The Foundation of the Spine: The Coccyx and the Sacrum

An analogy between the spine and a big tree will help to illustrate why many patients experience pain in this area. The trunk of a big tree (like the spine) has to support the canopy (the head) and numerous heavy branches (the upper limbs, ribs, and internal organs) that sprout from the trunk. This construction subjects the trunk to continuous mechanical stress and eventually the stress will affect the root system (the coccyx and sacrum bones).

The root system must be very strong and practically immovable to give adequate stability to the trunk and heavy branches of the tree. In calm weather, the tree ensures its symmetrical balance by having its branches spread in all directions and by evenly distributing gravitational stress among all the roots, which also spread in all directions. When a strong wind tilts the tree to one side, the symmetrical balance is lost and the roots from the opposite side of the tree sustain huge stress, which is many times higher than the weight of the tree (Figure 9-2). Using the physical principle of leverage, we can calculate the stress applied to the root system on the affected side of the tree. For example, if a tree weighs 500 pounds at its center of gravity, the affected part of the root system will sustain a stress of more than 5000 pounds.

Figure 9-2 Mechanical force sustained at the sacroiliac joint to balance the body is about 3 to 6 times the weight of the luggage if the spine is bent to pick up luggage. A similar mechanical stress occurs at the roots when the wind bends a tree.

The tree analogy explains why the foundation of the spine—the coccyx and sacrum—is so easily stressed and liable to be painful. Bending and twisting in an asymmetric manner are the predominant causes of lower back injury. The leverage described in the analogy with the tree is also applicable to our spine. For example, when a mother bends forward to pick up a 30-pound baby with both hands symmetrically, the stress on the spine and its foundation (sacrum and coccyx) could be 300 pounds. If the mother uses a correct bending posture, such as bending the knee first and staying close to the baby, the stress can be reduced to 100 pounds, which is distributed evenly between the muscles and joints on both sides of the body.

If our right hand picks up a 30-pound package (asymmetric action), the stress on the left sacroiliac joint and lumbar muscles on the left side can be more than 300 pounds, which will be distributed along the whole spine from the neck to the lower back. These are examples of the kind of potentially damaging stressful situations that our spine is exposed to daily, without our conscious awareness, in the workplace, at home, and during sports activities.

To correctly apply INMAS to the coccyx and the sacrum, an understanding of the anatomic structure of this area is important. The coccyx, which is also called the tailbone, is located at the base of the back. It consists of three to five fused bones. If we lose our balance and fall, the coccyx can break and a condition called coccygodynia may occur. We will discuss coccygodynia later in this chapter.

Above the coccyx are five more fused bones, the sacrum (S1-S5). The sacrum is a spade-shaped structure that is fixed between the two halves of the pelvis, which is the only structure that connects the spine to the lower limbs. Referring to the tree analogy, the two fused, relatively immovable bones—the coccyx and the sacrum—represent the roots of the tree. The two bones called ilium on either side of the pelvis make a joint on either side of the sacrum, and these are called the sacroiliac joints.

The sacroiliac (SI) joints differ from other joints. They are thicker and stronger and can move only a few millimeters (Figure 9-3). This relative immobility of SI joints stabilizes the spine against gravitational forces. The SI joints are also subject to the tremendous stresses and strains created by the forces of asymmetric imbalance as discussed in the above examples. The SI joints have to support the trunk, shoulders, arms, and head and to ensure a full range of motion.

Figure 9-3 Sacroiliac (SI) joints. A and B, Anterior and posterior views of the SI joints. C, Schematic horizontal section through the SI joints.

(From Jenkins D: Hollinshead’s functional anatomy of the limbs and back, ed 8, Philadelphia, 2002, WB Saunders.)

During locomotive activity such as walking, running, carrying weights, raising the arms, or dancing, the joints transfer weight from the spine to the hip bones. The pathological effect of excessive or overextended stress will accumulate in the joints and result in soft tissue disease.

These joints are innervated by the lower lumbar and sacral nerves, as a result of which pathological conditions in the joints can produce lower back pain and sciatica. For example, when the SI joints are inflamed, movement of the spine in any direction causes pain in the lumbosacral part of the spine. Usually the pain is more pronounced at the limit of forward flexion, since the hamstring muscles hold the hip bones in a relatively fixed position while the sacrum is rotating forward as the spine bends down.

INMAS is effective in treating painful symptoms related to the SI joint region. Most SI joint pain is caused by inflammation of the soft tissues such as nerves and ligaments. When needles are inserted into inflamed tissues, the needle-induced lesions break the blood vessels, thus stimulating the local defense immune reaction. As a result of the immune reaction, inflammation of the soft tissues of the SI joint is reduced. The needle-induced secretion of endorphins from the spinal cord and the brain reduces the physiological stress caused by the joint pain, thereby accelerating tissue healing. Eventually, this process restores normal SI joint function. The degree of recovery of SI joint function depends on the degree of the injury and the self-healing capability of the body.

