This chapter presents an overview of the background and basic concepts of Dynamic Chiropractic. The normal motions of spinal and related articulations, general considerations of spinal fixations, the different types of fixations, the significant physiologic mechanisms associated, a comparison of traditional and modern definitions of the vertebral subluxation complex, and other basic concepts are summarized.

In 1936, a small group of Belgium chiropractors began what was to be a long research project. Its aim was to study what chiropractors refer to as a subluxation, which is traditionally defined as an incomplete dislocation, a displacement in which the articular surfaces have not lost contact, or a partially reduced (spontaneously) dislocation.

Outstanding within the Belgium group were Drs. H. Gillet and M. Liekens. These investigators, who have been involved in this study for more than half a century, soon found that the clinical phenomenon of subluxation was a great deal more complicated than the effects of the oversimplified picture of "a bone out of place" that has been commonly proposed since the turn of the century. Their findings reported in the Belgium Research Notes are a testimony to their skillful observations. Although the theory of "a displaced vertebra" contained enough truth within it to constitute a basic therapeutic approach that could be justified by large numbers of positive benefits witnessed empirically, it was not sufficient to serve as a scientific hypothesis.

This investigative group did not have the advantage of any but personal funding and their own office facilities, it was decided to concentrate their studies on the normal and abnormal mobility of articular segments, especially those of the vertebral column and pelvis. As the findings of their investigations were reported, some basic assumptions of the profession were confirmed and others had to be discarded in light of the new knowledge obtained. For example, it was found that two basic concepts withstood the assault of the knowledge obtained year after year. These concepts involved vertebral position and motion:

1. Facts of Position.   It was determined that a subluxated vertebra has not "slipped out of place." It is not displaced from its physiologic boundary, nor has it exceeded its normal limits of motion. Thus, when a "subluxation" is adjusted, it is not really replaced, relocated, or reduced in the same context as would be a complete or partial dislocation for it is usually "freed" to function normally (made mobile).

2. Facts of Movements.   Vertebral movements describe an arc around a center of motion, from one extreme to the other. It was found that the basic movements of spinal segments are rotation about the longitudinal axis, lateral flexion (side bending, tipping) toward the right or left, posterior-anterior flexion, anterior-posterior extension, and long-axis distention. Factors may arise that can inhibit movement within any one or more of these directions, setting up a state of abnormal biomechanical translation and rotation leading to biomechanical and subsequent physiologic dysfunction.

Introduction to Fixation Terminology

The design of the spinal column's bony processes and its ligaments tend to stop the zygapophyses from exceeding their inherent range of motion. When this range is exceeded (eg, severe trauma, predisposing gross pathology), the articular surfaces lose contact and are in a state of dislocation.

      Bones Do Not Subluxate

A single vertebra cannot become subluxated or fixated. Only an articulation can subluxate or become fixated. As fixation-subluxations occur between two normally articulating surfaces, we speak about adjusting or mobilizing vertebral motion units (two apposing vertebral segments), not a single vertebra. Thus, articulations subluxate, not bones.

      The Perpetuation of a Misnomer

A state of "subluxation," in the surgical sense of the word, is difficult to achieve in gliding joints, and all zygapophyseal joints are gliding in nature. This is said to be one reason given why chiropractic theory has had such a difficult time being accepted by the general scientific community. It is thus paradoxical that the term subluxation, in the chiropractic sense, has forced its presence on all the health-care professions and is becoming widely used in circles beyond the chiropractic profession, while at the same time chiropractors have begun to understand that the term is a misnomer when all its pathophysiologic components are considered. For example, a vertebra may be in a hypomobile state of "fixation," unilaterally or bilaterally, that is well within its normal range of motion during the resting position yet be considered an articular aberration that can cause or contribute to many pathologic expressions.

      Articular Fixation Defined

For an articulation to remain in an abnormal state of "subluxation," something must be holding it there to restrict its mobility otherwise it would spontaneously reduce itself and produce little clinical concern. This "holding" or "mobility hindrance" mechanism is commonly called a "fixation." Thus,

(1) if a subluxation (a malfunction less than that produced by a dislocation) exists, a fixation also exists, and

(2) a fixation can exist even when the articular surfaces are in an ideal relationship during the static resting posture.

