Scientific Theories of
Chiropractic
Chiropractic is based upon three related scientific theories:
1. Pathological disease processes may be influenced by disturbances of the
nervous system. Many factors have been implicated as impairing health, such
as hereditary and genetic anomalies; improper rest; lack of exercise; inadequate
and improper nutrition; overindulgence; foods tainted by pesticides,
insecticides, herbicides, fertilizers and preservatives; improperly cooked
and/or processed foods; contaminated water; air pollution; stress, bodily
insults and trauma; and the relative virulence and density of pathogenic
organisms (bacteria and viruses). In addition to these factors, disturbances
of the nervous system mediated primarily by the musculoskeletal system may
also be an important factor contributing to disease etiology. Chiropractic
maintains that proper structural and biomechanical integrity are important
for the maintenance of homeostatic balance and resistance to disease. Agents
that irritate bodily organs and structures, upset homeostasis, precipitate
a bodily response that is mediated in part by the nervous system. An impaired
nervous system may diminish the body's defensive capabilities, its ability
to adapt to internal or external stress and environmental change thus
contributing to its susceptibility to disease etiology. Conversely, an impaired
nervous system may affect adversely homeostatic balance, lowering bodily
resistance as sometimes evidenced by functional disturbances without overt
pathology, and which tend to weaken the body's ability to resist disease.
In this manner, the nervous system may be the root of some pathological process.
2. Disturbances of the nervous system may be the result of derangements of
the musculoskeletal structure. Two broad and otherwise general theories have
been identified in chiropractic by scientific researchers. One has been called
the "biomechanics hypothesis," and the other the "nerve compression
hypothesis."(1)
According to research scientists, the former consists of "chronic vertebral
deviations (classical subluxations) or postural defects which may put mechanical
strain on soft tissues associated with the spine: the periosteum, ligaments,
fibrous capsules of joints, discs, as well as tendons, fascia and body muscles.
These tissues form an essential part of the spine as a mechanical system,
enabling it to support large loads through a wide range of movement. If the
mechanical disorder is uncorrected, the soft tissue may undergo change, and
these would exacerbate the disorder. Thus, discs may undergo thinning or
protrusion. Ligaments and joint capsules may become fibrotic and thickened.
Such changes would often tend to aggravate the mechanical disorder, further
disturbing the normal alignment of the vertebrae. Stretched muscles would
tend to contract, owing to reflex servomechanisms, and possibly go into spasms
or sustained contraction. The resultant asymmetry of forces may again exacerbate
the mechanical malfunctioning.
"These effects, sustained muscle contraction and irritation of the deep tissues
of the spine are potential sources of pain. Deep pain, originating in the
soft tissues of the spine may be referred to peripheral structures, especially
if the sensory fibers from the latter enter the cord through the same dorsal
roots as those conveying pain signals from the affected tissue of the spine.
The reflex reaction to the pain itself may put additional tensions on the
spine. In this way vicious circles are established, which prevent restoration
of normal mechanical relations within the spine and at the same time, generate
abnormal reflex activity, owing to stimulation of pain receptors and reflex
responses to stretch of muscles and tendons." (2)
In contrast, the nerve compression hypothesis contends that, "aberrant neural
activity results from mechanical disorders of the spine due to compression
of spinal nerves at the intervertebral foramina. This hypothesis still occupies
a central place in the chiropractic rationale ..." (3)
The latter hypothesis above represents the "classical subluxation" theory
in chiropractic. Recent research in spinal and musculoskeletal biomechanics
is beginning to receive increased attention in this area. Several important
research developments in the past ten years underscore the need for more
research on this aspect of chiropractic theory.
Recent studies have shown that the spinal nerve roots appear to be
uncharacteristically sensitive to pressure and compression in contrast to
previous studies on peripheral nerves. (4-6)
According to Sharpless at the University of Colorado,
"...the dorsal [nerve] roots are exquisitely sensitive to compression block
when they are compressed within a few centimeters of their entrance to the
[spinal] cord,far more than had been previously supposed. Compound action
potentials representing volleys of nerve impulses in myelinatedfibers are
reduced to about one-half their normal values by a pressure of approximately
20 mm Hg. [mercury] in the roots... " (5) and,
"A pressure of only 10mm Hg. produced significant conduction block, the potential
[of nerve impulses] falling under 60 percent of its initial value in 15 minutes.
