotations were less than their voluntary limits; seatbelt restraint use did not significantly influence occupant kinematics. Based on the tests, they proposed the following conclusions; a "convenient" threshold for single event injury ("transient acute neck and shoulder muscle strain injury and possible mild compressive irritation of the posterior neck") as 8 kph speed change. (approximately 6 kph barrier speed). The injury mechanism is due to the "ball and chain" effect on the rotated head, and headrest support is not necessarily relevant at these magnitude levels; low back injury is quite unlikely.

A second paper, Scientific Monograph of the Quebec Task Force on Whiplash - Associated Disorders: Redefining Whiplash and its Management, Spitzer et al, Spine, Vol. 20, 1995, was a statistical study conducted in the Province of Quebec. This was a medical based study, dealing with people submitting claims for whiplash injuries after a collision (4757 individuals), and it did not specifically differentiate between injury and impact origin or magnitude. This limits the applications of the test data to specific cases. Approximately 40% were rear-ended; 18% lateral; 12% frontal, and 30% undefined impacts. The results indicated regional variations in whiplash claims; 20% of insurance injury claims are whiplash in Quebec, compared with 68% and 85% for Saskatchewan and British Columbia. In Quebec, injury rates per 100,000 people are 86 (female) and 54 (male) compared to 13 for New Zealand, 106 for Victoria (Australia), and 700 for Saskatchewan. Of the Quebec claims, 25% are absent from work one week or less; 48% less than a month, 62% less than 2 months, 87% less than 6 months, and 98% less than 1 year. The average cost per claim is $3,200 with 15.5% of the claim costs for people absent 2 months or less, 38.5% of claim costs for people absent 2-6 months, 32.3% of claim costs for people absent 6-12 months, and 13.7% of claim costs for people absent 12 months. The study found that most therapeutic interventions are unproven, and recommended the following as effective: assure patients that any injuries are almost always self limiting, involve only temporary discomfort, and rarely result in permanent harm; interventions that promote activity; early return to normal activities no soft collars, prescription drugs used sparingly, physiotherapy should emphasize early return to usual activities. The study concluded with a guideline for patient care, and for minor injury complaints, recommended return to usual activities and minimal intervention. If unresolved after 6 weeks, a multidisciplinary team evaluation is recommended.

The last study is the most interesting, Natural Evolution of Late Whiplash Syndrome Outside the Medicolegal Context, Schrader et al, the Lancet, May 4, 1996. This will likely be the most widely referenced study for years to come, and involved a statistical analysis of whiplash for the country of Lithuania, where whiplash is mostly unheard of in the medical and legal communities. The findings were dramatic; of 202 people involved in rear-end collisions with significant front vehicle damage (defined as having the police called to the scene), none reported disabling or persistent symptoms as a result of the car accident. There was no relationship between impact severity and degree of pain, and the family history of neck pain was the most important risk factor for current neck symptoms.

In 11% of the accidents, the rear impacted car was undrivable; 44% had moderate damage, and 45% minor damage such as a bumper dent. 41% of the vehicles had no headrest and in 37% the headrest was too low to be effective. When interviewed from 1 to 3 years after the accident, neck pain was reported by 35% of the accident victims (33% for the control group who had not been in any accidents), with 8.4% having chronic pain (6.9% for control). Headaches were reported by 54% of accident victims (49.5% of control), chronic low back reported by 12% of accident victims (15% of control). The results indicated that complaints of headache, neck and back aches were similar for the accident victims and the non accident control groups, and of the same order as those reported in the general population of other countries.

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