Although this holding mechanism is commonly called a fixation, this term too can be the cause of confusion if it infers a state of complete immobility. In this text, the term fixation is used in its traditional sense in motion palpation referring to any physical, functional, or psychic mechanism that produces a loss of segmental mobility within its normal physiologic range of motion. Thus, ankylosis would be considered a fixation in its purest sense a 100% fixation. However, most fixations found clinically will be far less (eg, in the 20%–80% range of normal mobility).


Dr. Henri Gillet's Fixation Theory

The ability of a doctor of chiropractic to detect restricted articular motion or hypermobility may mean the difference between success and failure with many patients. The study of motion palpation offers the examining physician far greater insight and confidence in why, where, when, how, and how often to administer appropriate therapy especially a corrective adjustment.

In evaluating the state of the periarticular and intra-articular soft tissues (eg, muscles, ligaments, capsules, synovia, articular cartilages) involved in an articular fixation, it will generally be found that it is some abnormal state of these soft tissues that is preventing the articular surfaces from moving in a particular plane. Common examples are muscle spasm and fibrosis, ligament shortening, intra-articular adhesions, scar development, cartilage hardening and malformation, cartilaginous chips and fragmented loose bodies, and cartilage erosion that restrict motion. Subsequent bone erosion and exostoses may also be involved. Osteopaths established many years ago that the soft tissues involved in a "vertebral lesion" can vary from the simplest muscle contraction to degenerative fibrosis of the muscles or even further to complete ossification of the involved ligaments and bursae.

After years of study, Gillet and his associates concluded that abnormal spinal muscle tone and changes within periarticular ligaments and intraarticular soft tissues were the primary factors responsible for the subluxation complex. These elements were also found to be the ones most influenced by the "chiropractic adjustment." Gillet showed that the dynamic chiropractic adjustment does not replace a vertebra or realign a bone; rather, it tends to eliminate the reason for its so called "abnormal position." Once adjusted (mobilized), the vertebral motion unit readapts itself, rapidly or slowly depending on its state of adaptability, to its full range of motion often without further necessity of the doctor's intervention.

Because bony segments have not actually slipped out of place, an explanation is offered on why postadjustment static x-ray films frequently fail to show anatomical changes after the patient becomes symptom free. A freely mobile joint will rest in its most ideal midrange of motion possible a position of readiness. If structural changes have occurred that have altered the articular surfaces or otherwise impaired its dynamic motion and/or static position in anyway, the adaptive or compensating resting position may appear as a misalignment during roentgenographic analysis. This is the typical "malpositioned vertebra" so often described in chiropractic literature.

Gillet's studies of vertebral fixation do not amend basic chiropractic concepts regarding the potential effects of subluxation complex (eg, neurologic, myologic, circulatory, inflammatory, and/or cerebrospinal and axoplasmic fluid changes). They only place them in a more dynamic perspective. This will become clearer within the following sections of this chapter.

      Spinal Dynamics

In general, it would seem that a spine will not remain normal if it is not kept in a good state of mobility. This supports the necessity for voluntary exercise of normal joints as a prophylaxis to disease.

During normal spinal motion, cineroentgenographic and surgical animal studies have shown that

(1) the superior and inferior posterior articular facets constantly glide on one another, establishing a barrage of complex proprioceptive signals to higher central nervous system (CNS) centers;

(2) the intervertebral foramina (IVFs) are constantly opening and closing, and thus compressing and stretching the contents of the IVFs (viz, the spinal nerves, recurrent meningeal nerves, arteries, and veins).

This dynamic action is also thought to help "milk" cerebrospinal fluid both around the spinal cord and peripherally along the spinal nerves. Normally, these dynamic compressing and stretching actions only occur for a few seconds at each event of movement and only within physiologic limits. These momentary actions, which can be likened to mild massage, should not be confused with prolonged or severe compressing and stretching actions.