With higher levels of pressure, we have observed incomplete recovery after
many hours of recording." (6)
Further research has also shown that rapidly conducting and large diameter
nerve root fibers are the most susceptible to compression and pressure blocks
(7-9) and that small nerve fibers may be more sensitive to anoxia and ion
imbalances created by pressure on the nerve.(8-11) It has also been found
that axoplasmic flow, the movement of sustaining nutrients and chemical mediators
is also susceptible to various forms of compression. (9) Dr. Luttges (PhD)
another researcher at the University of Colorado has found that, "[nerve]
compression produced by constrictive cuffs (approximately one-third to one-half
reduction in nerve diameter) was found to produce degenerative effects different
from, but as profound as, those produced by nerve section." (10)
Intervertebral subluxations have also found a place in medical literature.
In fact in the early 1950's Hadley found evidence of nerve root compression
in many postmortem examinations. These subluxations were particularly prevalent
in the cervical and lumbar areas of the spine. (11-16) More recently, Epstein
indicated that nerve root entrapment and compression may be responsible for
such things as sciatica; intermittent claudication, an ischemic condition;
and other similar types of conditions. (12) This closely parallels Sunderlands
theory that "compression first leads to venous obstruction followed by capillary
circulation disturbances resulting in anoxia and finally irreversible ischemic
damage."
Sunderland feels that in the absence of overt pathology, e.g., osteophytic
enlargement [osteo-arthritis], malignancies, etc., that compression is the
result of apophyseal joint swelling secondary to [classical] subluxation
of the joint and trauma to the capsule reducing the cross-sectional area
of the intervertebral foramen through which the nerve passes resulting in
compressive distortions of the tissues in the foramen. (13)
Cailliet states that, "pain in and from the neck results from the mechanical
factor of encroachment of space and impairment of movement. Decrease in the
space in which pain-sensitive tissues lie or through which they pass compresses
these tissues, resulting in possible pain and loss of functions. Pain is
more apt to occur if pressure is acute and transient, whereas loss of function
is more likely as pressure is prolonged and continuous. The sites at with
tissues are most likely to compress are the intervertebral foramina and within
the spinal canal. The tissues in these specific areas are nerves and their
coverings, blood vessels, ligaments, joint capsules, and dura mater. Encroachment
of space resulting in pressure upon these tissues may result in pain or loss
of function."(14)
A prominent orthopedic surgeon and researcher Kirkaldy-Willis claims that
ninety percent (90%) of patients with low back pain have "dysfunction,"
indicating that changes exhibited are mainly those of abnormal function with
slight anatomic changes to the three joint complex, the intervertebral disc
and zygapophyseal joints. Of the remaining ten percent (10%) he claims that
fifty percent (50%) of those have lateral nerve root entrapment. With dynamic
recurrent lateral entrapment there is a laxity of the posterior joints and
of the annulus causing abnormal movement of the vertebrae resulting in a
narrowing of the lateral nerve canal and tapping on the main spinal nerve
as this passes along the canal. Dr. Kirkaldy-Willis indicates that manipulation
is an effective method of treatment for both patients with dysfunction and
lateral nerve root entrapment. (15)
Other conditions involving the motor and motion units of the spine are stretching
and traction injuries to the nerve roots and chronic irritations of the neural
complex from adhesions, osteoarthritis, fibrosis, etc. [nerve root entrapment],
and disc lesions such as herniations, discogenic diseases etc., will affect
the neural complex.
