Auto accidents can be described as either low-velocity (below 10 mph) or high-velocity (above 10 mph). In low-velocity accidents, the victim's body is thrown backward and forward in a rapid progression of acceleration and deceleration. Since it is unusual at this speed for victim to experience a second impact inside the vehicle (such as hitting the dashboard), the injuries usually result from the rapid movement of the body during the crash. Common low-velocity injuries include whiplash, muscle strain, seatbelt bruises, or traumatic brain injury (shaken baby syndrome). The onset of symptoms is often delayed with these injuries so that at the time of the accident the victim may not immediately realize an injury has occurred. Within 12 to 36 hours after the impact, however, the victim will begin to recognize pain and stiffness of the injured areas.

• In a series of recent human volunteer crash tests of low speed rear impact collisions, it was reported that the threshold for cervical spine soft tissue injury was 5 mph.
• Most injuries occur at speeds below 12 mph.
• The peak acceleration of the head is greater than the peak acceleration of the vehicle.
• A 5 mph delta V crash typically produces about 10-12 g of acceleration of the occupant's head.
• Other reports have shown that crashed cars can often withstand collision speeds of 10 mph or more without sustaining damage. Thus: the concept of "no crush, no cash" is simply not valid.
• Recent epidemiological studies have shown that most injury rear impact accidents occur at crash speeds of 6 mph to 12 mph--the majority at speeds below the threshold for property damage to the vehicle.
• A number of risk factors in rear impact accident injury have now been verified including: rear (vs. other vector) impact, loss of cervical lordotic curve, preexisting degenerative changes, the use of seat belts and shoulder harness, poor head restraint geometry, non-awareness of the impending collision, female gender, and head rotation at impact.
• Once thought to suggest minimal injury, a delay in onset of symptoms has been shown to be the norm, rather than the exception.
• Mild traumatic brain injury can result from whiplash trauma. Often the symptoms are referred as the post concussion syndrome. This condition, often maligned in the past, has now been well-validated in recent medical literature.
• A recent outcome study of whiplash patients reported in the European Spine Journal found that between one and two years post injury, 22% of patients' conditions deteriorated. This second wave of symptoms has been observed by others as well.
• Radanov et al. followed whiplash patients through time and reported that 45% remained symptomatic at 12 weeks, and 25% were symptomatic at 6 months. Other researchers have reported time to recovery in the most minor of cases at 8 weeks; time to stabilization in the more severe cases at 17 weeks; and time to plateau in the most severe categories as 20.5 weeks. Thus, the notion that whiplash injuries heal in 6-12 weeks is challenged. (Incidentally, there never has been any real support for this common myth.)
• Each year, 1.99 million Americans are injured in whiplash accidents.
• Of the 31 important whiplash outcome studies published since 1956 (19 published since 1990 pooling patients from all vectors of collision (I. e., rear, frontal, and side impacts), a mean of 40% still symptomatic is found. For rear impact only, a mean of 59% remain symptomatic at long-term follow-up.
• Although estimates vary, about 10% of all whiplash victims becomes disabled.
• The Quebec Task Force on Whiplash-Associated Disorders has been criticized on the basis of potential bias, study design, the use of ambiguous and misleading terminology, and for developing conclusions that are not supported by the literature.

Whiplash

Even though the car may have received little damage, occupants can suffer serious spinal injury. Injuries to the neck caused by the sudden movement of head, backward, forward, or sideways, is referred to as "whiplash."

Whiplash is most commonly received from riding in a car that is struck from behind or collides with another object. When the head is suddenly jerked back and forth beyond its normal limits, the muscles and ligaments supporting the spine and head can be overstretched or torn. The soft, pulpy discs between spinal bones can bulge, tear or rupture. Vertebrae can be forced out of their normal position, reducing range of motion. The spinal cord and nerve roots in the neck can get stretched and irritated. While the occupants can suffer considerable soft tissue injury, the car may be only slightly damaged.

The resulting instability of the spine and soft tissues can result in headaches, dizziness, blurred vision, pain in the shoulder, arms and hands, reduced ability to turn and bend, and low back problems. As the body attempts to adapt, symptoms may not appear for weeks or even months later.

After a thorough case history and examination, the doctor will recommend a series of visits to help restore proper motion and position of spinal bones. If caught early enough, inflammation can be reduced and scar tissue can often be minimized.