      Acute vs Chronic Spinal Fixations

The physiologic stretching, compression, and stimulation of the contents of the IVFs is normal and quite necessary to maintain a healthy state of the structures involved. To not occur would produce in the spine or any extraspinal synovial joint effects similar to those seen following prolonged immobilization of a limb such as disuse atrophy, ligament shortening, circulatory stasis, neurotrophic changes, etc. It is well recognized that the atrophy of disuse is one of degeneration; it is a pathologic state that produces minimal nerve excitability (irritation). This is undoubtedly why we find that an acute subluxation-fixation produces far more clinical expressions than a chronic subluxation-fixation and its effects tend to reflect signs of hyperactivity (eg, spasm, warmth, hyperesthesia, visceral hyperfunction). On the other hand, a chronic subluxation-fixation tends to express signs of hypoactivity (eg, weakness, coolness, numbness, visceral hypofunction, musculoskeletal degeneration).

Some authorities relate these changes with either the effects of neural facilitatory or inhibitory effects within the anterior, lateral, and posterior columns of the spinal cord. For example, facilitation would respectively manifest as motor excitation (eg, hypertonicity, spasm), sympathetic vasomotor excitation (eg, warmth), and sensory excitation (eg, pain, hyperesthesia). In contrast, inhibition would exhibit as motor depression (eg, hypotonicity, weakness), sympathetic vasomotor depression (eg, coolness, trophic changes), and sensory depression (eg, anesthesia).

      The Compensatory Factor

Whenever an articulation is deprived of carrying out its normal function (motion), at least one other articulation is forced to take upon itself the burden of compensatory excessive motion, which may include eccentric and/or out-of-plane movement. This additional role within the counterpart joint or an adjacent articulation in the kinematic chain leads to irritation to the degree of inflammation once its homeostatic reserves are surpassed. Therefore, it is often seen that a site of fixation is asymptomatic, while the compensating hypermobile joint is highly expressive. In such a situation, it would be contraindicated to adjust the already hypermobile segment even if it is the focal site of clinical symptoms and signs.

Because of this compensatory factor, vertebral position derangements are often only of the dynamic variety; ie, they only exist in compensation to motion stress applied to an adjacent articulation. If the stress applied on the compensatory hypermobile segment is prolonged, the greater the degree of related neuromuscular stress. We often see this with the neuromuscular complaints of someone who has engaged in an unaccustomed activity such as shoveling, painting the ceiling, weekend gardening, or after exercise by an unconditioned person.

The question arises that if this is true, why have results appeared to have been achieved in adjusting the symptomatic joint when it was not the basic cause of the symptoms? One possible answer is because a specific contact is extremely difficult to obtain on a specific vertebra as three motion units have been shown to be affected by a specific thrust. If a broader contact is used, the force of the adjustment is undoubtedly distributed to a larger number of neighboring fixated segments. Another possible explanation is that a major function of all perispinal ligaments is to serve as straps to prevent excessive motion; thus, if a force is applied to one end of these straps, they tend to move the adjacent structures to which they are attached (eg, a fixated adjacent articulation). Other biomechanical and possibly somatosomatic reflex mechanisms may also be involved.

It is important to remember that a partial unilateral fixation (eg, muscular, early ligamentous) produces symptoms on the opposite side because of the induced compensatory hypermobility. Thus, contrary to previous thought, correction is made by applying the adjustment (mobilizing the fixation) on the contralateral side of symptom expression.

      The Interrelationship of Fixations

Many speculations have been made in chiropractic of what has appeared to be certain vertebrae or areas in the spine having a dominating influence on the spine as a whole. Such topics as primary subluxations, secondary subluxations, "key" vertebrae, majors vs minors, etc have been discussed since the early years of chiropractic. Many DCs have been taught that because the sacrum is the base of the spine, it is almost solely responsible for the mechanical state of the whole spinal superstructure. Conversely, many others have been taught that because of its unique position near the brain stem, once the atlas is correctly adjusted the whole spine will automatically realign itself. Lieb, a dentist, shows pre- and post-therapy full-spine radiographs exhibiting that correction of a TMJ syndrome has resulted in the spontaneous correction of overt scoliosis, kyphosis, and lordosis. There is no doubt that there is both truth and some misinterpretations in these concepts. Nevertheless, they do, in part, help to explain many commonly witnessed clinical phenomena.

Gillet often observed that so-called lesser fixations frequently became spontaneously mobile after he adjusted what was felt to be the most fixated segment in the spine and/or extremities. It has also been the observation of Gillet and his associates that, as a general rule, any correction made in any part of the spine will help the whole spine to correct itself to a degree in relation to the importance of the local correction. A hypothesis for this phenomenon will be given later in this chapter.

