CHIROPRACTIC

The Scientific Brief Against Chiropractic:
Scientific Evidence Against Chiropractic

Chiropractic in Relation to Experimental Science

The fact that chiropractic is unsupported by any real scientific facts would alone be sufficient for its rejection as a method of treatment without further discussion. Nevertheless, it seems appropriate to examine the question objectively and consider the scientific disproof of the method.
In order to achieve a better understanding of the question, one must review as simply and clearly as possible certain concepts regarding the nervous system and the vertebral column. It is obvious that these few details cannot even approach a thorough survey of scientific knowledge on the subject.
The spinal nerves, which are the prime concern of chiropractic theory, extend from the vertebral column via the intervertebral foramina, which are short canals formed by the superimposition of pedicles jutting out from each vertebra. From the base of the skull to the pelvis, the vertebrae -- 7 cervical, 12 thoracic or dorsal, 5 lumbar, the sacrum, and the coccyx -- form a long bony mast which supports the head above and stands on the pelvis (of which the sacrum and coccyx are actually part.)
The sacrum and the coccyx are each a distinct bone. The sacrum is formed by the fusion of five sacral vertebrae into a single unit; the coccyx is a fusion of four to six rather rudimentary vertebrae. The cervical, dorsal, and lumbar vertebrae are all individual. The vertebrae have certain structural characteristics in common but also show certain regional differences in the various divisions of the vertebral column.
Each vertebra has a large cylindrical body anteriorly, with a bony arch extending backwards from it to form a circle; these circles, one above the other, form the spinal canal. On the bony arch, near its origin from the vertebral body on each side, there is a pedicle above and below. The vertebrae are so placed that each pedicle meets its neighbor, leaving between them and the vertebral bodies those orifices which are called intervertebral foramina. Through these foramina pass the spinal nerves.
Thus the vertebrae are aligned one above the other, vertebral body to vertebral body in front, and articular surface to articular surface on the arches behind. Between the vertebral bodies are discs which fill the spaces and are therefore called intervertebral discs. These discs resemble little cushions and are shaped like a biconvex lens. They are attached to the surfaces of the vertebral bodies above and below. They are relatively firm at their periphery, but soft and gelatinous in the center.
Finally, the bony arches of the vertebrae have two types of projection: one, called the spinous process, extends backwards from the arch in the mid-line (it is these spinous processes which are felt all down the back); the other, the transverse processes, extend laterally on each side from a position posterior to the intervertebral foramen.
If one now considers the vertebral column as a structural unit, one sees the column of vertebral bodies anteriorly, joined by the intervertebral discs as bricks are joined by mortar, with the bony arches behind. These bony arches have paired pedicles which enclose the intervertebral foramina on each side just behind the vertebral bodies. Farther back on each side one encounters the transverse processes, and finally in the mid-line of the back, the spinous processes. The whole column is bound together with various ligaments of great strength, on the anterior and posterior surfaces of the vertebral bodies and on the bony arches, their processes, and their joints. The muscles further strengthen and cushion the vertebral column.
Within the vertebral column, the circles formed by the bony arches described above are aligned to constitute a canal, called the spinal canal. The spinal canal contains the spinal cord, the trunk of nerves which is in continuity with the brain above. Neither the brain nor the spinal cord are in contact with the bones which protect them. These delicate nerve structures are completely enveloped by three concentric membranes, the meninges; respectively, the dura mater, the arachnoid, and the pia mater.
The dura mater is the most exterior membrane. Except over the first two cervical vertebrae, it is not attached to the walls of the spinal canal, but is separated from them by a space filled with fluid fat. Small fibrous bands fix it to the ligaments anteriorly. As each nerve trunk leaves the spinal cord, it receives a sheath of dura mater, a fibrous sleeve which accompanies it as far as the exit of the intervertebral foramen and there attaches to the periosteum.
The second meningeal layer, the arachnoid, adheres to the inner surface of the dura mater, separated from it only by a film of serous liquid. Further within, adherent to the spinal cord and to the nerves extending from it, is the third meningeal membrane, the pia mater. There is an appreciable space between the pia and the arachnoid, and it is in this space that the cerebrospinal fluid flows. The pia mater is connected to the dura mater by bands which cross the arachnoid.
At the exit of the intervertebral foramen, all of these membranes terminate on the nerve trunk; the pia, however, is continuous with the neurilemma, the membrane which covers the nerves beyond the limits of that foramen. There is appreciable play between the nerve and the bony walls of the intervertebral foramen. It will be shown later that it is illogical to postulate that constrictions can be produced at this site by small displacements of the vertebrae.
Turning now to the spinal nerves which pass through the intervertebral foramina, we find that there are 31 pairs -- 8 cervical (the first situated between the skull and the first cervical vertebra), 12 dorsal, 5 lumbar, 5 sacral, and 1 coccygeal. In addition, there are 12 pairs of cranial nerves which have their orifices in the base of the skull.
