Nearly everyone has been on the receiving end of a whiplash neck injury or knows someone who has been. “Whiplash” is defined as a flexion (forward bending) and extension (backward bending) injury of the neck often due to being struck from behind. This post will focus on the mechanism of whiplash and pain.
Many health care practitioners who treat this complicated syndrome contend that a motor vehicle accident (MVA) at as low an impact speed as 5 miles per hour (mph) can cause whiplash. Other studies have shown that the minimum rate of speed needs to be 9-10 mph.
The history and physical examination are the primary way in which this malady is diagnosed. Diagnostic studies for whiplash are helpful if positive findings are discovered. However, due to the rate of false negative findings (30%-50% in some studies), the absence of findings with diagnostic studies does not prove malingering.
- 1 Whiplash Factoids
- 1.1 A Brief Review Of Neck Anatomy
- 1.1.1 A Brief Review Of Neck Physiology
- 1.1.2 Which Whiplash Therapies Work The Best?
- 1.1 A Brief Review Of Neck Anatomy
- 2 Summary
A Brief Review Of Neck Anatomy
The average adult human head weighs about 10 to 11 pounds. It makes up about 8% of the weight of an ideal human body weight. The average weight of a bowling ball is 6 to 16 pounds…in a sense the human head is a “bowling ball” perched on a stick.
The muscles of the neck “balance” the head on the cervical spine. The muscles of the neck are attached to bones with tendons and some are directly attached to the bones of the head and neck without tendons.
The way a muscle is attached to bone effects how easily it is damaged. Muscles attached without a tendon are injured more easily than those attached with one. Ligaments also support the attachment of bones to bones in the neck.
Ligaments and tendons have a rich nerve supply and a limited blood supply. Because of this, injury to these structures can produce a great deal of pain and heal slowly.
The vertebrae of the neck are guided in their motion by discs and facets. The discs serve as a “cushion” between the vertebrae. The facet (or process) is a small synovial joint (it has the same cartilage as the knee) that guides the motion of the spine. They are located at nearly all levels of the spine normally.
The facets of the cervical spine are positioned in a manner that allow the head to rotate easily. However, their position does not protect the neck from injury by extreme forward and backward bending. The most vulnerable position for injury in whiplash is a rotated head upon the neck.
Whiplash can injure the discs and facets of the cervical spine quite easily. These structures have abundant nervous connections and a limited blood supply. Therefore, they too can generate significant pain and heal slowly.
Due to the mechanical disadvantage of the head “balanced” on the neck, the head and neck unit is subject to injury by forces that would normally be considered not too severe. The mechanical disadvantage can multiply the forces applied to the head and neck causing chronic pain.
The neck is also a location where the spinal cord, major blood vessels, and spinal nerves are located. The mechanical disadvantage of the head and neck mechanism also places unusually high stress on these structures in whiplash. In high velocity impacts, injury to these structures is often a cause of death. Generally, whiplash does not result in death as most injuries occur at much lower velocity.
A Brief Review Of Neck Physiology
Though the head is “balanced” of sorts on the neck, the weight of the head tends to draw the head forward and down. The head is mostly supported by continuous contraction of the neck muscles on the back of the neck.
These muscles, as well as several on the front of the neck, are easily over-powered by a force from any direction. Whiplash can occur with a force from any direction applied to the head and neck mechanism.
Rotation, compression, stretching, flexion, and extension of the head-neck mechanism can all occur with extreme speed and tension during a whiplash injury. The recollection of a person, as to how their neck injury occurred, is notoriously inaccurate as a way to determine mechanism of injury.
Most whiplash neck injuries occur so quickly that mental processing cannot keep up with the speed (not to mention the effect this type of injury can have on intact memory). Patients will typically under-report the actual traumatic event (a “set-up” for being accused of malingering later).
What Is The Whiplash Mechanism?
Determining the actual mechanism for the whiplash injury of any given person is helpful in being able to predict cause of pain, a treatment approach, and likelihood of recovery. As previously stated, the reportage of this is challenging.
