This article first appeared in the November 2019 issue of Lifelines, the Life West student magazine.There is no denying the central nervous system is responsible for all communications that happen within the human body. Sensory information travels afferently to the brain and motor information travels efferently to the target cell, tissue, or organ. Both of these pathways utilize the spinal cord to transmit their messages almost instantaneously. It stands to reason that instability within this super highway’s infrastructure could become problematic if not addressed. B.J. Palmer and other founding figures of the chiropractic profession recognized this more than 100 years ago and identified “excessive trauma or toxins or thoughts” as key factors that contribute to spinal instability, which White and Panjabi  defined as an inability of the spine to maintain its proper alignment under physiologic load, which results in pain, tissue deformation, and nerve/spinal cord irritation. In order to understand how spinal instability develops, it is important to know the workings of the spinal column itself.
Similar to a metal spring, the spine functions to disperse stresses and loads throughout the human body. Although the spine looks like a single unit, the intricate relationship of the bones and layers of ligaments actually compartmentalizes the spine into three separate columns , each with a different capacity to withstand physiologic loading. The first column is made up of the anterior longitudinal ligament as well as the anterior portion of the vertebral bodies and intervertebral discs (IVD). The middle column consists of the posterior portion of the vertebral bodies and IVDs. The posterior column consists of the facet joints, pedicles, interspinous ligaments and spinous processes. Together, the anterior and middle columns bear 75-97% of the load the spine experiences, while under normal conditions the posterior column bears only 3-25% . The spine is no longer considered a stable unit when two of the three columns are unable to retain their proper form during physiologic loading. Considering the sheer number of structures that are involved with the stability of a single column, the number of factors that could affect the integrity of the entire spine is quite high.
Take, for instance, changes in the facet joints of the lumbar spine from something like sitting in a chair. In one study of 20 asymptomatic subjects , the normal lordosis of the lumbar spine while standing was shown to be 48.8° ± 14.7°. In a seated or kneeling position, the lumbar lordosis decreased to 16.6° ± 15.6°. Not only does the degree of the lumbar curve drastically change, the average height of discs in the lumbar spine also decreased when the subjects transitioned from a standing to a seated position (from 40.5 ± 7.7mm standing to 36.9 ± 7.1mm). This decrease in lordosis and disc height in the lumbar spine changes the normal load of each of the three columns of the spine, increasing the weight the anterior column bears while simultaneously decreasing the load upon the posterior column.
Capsular deformation that may accompany altered spinal curvature can trigger a wide range of neuronal and inflammatory effects . The facet capsular ligament is widely believed to be not only for structural integrity of the spine but heavily involved with mechanoreception and nociception [3,5]. Chronic inflammation can reinforce altered motion patterns within the joint and lead to a self-perpetuating cycle of pain, instability, and ultimately degeneration of the spinal column.
Toxins affect the spine much more slowly than trauma but still produce marked changes. It has been widely known since the 1940s that tobacco smoking causes lung cancer, but the effects that this toxin may have on the spinal column, namely the intervertebral disc, should not be forgotten. A recent in vitro study showed that high concentrations of nicotine (25nmol/L-300nmol/L) causes a significant decrease in DNA, glycosaminoglycans (GAG), and collagen content within the intervertebral disc . These three factors are key for maintaining the integrity of the intervertebral disc and ultimately, the stability of the anterior and middle columns of the spine. A decrease in DNA and GAG content within the IVD would lead to a degradation of the matrix, thus a decrease in the joint’s ability to maintain alignment during physiologic loading.
Thoughts are the final factor in disease cited by B.J. Palmer, and it has been demonstrated that psychosocial wellbeing plays a significant role in determining one’s rate of disability and pain . Somebody expressing chronic mental or emotional stress could experience elevated levels of cortisol release. When cortisol is continually released from the adrenal cortex during periods of emotional stress, the mechanism by which it functions as an anti-inflammatory begins to malfunction. Whether the chronic release of cortisol results in a down-regulation of glucocorticoid receptors and cortisol-resistance, or simply cortisol depletion, the result will always be inefficient modulation of inflammation and pain. This hypocortisolism has been linked to many diseases such as rheumatoid arthritis and osteoporosis as well as muscle and systemic tissue damage .
Functional spinal units that lack stability due to the effects of trauma, toxins, or thoughts will be unable to maintain their proper motion and alignment during physiologic loading. Oftentimes, the underlying issues of instability within the spine are cyclic and self-perpetuating, requiring an outside intervention to stop further problems from developing. Due to the multifaceted nature of spinal degeneration, when treating spinal dysfunction a chiropractor must be prepared to address all three aspects of the human condition.
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- Denis F. The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine (Phila Pa 1976) 1983;8(8):817–831.
- Bermel EA, Barocas VH, Ellingson AM. The role of the facet capsular ligament in providing spinal stability. Comput Methods Biomech Biomed Engin. 2018;21(13):712–721. doi:10.1080/10255842.2018.1514392
- Alamin TF, Agarwal V, Zagel A, Qeli A. The effect of standing vs. variants of the seated position on lumbar intersegmental angulation and spacing: a radiographic study of 20 asymptomatic subjects. J Spine Surg. 2018;4(3):509–515. doi:10.21037/jss.2018.08.03
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