These 12 pairs of cranial nerves and the 5 pairs of sacral nerves are manifestly out of reach of chiropractic treatment, since the bones which form their orifices have in both cases fused into a single bone. Thus of the total of 43 pairs of nerves, only 26 pairs of spinal nerves can be influenced. It remains to be determined whether illnesses can be fostered or caused by pinching or irritation of these 26 pairs of nerves.
The spinal nerves are extensions of the spinal cord. The spinal cord is a nerve trunk connected above to the brain through a large orifice in the base of the skull called the foramen magnum; it extends from the foramen magnum down most of the length of the spinal canal. The spinal cord is therefore, anatomically, a prolongation of the brain, but its function is far less complex.
The spinal nerve which passes through the intervertebral foramen is formed of two nerve roots which derive from the spinal cord and unite into a single trunk before entering the intervertebral foramen. These two roots, one anterior and one posterior, are attached to the anterior and posterior surfaces, respectively, of the spinal cord, a little to the side of the mid-line. The nerve fibers of the posterior root are sensory: they bring impulses deriving from the stimulation of end-organs of general sensation to the spinal cord, brain centers. The fibers of the anterior roots are motor; they bring impulses deriving from the stimulation of motor cells to the striated or voluntary muscles. This stimulation may be the result of a simple automatic reflex, or a complex reflex mechanism, or a voluntary act brought about by a highly organized function of the brain.
In addition to these voluntary motor fibers, the anterior roots from the first dorsal to the second lumbar segments inclusive contain other nerve fibers which are called autonomic. The autonomic fibers innervate the smooth or involuntary muscles, i.e., those of the blood vessels, digestive tract, respiratory system, urinary and genital systems, and also secretory glands. They also innervate the heart. The result of their stimulation may be either an activation or an inhibition of the function concerned.
It must also be noted that these autonomic fibers which arise from the thoraco-lumbar region of the spinal cord distribute themselves widely throughout the body, thus forming the peripheral elements of that part of the autonomic system which is called sympathetic. But these are not the only autonomic fibers which innervate the smooth muscles and the glands. A separate system of autonomic fibers, called parasympathetic, are contained in the third, seventh, ninth, and tenth pairs of cranial nerves and in the second, third, and fourth pairs of sacral nerves. As we have seen, these nerves have their orifices in fused and immovable bones, and are therefore inaccessible to chiropractic. The entire parasympathetic system is thus beyond the influence of subluxations and of chiropractic.
According to chiropractic theory, a major cause of illness is the structural disturbance of that part of the vertebral column which is accessible to manipulation, and this disturbance provokes an alteration of nervous flow in the body in different ways. The brain and the spinal cord are nerve centers which innervate the body through 43 pairs of nerve trunks. Of these, only 26 pairs of spinal nerves can be the objects of chiropractic theory, which is therefore remarkably limited in scope. The brain, the spinal cord, 12 pairs of cranial nerves, and 5 pairs of sacral nerves are anatomically protected from subluxations and from chiropractic manipulation. But these inaccessible structures are of very great importance.
The importance of the brain and spinal cord is self-evident. The cranial nerves not only innervate the head, including the senses of smell, taste, hearing, and sight; but the tenth pair of cranial nerves, the vagus nerves, innervate also the organs of the neck, the respiratory apparatus, the heart and other structures of the thorax, and a large number of abdominal organs such as the stomach, the small intestine, part of the large intestine, the pancreas, the gallbladder, the liver, the spleen, and the kidneys. The sacral nerves innervate the pelvic organs and a considerable part of the lower limbs.
These details are set forth, not for the pleasure of confounding the chiropractors, but to set straight the record of anatomic truth. Why should the 26 pairs of spinal nerves accessible to manipulation have so much importance, and the rest so little? But the fundamental question must now be studied: can subluxation cause disease?
According to chiropractic theory, as outlined before, "structural defects" impair the distribution of nervous impulses. In other words, imbalances or displacements of vertebrae diminish or accentuate nervous impulses or their effects.
Let us first examine the former situation, that of diminution. In this case there may be in the intervertebral foramen (or elsewhere, for that matter) a partial or total blockage of nervous impulses. If there is partial blockage of impulses in a nerve fibre, the research of many neurophysiologists (Verworm, Kato, Fredericq, and numerous other eminent scientists of various countries) showed several decades ago that the impulse is transmitted more slowly in a zone of partial blockage, and resumes all its characteristics as soon as it reaches normal tissue. This is comparable to the effect of a damp zone in a powder train; the combustion would be slowed by the dampness, but would flare up in full force again as soon as it reached dry powder.
Thus, it is impossible for a partial blockage of nerve impulses in a particular zone of the nerve to affect the flow, since the impulses would resume their normal flow beyond the affected zone. The slowing effect would be limited to a distance of a few millimeters in the canal of the intervertebral foramen.
There remains the case of total obstruction of nervous flow. When no impulses pass in a nerve fibre, certain specific effects occur. The muscle it innervates becomes immediately paralyzed and limp, loses its reflex responses, and soon diminishes in thickness. Sensations are also lost. Trophic disturbances may also be observed: the skin becomes dry, thin, and abnormally smooth; the nails develop longitudinal ridges and become curved and brittle. The secretion of sweat is also disturbed.
