Bend Spinal Care
Occupational Therapy – Chiropractic – Massage Therapy
Factors that Influence the Extent of Injury
Headrests are the best protection in rear-end collisions. However if the headrest is set too low, the head is able to roll over the top of the headrest, producing even more hyperextension.
Experiments simulate relaxed necks of unexpected passengers in struck vehicles. Without a headrest, the neck extension can become almost 60 degrees, which is a potential danger limit of whiplash at collision speeds as low as two mph.
The exact position of the head at the moment of impact is important to know. If the head is turned, the injury will be greater on the side it is turned to. When head rotation is present, the pattern of tissue injury is potentially more severe.19
A surprise collision will usually cause more injury because the ligaments will be injured more than the muscles. When a person knows they are going to be struck, they will tense up the muscles and therefore injure the muscles first. MacNab states: “In impacts up to 15 mph the right front seat passenger stands in greater danger of injury than does the driver, because the driver can brace himself to some extent by holding onto the steering wheel.”
Common predisposing factors include degenerative joint disease and spinal stenosis. The potential for injury is increased because the neck is less resilient.
The seatback stiffness requires investigation. The harder/stiffer the seatback the less forward acceleration and therefore the less injury. The less stiff the seatback the more forward acceleration and therefore the risk of increased injury.
Jackson states: “The belt has very little if any deterring effect on the cervical spine as the head and neck continue forward motion. Even the addition of a shoulder harness will not relieve but will only increase the forces which must be absorbed by the head and neck, although such a harness may prevent contact injuries.”12 Seat belts save lives by preventing occupants from going through the windshield, but they contribute to the neck injury.
The Office of the Chief Scientist (London), Department of Health and Social Security, had this comment regarding seat belts in 1985: “We predicted an increase in the case of two injuries: sprains of the neck and fractures of the sternum. Both were confirmed. The other apparent increase in a major injury which was not predicted was abdominal injuries of organs other than the kidney and bladder.”
The car fender or bumper is designed to avoid or reduce damage in a low-speed collision. It is not a safety device to prevent or reduce injuries to people in the car. The government requires bumpers on passenger cars to prevent damage to the car body and parts, such as headlights, tail lights, grille, hood and trunk latches, at barrier impact speeds of up to 2 1/2 mph. This is equivalent to a five mph crash into a parked vehicle.
Chiropractic Physician Brad D. Welker, D.C.
Occupational Therapist Heather Larson, O.T.
Massage Therapist Patricia Alvarez, L.M.T.