Whiplash describes the injury of soft tissues which resulted from /acceleration/deceleration force. The most common mechanism is a motor vehicle accident. More specifically, when the patient was a passenger that gets hit from behind or the rear impacted car. Recently more information has been gathered due to the large economic impact of this injury on society. It seems that these injuries are complex and involve the following: Facet joints, intervertebral disc, altered motion of the neck, and centers in the brain the perceive pain. These may cause temporary or chronic pain that depends on the extent of injury.
Law of physics dictates that energy from one object must be dissipating completely to another either by deforming the other object, or changing its velocity. As car No 1 strikes car No 2, several changes occur. The speed of car one decreases, car No. increases speed, and energy is absorbed by car No 2 which deforms it and increases its velocity. This force is transferred to the passenger and causes the soft tissue injuries. Also the most mobile section of the spine while seated is the neck. This leads to abnormal and violent motion of the neck leading to bony or soft tissue injuries. The neck is first forced forward, and then rebounds back ward and strikes the head rest until the force is diminished.
Studies have shown that if the impact is anticipated the extent of injury is lowered. In situations that the impact is anticipated, reflex muscle contractions stabilize the neck and decrease the extent of injuries. Furthermore, postural difference will also dictate the extent of injury. The stabilizing reflex is most efficient when the neck is held in good straight posture. Stronger muscles also promote better stabilization of the neck and result in more minor injuries compared to a weak neck musculature. Since the drivers of the cars are usually more aware of the impact prior to its occurrence, we usually see higher level of injury with the passengers. Women usually sustain greater injuries due to the weaker musculature.
Pain is usually most pronounced 2 days after the impact and resolves within 2 weeks. This scenario is the most common and is caused by a simple muscle strain. If other structures are injured, the pain and dysfunction may persist leading to a worse prognosis. If symptoms last more than 6 months the patient has 43% chance for continued pain and dysfunction. Injury to intervertebral disc, neural tissue, and joint capsule carry worse prognosis. Delay in treatment may also compromise recovery since it may delay diagnosis and further injury from instability. Occupants that are older than 65 and have weaker muscular support is at increased risk as well. Head restraints that are more than 2 inches away from the occupants head allow greater motion of the neck and head prior to stopping it. This allows greater injury and leads to lower recovery potential. If the passenger has prior history of neck pain due to degenerative disc disease, prior neck operations, or prior whiplash injury, the likelihood of greater injury is higher. The smaller the size of the car, the less energy it will absorb. The remaining energy must dissipate on the passenger concluding that smaller cars will cause more soft tissue injury to the passengers.
Judging the severity of the impact based on damage to the car can be misleading. The energy of the impact must dissipate either in the frame work of the car or the passenger. If the energy of impact is just below the force required to deform the frame of the car, then most of the energy will dissipate with the patients. This situation will cause injury to the passengers but will spare the structure of the car.
If your pain has not resolved, or is worsening, you should consult with your spine specialist. Almost all cases can be treated with a course of anti-inflammatory medication along with a physical therapy regime. However, a small subset of patients will require further diagnostic studies to arrive at a more precise diagnosis.