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Whiplash Injuries in Low Impact Collisions

Whiplash is the most common insurance claim injury after a rear-end accident. There is no doubt that even in very low speed, rear-end impacts, soft tissue trauma can be sustained. However, in the past, it has been the degree of damage to the vehicle that has been the main criteria adopted by both defence solicitors and expert witnesses for arguing whether or not a whiplash injury has been sustained.

Perth chiropractor, Dr Adam Rocchi reports that research is suggesting however that injuries can occur in the neck without any obvious damage to the car.

Examination by a Chiropractor can determine any changes to segmental cervical vertebrae motion as well as muscular spasm, postural distortion and localised pain. Further investigation with stress Radiography, MRI and other diagnostic equipment, may reveal ligament injury, inflammatory and neurological function changes.

The Cause Of Whiplash Injury

In a car crash, the body and the head act like two separate entities, each with their own inertia and joined by the neck, the cervical spine. In a rear-end collision, the body of the driver or passenger is propelled forward by the seat on which they are sitting. The head, however, remains still which causes the neck to be forced backward as the body moves forward. The result is soft tissue damage to all the structures within the cervical spine.

Speed Versus Acceleration In A Collision

In the past, the speed of the collision was the guiding factor, with damage to the rear of the vehicle being the main determining factor as to whether a whiplash injury could have occurred. However, Chiropractors treating whiplash injury patients classify these injuries as ‘inertial acceleration injuries’ as it has been found that the severity of the damage to the cervical spine is in direct relationship to the acceleration caused to the vehicle that has been struck from behind.

This was explained by Navin and Romilly in their investigation into ‘vehicle and occupancy response’ in low-speed rear impact collisions. Their findings were presented at the Multidisciplinary Road Safety Conference in New Brunswick in 1989:-

“Rear vehicle impacts between 5-12 mph indicate that some vehicles can withstand a reasonably high speed impact without significant structural damage. The resulting occupant motions are marked by a lag interval, followed by a potentially dangerous acceleration up to speeds greater than that of the vehicle.”

These findings are re-enforced by Robbins in his Society of Automotive Engineers technical paper of 1997 entitled “Lack of Relationship Between Vehicle Damage and Occupant Injury”. In this, he provides supporting data, Mathematical models and equations to explain why the concept that there is a direct correlation between the degree of damage to the struck vehicle and the severity of injury to the occupants in rear impact collisions is erroneous. The cause, in fact, is the magnitude of acceleration by the vehicle struck from behind.

The Awareness Factor

Because whiplash injuries happen in rear-end accidents, passenger awareness is a major factor in the severity of the injuries sustained even though the forces at play may be significantly less than when playing a contact sport (for example). The fact that the person quite literally does not see the impact coming, gives no opportunity to brace and protect him or herself.

In the results of a study conducted by Lord into Cervical Flexion-Extension/Whiplash Injuries published in 1993 (Hanley & Belfus, Sept. 1993, p. 360) it is reported that the acceleration and deceleration movements experienced by the neck in a whiplash injury happen within 250 milliseconds, giving no time for the voluntary reflex muscles to respond in an effort to prevent injury.

Without the opportunity to brace, it appears that there is a possibility of injury when a person is caught ‘off-guard’ in this type of collision with a change of velocity as low as 2.5 mph.

The Position of the Head at Time of Impact

There is an increased risk of injury if the driver or passenger’s head is turned to the side at the time of impact. Caillet explains this succinctly in his 1981 report:

“not only will the already narrowed foramen be compressed more, but the torque effect on the facets, capsules, and ligaments will be far more damaging.”

There is no doubt that rotation of the head produces greater severity of injury in a person with head turned at the time of impact than in a person facing forward in the same rear-end collision, exhibiting a greater number of symptoms and more headache and neck pain. In addition, there is more likely to be visual disturbance, cranial nerve or brainstem dysfunction and radicular deficit.

To Sum Up

All the evidence points to the fact that in rear end accidents, the amount of damage to the vehicle struck is not an indicator of the likely severity of injury to the vehicle occupants. Nor does it provide any indication of the recovery time.

The degree of injury is directly related to the acceleration of the vehicle in which they were seated and, whether they had any opportunity to brace before impact. In addition, there are a number of other factors relating to the position of the person’s head at the time of impact, their level of physical fitness, any pre-existing medical conditions, etc.

It is evident that the most reliable determination of the level of injury and prognosis in whiplash injury is the thorough examination and evaluation by a skilled practitioner such as a Chiropractor.



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Spine Scan - Combined Office

Unit 201, 94 Mill Point Road
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Western Australia
Phone: 0412 052 163

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