      Normal Intervertebral Relationships

Because of our training in postural analysis, many of us have developed the habit of mentally picturing a healthy spine as one in which each vertebra is stacked upon its neighbor, with the ends of the spinous processes representing a dotted vertical line when the patient is standing or sitting and facing forward. While this is generally true, this viewpoint of the spine in such static attitudes is far removed from its role in daily living in which the spinal segments (motion units) are constantly rotating, bending, flexing, and extending. Except for possibly a few seconds at a time, the spine and its associated tissues are never at rest.

In any given movement, a joint will assume the position demanded of it by its anatomical plane and the gravitational and muscular forces directed on it. This is obvious in a "short leg" syndrome when the spine is examined in the upright position, where the hip, sacroiliac, and lumbar articulations must attempt to accommodate themselves functionally to compensate for the unlevel base of support. This mechanism is evident during all normal body motions, for a movement of any body part requires a compensatory reciprocal action by other body parts to maintain equilibrium. The same biomechanical process is true in every case in which a vertebra is fixed at or near its extreme range of normal motion, causing other articulations to "displace" themselves in adaptation to the fixation during some or all motions, depending on the site and extent of the fixation. Thus, an "abnormal segmental position" by itself is not pathognomonic of subluxation. It is for this reason that the editor of the ACA's Basic Chiropractic Procedural Manual chose to take several pages to just summarize the criteria indicative of a subluxation.


Effects of Common Trauma

Ligaments are never tender unless they are in a pathologic state. Trauma far less than that causing fracture or dislocation produces an inflammatory reaction similar to that caused by a bacterial invasion. The reaction to bacterial invasion is designed to contain and wall off the bacteria to prevent further spreading of the infection. After trauma, localization serves to contain the products of the injured tissues. Unfortunately, the resolution of inflammation (scarring) can be especially harmful if the joint has not returned to normal mobility. This occurs because normal periarticular soft tissues are flexible, elastic, plastic, and generally richly vascular. Scar tissue, on the other hand, tends to be stiff, unyielding, and poorly vasculated. For this reason, reinjured joints that were not properly attended initially are extremely slow to heal. Every individual has sustained numerous bumps, strains, and sprains within his life.

Acute inflammation can develop into chronic inflammation that may continue for decades. Therefore, it is necessary to treat each trauma until all pain, tenderness, swelling, immobility, etc, are eliminated. Partial treatment is not adequate.

The diagnosis should be accurate and comprehensive. More than one tissue is usually affected by a single traumatic incident, and the treatment should be specific for each tissue affected. Determining the cause is not an easy task. For example, tender hypertonic perivertebral tissues found in the upper thoracic region of the spine may be from:

(1) overworked tissues (eg, unaccustomed activity of chopping wood or shoveling),

(2) unusual sustained postures (eg, prolonged spinal extension as in painting a ceiling),

(3) a viscerosomatic reflex (eg, heavy smoking, lung or heart disease),

(4) excessive compensatory segmental hypermobility owing to one or more fixated lower cervical or midthoracic vertebral motion units, or

(5) a combination of two or more of these factors.

The basic direction of case management can be considered as progressing through two phases. The first goal is to reduce the swelling and relieve the associated pain and soreness by R-I-C-E (rest, ice, compression, and elevation) and other physiotherapeutic measures when appropriate. The second objective is to promote healing and movement (eg, by manipulation, massage, stretching, passive and active exercise, and other standard regimens. It is also imperative to relieve any attending neurologic disorder in the spine, as this often cuts the reflex feedback cycle that facilitates prolonging the effect and also eliminates a possible source of a secondary or contributing subluxation complex.


Joint Play and Its Restrictions

In addition to the normal active and passive ranges of motion, there is a third type of motion called "joint play." This small but precise accessory movement within synovial joints cannot be influenced except passively. Although joint play is necessary for normal joint function, it is not influenced by a patient's volition. Thus, joint play can be defined as that degree of end movement or distention allowed passively that cannot be achieved through voluntary effort. In other words, total joint motion is the sum of the voluntary range of movement plus or minus any joint play exhibited.

