Low Speed Injury and Whiplash

Resource of Record for
Low Speed Injury
and
Whiplash

Michael D. Freeman
2480 Liberty Street, NW
Suite 180
Salem, OR 97303
503-763-3528
503-763-3530 fax

Dr. Michael D Freeman, SafetyForum's Resource of Record for Low Speed crash injuries and whiplash, is an internationally recognized and respected epidemiologist and authority on neck and other spinal injuries. A Clinical Assistant Professor at the Oregon Health Sciences University School of Medicine, Freeman has published numerous studies and papers on back and neck injuries. He is on the peer review boards for the respected medical journals Spine and The Lancet.

L O W S P E E D I N J U R Y
& W H I P L A S H

Whiplash: Low Speed Crashes
Can Inflict Long-Term Pain

After a third of a century of federal standards mandating the safety performance of everything from bumpers to dashboard controls, it might be reasonable to conclude that occupants are walking away from low-speed crashes without significant injury. The opposite is happening: a General Motors study found that many injuries are occurring in crashes at speeds below 8 miles per hour. Indeed, "whiplash" injuries, the soft tissue damage commonly suffered in these low-speed collisions, now account for more than half (53 percent) of all motor vehicle crash-related injuries.

Although these injuries are typically classified as minor (AIS 1, the least severe rating), 27 percent of the 2.9 million persons who sustain low-speed injuries each year still have neck pain three years later. The injuries often lead to permanent disability, and as one Swedish study concluded, "This could be the case even when the neck injuries are primarily assessed as minor." A New England Journal of Medicine editorial noted in 1994 that 20 to 40 percent of people with whiplash have symptoms that last for years, and some never recover.

Although rear end collisions account for only 5 percent of all automobile fatalities, whiplash is both most likely to occur in such collisions and, when it does, more likely to cause permanent damage: one study found that almost one in 10 whiplash victims in rear end collisions are permanently disabled, compared to fewer than 4 in 10 in non-rear end impacts.

The 'How' Debate

In whiplash, the cervical spine apparently suffers soft tissue damage when the head snaps backward at the same time as the shoulders rebound forward off the seat back during the collision, but the sequence of events is in dispute. Partly this is because the dynamics of low-speed collisions have not been studied as thoroughly as high-speed collisions. A complicating factor is that human head and neck actions are more complex than those of Hybrid III crash test dummies.

The traditional view - that whiplash occurs when crash forces first flex the neck and then hyperextend it backward - is "both incomplete and inaccurate," according to Biodynamics Research Corp., which reports that its low-speed tests "suggest a compression-tension injury causation mechanism." Still other researchers say "the opposite (of flexion-hyperextension) is true,…that flexion sometimes follows the initial extension of the cervical spine."

Several factors appear to affect
the severity of whiplash:

•	*Ramping.*When the occupant slides up the seatback during the collision, it adds to the whiplash motion.

•	*Gender, Age, Height.*Women (probably because their necks tend to be less muscular than men's) and older and taller people are more likely to sustain the injury.

•	*Turning.* An occupant whose head is turned to the side may suffer greater injury because the whiplash motion turns the head even more.

•	*Awareness.* Occupants who were aware of the impending crash suffered fewer neck injuries in one study.

•	*Small Cars.* Occupants of smaller cars are more likely to suffer whiplash than those in larger cars.

•	*Vehicle Stiffness.* "Stiff" vehicles that do not absorb sufficient crash forces in low-speed impacts may reduce vehicular damages, but they transmit more crash forces to occupants, increasing the risk of injuries, including whiplash.

•	*Seat and Head Restraint Design.* Seat and head restraint stiffness and height can aggravate whiplash injuries.

Whiplash: Faked or Real?

Auto insurers tend to blame increased whiplash injury claims on fraud. They say up to half of all fraudulent claims are for whiplash, noting that such claims are rising while vehicle damage claims are decreasing. The Insurance Institute for Highway Safety, while acknowledging that some neck sprains are real, says they are "easy to fake or exaggerate into fraudulent insurance claims" because they do not result from impact with the car's interior and they often cannot be detected by standard clinical or radiological exams.

In its 1994 editorial, however, the New England Journal of Medicine pointed to studies that show most people don't know the symptoms well enough to fake whiplash for profit. In addition:

•	A 1995 Australian study found compelling data that supports an organic basis for chronic whiplash pain.

•	The same study found no evidence that desire for monetary gain affected the prognosis for whiplash patients.

•	Canadian doctors who examined 28 whiplash patients found that the injury "bore a direct etiologic relationship to internal derangements…in [22 of the 25] patients who underwent arthographic investigation."

The Australian researchers said the only known way to confirm reliably a patient's whiplash injury claim is through anesthetic blocks of the affected joints.

Head Restraints: Solution or Problem?

Swedish researchers found that over five years, head restraints prevented neck injuries in about one-fourth of the rear-end collisions it reviewed, but concluded that the restraints did not affect the severity or outcome of the injury.

The head restraint requirement of the National Highway Traffic Safety Administration (NHTSA) has significantly lowered the incidence of crash-related neck injuries since it became law in 1969. The rule, however, allows both fixed and adjustable restraints, and although fixed restraints are more effective and less expensive to install, most U.S. cars have adjustable restraints because, automakers claim, consumers consider them more luxurious. Yet, adjustable restraints are often improperly positioned:

•	General Motors found 83 percent of adjustable head restraints could have been better positioned to protect occupants.

•	The Insurance Institute for Highway Safety found that 65 percent of adjustable restraints weren't positioned high enough or close enough to the back of occupants' heads. (The study also found the same problem in almost half of the cars equipped with fixed restraints.)

•	The Insurance Institute rated as "good" the head restraint systems of only five of 164 car models in 1995; 117 were rated "poor," half of them cars with fixed restraints.

As early as 1974, NHTSA recommended more closely integrating head restraint and seat back designs, but the recommendation has never been adopted. Australia, which started with the same standards as the U.S., upgraded its requirements to a minimum head restraint height of 28 inches, even for adjustable restraints in the down position.

'Catcher's Mitt' Seats

Delphi Automotive Systems, formerly a part of General Motors, has a unified seat and head restraint that it claims will reduce the risk of whiplash and other injuries by 40 percent. The redesigned seat, which will allow the head and body to move together in a rear impact, was initially introduced in 1998 on cars produced by GM's Swedish partner, Saab. The 2000 Buick LeSabre is the first domestic car to offer the "Catcher's Mitt" seat.

(06/13/00)