Scientific Theories of Chiropractic
Chiropractic is based upon three related scientific
- 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.
- 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
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
"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."
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."
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
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
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.
- 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
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.
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 doctor of chiropractic 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,
Chiropractic treatment methods are determined by the
scope of practice authorized by New York 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 doctor of
chiropractic 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
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
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
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, 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
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.
- 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.
- Ibid., p. 11-12.
- Ibid., P. 26.
- Gelfan S. Tarlov I. Physiology of
the Spinal Cord, Nerve Root and Peripheral Nerve Compression.
Amer J Physiol 1956; 185: 217-229.
- 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.
- 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.
- 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.
- Haldeman S, Meyer BJ. The effect
of constriction on the action potential of the sciatic
nerve. S Afr Med J 1970; 44: 903.
- Luttges MW, Kelly PT, Gerren RA.
Degenerative changes in mouse sciatic nerves: electrophoretic
and electrophysiologic characterizations. Exp Neurol
1976; 50: 706.
- Wilcox G. Doctoral dissertation.
University of Colorado, 1975.
- 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.
- 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,
- 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.
- Hadley LA. Intervertebral joint
subluxation, bony impingement and foramen encroachment
with nerve root changes. Am J Roent Rad Ther 1951;
- Hadley LA. Constriction of the Intervertebral
Foramen. JAMA 1949; 140: 473-476.
- Hadley LA. Roentgenographic studies
of the cervical spine. Am J Roent 1944; 52: 173-195.