Joint play occurs because normal joint surfaces do not appose tightly. Because joint surfaces are of varying radii, movement cannot occur about a rigid axis. The capsule must allow some extra play for full motion to occur. In addition to translatory and rotational joint play, a degree of distraction must exist. If any one of these involuntary movements is impaired for some reason, the articular surfaces become closely packed (compressed) and motion will be restricted. Added to this is the factor that there are small spaces created by articular incongruence necessary for hydrodynamic lubrication. Prolonged compression would lead to poor lubrication and possible ischemia, likely progressing to degenerative joint disease due to abrasion irritation.

Joint play cannot be produced by phasic muscle contraction. However, voluntary action is greatly influenced by normal joint play. The loss of joint play results in a painful joint that becomes involuntarily protected by secondary muscle spasm. Thus, motion palpation to detect restricted joint play is an important part of the biomechanical examination of any painful and spastic axial or appendicular joint. Pain and spasm result when a joint is moved (actively or passively) in the direction in which normal joint end-play is lacking. Once normal joint play is restored, the associated pain and spasm subside.

Joint play should exist in all ranges of motion that are normal for a particular joint. That is, if a joint functions in flexion, extension, abduction, and adduction, the integrity of joint play in all these directions plus distraction should be evaluated. It is not unusual for joint play to be restricted in some planes but not others.

A common cause of articular fixation and the resulting motion restriction is disuse. Many occupations require that certain joints move only in one or two planes but not all planes available. For example, a joint that is continually flexed but rarely extended will exhibit normal or abnormal joint play in flexion and frequently restricted joint play in extension. A similar situation occurs in a joint that is frequently abducted but rarely adducted or frequently rotated toward the left but rarely to the right.

The importance of freeing articular fixations (eg, by chiropractic adjustments, mobilization) is brought out by Mennell. Normal muscle function depends on normal joint function, and vice versa. If joint motion is not free, the involved muscles that move it cannot function and cannot be restored to normal. Thus, impaired muscle function leads to impaired joint function, and, conversely, impaired joint function leads to impaired muscle function. In this clinical cycle, muscle and joint function cannot be functionally separated from each other.

In summary, Faye emphasizes the following major points of joint play:

1.   Total joint movement is the voluntary range of movement plus or minus the joint play present.

2.   Voluntary action depends on normal joint play, but voluntary motion and exercise cannot produce or restore joint play. The presence or absence of joint play can only be demonstrated by an examiner; ie, passively.

3.   Loss of joint play produces pain on testing; ie, whenever that direction of joint play is challenged. When restricted joint play is restored by manipulation, the related pain abates. A painful joint produces secondary muscular changes; ie, spasm, which is nature's way of preventing injurious joint movement. If painful joint movement occurs because of joint play restriction, the joint play must be restored to near normal to obtain a permanent reduction of the spasm. [See Clinical Comment 1.1]

4.   Muscles that move a joint with joint dysfunction become hypertonic in response to the pain from irritation; therefore, the active range of motion is also restricted.

5.   Joint play can only be restored by a mobilizing force (maneuver, thrust, impulse) delivered satisfactorily; ie, in line with the plane of articulation and against the motion resistance (fixation).

      DR. FAYE'S CLINICAL COMMENT #1.1

The pain experienced by the patient when joint play is restricted is sharp and only lasts as long as the doctor presses into the restriction during the examination. This must not be confused with the joint pain associated with an inflamed joint that produces a lingering type of pain when challenged.

Although the gross movements of the spine and pelvis have been the subject of numerous studies, information about typical movements between individual segments was relatively obscure (except for the findings of Gillet) until Kapandji, White, and Punjabi reported their findings.

To fully appreciate the concepts of motion palpation, the mental picture of the spine being a straight, vertical, static structure (as viewed on a radiograph) must be discarded. The spine is a living, dynamic, segmented organ that is in constant motion during locomotion, work, and with every breath taken during rest. As most organs of the body, during day or night, work or rest, the spine never rests it is in constant motion, constantly dynamic.

Because a force may act along a single line in a single plane or in any direction in space, this factor must be considered in any reference system. Such a reference system is necessary if we are to effectively communicate with each other about joint position and motion. Thus, this section will review pertinent terms and principles that will enhance our communicative skills as well as deepen our understanding of spinal dynamics.


The Planes of the Body and Related Considerations

Many basic considerations in biomechanics involve time, mass, center of mass, movement, force, and gravity which operate in accordance with the laws of physics. However, while numerous parameters of movement are interrelated, no one factor is capable of completely describing movement by itself.

