Massage & Bodywork

MAY | JUNE 2019

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88 m a s s a g e & b o d y w o r k m a y / j u n e 2 0 1 9 technique CLINICAL EXPLORATIONS Dissecting Disk Pathologies By Whitney Lowe 1 about spinal function and intervertebral disk structure, the more we have realized disk pathology is not a simple structural problem at all. In addition, we can no longer say with any certainty that simply because somebody has disk damage or herniation and corresponding pain, that the two are causally related. So, let's explore what we have learned about the disk and how this plays a role in many of the back and leg complaints clients bring to us. ANATOMY There are two primary components to the intervertebral disk. The gel-like structure in the center is called the nucleus pulposus. The softer nucleus is surrounded by concentric layers of fibrocartilage with fibers in alternating directions. These concentric layers of fibrocartilage make up the annulus fibrosus (Image 1). The alternating layers in the annulus give it both pliability and strength. The primary function of the intervertebral disk is to manage the compressive loads of the spine during movements in multiple planes. The spine is curved to help manage and absorb some of these loads. Consequently, the disk shape has to accommodate the spinal curvature as well. So, in the lumbar region, where there is a natural lordotic curvature, the intervertebral disk is taller on the front side than the back (Image 2). If the spine loses its natural curvature, there are unequal forces on the disk and these long-term compressive loads lead to disk pathologies. The intervertebral disk has fibers that are enmeshed into the body of each adjacent vertebra. This helps maintain structural integrity between the disk and the vertebra. Realizing that there are fibers deeply embedded between the disk and the body of the vertebra helps debunk a common image that goes along with the layperson's term of a "slipped disk." In most cases, the disk does not actually slip (except in the instance of a condition called spondylolisthesis mentioned on page 89). Instead, compressive loads may cause the disk to change shape or bulge out in a particular direction. This pathological process is described in the pages that follow. Annulus fibrosus and nucleus pulposus. Mediclip image copyright (1998) Williams & Wilkins. All rights reserved. Annulus fibrosus Nucleus pulposus In 1934, William Mixter and Joseph Barr published a groundbreaking study in the New England Journal of Medicine. It was the first study that made a strong correlation between intervertebral disk herniation and the symptoms of sciatica. It set off several decades of intense focus on addressing disk pathologies that were blamed for a vast array of low-back pain problems. This time period has frequently been referred to as the "Dynasty of the Disk," during which many surgeries were performed to address back and lower-leg pain. Unfortunately, what became painfully clear was that many people not only didn't improve from the surgeries, but a large number actually got worse. In the latter part of the 20th century, advanced medical imaging technology allowed us to look at the disk with greater accuracy without invasive surgery. As a result, we now have a better understanding about the structure of the disk, factors that lead to degeneration and disk damage, and the role disk pathology may play in certain pain conditions. Interestingly, the more we have learned

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