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1st Nov

2018

Understanding Whiplash Injuries: Basic Science and Treatment

I have in past newsletters described how whiplash injuries, most typically seen following car accidents, result from excessive strain or loading on tissues in the neck, as it “whips” through a characteristic S-curve. This produces microstructural damage to collagen fibers of the facet joint capsular ligament, and may pinch a fold in the joint capsule, or cause or aggravate degenerative changes in the joint cartilage (arthritis).

Pain stemming from the facet joint capsular ligament is believed to be the most prevalent and severe.

Research studies have shown that a number of microstructural changes often occur, which all contribute to the pain, and often persistent pain.

Mechanically, the injury creates abnormal mechanics of certain joints in the neck, often the most mobile ones, leading to deformation of the mentioned capsular collagen fibers, which then become weakened, and the joint loses its normal movement pattern and stability, also in part because of a reflex response of the deep stabilizing muscles, which either go into spasm or become inhibited and quickly start to atrophy.

An inflammatory response also occurs locally in the injured region, further adding to our pain, and loss of joint stability.

Furthermore, structural changes often develop in the nerve endings embedded in the capsule (which normally give us information of movement and position), including swelling and signs of cell damage and degeneration, also contributing to increased pain sensation and loss of joint control.

Unfortunately, a significant number of people experience persistent pain for several months, or in some severe cases even years. Some of them develop what is called peripheral and central sensitization, which can occur in other forms of chronic pain as well.

Sensitization is the increased responsiveness of nerves to a normally non-painful stimulus, and/or a pain reaction to a stimulus which normally does not reach the threshold where we would experience pain. A normally painful stimulus may become excessively painful (hyperalgesia), or a normal/benign stimulus creates pain (allodynia).

The hypersensitivity is typically to mechanical stimuli such as movements/stretch, compression or external pressure; as well as heat and cold. It often starts in the neck and spreads to the shoulders in a “coat hanger” pattern, but may also affect entire arms, and often includes in particular the front of the calves.

With central sensitization, there is a change in neural processing in the brain, resulting in a spread of perceived painful areas. In the spinal cord, it has has been found that there can be a 50% increase in nerve endings (synapses) responsible for pain perception, and a decrease in the number of nerve endings that normally block or inhibit such perception. Some of the nerve fibers which normally tell us about position and movement, are being replaced by pain nerve fibers (nociceptive fibers). Specialized nerve cells called glia have been found to be activated and contribute to neural inflammation.

This mechanism explains why it can be difficult for some people to recover from whiplash injuries, and why early and appropriate treatment is of utmost importance. Promising studies have been performed on animals today to prevent these central nervous system abnormalities, so there is hope that more effective medical treatment will become available in the not too distant future. It should also be pointed out, that central sensitization, or at least more severe forms of it, occurs in a minority of people who suffer whiplash injuries.

There is much that can be done conservatively today for the vast majority of people who have sustained whiplash injuries. Early pain control is important, as the pain itself can promote the abnormalities that I have discussed, especially if there are signs of sensitization. Frequent 5 minute ice applications, short-term anti-inflammatory medications or pain medications may at first be indicated, an anti-inflammatory diet, possibly a soft neck collar for a limited time only in more severe cases, and gentle neck movements are usually helpful. The goal initially is to reduce pain and inflammation, while preventing loss of motion and promoting tissue healing. Stretching to the neck is to be avoided, as it would further irritate or compromise the injured collagen fibers.

Since the injury has led to altered joint mechanics and loss of normal movement pattern and stability in the neck, physical therapy treatment is subsequently progressed to activating and rehabilitating stabilizing musculature, while reducing tension in guarded muscles- all done with specific and progressed exercise without pain. Manual soft tissue mobilization is also beneficial, to reduce protective muscle guarding, and thereby also reducing pain.

Continued specific home exercise is also crucial, to fully strengthen the injured collagen tissues (capsule/ligaments) and restore normal muscle function and stability of the injured joints. This can often require at least 9-12 months of regular home exercise, 3 times per week. This effort is a small price to pay, in my opinion, to be able to regain a normal lifestyle and quality of life.

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