The force of gravity is always directed toward the earth's center. Thus, the gravity line of action and direction are constants. In the upright "rigid" body posture, the gravitational force on the entire mass can be considered a single vector through the center of mass that represents the sum of many parallel positive and negative coordinates (Fig. 1.1).

      Describing Positions in Space

In a two-dimensional reference system, the plane is simply divided into four quadrants by a perpendicular vertical ordinate line (Y axis) and a horizontal abscissa line (X axis). A third axis (usually labeled Z) can be used to locate points in three dimensions. The Z axis crosses the origin and is perpendicular to planes X and Y.

There are several reference systems. This particular system is the Cartesian coordinate system in which:

(1) flexion/extension rotation is rotation about the X axis,

(2) axial rotation is rotation about the Y axis, and

(3) lateral flexion rotation is rotation about the Z axis.

All Z points in front of the X-Y plane are positive, while those behind are negative (Fig. 1.2). By using X, Y, and Z coordinates, any point in space can be located and depicted. However, a minimum of six coordinates is necessary to specify the position of a rigid body (eg, a vertebra).

In biomechanics, the body's reference origin is located at the body's center of mass. This is usually just anterior to the S2 segment. When this point is known, gross body space can be visualized as being in the sagittal (right-left) Y-Z plane, frontal or coronal (anterior-posterior) X-Y plane, or horizontal or transverse (superior-inferior) X-Z plane. With such a reference system, movement of any body segment in these planes can be described by placing a coordinate system at the axis of a joint and projecting the action lines of the muscles involved.

      Axes

An axis is a straight line around which an object rotates, a line serving to orient a space or object (about which the object is symmetrical), or a reference line in a system of coordinates. Most body movements are rotations about joint axes and are rarely confined to a simple arc. Such motions vary to compensate for muscle-joint restrictions, bones twisting about their axes, and the transfer of power from one set of muscles to another within the range of movement. The joint surfaces of spinal joints are usually convexo-concave in design; ie, the convex surface is larger than the concave surface. This relationship is exaggerated in all extraspinal ball-and-socket joints.

If the anatomical position is used as a reference point, joint movements occur in a definite plane and around a definite axis. Flexion, extension, and hyperextension are movements in the sagittal plane about a frontal axis. Abduction and adduction are movements in the frontal plane about a sagittal axis. Rotation, pronation, and supination are movements in the transverse plane about a vertical axis. And circumduction is movement in both the sagittal and frontal planes. See Table 1.1.

Movement          Plane             Axis     
Flexion           Sagittal          Frontal
Extension         Sagittal          Frontal
Abduction         Frontal           Sagittal
Adduction         Frontal           Sagittal
Rotation          Transverse        Vertical
Pronation         Transverse        Vertical
Supination        Transverse        Vertical

      Linear and Circular Motion

The two basic types of body movement are linear movement and circular movement. Linear movement is that in which the body as a whole or one of its parts can be moved as a whole from one place to another in a straight line. One example of linear (sliding, gliding, translation) movement without any circular motion is long axis distraction of a finger joint.

Circular movement (angular, rotational) is that in which the body or a part can be moved around the arc of a circle. An example of circular motion is seen between the long bones of the extremities and in the spinal column. Circular movements occur in definite planes and around a definite axis (center of rotation). They comprise an important diagnostic viewpoint in musculoskeletal disorders, and, as previously described, each of these three axes of rotation is perpendicular to the plane in which motion occurs.


Structural Motion

From a clinical viewpoint, structural motion can be defined as a body segment's relative change of place or position in space within a time frame and about some other object in space. Thus, motion may be determined and illustrated by knowing and showing its position before and after an interval of time. While linear motion is readily demonstrated in the body as a whole as it moves in a straight line, most joint motions are combinations of translation and angular movements that are more often than not diagonal rather than parallel to the cardinal planes. For example, a vertebra cannot move in the A-P plane because its articulating facets are slanted obliquely. In addition to muscle force, joint motion is governed by factors of movement freedom, axes of movement, and range of motion.

