From a doctor’s perspective and perhaps from an attorney’s, one of the most difficult aspects of dealing with a whiplash victim is appreciating the magnitude of the sustained injury. A whiplash or neck sprain/ strain injury often occurs from what seems to be a relatively minor impact.
Additionally, as whiplash is an injury where there are a minimum of totally objective tests with which to demonstrate its existence, the tendency to underestimate it is ever present. Understanding some of the research findings on this subject adds some clarity to this matter.
Rear end impacts or acceleration neck sprains are the most injurious of the whiplash type accidents. At impact, the body is at rest and tends to remain at rest while the automobile moves forward. The seat finally begins to accelerate the body forward but because the head is usually unsupported, it stays at rest causing the neck to hyper extend. At about the same time the head is maximally extended, the seat reaches maximum compression, recoils, and throws the individual forward causing greater acceleration of the body and arching of the neck.
Extension or backward arching of the neck is resisted only by the joint soft tissues of the neck. As these tissues stop extension they undergo variable degrees of internal tearing. The soft tissues eventually are able to resist further extension and cause a rebound phenomenon where the head is now thrown forward at a greater force than it was extended.
An angular acceleration or whipping of the head of 1800 radians/second 2 has a 50% probability of causing brain concussion even without striking the head. Acceleration of the head at this rate causes the brain to strike the inside of the skull bone significantly enough to create concussion injury. A rear-end impact that causes the struck vehicle to accelerate instantaneously only 10 mph will produce a 1800 radians/second movement of the head.2 This phenomenon depicts the magnitude of neck/head movement that can be generated by a relatively slow impact. This same impact has an equal chance of exceeding the elastic limits of the soft tissues of the neck, causing a sprain/strain injury.
A rear impact that causes a 10 mph acceleration produces a 5g force on the vehicle, a 12g force of extension of the head and a 16g force of flexion of the head during recoil.1 (One g equals the force of gravity.)
If the mechanics of an 8 to 10 mph impact are analyzed, it can be appreciated that the passengers may fare worse than the vehicle.
1 Bogduk N. The Anatomy And Pathophysiology Of Whiplash. Clinical Biomechanics. 1986;1:99-100.
2 White A, Panjabi M. CLINICAL BIOMECHANICS OF THE SPINE. J.B. Lippincott Co., Philadelphia, 1978.
Deans GT, McGalliard JN, Rutherford WH. INCIDENCE AND DURATION OF NECK PAIN AMONG PATIENTS INJURED IN CAR ACCIDENTS. British Medical Journal. 1986;292:94-95.