A Matter Of Life Or Death: The Case For Safety Belts

Press, Volume XCIX, Issue 29269, 29 July 1960, Page 11

A Matter Of Life Or Death: The Case For Safety Belts

. ?*hig article, written by <m orthopaedic raryeon, to r«grttued by arrangement with the Guardian,** Manchester.

'pHERE are three main types of motor accident: L The head-on collision, either with a stationary object or with another vehicle coming in the the opposite direction. 2- The "roll-over” accident 3. Being run into from behind. Each of these has its special features and problems. If the car sufns$ u fns over, the occupants may be injured in one of three different ways—either they may be thrown upwards (that is, relative to the car) and hit their heads against the roof, sustaining skull or neck injuries; or they may be thrown out—almost inevitably when a car turns over the doors spring open; or they may be thrown sideways against the side of the body which simultaneously may be pushed in. There are, therefore, two problems; the first is to have a body and roof that are strong enough not to collapse when the car turns over, and the second is to have some means of holding the car • occupant in his seat so that he does not come into contact with the roof or sides and is not thrown out Overturnings There have been cases where cars have turned over at high speed and perhaps rolled over several times, and yet the occupant has climbed out of his car almost uninjured. This may happen if the driver has managed to hold himself in position by means of the steering-wheel, but a properly designed safety belt will hold a car occupant in his seat, and minimise the risk of injury even after a severe turn-over. A simple lap belt such as is supplied to passengers in aeroplanes is sufficient to hold him in his seat in this type of accident but a belt that also includes the shoulders gives additional safety and is

essential in other types of accidents.

In a head-on collision the caroccupant’s body is thrown upwards and forwards. If the passenger is in the reclining position it is probable that his knees will hit the dashboard first and he will sustain injuries such as a fractured patella, broken femur, and dislocated hip. The driver will probably be thrown forward against the steering-wheel and may sustain a crushed chest and broken ribs, with serious damage to the heart and lungs. If the passenger or driver is sitting Upright or leaning forward, it is probable that his head will hit

the roof or windscreen of the car and he will sustain damage to his brain or cervical spine. When a stationary car is run into from behind, it is jerked violently forward, much as when one croquet ball is hit by another. A certain amount of kinetic energy is imparted to the occupants. The car itself then stops, having considerable inertia, but the body of the occupant being lighter continues to travel forward and his head hits the dashboard or windscreen, much as in a collision. Even if the occupant’s body does not leave the seat completely, his head may, so to speak, be left behind sustaining an extension or backward-bending strain of his neck or, in his efforts to counteract this, he may contract his neck muscles violently, flexing or bending his neck, forward. Wlyslash Injury Any case of injury to the occupant’s neck that may result is often loosely termed a “whiplash injury,’’ though the term is used ambiguously to include both extension and flexion injuries of the cervical spine. It will be seen that a really efficient safety belt which holds the car occupant firmly in position would prevent most injuries from a roll-over and head-on collision and minimise those from rear-end collisions. The objection has often been raised that although a safety belt would eliminate injuries to the trunk, abdomen, chest,

and head, it would increase the risk of serious neck injuries. Recently some experimental work has been performed on this subject The healthy human cervical spine has a considerable tolerance to compression, elongation, flexion, and extension forces; injury to a healthy cervical spine cannot occur from a flexion force as the chin hits the breast bone before the spine is damaged. In fact experiments show that flexion alone cannot cause a dislocation of the neck. If, however, the spine is already abnormal, from disease or age. then the comparatively

trivial injury may cause serious damage. It is well recognised that elderly people may sustain a minor knock on the head and sustain severe damage to the neck and spinal cord. Neck Injuries If the force is a twisting force, that is producing rotation of the head to one or other side, ligamentous damage is more likely to occur, and serious consequences, such as dislocation and injury to the spinal cord, may ensue. Therefore, in certain circumstances the human neck may be very vulnerable to injuries, particularly if the car occupant is thrown forward and his head hits the dashboard or windscreen obliquely, that is, it is slightly turned to one side. The risk is much greater in elderly people or those who already suffer from arthritis of the neck. The risk of serious damage to the neck from a straight-forward flexion strain, that is from the type of injury which occurs when the body is restrained and the head continues to travel forward, is much less, though this may also occur in elderly people. The opposite injury, from behind that is, when the occupant’s body is thrown forward and his head, so to speak is left behind—is much less likely to occur if the body is restrained than if it is unrestrained. If the

body is unrestrained, it is shot forward put of its seat just as when one billiard ball is hit by another, and this may cause quite a severe sprain of the ligaments of the spine; but if the occupant’s body is restrained by a safety belt the neck movement is less. Motion picture studies of restrained and unrestrained dummies in experimental rear-end collisions show this clearly. In an analysis of 189 motor casualties with injuries to the neck and back, approximately 40 per cent were to the neck and 60 per cent to the rest of the spine. Most of the neck injuries from rear-end collisions were comparatively trivial, in the sense that there was no major fracture, or dislocaItion, or damage to the spinal cord. The general conclusion is that while it is unpleasant and troublesome to have a painful neck, this is better, than being dead or paralysed. Risk Minimised

A properly fitting safety belt, which includes the shoulders will minimise the risk of damage to the cervical spine, although this risk still exists, especially in elderly people, and the driver of a car containing an elderly person should take special care. If a properly fitted head rest were attached to the seat of the car, the risk of damage to the neck would be still further reduced. Certainly if the passengers of a car wish to doze, they should be provided with a head rest and brow band. (Incidentally, a wellfitting head rest is a great source of comfort in a long car drive.)

The ideal safety belt should be fixed to the chassis, it should be comfortable, durable, and easily adjustable; it should hold the occupant’s pelvis and shoulders, not his abdomen, chest, or neck; it should be easy to put on and release; It should not get in the way and it should not restrain the wearer’s body uniformally over a distance of six to nine innches. Lap Belt Wearing a lap belt, the car occupant can be thrown violently forward, striking his head against the windscreen or dashboard and even if he escapes this hazard, a violent forward flexion strain will often cause rupture of liver, kidneys, or aorta with fatal results. All evidence from autopsies on passengers killed in air and motor crashes agrees on this point, and it would appear that the standard instruction in aircraft of leaning forward in tee event of a crash is probably mistaken. An adequate safety belt must hold the motorist’s shoulders as well as his pelvis and it should be stated at once that such a belt must inevitably take a few seconds both to put on and take off. Even after the catch is released, the occupant is not completely free, and has to wriggle his shoulders out of the harness; it is also true that reversing is rather difficult when wearing a safety belt as the driver has to release tee belt before he can turn sufficiently in his seat.,