In all likelihood a multiplicity of factors are responsible for the clinical
manifestations that chiropractors experience in practice rather than a single
mechanism. Many of the different categories or theories of causation, however,
may be classified as variant forms of subluxations in chiropractic so that
the term "subluxation" assumes a broader and more diverse meaning in chiropractic
than in classical literature. The above information demonstrates, albeit
briefly, that musculoskeletal derangements may indeed have an affect on the
nervous system. Subluxations of vertebral and pelvic segments represent common
chiropractic mechanical clinical findings in man. Extended abnormal secondary
involvement of the nervous system may result from disturbances, strains,
and stresses arising with the musculoskeletal system due to mankind's attempt
to maintain an erect posture. These mechanical lesions or subluxations are
a common result of gravitational strains, asymmetrical activities and efforts,
and developmental defects or other mechanical, chemical, or psychic irritations
of the nervous system.
3. Disturbances of the nervous system may aggravate pathological processes
in various parts or with various functions of the body. Vertebral and pelvis
subluxations may be involved in common functional disorders of a visceral
and vasomotor nature, and at times may produce phenomena that relate to the
special organs.
Under predisposing circumstances, almost any component of the nervous system
may directly or indirectly cause reactions within any other component by
means of reflex mediation. The conjunction of independent causes of bodily
dysfunction may jointly have more serious debilatory effects than either
cause might have had separately. Subluxations may contribute to the "triggering"
or exacerbating of certain types of neurovascular and neurovisceral
instabilities. Correction of the spinal [manipulative] lesion is often imperative
for effective total management of a patient's case.
Diagnostic Methods
The doctor of chiropractic conducts a systematic and thorough physical
examination using the methods, techniques, and instruments that are standard
with all health professions. In addition, a postural and spinal analysis
is included.
The chiropractic physician uses the standard procedures and instruments of
physical and clinical diagnosis and is well acquainted with the need for
differential diagnosis. Diagnostic roentgenology, especially as it relates
to the skeletal system, is a primary clinical diagnostic aid in chiropractic
and has been since the early 1900's.
In addition, doctors of chiropractic are knowledgeable in the standard clinical
laboratory procedures and tests usual to modern diagnostic science. Each
accredited college has a laboratory licensed to carry on clinical laboratory
examinations, including work in cytology, chemistry, hematology, serology,
bacteriology, parasitology, and electrocardiography.
Treatment Methods
Chiropractic treatment methods are determined by the scope of practice authorized
by Kansas law. Essentially, treatment methods include chiropractic manipulation,
necessary dietary advice and nutritional supplementation, adjunctive
physiotherapeutic and supportive measures, and professional counsel.
The most characteristic aspect of chiropractic practice is the correction
(reduction) of a subluxated vertebral or pelvic segment(s) by means of making
a specific, predetermined adjustment. The purpose of this correction and
its determination is to normalize the relationships of segments within their
articular surfaces and relieve any attendant neurological, muscular, and
vascular disturbances.
The corrective structural adjustment by a chiropractic physician should not
be confused with other forms of manipulation. Manipulative therapy in one
form or another is used in all the healing arts. Mobilization is putting
a joint through its normal range of motion, by a therapist, in order to stretch
muscles and break adhesions. Osteopathic manipulation is designed to increase
joint motion and relieve fixations. On the other hand, chiropractic corrective
adjustment is made only after careful analysis, delivered in a specific manner,
to achieve a predetermined goal. It is a precise, delicate maneuver, requiring
special bio-engineering skills and a deftness not unlike that required for
other specialties. Rarely is the process painful.
Most chiropractic corrective adjustments involve the articulation of the
spinal column and extremities. Some techniques, however, are light-touch
reflex adjustments that involve the neurovascular, neurolymphatic, and
neuromuscular systems, gentle manipulation and passive mobilization.
Vitamin and mineral food supplementation can, if professionally supervised,
serve to prevent the onset or assuage the existence of some types of dysfunction
of the nervous system and other tissues. If deemed necessary in case management,
dietary regimens and nutritional supplementation are often advised as adjunctive
therapy.
Physiotherapeutic methods and procedures are frequently used as adjunctive
therapy to enhance the effects of the chiropractic adjustments. Such procedures
may include the use of diathermy, galvanic currents, infrared and ultraviolet
light, ultrasound, traction, paraffin baths, hot or cold compresses, acupuncture,
hydrotherapy, heel or sole lifts, foot orthotics, and other commonly utilized
modalities when indicated. Taping and strapping and other forms of first
aid are often used in injuries of the extremities. Injuries of the neck,
lower back, elbow, knee and ankle may call for the use of supportive collars
and braces during recuperation, to guard against re-injury, and to assist
healing and strengthening. Rehabilitative exercises, as a physical therapy,
comprise an important aspect of professional counseling to assist recovery
and prevent further strain.