The INMAS protocol for treating SI joints is provided at the end of this chapter.

Lumbar Spine (L1-L5)

The lumbar part of the spine is situated above the sacrum. The lumbar spine has five large vertebrae, and each vertebra has two upper facets (superior articular facets) that emerge from the top and two lower facets (inferior articular facets) that descend from the bottom (Figure 9-4).

Figure 9-4 Representative vertebrae from the spinal column. A, Cervical region. B, thoracic region. C, Lumbar region.

The functional unit of the lumbar spine consists of two adjacent vertebrae with an interposed intervertebral disk. The disk is a hydrodynamic structure that permits weight bearing and ensures the mobility of the unit itself and the mobility of the entire vertebral column. The two inferior facets of the vertebra above are loosely joined to the two superior facets of the vertebra below. During forward-and-back motion such as in fast dancing, the facets slide across each other. A side view shows that the lumbar spine is concave relative to the back of the body, and this is termed the lordotic curve.

The lumbar spine is located between two different and functionally conflicting parts of the spine and therefore is always subjected to substantial stress. Below the lumbar spine is the immobilized stability of the sacrum and above it are the heavy but flexible structures of the thoracic and cervical spine, which are required to be able to maintain a full range of spontaneous and rapid movement. This is why the lumbar spine is constantly engaged in trying to mediate an acceptable compromise between two conflicting functions, providing enough of both strength and flexibility at the same time.

Additional stress on the lumbar spine is created when a person holds weight in their hands with the arms extending away from the center of gravity of the body. In an upright posture the lumbar spine is supporting the axial compressive forces from the weight of the head, which is about 10 to 15 pounds, the weight of the upper limbs, and any additional loads that the upper limbs are carrying. When this compressive force is greater than half the body weight, particularly, the spine becomes unstable.

Because of these factors the lumbar spine is subject to a greater amount of constant stress than any other part of the spine, due to:

Thoracic Spine (T1-T12)

The thoracic spine has 12 vertebrae, and each vertebra has a pair of ribs attached to it. The ribs form a cage that holds open a space for creating a partial vacuum for inflating the lungs. The rib cage also protects the heart, lungs, and liver. The upper 10 ribs arise from the spine and are joined at the front. This allows the spine only a limited range of motion. Side views show that this part of the back is slightly concave relative to the front of the body, and this is termed the kyphotic curve.

The two lower ribs are short and are called floating ribs. They do not enclose anything, but they allow a broader range of motion than the first 10 thoracic vertebrae. The joints between the last thoracic vertebra and the first lumbar vertebra (between T12 and L1) also facilitate side-to-side rotation of these relatively immobile regions. This rotation implies a significant amount of wear and tear on these lowest two thoracic vertebrae and may result in various pain syndromes and degenerative diseases like osteoarthritis.

Cervical Spine

The cervical spine has seven vertebrae. These vertebrae get progressively smaller as they approach the bottom of the skull (see Figure 9-4). The cervical spine is the upper part of the spine and is capable of a great range of motion, in contrast to the foundation of the spine, the sacrum and coccyx, which has fused bones and almost immovable sacroiliac joints. For instance, the cervical spine allows the neck to turn 90 degrees in either direction, the ear to almost touch the shoulder, and the head to lean backwards more than 70 degrees.

The cervical spine differs from other parts of the spine in its agile motion and its ability to perform other important tasks; for instance, in addition to supporting the head, the neck provides a passage for air, food, nerves, and blood vessels.

The cervical spine is composed of two major complexes: the upper cervical segment (C1 and C2) and the lower cervical segment (C3 to C7). The occipital bone of the skull sits on the ring-shaped bone C1, which is called the atlas. The joint between them (0-C1), which is the first joint of the cervical spine, is called the atlantooccipital (AO) joint. This joint provides a very important function by anchoring the skull to the spine, and it is therefore necessarily the most immobile joint of the neck spine.

The second cervical vertebra, the axis, is the strongest of the cervical vertebrae. C2 has two large horizontal flat bearing surfaces called the superior articular facets. The atlas, C1, bearing the skull on top of it, rotates on these articular facets.

The distinctive feature of C2 is a blunt toothlike process called the odontoid process, or dens, projecting superiorly from the body (Figure 9-5). C1 uses the dens of C2 as its pivot for rotation. The front inner surface of the ring-shaped C1 is attached to the dens of C2, allowing C1 with the skull on top of it to rotate against the dens.

