Introduction
Anatomy
Cause
Symptoms
Diagnosis
Non-surgical treatment
Surgical treatment
Rehabilitation
Prevention
Whiplash injury is the most common neck injury sustained in motor vehicle accidents. When a motor vehicle is struck from behind, the head will be thrashed backward initially. Then the vehicle will come to a stop within a millisecond. As the body is kept still by the seat belt, the head and neck continue to be pushed forward. This rapid backward and forward movement is similar to the action of a whip, hence the name “whiplash”.
“Whiplash syndrome” refers to a group of neck injuries caused by a sudden jerky movement of the neck that exceeds the normal physiological range of motion. This movement causes tissue damage to the neck tendons or ligaments and in severe cases, damage to inter-vertebral discs and bones.
In a car accident, if the passenger’s head is not supported properly – say, if the head rest is too low and thus unable to prevent the head’s backward movement – it will be thrown back in a hyper-extended movement, causing further damage to the neck. Biomechanical studies have shown that the degree of injuries is proportional to the distance between the head and the head rest, which is defined as the “backset”.
Symptoms may occur soon after the accident or they may show up days afterwards. The range of symptoms includes neck pain and stiffness; pain radiated down the upper limbs and upper back; headache, dizziness and even visual impairment; poor memory and poor concentration; insomnia, mood changes and depression. In severe cases, the victim could suffer from significant neurological defects or functional loss.
An accurate diagnosis can be made by questioning the patient about the accident, and by conducting a detailed examination. Usually an X-ray can tell if there is any bone injury. If more serious damages are suspected, Computerised Axial Tomogram (CT) and Magnetic Resonance Imaging (MRI) may be necessary.
If there are no significant ligament or bony injuries, the treatment is fairly simple. A bag of frozen peas can be applied to the neck, which would mould to the shape of the neck better than an ordinary ice pack. Simple painkillers or non-steroidal anti-inflammatory drugs can be used.
Surgical treatment may be necessary either because of persistent and disabling pain or the presence of neurological complications. The cause of symptoms may originate from the vertebral discs or the facet joints between vertebral segments. Meticulous clinical examinations supported with detailed imaging investigations such as CT scan and MRI are mandatory for locating the responsible pathologies before a surgical plan can be formulated.
Surgical options include surgical decompression of neural structures; stablilisation or fusion procedures for segmental subluxation; and possibly replacement of injured discs.
Physiotherapy and neck exercises are recommended as they contribute to an early recovery. Some patients may need a soft neck collar for a few weeks. The symptoms may last for weeks or even months; however, the chance of complete recovery is good.
The key to preventing a whiplash injury is to keep the differential motion between the body and neck to a minimum during the accident. This can be achieved through a better car seat design. According to the new standard for safe car seats drawn by the U.S. National Highway Traffic Safety Administration, there should be a minimum of 29.5 inches from an occupant’s hip to the top of a head rest and the distance between the head and the head rest should be fewer than 2 inches. However, only very few current car seat designs actually satisfy this requirement. Therefore, additional head supports should be used.
The vehicle seat should be designed in such a way that it won’t slide backwards during a rear impact, which would move the attached head rest away from the driver’s or passenger’s head. The seat material should not be too stiff so it can allow an occupant to sink into it after the impact, moving the head closer to the head restraint. The top of the head rest should be set at or above the level of the occupant’s ears (around 3.5 inches below the top of the head).
The driver and passengers should always keep their backs straight against the seats and their heads resting on the head rest to decrease the “backset” during an unexpected rear-end impact. The driver should hold the steering wheel with the elbows straight.
Dr. NGAI, Wai-kit