| Whiplash | |
|---|---|
| Classification and external resources | |
| ICD-10 | S13.4 |
| ICD-9 | 847.0 |
| DiseasesDB | 14122 |
| MedlinePlus | 000025 |
| MeSH | D014911 |
Whiplash is a non-medical term describing a range of injuries to the neck caused by or related to a sudden distortion of the neck[1] associated with extension.[2] The term "whiplash" is a colloquialism. "Cervical acceleration-deceleration" (CAD) describes the mechanism of the injury, while the term "whiplash associated disorders" (WAD) describes the injury sequelae and symptoms.
Whiplash is commonly associated with motor vehicle accidents, usually when the vehicle has been hit in the rear;[3] however, the injury can be sustained in many other ways, including falls from stools, bicycles or horses. It stands out as one of the main injuries covered by the car insurers. In the United Kingdom, 430,000 people made a claim for whiplash in 2007 (75% of the UK's motor insurance claims), accounting for 14% of every driver's premium.[4]
Before the invention of cars, whiplash injuries were called “railroad spine” as noted mostly during train collisions. After the invention of cars, the number of whiplash-related injuries have risen sharply due to an increase in rear-end motor vehicle collisions. The first case of severe neck pain arising from a train collision was documented around 1919.[5] Given the wide variety of symptoms that are associated with whiplash injuries the Quebec Task Force on Whiplash-Associated Disorders, coined the phrase, Whiplash-Associated Disorders.[5]
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Symptoms reported by sufferers include: pain and aching to the neck and back, referred pain to the shoulders, sensory disturbance (such as pins and needles) to the arms & legs and headaches. Symptoms can appear directly after the injury, but often are not felt until days afterwards.[3] Whiplash is usually confined to the spinal cord, and the most common areas of the spinal cord affected by whiplash are the neck, and the mid-back (middle of the spine).
The exact injury mechanism that causes whiplash injuries is unknown. A whiplash injury may be the result of impulsive stretching of the spine, mainly the ligament: anterior longitudinal ligament which is stretched or tears, as the head snaps forward and then back again causing a whiplash injury.[6]
A whiplash injury from an automobile accident is called a cervical acceleration-deceleration injury. Cadaver studies have shown that as an automobile occupant is hit from behind, the forces from the seat back compress the kyphosis of the thoracic spine, which provides an axial load on the lumbar spine and cervical spine. This forces the cervical spine to deform into an S-shape where the lower cervical spine is forced into a kyphosis while the upper cervical spine maintains its lordosis. As the injury progresses, the whole cervical spine is finally hyper-extended.
Whiplash may be caused by any motion similar to a rear-end collision in a motor vehicle, such as may take place on a roller coaster [7] or other rides at an amusement park, sports injuries such as skiing accidents, other modes of transportation such as airplane travel, or from being hit, kicked or shaken.[8]Shaken baby syndrome can result in a whiplash injury.[6]
Whiplash associated disorders sometimes includes injury to the cerebrum. In a severe cervical acceleration-deceleration syndrome, a brain injury known as a coup-contra-coup injury occurs. A coup-contra-coup injury occurs as the brain is accelerated into the cranium as the head and neck hyperextend, and is then accelerated into the other side as the head and neck rebound to hyper-flexion or neutral position.
Whiplash symptoms might not always have any pathological (injury) explanation. "Volunteer studies of experimental, low-velocity rear-end collisions have shown a percentage of subjects to report short-lived symptoms", which can not be attributed to any pathogenic effect on the subjects neck.[9]
Diagnosis occurs through a patient history, head and neck examination, X-rays to rule out bone fractures and may involve the use of medical imaging to determine if there are other injuries.[10]
The Québec Task Force (QTF) has divided whiplash-associated disorders into five grades.[11]
The focus of preventive measures to date has been on the design of car seats, primarily through the introduction of headrestraints, often called headrests. This approach is potentially problematic given the underlying assumption that purely mechanical factors cause whiplash injuries - an unproven theory. So far the injury reducing effects of head restraints appears to have been low, approximately 5-10%, because car seats have become stiffer in order to increase crash-worthiness of cars in high-speed rear-end collisions which in turn could increase the risk of whiplash injury in low-speed rear impact collisions. Improvements in the geometry of car seats through better design and energy absorption could offer additional benefits. Active devices move the body in a crash in order to shift the loads on the car seat.[3]
In order to understand what causes whiplash injuries, it is useful to take a look at how your vehicle seat and your body interact during a rear-end collision. Below you can see in slow motion the way your body moves when your vehicle gets hit from behind. While the time associated with a specific collision will vary, the following provides an example of the occupant and seat interaction sequence for a collision lasting approximately 300 milliseconds.
