Syndromes, Injuries and Diseases
 
Whiplash injuries
Whiplash can be classified as an acceleration-deceleration injury during which indirect forces are transferred to the neck.It may result from rear-end or side-impact motor vehicle collisions, but can occur during diving and other mishaps. The impact may result in bony or soft-tissue injuries which may lead to a variety of clinical manifestations.The term whiplash has a common usage, but is controversial and has no universal understanding or acceptance of its definition. The more proper term is "cervical spine hyperextension injury."

Occasionally, an injury of this type is called a "cervical strain-sprain injury."

In a rear-end collision, the body is propelled in a forward direction. The head abruptly moves backward, necessitating acute hyperextension of the cervical spine. This is followed by a recoil of the head with severe cervical neck flexion and finally a return to the neutral position. The opposite sequence occurs in head-on collisions.

Neck injuries often result from automobile accidents. Approximately 60 percent of the patients who are injured in a car accident and who go to a hospital will have neck pain. This is a condition that may affect all adults, but appears to be more common in the age group of 30 to 50. The female:male ratio is 5:1, which is remarkable since there is a male preponderance in all other motor vehicle injuries. The symptoms last more than 6 months in 75 percent of whiplash patients who lose an average of 8 weeks of work.

The neck can also be injured in a hyperflexion injury. There may be compression of the anterior column and injury to the cervical extensor muscles. Therefore, the typical whiplash injury may have both a hyperextension and a hyperflexion component. The initial motion is of hyperextension, followed by a rebound element of hyperflexion.

The frequency of whiplash-associated disorders is high, the residual disability of the patients is significant and the costs of care are sizable and rising. There is considerable inconsistency in the medical community about appropriate diagnosistic criteria , therapeutic interventions and the role of rehabilitation.

However, multiple, well-controlled studies have shown that cervical facet joint injury is the most common basis for chronic neck pain after whiplash . This condition cannot be diagnosed other than by using specific diagnostic blocks.

Mechanism of Injury

The majority of cases result from motor vehicle accidents or sporting injuries. The classical description is of a rear-end accident. This causes an acceleration of the trunk, with the head being left behind relative to the body, producing a hyperextension injury of the neck. Because of the speed of the movement there is no time for the normal protective muscle reflex contraction to occur, which would ordinarily protect against such a hyperextension injury. If there is a head rest, the degree of hyperextension can be limited. Without that physical restraint there is nothing to stop the head until it hits the midscapular region of the back.Following this initial movement, the trunk is then held either by the safety belt or steering wheel and the head and neck now flex forward. The degree of flexion is limited physically limited by the chin hitting the chest.

There are multiple structures in the neck that have been proven capable of causing pain including ligaments, intervertebral discs, facet joints, muscles and nerve roots.A severe sprain of the neck will cause subluxation of the facet articular surfaces. In patients who have neck pain for more than 6 months following a whiplash injury, the cervical facet joints are the responsible etiology in more than 60 percent.

Another structure that may be stretched with resultant pain includes the anterior longitudinal ligament. Spasm of the interscalene muscles may be responsible for vague radicular symptoms in the upper extremities such as tingling of the hands and fingers.

Many patients who suffer from a whiplash injury report chronic severe headache symptoms. The headache may be limited to the occipital area or spread to include the vertex, temple, frontal and retrobulbar areas as well. Pain is described as dull, aching and squeezing with occasional pounding and throbbing components. The cervical pain is aggravated by movements of the neck. The head and neck pains persist for days or weeks and in some cases become chronic and last for months or longer.

Exacerbation of pre-existing arthritic or discogenic disease may occur. In some cases, the occipital neurovascular bundle at the level of the occipital ridge may be traumatized secondary to prolonged muscle contraction. Injuries to the superficial and deep structures of the neck, involving muscle, ligaments, discs, bone or nerve roots produce cervical pain that may be referred to the head. Other causes include injury of the trapezius muscle insertion or subluxation of higher cervical spine segments. These headaches usually originate at the base of the skull and may have a forward radiating component.

CLINICAL CLASSIFICATION OF WHIPLASH ASSOCIATED DISORDERS
Grade 0: No Neck pain. No physical signs.
Grade I: Neck complaints. No physical signs.
Grade II: Neck complaints. Musculoskeletal signs are present.
Grade III: Neck complaints. Neurologic changes are present.
Grade IV: Neck complaint of pain. Fracture or dislocation is present.