      Degrees of Joint Movement Freedom

The body is composed of numerous uniaxial, biaxial, and multiaxial joints. Joints with one axis have one degree of freedom to move in one plane such as pivot and hinge joints, joints with two axes have two degrees of freedom to move in two different planes, and joints with three axes have three degrees of freedom to move in all three planes (eg, ball-and-socket joints). Thus, that motion in which an object may translate to and fro along a straight course or rotate one way or another about a particular axis equals one degree of freedom.

To know the actual degrees of freedom (ranges of motions) available to a part of the body, one must sum the degrees available of adjacent joints to appreciate the amount of free motion of one part about another part. The degrees of freedom of a fingertip about the trunk, for example, are the sum of the degrees of freedom of all the joints from the distal phalanges to the shoulder girdle. While the distal phalanges have only one degree of freedom (flexion-extension), the entire upper extremity has 17 degrees in total. This summation process is an example of a living, open kinematic chain.

      Combined Movements

Simple translatory motions of a body part invariably involve movements of more than one joint. This requires reciprocating actions of three or more segments at two or more joints if parallel lines are to be followed. For example, a fingertip cannot be made to follow the straight edge of a ruler placed in front when the wrist, elbow, and shoulder joints are locked. The fingertip must follow an arc and not a straight line. Thus, human motion can be described as translation that gains major contributions from linear, angular, and curvilinear motions. The terms general or three-dimensional body motion infer that a body part may move in any direction by combining multidirectional translation and multiaxial rotation.

      Plane Motion

Any motion in which all coordinates of a rigid body move parallel to a fixed point is referred to as plane motion. Such motion has three degrees of freedom (ranges of motions); viz,

(1) moving toward the anterior or posterior,

(2) laterally moving toward the right or left, and

(3) spinning in one direction or the other.

In other words, plane motion has two translatory degrees of motion along two mutually perpendicular axes and one rotational degree of motion around an axis perpendicular to the translatory axes. Thus, when an individual flexes his spine forward, the vertebrae flex and rotate in a single plane about an axis that is perpendicular to the sagittal plane. In such plane motion, various points on a particular vertebra will always move in parallel planes.

      The Instantaneous Axis of Rotation

Plane motion is described by the position of its instantaneous axis of rotation and the motion's rotational magnitude about this axis. In the above example of spinal flexion, for instance, as a vertebra moves in a plane, there is a point at every instant of motion somewhere within or without the body that does not move. If a line is drawn from that point so it perpendicularly meets the line of motion, the point of intersection is called the instantaneous axis of rotation for that motion at that particular point in time (Fig. 1.3). Most joint movement is to a great extent rotational motion, but the axis of motion may change its location and/or its orientation during a complete range of motion.

      Out-of-Plane Motion

As contrasted to plane motion, out-of-plane motion is a type of general body motion with three degrees of freedom: two rotations about mutually perpendicular axes and translation perpendicular to the plane formed by the axes. Thus, in out-of-plane motion, the body as a whole or a segment can move more than in a single plane. For example, if a person bends laterally, a midthoracic vertebral body translates from the sagittal plane towards the horizontal plane (Fig. 1.4). This is not plane motion because various points on the vertebra do not move in parallel planes.


Motion Barriers and Their Significance in Manipulation

All types of joint manipulation impose static and dynamic forces across joint surfaces. Within its anatomical range of motion, a normal joint exhibits in all planes of motion:

(1) a large voluntary active range,

(2) an involuntary stress-less passive range, and

(3) a slight paraphysiologic range that is determined by ligamentous plasticity, elasticity, and viscoelasticity (joint play). These ranges are used in voluntary exercise, mobilization, and adjustive techniques, respectively. To appreciate this more fully, an understanding of the barrier concept is necessary.

If a joint is tested passively to determine its range of motion, the examiner will note increasing end resistance to motion referred to as a "bind," the physiologic motion barrier, or the elastic barrier. If the joint is slowly carried past this point, the added motion becomes uncomfortable to the patient. If carried still further to a point just short of injury, this point is the anatomical motion barrier. That slight range of motion between the elastic barrier and the anatomical limit is the involuntary paraphysiologic space or range, the area of passive joint play. At the end of joint play, the anatomical barrier, the joint tissues are stretched to their structural limits.

A spinal fixation has been previously defined as some abnormal factor that blocks or inhibits passive motion. It has also been described that the term fixation is not synonymous with the term subluxation; fixation is only one, but highly necessary, characteristic of the subluxation complex.