Counsel is often given in such areas as dietary regimens, physical and mental
attitudes affecting health, personal hygiene, occupational safety, lifestyle
habits, posture, rest, work, and the many other activities of daily living
which would enhance the effects of the chiropractic adjustment. Chiropractic
is concerned with the total individual; his or her health, welfare, and survival.
Professional chiropractic councils on diagnosis and internal disorders,
diagnostic imaging, behavioral health, neurology, nutrition, orthopedics,
physiological therapeutics, sports injuries and physical fitness, and technique
strive to keep the field abreast of the latest scientific and technological
advancements providing even more efficient methodology.
Consultation and Referral
Under chiropractic care, a patient is either treated or referred after a
comprehensive examination, arrived at by utilizing an orthopedic and neurological
examination, an x-ray examination, laboratory procedures, or whatever other
procedures are necessary to determine the type health care best suited for
the patient's complaint.
References
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Suh CH, Sharpless SK, Macgregor RJ, Luttges MW, Researching the
Fundamentals of Chiropractic (Summary of Research, 1971-1973). The University
of Colorado, Boulder, Colorado, 1974, P. 11.
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Ibid., p. 11-12.
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Ibid., P. 26.
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Gelfan S. Tarlov I. Physiology of the Spinal Cord, Nerve Root and
Peripheral Nerve Compression. Amer J Physiol 1956; 185: 217-229.
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Sharpless SK, Groves P, Cobb S, et. al. Neurophysiology of Nerve
Compression and joint Fixation. The Fifth Annual Biomechanics Conference
of the Spine, Biomechanics Laboratory, University of Colorado, Boulder, Colorado,
December 1974, p. 219-277.
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Sharpless SK, Susceptibility of spinal roots to compression block.
In: Goldstein M. The Research Status of Spinal Manipulative Therapy, US
Department of Health, Education and Welfare, Public Health Service, National
Institute of Neurological and Communicative Disorders and Stroke monograph
no. 15, Bethesda, MD 20014, DHEW Publication No. (NIH) 76-998, February 1975,
p. 155.
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Gasser H., Erlanger J. The role of fiber size in the establishment
of nerve block by pressure or cocaine. Am J Physiol 1929; 88: 581-591.
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Haldeman S, Meyer BJ. The effect of constriction on the action potential
of the sciatic nerve. S Afr Med J 1970; 44: 903.
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Luttges MW, Kelly PT, Gerren RA. Degenerative changes in mouse sciatic
nerves: electrophoretic and electrophysiologic characterizations. Exp Neurol
1976; 50: 706.
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Wilcox G. Doctoral dissertation. University of Colorado, 1975.
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Jones D, Luttges MW. Alterations in passive electrical parameters
of nervous tissue and their relation to conduction block. AAAS, Southwestem
and Rocky Mountain Abstract 180, 1977.
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Sjostrand J, et al. Impairment of intraneural micro-circulation,
bold-nerve barrier and axonal transport in experimental nerve ischemia and
compression, In: Korr IM, The Neurobiologic Mechanisms in Manipulative Therapy,
New York, Plenum Press, 1978, p. 337-355.
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Luttges MW, Gerren RA. Compression Physiology: Nerves and Roots. In:
Haldeman S, Modern Developments in the Principles and Practice of Chiropractic,
New York, Appleton, Century & Crofts, 1980, p. 65-92.
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Hadley LA. Intervertebral joint subluxation, bony impingement and
foramen encroachment with nerve root changes. Am J Roent Rad Ther 1951; 65:
377-402.
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Hadley LA. Constriction of the Intervertebral Foramen. JAMA 1949;
140: 473-476.
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Hadley LA. Roentgenographic studies of the cervical spine. Am J Roent
1944; 52: 173-195.
