Low Speed Car Accidents May Cause Serious Injuries

An adjuster recently told us that Allstate would pay only $1,500 total settlement for personal injuries resulting from a car accident if there is little or no property damage. The adjuster said, in effect, “Yes, I believe your client was hurt, but I don’t think a jury will believe it.” That is, He is confident a jury will believe that someone could not have been hurt in an accident yielding little or no damage to the cars.

But this assumption is simply not true. Unfortunately, all the physics and biomechanics involved in analyzing the effects of a low speed car crash on the body of a person in the car is complex – so complex, that it takes an expert to explain it to a jury, an expert your patient cannot afford.

As, a treating doctor, you can observe and document the effects low speed collisions have on your patient’s body in a way which gives a jury the information it needs to avoid assumptions and make the right decision. This article gives an overview from a recent Book on this subject.

In the book, Low Speed Automobile Accidents: Accident Reconstruction and Occupant Kinematics, Dynamics and Biomechanics,1 authors Watts, Atkinson and Hennessy point out that, “blanket statements about injury causation are simply not tenable for low speed accidents.” They then go on to discuss “whiplash”, head impact, rib/chest problems, leg fracture, pelvic damage due to side impacts and the possibilities for induced carpal tunnel problems (CTS) and temporomandibular joint problems (TMJ).

The most common challenge is the low-speed, rear-end collision where insurance companies inevitably question the extent of the patient’s pain and treatment.

The basic physics of the “whiplash” injury is that the head’s mass on the flexible stem of the neck moves at a different speed and in a different manner after a sudden impact than the shoulders and torso, which are ensconced in the car seat. The neck and all the muscles, ligaments and discs in the spinal column running through it, must absorb all these differences.

The terms “acceleration/deceleration” or “flexion/ extension” better describe the motion commonly called “whiplash.” The body is accelerated forward faster than the vehicle is moved only by the neck, resulting in the head flopping backwards like that of a rag doll. Even in a very low-speed (2+ mph) impact, there is not time for a person to respond and innervate the neck muscles to resist the rearward extension, which then rapidly exceeds the normal extension of 60 degrees, simultaneously over-stretching ligaments and muscles and placing a “load” on the six cervical discs.

If the muscles are lax, stretching injuries and damage to the ligaments will occur first. If the muscles are taut, they may be injured instead of or in addition to the ligaments. Extreme stretching of muscles and ligaments makes the discs vulnerable to tensile and/or shear damage. High loadings also can cause the bones to ride over each other (subluxation) or become dislocated.

Damage to the spinal nervous system can result: 1) from transient impingement by relative motions of the ligaments, muscles, bones and discs; or 2) by disc herniations; or 3) due to localized induced tissue inflammations. Damage may occur at lower load levels if there are vertebral bone spurs which can impinge on the disc or nerve during violent movements.

A well-positioned headrest may stop the backward rotation of the head and help prevent over-extension injuries. Unfortunately, about 91% of modern cars have headrest designs that are marginal, poor or bad, according to a 1995 report by the Insurance Institute on Highway Safety.

One of the most important revelations of Low Speed … was the unexpectedly large vertical accelerations and decelerations along the necks of rear-ended occupants (in addition to the normally expected longitudinal ones) in very low speed (1.9 to 5.0 mph) tests. This was the result of a “wedge” or “ramping ” effect of the seat angle causing an initial upward thrust on the body making the head rise higher against the headrest, then rotate down onto the headrest, pushing it from its raised position into the seat.

Another effect is the rapid straightening of the occupants’ spines, also contributing to early upward neck thrust. The result is a lower threshold for cervical strain injuries than earlier (11 mph) studies would have indicated. Such strong vertical thrusts can be expected in most very low-speed collisions since braking vehicles impact with a nose-down attitude.

In any low-speed accident, the following factors also affect the type and extent of injuries: angle of crash; whether the head was turned; the seat-back angle, design, elasticity and resultant “bounce” pre-existing neck damage (such as prior disc degeneration and/or ligament scarring); hack and spine motion; strength and tautness (pre-tensing) of neck muscles; and even the length of the neck (women, who tend to have longer necks, are more vulnerable).

Ligamentous damage can occur at “torso push speeds” above 7.5 mph where the headrest is absent or not properly set, the muscles are lax (not expecting the hit) and the head is turned side-ways. Muscle pains and/or spasms that can last up to several months can be expected from impact “push speeds” in the 5 mph range.

Your treatment records are vital evidence in these claims. Insurance attorneys attempting to defeat low-speed/low-impact claims will count on a medical history that is erroneous or mistaken. Your options are: 1) take a detailed, very accurate history; or 2) make only a very general statement (“this patient was rear-ended”), so the insurance lawyer can find no reason to say the doctor was misled or based his/her opinion on incorrect facts. For example, there’s no need to include your patient’s estimate of the speed of the other car.

Also, it is important to document objective observed evidence of injuries, such as muscle spasms and hypertonicity, evidences you can detect by palpation but which may not be verifiable any other way. These provide an important basis for your testimony or that of a subsequent treating doctor who is relying on your records.

If we don’t want low-ball offers to add insult and financial hardship to the injury and pain or clients/patients have already suffered, we need to educate ourselves and juries so as to put to rest the “bent-metal” myth.

1 Lawyers & Judges Publishing Company, Inc. 1996

This article was prepared by Dennis H. Black.