| 0 Milliseconds
• Rear car structure is impacted and begins to move forward and/or crushes • Occupant remains stationary • No occupant forces |
100 Milliseconds
• Vehicle seat accelerates and pushes into occupant’s torso (i.e. central portion of the body in contact with seat) • The torso loads the seat and is accelerated forward (seat will deflect rearward) • Head remains stationary due to inertia |
150 Milliseconds
• Torso is accelerated by the vehicle seat and may start to ramp up the seat • Lower neck is pulled forward by the accelerated torso/seat • The head rotates and extends rapidly rearward hyper-extending the neck |
| 175 Milliseconds
• Head is still moving backwards • Vehicle seat begins to spring forward • The torso continues to be accelerated forward • The head rotation rearward is increased and is fully extended. |
300 Milliseconds
• Head and torso are accelerated forward • Neck is “whipped” forward rotating and hyper-flexing the neck forward • The head accelerates due to neck motion and moves ahead of the seat back |
For the last 40 years, vehicle safety researchers have been designing and gathering information on the ability of head restraints to mitigate injuries resulting from rear-end collisions. As a result, different types of head restraints have been developed by various manufactures to protect their occupants from whiplash.[12] Below are definitions of different types of head restraints.[13]
Head restraint - refers to a device designed to limit the rearward displacement of an adult occupant’s head in relation to the torso in order to reduce the risk of injury to the cervical vertebrae in the event of a rear impact.
Integrated head restraint or fixed head restraint - refers to a head restraint formed by the upper part of the seat back, or a head restraint that is not height adjustable and cannot be detached from the seat or the vehicle structure except by the use of tools or following the partial or total removal of the seat furnishing”.
Adjustable head restraint – refers to a head restraint that is capable of being positioned to fit the morphology of the seated occupant. The device may permit horizontal displacement, known as tilt adjustment, and/or vertical displacement, known as height adjustment.
Active head restraint – refers to a device designed to automatically improve head restraint position and/or geometry during an impact”.
Automatically adjusting head restraint – refers to a head restraint that automatically adjusts the position of the head restraint when the seat position is adjusted.
A major issue in whiplash prevention is the lack of proper adjustment of the seat safety system by both drivers and passengers. Studies have shown that a well designed and adjusted head restraint could prevent potentially injurious head-neck kinematics in rear-end collisions by limiting the differential movement of the head and torso. The primary function of a head restraint is to minimize the relative rearward movement of the head and neck during rear impact. During a rear-end collision, the presence of an effective head restraint behind the occupant’s head can limit the differential movement of the head and torso. A properly placed head restraint where one can sufficiently protect his/her head lower the chances of head injury by up to 35% during a rear-end collision.[14], [15]
In contrast to a properly adjusted head restraint, research suggests that there may be an increased risk of neck injuries if the head restraint is incorrectly positioned. More studies by manufacturers and automobile safety organizations are currently undergoing to examine the best ways to reduce head and torso injuries during a rear-end impact with different geometries of the head restraint and seat-back systems.
In most passenger vehicles where manually adjustable head restraints are fitted, proper use requires sufficient knowledge and awareness by occupants. When driving, the height of the head restraint is critical in influencing injury risk. A restraint should be at least as high as the head's center of gravity, or about 9 centimeters (3.5 inches) below the top of the head. The backset, or distance behind the head, should be as small as possible. Backsets of more than 10 centimeters (about 4 inches) have been associated with increased symptoms of neck injury in crashes. In a sitting position, the minimum height of the restraint should correspond to the top of the driver’s ear or even higher. In addition, there should be minimal distance between the back of head and the point where it first meets the restraint.
Due to low public awareness of the consequence of incorrect positioning of head restraints, some passenger vehicle manufactures have designed and implemented a range of devices into their models to protect their occupants.
Some current systems are:
The Insurance Institute for Highway Safety (IIHS) and other testing centers around the world have been involved in testing the effectiveness of head restraint and seat systems in laboratory conditions to assess their ability to prevent or mitigate whiplash injuries. They have found that over 60% of new motor vehicles on the market have “good” rated head restraints.
To find vehicles with “good rated” head restraints and other safety features please visit the following research-based information sources. North America Insurance Institute for Highway Safety www.whiplashprevention.org
United Kingdom Thatcham Motor Insurance Repair Research Center
According to the recommendations made by the Quebec Task Force, treatment for individuals with whiplash associated disorders grade 1-3 should include manipulation, mobilizations and range of motion exercises. Non-narcotic analgesics and non-steroidal anti-inflammatory drugs may also be prescribed in the case of WAD 2 and WAD 3, but their use should be limited to a maximum of 3 weeks. A cervical collar should not be used for longer than 72 hours as it may lead to prolonged inactivity. Return to normal activities of daily living should be encouraged as soon as possible to maximize and expediate full recovery.[19]
A different approach is taken by the National Institute for Neurological Disorders and Stroke, who suggest that treatment for individuals with whiplash may include pain medications, nonsteroidal anti-inflammatory drugs, antidepressants, muscle relaxants, and a cervical collar (usually worn for 2 to 3 weeks). Range of motion exercises, physical therapy, and cervical traction may also be prescribed. Supplemental heat application may relieve muscle tension.[20]
The consequences of whiplash range from mild pain for a few days (which is the case for most people),[21] to severe disability caused by restricted head movement or of the cervical spine, sometimes with persistent pain.
Alterations in resting state cerebral blood flow have been demonstrated in patients with chronic pain after whiplash injury. [22]
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