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Abstract
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Whiplash is a colorful term which has been forced upon us by its frequent usage. In spite of efforts by physicians to relegate this bit of slang to its proper place, usage of the term is more common than ever, particularly by lawyers and layman. In actual usage, the term whiplash is used to mean an acute cervical strain or sprain and will be used in this was in this paper. Although the term lacks precision and evokes emotional overtones, it is commonly and widely used and allows effective communication with the non-medical public. Ian McNab in 1965 defined whiplash as "essentially an extension strain of the cervical spine produced by sudden acceleration." He suggested an alternate term, "acceleration extension injury."
The prolonged symptoms and disability which follow neck injury caused by minor automobile collisions are an enigma which perplexes many physicians. Such injuries are nearly always caused by minor accidents with very little vehicle damage. The patients history may reveal that his symptoms were delayed in onset but continue interminably. Most perplexing and frustrating is the lack of physical, radiologic or other objective evidence of injury and the prolonged treatment and observation period which may last a year or more.
Neck injuries are most commonly caused by rear-end impacts which hyper-extend the cervical spine beyond its physiological limits. Animal necropsy studies of McNab, Wickstrom, Ommaya and human volunteer studies of Matthewson and Patrick have revealed that injuries occur which do not produce objective clinical findings. Accident studies reveal that head-on, lateral impact and roll-over accidents cause neck injuries, but require higher impact energies than rear-end accidents. Significant neck injury can occur with rear-end impacts of 10 miles-per- hour.
The injury producing forces caused by rear-end impacts and delivered to the occupants seat increase only slightly with impact speeds of between 10 and 30 miles-per-hour. Seat back failure protects occupants from neck injury in higher speed accidents.
Certain patients, particularly women, are more susceptible to neck injury, presumably because their neck structures are smaller and their lighter body weight is less likely to cause seat back failure.
The initial step for the reduction and prevention of neck injury was the introduction of head rests. Although neck injury may still occur with head rests in use, the severity and frequency promises to be much less. Energy absorbing bumpers and rear body structures also promise to reduce neck injuries. Both require research and development before optimal protection is achieved.
Seat belts increase the incidence and severity of neck injury in rear-end collisions when head rests are not used; head rests eliminate this risk. |