Whiplash, whose formal term is whiplash associated disorders (WAD), is a range of injuries to the neck caused by or related to a sudden distortion of the neck associated with extension, although the exact injury mechanisms remain unknown. The term "whiplash" is a colloquialism. "Cervical acceleration–deceleration" (CAD) describes the mechanism of the injury, while WAD describes the subsequent injuries and symptoms.
Whiplash is commonly associated with motor vehicle crashes, usually when the vehicle has been hit in the rear; however, the injury can be sustained in many other ways, including headbanging, bungee jumping and falls.(2010). Retrieved January 16, 2013 from http://www.njpcc.com/conditions-of-the-spine/neck-paininjury.html It is one of the most frequently claimed injuries on vehicle insurance policies in certain countries; for example, in the United Kingdom, 430,000 people made an insurance claim for whiplash in 2007, accounting for 14% of every driver's premium. In the United States, it is estimated that more than 65% of all bodily injury claims are whiplash related, translating to around $8 billion in economic costs per year.
Before the invention of the car, whiplash injuries were called "railway spine" as they were noted mostly in connection with train collisions. The first case of severe neck pain arising from a train collision was documented around 1919. The number of whiplash injuries has since risen sharply due to rear-end motor vehicle collisions. Given the wide variety of symptoms associated with whiplash injuries, the Quebec Task Force on Whiplash-Associated Disorders coined the phrase 'Whiplash-Associated Disorders'.
While there is broad consensus that acute whiplash is not uncommon, the topic of chronic whiplash is controversial, with studies in at least three countries showing zero to low prevalence, and some academics positing a linkage to financial issues.NY Times - In one country chronic whiplash is uncompensated - and unknown
Signs and symptoms
Symptoms reported by affected people include: pain and aching to the neck and back, referred pain to the shoulders, sensory disturbance (such as pins and needles) to the arms and legs, and headaches. Symptoms can appear directly after the injury, but often are not felt until days afterwards. Whiplash is usually confined to the spine. The most common areas of the spine affected by whiplash are the neck and middle of the spine. "Neck" pain is very common between the shoulder and the neck. The "missing link" of whiplash may be towards or inside the shoulder and this would explain why neck therapy alone frequently does not give lasting relief.Gorski JM and Schwartz LH, Shoulder Impingement Presenting as Neck Pain. The Journal of Bone and Joint Surgery Vol 85-A · Number 4 · April 2003 p635-638
Cognitive symptoms following whiplash trauma, such as being easily distracted or irritated, seems to be common and possibly linked to a poorer prognosis.
Cause The exact injury mechanism that causes whiplash injuries is forceful sudden hyperextension followed by hyperflexion of the cervical vertebrae, mainly spraining the nuchal ligament and the Anterior Longitudinal Ligament respectively. A whiplash injury may be the result of impulsive retracting 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.
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 coasterRoller Coaster Neck Pain, from the Spinal Injury Foundation 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..
Whiplash associated disorders sometimes include injury to the cerebrum. In a severe cervical acceleration–deceleration syndrome, a brain injury known as a coup contrecoup injury occurs. A coup contrecoup 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.
"Volunteer studies of experimental, low-velocity rear-end collisions have shown a percentage of subjects to report short-lived symptoms",
From this type of research, it has been inferred that whiplash symptoms might not always have any pathological (injury) explanation.
However, over the last decade, academic surgeons in the UK and US have sought to unravel the whiplash enigma. A 1000-case, four-year observational study published in 2012 said that the "missing link" in whiplash injuries is the trapezius muscle which may be damaged through eccentric muscle contraction during the whiplash mechanism described above and below. Another studyGorski JM and Schwartz LH, Shoulder Impingement Presenting as Neck Pain . The Journal of Bone and Joint Surgery April 1, 2003 vol. 85 no. 4 p635-638 suggested that "shneck pain" was in the nearby supraspinatus muscle and this resulted from a seemingly asymptomatic form of shoulder impingement. Shoulder impingement is commonly asymptomaticYamaguchi K, Ditsios K, Middleton WD, Hildebolt CF, Galatz LM, Teefey SA. The demographic and morphological features of rotator cuff disease. A comparison of asymptomatic and symptomatic shoulders" J Bone Joint Surg Am 2006;88:1699-704 and the shoulder may be injured along with the neck in a motor vehicle accident. Whiplash due to The Referred Shoulder Impingement Syndrome was successfully treated using conventional treatments for shoulder impingement including anti-inflammatory steroids and non steroids, and by avoiding the overhead position of shoulder impingement during the day and night time.Gorski JM and Schwartz LH, Shoulder Impingement Presenting as Neck Pain. The Journal of Bone and Joint Surgery VOL 85-A · NUMBER 4 · APRIL 2003 p635-638(ibid) All of this work demonstrates that historically and indeed presently whiplash patients' pain sources may be missed if it is outside of the neck. Hence the pathology in whiplash may have been missed and the treatment ineffective.
Mechanism Whiplash can be described as a sudden strain to the muscles, bones and nerves in the neck. The neck is made up of seven vertebrae, referred to as the cervical vertebrae. The first two cervical vertebrae, the axis and atlas, are shaped differently from the remaining five. The atlas and axis are responsible for movement of the skull from side to side (cervical rotation to the right and left); also moving forward and backward (cervical flexion and extension). Excessive extension and flexion can disrupt the vertebrae.
There are four phases that occur during "whiplash": Initial position (before the collision); retraction; extension; and rebound. In the initial position, there is no force on the neck; it is stable due to inertia.Stemper, D. B., Yoganandan, N., Pintar, A.F., and Rao D.R. (2006) Anterior longitudinal ligament injuries in whiplash may lead to cervical instability.Medical Engineering And Physics, 28(6), 515-524. They explain that during the retraction phase that is when the actual "whiplash" occurs, since there is an unusual loading of soft tissues. The next phase is the extension: the whole neck and head switches to extension, and it is stopped or limited by the head restraint. The rebound phase transpires as result of the phases that are mentioned.
During the retraction phase, the spine forms an S-Shaped curve, caused by the flexion in the upper planes and hyperextension at the lower planes. If this exceeds their physiological limits, in this phase the injuries occur to the lower cervical vertebrae. In the extension phase, all cervical vertebrae and the head are fully extended, but do not surpass their physiological limits. Most of the injuries happen in C-5 and C-6.
Pathophysiology 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 ms Rear car structure is impacted and begins to move forward and/or crushes Occupant remains stationary No occupant forces100 ms 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 inertia150 ms 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 neck175 ms 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 extended300 ms 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
Diagnosis 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.
Québec Task Force The Québec Task Force (QTF) has divided whiplash-associated disorders into five grades. Grade 0: no neck pain, stiffness, or any physical signs are noticed Grade 1: neck complaints of pain, stiffness or tenderness only but no physical signs are noted by the examining physician. Grade 2: neck complaints and the examining physician finds decreased range of motion and point tenderness in the neck. Grade 3: neck complaints plus neurological signs such as decreased deep tendon reflexes, weakness and sensory deficits. Grade 4: neck complaints and fracture or dislocation, or injury to the spinal cord.
Prevention
The focus of preventive measures to date has been on the design of car seats, primarily through the introduction of head restraints, 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 crashworthiness 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.
A Head restraint is 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. The most effective head restraint must allow a backset motion of less than 60 mm to prevent the hyperextension of the neck during impact.
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.