It usually requires the clinician to “reverse engineer” the mechanism from First Responder reports at the scene of the accident, the scant history recalled by the patient, and apparent pain pattern determined by the clinician. It can be as much art as science. All sources of information are subject to error (this has been studied by many published trauma studies).
However, in my research for this article, I have synthesized what seems to be the prevailing mechanism for most whiplash injuries:
This mechanism results in the history and physical findings that we will discuss in the next section.
What May Be Expected On a Whiplash History And Physical?
The following is a listing of symptoms that can occur in a whiplash injury. Some of the symptoms are remarkable for their apparent lack of relationship to the actual mechanism for the injury:
Neck Pain: there may be little pain in the first 12 hours after a whiplash injury. It is not uncommon for the pain to be delayed for up to 24 hours after the injury.
Shoulder Pain: as above (this can also be contributed to by the restraint of the shoulder harness).
Facial Pain: this is more common with air bag deployment.
Headache: as the head and neck mechanism has been injured headache is a common occurrence.
Tinnitus (ears ringing): the mechanism for this is unknown.
Visual Disturbances: the mechanism for this is unknown.
Dizziness: mechanism probably related to the neurologic connection between the neck and the balance centers of the brain.
Concussion: especially true if the head is struck.
Arm Weakness or Numbness: this requires evaluation of the spinal cord in the neck.
Insomnia: usually due to pain.
Disturbances of Memory and Concentration: mechanism may be similar to concussion where there is a “to and fro” motion of the brain within the skull.
Bladder and Bowel Dysfunction: mechanism unknown.
On physical examination the following may be found:
Neck Muscle Spasm: the neck attempts to “splint motion” in response to injury.
Restriction of Motion of the Neck: as above
Point Tenderness: a worrisome finding and requires neck fracture to be investigated.
Neurologic Weakness or Numbness: also worrisome and requires evaluation of the spinal cord.
What Diagnostic Studies Should Be Done For a Whiplash Injury?
The following tests may applied in the acute phase presentation of whiplash or later as the patient’s recovery is delayed:
Which Whiplash Therapies Work The Best?
The first axiom in whiplash therapy is to make sure there has not been a serious injury to the brain, spinal cord, or neck structures. Serious injury will require specialty consultation and possibly transfer to a specialty unit.
This is guided by the history and physical. Important historical considerations that suggest that significant kinetic energy was involved in the injury would be:
The above events, as well as the history and physical, will help guide the therapy for a person with whiplash.
The second axiom in whiplash therapy is early, active therapeutic exercises. The method of rest, passive therapies (hot/cold packs), medications, soft collar for the neck, and Chiropractic adjustments have not been shown to improve the rate of healing.
Many of these modalities may give temporary relief of pain. However, studies are generally lacking as to their effectiveness in improving healing rates and prevention of long term pain.
The following therapies have been shown to offer relief (click the links for your desired topic):
My third axiom for whiplash therapy is for each patient to have one primary care practitioner coordinate the treatment plan. What typically happens is the treatment plan becomes fragmented and the patient’s care becomes suboptimal (a common occurrence in modern medicine).
What Is The Expected Whiplash Outcome?
Despite optimal care it can be expected that up to 33% of patients with a whiplash injury will go on to have chronic pain. This is presumably due to the micro-tearing that occurs with this type of mechanism of injury. In structures with a scant blood supply this is to be expected (tendons, ligaments, discs, cartilage, etc.).
I hope you have enjoyed this blog post on whiplash and pain. As you can see, whiplash injuries are much more complicated than you may have initially believed. Many clinicians minimize the serious nature of these injuries because they do not understand the physics of the mechanism of whiplash injury.
Furthermore, the Late Whiplash Syndrome is often not taught to physicians in there training so that a delayed presentation of symptoms is often interpreted as malingering.
Most people treated by a medical practitioner who understands the nuances of Whiplash injuries (a Rehabilitation specialist for instance) will do well even if their neck pain becomes chronic. Be careful seeing clinicians to whom you have been referred for legal reasons. Your treating clinician should be supervising and adjusting your care at regular intervals.
If you have further questions or comments, submit them to the page. I’d like to hear from you.
We wish you good health and good luck in life,