Whiplash Injuries in Motor Vehicle Accidents

A comprehensive survey of whiplash-related musculoskeletal injuries, diagnoses, and treatment modalities.
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Motor vehicle accidents are the most common mechanism of trauma and are frequently associated with musculoskeletal injuries. In the United States, trauma is a major cause of death in persons less than 40 years of age, and motor vehicle accidents account for 42,000 deaths annually, with an annual cost of $14 billion.1 Statistics show that 85% of traumatic neck injuries are due to motor vehicle accidents, and there is a higher prevalence in females.2

With the design of vehicles, seat belts, shoulder harnesses, air bags, head rests and child seats, the safety of passengers has improved significantly resulting in reduced critical injuries. However, air bags do not decrease the likelihood of significant lower extremity trauma which may result in death from minimal impacts, particularly in those individuals who are short. With a general reduction in critical injuries, there is a greater proportion of soft tissue injuries including strains, sprains, contusions, abrasions and lacerations following motor vehicle accidents.2

Mechanism and Pathophysiology

Cervical whiplash is considered a soft tissue injury involving the muscles, tendons, ligaments, and facet joints. Dr. H. Crowe described whiplash in 1928 as an acceleration/deceleration mechanism of energy transfer to the neck. This term has a negative connotation, and is better described as a musculoligamentous injury to the cervical spine.3 An impact of 2-5 mph is sufficient to produce enough force to result in musculoskeletal injury, which may be transient.4 Forces on the head, which weighs about 13 pounds, can be 3 to 14 times the acceleration of gravity, resulting in musculoskeletal injuries to the relatively thin, rod-like cervical spine and other vulnerable joints (i.e. jaw).5 The injuries sustained are, in part, based on the relative mass and speed (inertia) of both vehicles involved, as well as the displacement that occurs during impact. The literature suggests that there is less injury to the cervical spine during hyperflexion due to the limiting factor of the chin hitting against the chest. Thus, low velocity front-end collisions tend to result in less disability than rear-end collisions. It is difficult to predict, based on the mechanism of accident and property damage, the extent of a passenger’s injury. Some studies suggest that an occupant who sustains a rear-end collision is more likely to have symptoms of cranial nerve or brain stem dysfunction. In many neck injuries, there is also a rotational component, which may be related to the position of the neck, or oblique force vectors at the moment of impact, resulting in greater compressive forces to the facet joints and nerve roots. There is also a vertical force component, lifting the victim upward, which may affect the location of the headrest during the hyperextension phase. Following a motor vehicle accident, unprepared occupants have a higher frequency of multiple symptoms including headaches.1

A sprain is a tear or stretch injury to the ligaments. During forced extension or lateral bending of the cervical spine, there may be a tear of the anterior longitudinal ligament, which may also result in compressive forces to the posterior elements of the spine. This, in turn, may result in stretch or hemarthosis of the cervical facet joints. In forced flexion, there may be a tear of the inter-spinous ligament. Healing of the ligaments can result in fibrosis, with reduced elasticity and restricted joint motion, which may make the patient more susceptible to recurring injuries from relatively mild trauma. A musculotendonous strain is a stretch injury to the tendon, myofascial sheaths and muscles. Pathologically, there may be tears, or even rupture, resulting in local tissue hemorrhage and may ultimately result in fibrosis. In more severe injuries, particularly if there is head trauma, there may be 1) disruption of the annular fibers of the anterior cervical disk through shearing forces and forced extension, 2) injury to the cervical sympathetic nerve fibers during forced extension, 3) vertebral artery spasm during forced extension with lateral bending, and 4) vertebral fractures as the result of compressive forces to the anterior elements.3

Symptoms and Evaluation

A patient who presents with acute whiplash generally complains of:

  • neck pain (90-100%)
  • restricted neck range of motion (40-95%)
  • headaches (50-90%)
  • referral into the shoulder and arm (40-70%)
  • radiating symptoms (10%)
  • hand paresthesias (10-15%)
  • upper extremity paresthesias (45%)
  • back pain (35%)
  • dizziness or unsteadiness (20-70%)
  • blurred vision (20-45%)
  • photophobia (30-80%)
  • tinnitus (4%)
  • nonspecific upper extremity weak ness or generalized fatigue (60%)
  • anxiety (45-50%)
  • depression (45%)
  • irritability (20%)
  • impaired concentration (20-60%)
  • insomnia (35%)
  • dysphagia (7%)
  • sexual dysfunction (7%)
  • myelopathy (4%)

If there is a cervical disk disruption, it may result in radiating symptoms into the upper extremity associated with focal weakness, reflex changes and sensory deficits. If the cervical disk disruption affects the spinal cord, then the patient may present with myelopathy, including spasticity, bowel, bladder, sexual, and gait dysfunction.1,2,6

The Quebec taskforce in 1995 classified the severity of cervical sprain as in Table 1.6

An appropriate history is important to exclude significant pathology affecting the neck including spinal cord, nerve root, head injury, fractures and hematomas. An appropriate physical examination includes a complete musculoskeletal and neurologic assessment, with careful attention in evaluating the soft tissue findings including a posture, restricted range of motion, myofascial trigger points, subtleties in weakness and imbalance of muscles.

With grade 2 or more injuries, the patient will present with guarded and restricted neck motions, often associated with cervical paraspinal muscle spasm. There is usually palpable tenderness in the muscles, fascia, tendons, which may, in turn, elicit a characteristic referral pattern of pain, numbness or tenderness known as a myofascial pain syndrome. Frequently, the muscles involved during the hyperextension component are the sternocleidomastoid (SCM) and scalene, particularly if the headrest was not adjusted properly, and during the hyperflexion component, the trapezius, levator scapulae and cervical paraspinals are affected. Often, these patients present with contralateral pain on neck rotation, bending and flexion. There are some patients that present with post-traumatic cervical torticollis, possibly related to excessive hypertonicity of the SCM muscle, and may require anticholinergics or botulinum toxin injections. There may also be segmental hyper- or hypo-mobility of the facet joints often manifested by unilateral pain with neck rotation, bending and extension.

First published on: September 1, 2002