These general effects, and others as well, according to the particular function of the affected nerve, may be observed daily in our hospitals -- not only as acute cases, but also as chronic cases in which the nerve pathways had been interrupted a long time before. A nerve which has been cut may be sewn together again, and the regeneration and return to function of the fibers may be observed. Never has any cause-and-effect relationship between loss of nerve function and other diseases been established. Only the specific disturbance caused by the particular loss of innervation can be demonstrated.
Obstruction in the intervertebral foramen with blockage of nerve impulses used to be the only basic hypothesis of chiropractic theory. More recently, however, chiropractors have tended to postulate a state of excitation in the intervertebral foramen. This state of excitation has never been proven by direct observation, nor has it been reproduced experimentally by proponents of chiropractic. What, then, is this other hypothesis worth?
Excitation of motor fibers produces contraction or tension in the muscle; excitation of sensory fibers sends sensory messages to the spinal cord via the posterior nerve roots. These sensory stimuli may cause a reflex response (that is to say, a direct stimulation of the corresponding motor fibre to the muscle or organ), or may be relayed to the brain, where the), would give rise to various sensations, notably that of pain.
Finally, there are the sympathetic nerves of the dorso-lumbar region which have been described above; they supply the vessels and the organs. The effects of their stimulation and of their interruption have been most thoroughly and successfully studied, beginning with the work of Claude Bernard in the earliest days of modern physiology. The resultant illnesses are clear-cut, few in number, and well documented. They are, in fact, rather rare.
In addition, scientific studies have shown some years ago that the action of these nerves is communicated to the vessels and organs by the intermediary of noradrenalin, a substance liberated at the nerve endings when the nerves are stimulated, or by acetylcholine in the case of the adrenal medulla. Scientists have also isolated or synthesized a whole series of drugs which block or neutralize the action of noradrenalin or of acetylcholine, and which are administered to patients when specifically required.
There is, therefore, nothing whatsoever in the scientific facts established by the masters of normal and abnormal neurophysiology -- facts which can be consistently reproduced experimentally, or observed clinically in patients -- to sustain chiropractic's fundamental hypothesis that obstructions in the mechanical structure of the human body are true causes of disease.
Indeed, in the field of human biology, chiropractic theory ignores a host of other facts discovered by human intelligence, facts which have infinitely widened the horizons of our knowledge and have provided explanations for many of nature's most important phenomena.
In biology there are, in addition to the nervous system, other systems, perhaps even more fundamental, which are relatively independent of the nervous system and which regulate bodily function. The research of the last three-quarters of a century has demonstrated the existence and the methods of function of the whole system of regulation of biologic activities by the endocrine glands. The materials secreted by these glands (hormones) enter directly into the circulation and are absorbed by the appropriate organs, and regulate the function of those organs by direct action on their cells.
These effects do not require the participation of the nervous system. In numerous experiments, they have been observed in tissues removed from the body and separated from all connections with the nervous system. Hundreds of thousands of studies have been done on the endocrine glands and their hormones; no scientist has ever traced a disease of (or related to) the endocrine glands to a mechanical obstruction affecting a peripheral nerve trunk.
Still more basic than these two regulatory systems, nervous and endocrine, is the inherent automatism which governs the function of organs as important as the heart, the digestive system, the urinary system, the smooth muscles, and the blood vessels. For example, the perfused heart, even though cut off from all nervous or endocrine influence and even if removed from the body, continues to beat as long as it is surrounded by a suitable medium. This was shown in the classic perfusion experiments. The same phenomena may be obtained with the other organs mentioned.
This is not to minimize the importance of the nervous system, nor of the system of endocrine glands. But their importance does not vitiate that of these other mechanisms, which may be considered more fundamental and are much more stable.
At the cellular level, to which chiropractic theory claims to extend, the same conclusions must be drawn. The media of public information have made the average citizen aware of the existence of the electron microscope and of the possibilities of its use in the study of cellular biology. In the body of a cell there are a whole series of submicroscopic components: mitochondria, microsomes, lysosomes, particles of endoplasmic reticulum, etc. Chemists have succeeded in isolating them and subjecting them to analysis. These particles contain enzymes, biochemical catalysts of reactions within the cell.
Nowhere in these extraordinary studies, constituting as they did an objective and systematic search for truth, was chiropractic theory validated. On the contrary, it was possible to attribute certain diseases to absences of certain enzymes from body cells. This type of cellular research has reached so high a degree of precision that it has been possible to specify which chemical molecule is responsible for a particular disease. Thus it has been found that the cause of certain blood diseases resides in the chemical composition of the hemoglobin molecule of the red cell -- more specifically in the absence of one of the amino acids which are component fragments of the hemoglobin molecule.
Not all illnesses are as yet so precisely understood, but one can already envisage the day when their causes will be understood down to the molecular level. These intracellular mechanisms are fundamental, and are completely independent of the nervous system. Chiropractic, therefore, scrutinized in relation to the cell itself, remains a contradiction to science.
Even though it is in opposition to true science, could not chiropractic have a practical value comparable to that of scientifically-oriented medicine?