Figure 9-5 Posterosuperior views of the atlas (A) and axis (B). C, Superior view of the atlantoaxial joint.

(From Jenkins D: Hollinshead’s functional anatomy of the limbs and back, ed 8, Philadelphia, 2002, WB Saunders.)

The joint between C1 and C2, called the atlantoaxial (AA) joint, is the most mobile part of the spine. Fifty percent of all cervical rotation occurs at the AA joint.

The first two vertebral joints differ from all other vertebral joints because their main function is to allow head rotation. C1 and C2 are jointed by ligamentous integrity, and not by bony facets as are all other typical vertebrae.

Among all vertebral joints the AO joint is the most immobile, whereas the AA joint is the most mobile. This functional characteristic makes the AA joint more vulnerable to wear and susceptible to pathological conditions like inflammation and arthritis.

The use of homeostatic acupoints (HAs) to implement functional restoration, as well as reducing or eliminating pain, makes it an effective modality in reducing inflammation, rebuilding the function of the joints, and relieving and controlling related pain syndromes.

The facet joint between C2 and C3 is a transitional structure located between the rotation joint above C3 and the flexion-extension joints below C3. The cervical spine from C3 to C7 is organized such that it can rotate and simultaneously flex forward or laterally, or extend backward. The cervical vertebrae have to maintain enough stability to support the head, which weighs 10 to 15 pounds, while providing enough flexibility to perform these motions.

The peripheral nerve network in the neck region is some of the most complicated nervous wiring in the body. Eight cervical nerves emerge from the intervertebral foramen to form the cervical plexus from C1 to C4, and brachial plexus from C5 to T1. The intervertebral foramen is the passage from which the spinal nerve emerges. The neck is also the passage for the autonomic nervous system, which balances the physiological activities of the majority of the internal organs. Thus, pathological neck problems will affect not only the head and the arms but many different organs ranging from the brain to the large intestine.

A functional unit of the spine consists of two neighboring vertebrae: one above and one below. Examination of what happens to a typical cervical functional unit during a car accident will help to explain how excessive motion of the neck or exposure to sudden external forces can cause neck problems and pain.

In a car accident a sudden external force causes the head to bend forward (forward flexion) and the upper vertebra slides forward about an axis of rotation. The anterior intervertebral disk space narrows, the posterior intervertebral disk space widens, and the intervertebral disk deforms. As a result of this excessive narrowing of the anterior intervertebral space, there may be damage to the cartilage of the anterior joint surface, and the intervertebral disk may be broken and pushed backward. The widened posterior joint may break the joint capsule or even cause tearing of the ligaments. The broken intervertebral disk becomes herniated and the damaged joint surface produces pain and can cause arthritis in the future.

Rotation of the cervical spine is a coupling motion that involves both rotation and lateral flexion. For example, when the head turns to the left, the upper vertebra rotates to the left while its left intervertebral disk space narrows and its right intervertebral disk space widens. When this rotation is caused by violent force, the sudden closure of the left intervertebral disk space will cause damage to the cartilage of the joints, break the intervertebral disk, and force it to the right. Rotation caused by violent force also may cause injury to the spinal nerves: the left intervertebral foramen becomes smaller and pinches the left spinal nerve, and the broken intervertebral disk bulges to the right and pushes the right spinal nerve.

During a whiplash accident, the horizontal force from the back causes the neck to overextend and overflex (Figure 9-6), which causes damage to both posterior and anterior joints. In addition, the translational back-and-forward movement of the upper vertebra closes the vertebral canal, which causes injury to the spinal cord. Understanding the basic mechanical structure of the spine and the nature of pathological damage sustained by the spine during an accident is the key to effective acupuncture treatment for back pain.

Figure 9-6 Overextension and overflexion during a “whiplash” injury.

(From Wall P, Melzack R: Textbook of pain, ed 4, Edinburgh, 1999, Churchill Livingstone.)

The INMAS protocol for treating whiplash will be provided in the end of this chapter. Please note that in the case of whiplash, pain symptoms such as neck pain, lower back pain, and upper back pain are all closely related because functionally and anatomically all three parts of the spine—the neck, the upper back, and the lower back—are interrelated structures that should be understood as one whole entity and treated as such.

All the components of the back are so dependent upon each other that a problem in one structure can damage all the others. For example, a mechanical neck injury causes inflammation in spinal joints, which will strain muscles, and chronic muscle strain can contribute to arthritis in the spinal joints. Neck pain and back pain are clinically coupled.

Muscle strain can lead to disk displacement, and displaced disks can further strain the muscles. Motions such as excessive forward flexion, excessive backward extension, or excessive lateral rotation cause injuries to bony joints that involve cartilages, disks, capsules, and ligaments. These injuries strain the muscles, and strained muscles irritate the spinal nerves. All these pathological changes to the basic mechanical structure of the spine produce pain, and eventually this pain can trigger chronic problems such as arthritis and degenerative diseases.

