Chiropractors have long used spinal traction methods to relieve abnormal pressure and bulging of the IVD. The more popular methods have employed long axis traction and/or flexion distraction to relieve IVD (intervertebral disc) pressure. Consequently, many doctors are reluctant to employ extension traction methods which seem so radically different. I'm frequently asked if extension traction is good for injured discs and the answer is unequivocally, yes and no. The reason for my ambiguity is hidden in a text you probably studied in college.
In 1978, White and Panjabi described the finer points of spinal motion in their landmark text, Clinical Biomechanics of the Spine. Just in case your memory is a bit fuzzy (like mine), here's what's pertinent to our discussion. The axis of vertebral motion during extension varies widely from one area of the spine to another. Consequently, the effect of extension traction on the disc may vary widely from area to area as well. For instance, the axis of motion in the cervical spine is in the anterior portion of the disc whereas, in the lumbars, it's located posterior to the disc in the anterior portion of the spinal canal. Here's why this is relevant.
Under normal conditions, when the spine extends about the red axis seen here, the entire disc space opens up. The result, of course, is that mechanical loading onto the disc is reduced while the facet joints bear more weight and begin to slide over one another. In other words, the amount of pressure onto the disc is dramatically reduced during extension. Seen in this light, it's easy to visualize how spinal extension can be an effective tool for relieving pressure on the disc and promoting a reduction of disc bulging toward the posterior. This unloading of the disc in extension is no doubt responsible for much of the success associated with the famous McKenzie methods of lumbar extension exercise.
Conversely, the axis of motion during flexion (Yellow dot in Fig.1) is well forward in the disc, producing increased loading of the anterior disc space and unloading of the posterior portion of the disc. This large difference in the two axes of motion may explain why popular flexion-traction techniques, such as those developed by chiropractic pioneer James Cox, have also been so successful in helping to reduce the symptoms associated with bulging or herniated lumbar discs. Once you start to understand the underlying mechanics, it seems that both flexion and extension movements may have real utility as we attempt to reduce lumbar disc herniation. Unfortunately, many chiropractors still think of lumbar traction only in terms of simple long axis stretching or "decompression."
Okay...so it's simple then. Both, flexion and extension are just dandy for the lumbar discs...right? Well...yes and no. In a perfect world, we could simply measure the spine, determine if it is hyper or hypolordotic and then prescribe flexion or extension traction or exercise as indicated. Unfortunately, things are rarely that simple. As it turns out, the actual axis of motion for any individual may vary wildly if the disc is degenerated or injured. As a result, regardless of the patient's posture, it may be difficult to predetermine whether flexion or extension will be most beneficial in reducing disc symptoms. So, in keeping with the best traditions of science, I generally resort to trial and error. For example, if the L-spine is hypolordotic, I will generally try extension traction/exercise first. If extension is well tolerated, great! But if not, then I'll switch to flexion movements. My goal is always to stabilize the patient symptomatically prior to concerning myself too much about long term spinal correction. On the other hand, a hyperlordotic spine may encourage me to try flexion movements initially; but, if that doesn't work, you can be assured I'll switch to extension as I try to relieve the disc symptoms.
Okay...so what about the cervical spine, you say? Does it follow then that extension traction is necessarily a good thing for injured cervical discs as well? Unfortunately, the answer is probably, no. Fig. 3 shows the axes of motion during extension (red) and flexion (yellow) for the cervical vertebrae. As you can see, extension of the vertebrae around either axis will probably result in increased loading on the posterior disc space. While this is a motion well tolerated by healthy discs, it's not a great thing to be doing to a bulging or herniated disc. With this in mind, I have always taught that cervical disc symptoms should be considered a contraindication to extension traction methods.
The use of extension methods for disc decompression is foreign to many doctors. Hopefully, this article has stimulated your thoughts as to how extension movements may have a useful role as well in the treatment of lumbar disc disorders. Regardless of what method you choose, it bears remembering that any procedure which provokes or increases radicular pain should be discontinued or modified immediately. In other words, if it hurts when you do that, don't do that.
Dr. Mark Payne is the president of Matlin Mfg., a manufacturer and distributor of postural rehab products since 1988. For a Free, unabridged copy of this article or other information on postural chiropractic, please contact Matlin Mfg. Inc. at 1-334 448 1210.