Whiplash syndrome is more properly termed "cervical spine hyperextension injury" and is commonly the result of a rear-end motor vehicle accident, but other mechanisms of injury are possible. The frequency of whiplash-type injuries is high following certain types of accidents, and the residual disability can be significant with symptoms lasting more than 6 months in many patients suffering from this condition.


Recently, a clinical classification of whiplash associated disorders has been suggested that grades the patient based upon subjective and objective findings. (Please see the previous edition of The Pain Management Letter for this grading system.)

Following a whiplash-type injury, neck pain and other symptoms may be delayed 24 to 48 hours. The pain is usually a dull ache radiating from the midcervical spine up to the occiput. It may spread laterally into the trapezius muscles, and may radiate into the upper extremities. Movement and any physical effort tend to aggravate pain symptoms. Cranial symptoms include headaches, dizziness, visual disturbances and tinnitus. A small percentage may complain of arm or hand numbness.

Many patients do not seem to have significant objective signs on physical examination. If present, they are reduced range of motion in the cervical spine. Swelling is rarely seen. Cervical muscle spasm may be present. If peripheral neurologic signs are present, it may indicate a more severe injury such as intervertebral disc disease.

Plain radiographs in several views should be performed as part of the initial evaluation. This includes an anteroposterior view, lateral view in extension and flexion, oblique views and a odontoid view. Some patients may have an abnormal curve pattern on the lateral X-ray with loss of cervical lordosis and even a reversal of the curve. This is usually associated with spasm of the paravertebral muscles and is neither a fixed nor structure deformity. Cervical spondylosis should be noted since this is associated with more severe and prolonged symptoms. If neurologic injury is suspected, patients should be evaluated with more involved testing such as MRI exams or EMG studies.

Treatment of Whiplash Associated Disorders

A timeline for treatment of WAD has been recommended. This timeline refers to patients with Grade I through III injury. Patients with Grade IV require immediate surgical consultation. The clinical management of WAD patients should recognize that most cases of whiplash unassociated with other injuries are usually self-limiting.

Thus reassurance, promotion of activity and conservative management are recommended in early treatment for Grades I to III. The most important principle of treatment is to prevent the development of a chronic pain syndrome.

Acute Mild Injury

Treatment must be initiated early, preferably within hours of the injury, but no longer than a few days. Treatment must be aggressive but gentle. Soft tissue injury may involve inflammation, edema and possible microscopic hemorrhage. Immediate rest of the neck is indicated. A soft collar allows support of the head. Early use of ice (within 24 hours) is indicated to decrease pain, and reduction of edema and hemorrhage.

Following this early period (24-48 hours) the use of heat is indicated to promote blood flow. Heat causes vasodilation and increases blood flow to wash out the accumulating toxins. Heat is also sedative and soothing. Prolonged use of ice becomes painful and causes vasoconstriction and additional local ischemia. Lengthy use of a soft cervical collar is contraindicated. Within several days, a collar becomes addictive and prolonged immobilization allows stiffening of cervical structures and deconditioning of supporting muscles. Active and carefully guided passive range of motion is indicated.

Acute Severe Hyperextension Injury

A severe injury implies significant injury far exceeding that of the mild acute injury. In an injury of this nature there may be tear or avulsion of the anterior longitudinal ligament, tear of the anterior flexor muscles or tear of the annular layers of the intervertebral disk. Skeletal damage may be present and injuries of this nature require neurosurgical evaluation.

Chronic Whiplash Pain

Cervical pain that lasts longer than 2-3 months should be considered chronic in nature. This type of pain requires aggressive evaluation and treatment to prevent a permanent disability.

In patients who have neck pain for more than 6 months following a whiplash injury, the cervical facet joints are responsible in approximately 60-80 percent. Multiple, well-controlled studies have shown that cervical facet joint injury is the most common basis for chronic neck pain after whiplash . This condition can only be diagnosed by using specific diagnostic nerve blocks.

Therefore, patients who fall into this category should undergo diagnostic cervical facet joint injections. If greater than 50-60% of the pain symptoms are relieved with this diagnostic approach, the patient should be considered an appropriate candidate for radiofrequency thermocoagulation of the responsible spinal nerves. This technique is safe and reliable, and can provide long-lasting relief of pain. Resolution of chronic neck pain can also provide reduction of pre-operative psychological stress.Many times, the psychological distress exhibited by whiplash patients is a consequence of the chronic somatic pain.