The Shortened Muscle Syndrome

Muscles become shortened for protective reasons, to prevent further damage to healthy muscle tissue when it is subjected to pathologic factors, such as cold, fatigue, repetitive overuse or overstretching, low oxygen, or deficient blood circulation. When a muscle becomes shortened a domino effect is initiated that can generate many painful conditions. Muscular shortening gives rise to tension in the tissues by pulling tendons and their attachments and by offering resistance to healthy stretching. Thus, the shortened muscles and the stressed tendons and attachments eventually cause such symptoms as neck and back pain, epicondylitis, tendinitis, and tenosynovitis. All of these symptoms share the same etiology, although they appear dissimilar and occur at different anatomic sites.

Shortened muscles limit the range of motion of joints. For instance, a pathological condition called “frozen shoulders” is a result of shortening of all the muscles around the shoulder joint in addition to a capsular problem like inflammation. The shortened muscles increase pressure on the articular surface of a joint, which results in joint pain (arthralgia). Muscle shortening is also often responsible for joint misalignment. For example, the shortened muscle (extensor hallucis longus) of the foot causes angulation of the great toe (hallux vulgus) and a painful bunion. Muscle shortening contributes to pathologic conditions of joints, such as restriction of the range of motion and misalignment, and eventually leads to degenerative arthritis and osteoarthritis. Shortened muscles also put pressure on the nerves and produce an entrapment syndrome. For example, carpal tunnel syndrome is a result of shortening in the pronator teres or pronator quadratus muscles.

The paraspinal muscles, when shortened, draw two adjacent vertebrae closer together, which narrows the intervertebral space and foramen (Figure 9-7). The results are a bulging disk and a compressed nerve root. A vicious circle is gradually built up: shortened muscles cause compressed nerve roots (radiculopathy), and compressed nerve roots lead to further muscle shortening.⁴

Figure 9-7 Shortened paraspinal muscles across an intervertebral space compress the disk and nerve root.

(From Filshie J, White A: Medical acupuncture: a Western scientific approach, Edinburgh, 1998, Churchill Livingstone.)

Acupuncture treatments can break this vicious circle by using needles to produce a minimal tissue injury, which stimulates the relaxation of muscle stress. The primary goal in the treatment of muscle shortening is relaxation of the affected muscle, and acupuncture needling achieves this goal more swiftly and precisely than any other medical modality. When a fine acupuncture needle pierces a muscle, it pushes aside tissue, disrupts the cell membrane, and inflicts a minute tissue injury, which mechanically creates a brief outburst of microcurrents (injury potentials). The microinjury that results from needling generates relatively longlasting currents that stimulate the mechanism of repair and regeneration of the affected tissue (see Chapter 3). Thus, acupuncture treatment eliminates the pathological condition responsible for muscle shortening. After treatment a patient feels either no pain or a significant alleviation of pain.

This mechanism explains the efficacy of acupuncture treatment in addressing pain syndromes resulting from radiculopathy or pathological conditions of the joints such as osteoarthritis.

Bursitis

A bursa is a small fluid-filled sac that reduces friction between tissues. Excessive or repetitive use of a joint irritates the bursa and causes it to swell, resulting in pain during movement. The principal symptom of acute bursitis is sudden severe pain resulting in limitation of motion of the affected joints. A chronic bursitis condition may develop if an attack of acute bursitis is left untreated. Acupuncture needling is a very effective modality for treating acute bursitis but its effectiveness decreases proportionally to the degree of development of the chronic stage of the disease. Bursitis causes pain in the bursa and also in the muscles. The affected muscles become shortened and blood circulation is reduced. Needling is able to relax the muscles and increase blood circulation as well as stimulating an immune reaction and thus reducing the inflammation of the bursa.

Spinal Stenosis

Lumbar spinal stenosis is defined as a condition involving any type of narrowing of the spinal canal, nerve root canal, or tunnels of intervertebral foramina.⁵ Spinal stenosis can be either congenital or acquired. Acquired stenosis may be due to degenerative conditions (spondylolisthesis, see below), failed medical procedures (postlaminectomy, postfusion, postchemonucleolysis), or posttraumatic injuries, or it may be secondary to disk herniation (see below). Narrowing can occur in one or several locations of the same vertebral segment or it can affect several segments. The canal space can be narrowed by pathological changes in the soft tissues, scar tissue, or bony tissue impingement (bone spurs). Severe stenosis results in nerve compression. Soft tissue encroachment or abnormal bone growth such as osteophyte formation reduces the size of the intervertebral foramen and causes foraminal stenosis.

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