Wednesday, December 21, 2005

A New Spin on Sudden Onset Low Back Pain

Low back pain is the most common form of personal injury, and it can come from many sources. The most debilitating form of low back pain is the sort that comes on suddenly, and often leaves the patient in a lot of pain with very limited mobility (Sudden onset low back pain). Now do not be deceived, this kind of pain can be related to something as simple as muscular spasm, or it can be caused by many more serious conditions related to multiple internal organs, such as the abdominal aorta, or can also be a result of metastatic disease. The musculoskeletal cause of back pain, (muscles, ligaments, nerves, and joints) is by far the most common, but the best way to distinguish between causes is to visit a health professional.

For the purpose of this article, I will be focusing on the musculoskeletal causes of low back pain. As a chiropractor, I get to see many different injuries, among them sudden onset low back pain. A common statement I hear from patients is “I don’t know what I did, I was just bending down to pick something up, and it locked up on me”. The onset can be related to something as simple as picking up a pencil. The patient then experiences debilitating low back pain and muscular spasm. The most common diagnosis that I have seen among other health professionals is “disc bulge” or “disc injury”. It is an easy diagnosis, because disc injuries can occur suddenly with minimal trauma. However, 30% of the population are walking around with "disc bulges" and they don't even know it because it is not putting any pressure on the spinal cord. The spinal canal is actually 1/3rd spinal fluid, so you need a fairly severe discal protrusion for it to cause any pain. Discal protrusions or herniations that are severe enough to impinge on the spinal cord will cause severe shooting electric pain down into the legs, sometimes all the way down to the heel and toes. So for the person presenting with acute low back pain, who is not experiencing symptoms into the leg, there is another explanation. The notion of “acute spinal buckling” has been investigated only recently, and there is much research coming out now on the topic. It is a fairly complicated sequence of events, but I will do my best to describe it simply.

There are muscles in the body that have “feed-forward” properties. What this means is, before your body initiates movement, there are certain muscles that become activated and contract before the movement is actually made. These muscles have stabilizing properties that prevent injury. One such muscle is called the multifidus, the most important of your spinal stabilizing muscles. The multifidus is a very tiny muscle that runs up 2-3 spinal levels from vertebrae to vertebrae. It is known as a "local mover", which means that it has the capacity to create movement only in a local small area. "Global movers" are muscles that can create movements on a larger scale. Local movers will create movement between individual vertebrae, whereas global movers create movement between groups or 'blocks' of vertebrae. To illustrate an example of the sequence of movement, think of the action of bending forward to pick something up (even something as small as a pencil). Before you initiate the action, your multifidus should contract in order to stabilize the spine so that you can complete the movement without damaging any spinal structures. When the multifidus does not contract, the global movers of your spine will contract first, which will cause 'block movement' of your vertebrae, which results in micro-trauma and increased stretch of the muscles, joint capsule, and ligaments adjacent to that level. This phenomenon is known as “spinal buckling” which will create resultant muscular spasm of the multifidus. Whenever an injury occurs, nearby muscles respond by going into a strong contraction to prevent further injury. While this is a protective function, it is the muscular spasm that causes the pain and limited range of movement that is characteristic of sudden onset low back pain. This "buckling" is what creates the sensation of the back "locking up".

Now you might be wondering “why wouldn’t the multifidus contract in the first place?” The answer is multi-factorial. It can be related to fatigue of the muscles or a lack of physical fitness, which will cause a de-conditioning of the muscles that stabilize the spine. It can also be related to chronic episodes of low back pain, which will cause an inhibition of these same muscles over time. Another cause is the concept of “visco-elastic creep”. While this term may seem complicated, it is relatively easy to understand. In effect, if a muscle is placed in a lengthened position for a long period of time, it loses its visco-elastic properties, meaning that its ability to “spring back” into its normal tension and contractility are compromised. So if you are the type of person that spends a lot of time bending forward to lift objects, or even if you spend a lot of time bent over a computer desk, the muscles in your back are being held in a lengthened position, which will eventually compromise their ability to return to their normal state, making you more susceptible to minor traumas as a result of normal movement. Studies have shown that if you spend 15 minutes in a forward flexed posture, it takes 3 times as long (45 minutes!) for your muscles to return to their original state. During this period of transition, subtle movements that would otherwise not cause injury could do just that. This is why many people will experience extreme pain after picking up a very light object. The firing of the stabilizing muscles of the spine is compromised, and small trauma to the spine will result, which will initiate the pain-spasm cycle described above.

While this might all seem very complicated, the treatment and prevention of this kind of low back pain is not. The first step of treatment is to release the muscular spasm. While this can be accomplished in a variety of ways, the most successful treatment I have encountered is that of Active Release Techniques. By breaking up the pain-spasm cycle, the patient then becomes mobile enough to function, and to start the next phase of treatment. This second step is that of rehabilitating the stabilizing muscles of the spine. In most cases, these muscles need to be stimulated and strengthened so that the next time a movement is initiated, these muscles will contract first, preventing further injury. These muscles have subtle movements, and just because the multifidus attaches to the spine, does not mean that it is strengthened by doing hundreds of back extensions. In fact, this could actually cause more harm than good. The multifidus when contracted causes a very subtle movement and stabilization of the spine, that can be taught by the appropriate health care practitioner. By teaching how to contract these muscles, and by increasing their muscular endurance, the patient will eventually be able to contract these muscles without having to think about it. Then the feed-forward mechanism discussed above is restored and the patient is protected for further episodes of low back pain so long as they continue to perform their exercises.

Many patients feel victim to recurring low back pain, but with this simple approach, patients can now gain control of their symptoms and prevent more episodes in the future.