There are four general types of fixations:

(1) muscular,

(2) ligamentous,

(3) articular, and

(4) bony. It is clinically important to attempt to judge the degree of fixation and the nature of the fixative element to evaluate the minimum amount of force necessary during an adjustive thrust to "break down" the fixation if it is logical to do so (breaking an ankylosis, for example, would usually be contraindicated). This is true whether the cause is a spasm, a shortened ligament, an interarticular adhesion, or some other amelioratable factor.

Muscular (Class I) Fixations

In relation to spinal fixations, the term muscular spasm is used by Gillet to describe the state of a muscle or muscles that fixate vertebrae and hinder their normal movement. Yet, he does this with misgivings because he states that such contractions are somewhat different from the spasms and cramps which occur in other muscles of the body. For example:

1.   Spasms and cramps that occur in other parts of the body (eg, calf "Charley horse," intestinal colic, diaphragmatic spasm of "windedness") are acute contractions that are extremely painful. In contrast, the spasms associated with spinal fixations are usually only sensitive to deep pressure and otherwise go unnoticed by the patient.

2.   Except for spastic paralysis (eg, poststroke), spasms in other parts of the body have a short duration. In contrast, the spasms associated with spinal fixations may endure for months or years without change. In spite of the chronicity, the muscles involved do not necessarily degenerate or become fibrotic as other muscles normally do under such conditions.

There is no doubt that these perivertebral spasms exist because they can be palpated. The most common ones found are of the rotatores, multifidi, interspinales, intertransversarii (cervical), obliquus capitis (atlas-axis), levatores costarum, spinalis groups, and different portions of the quadratus lumborum. While areas of spasm can sometimes be palpated in the large-long muscles of the back, they are rarely found to be responsible for individual fixations. Gillet's findings to date have tended to confirm Palmer's concept of a single segmental subluxation (the "major" concept) rather than Carver's hypothesis of abnormal curves of the spine (summation of the whole area) being the focus for pathologic expression. Regardless, further research is necessary for uncontested confirmation of either theory.

      Muscle Tonicity vs Phasic Contractions

In all healthy skeletal muscles, there is a combination of two major neurologic factors at work:

(1) The sustaining or resting tone (tension, firmness) of a muscle (an involuntary mechanism) is controlled by the sympathetic nervous system through low-frequency asynchronous impulses from the spinal cord. Its purpose is to keep the muscular system in a neurochemical and functional state of readiness to act and maintain static postural equilibrium (sustained by the stretch reflex). It is active during both rest and work, and is especially developed in the antigravity muscles.

(2) The voluntary and involuntary gross contraction of a muscle, under the control of both the cerebrospinal motor system and cord reflexes, directs all postural, ballistic, and tension movements.

It is electrically silent during rest and relatively silent during the relaxed upright position if the body is well balanced over weight-bearing joints. Voluntary muscle contraction is always superimposed on the involuntary intrinsic tone of the muscles involved in any musculoskeletal action.

Gillet postulates that the palpable spasm associated with a vertebral fixation could be an involuntary state of abnormal hypertonus rather than a cord reflex initiating a spasm via a phasic contraction as seen in typical spasms and protective "splinting." This theory could explain why the hypertonic muscles associated with fixations are tender to palpation but not otherwise painful.

      Gillet's Theory of the Cause of Fixation-Related Hypertonicity

It is empirically evident that "subluxations" are often caused by trauma (direct or indirect) such as in blows, falls, and strains or indirect micro-trauma such as from the various effects of biomechanical imbalance. The neuromuscular response to trauma is either contraction to a degree that varies with the severity of the trauma either a strong rapid contraction or a slow contraction of long duration. In this context, paraphrasing Gillet, let us suppose that as soon as the contraction goes beyond a certain limit in force or duration the autonomic fibers controlling muscle tonicity become abnormally stimulated. As any neural stimulation of high intensity tends to "jump" impulses from sensory to motor tracts, via internuncial neurons in the spinal cord, instead of or before traveling up the cord, it is possible that such a mechanism could be established as a fixed pattern of behavior, a vicious self- perpetuating neuromuscular cycle.

If such a hypertonicity is sufficient enough and if it is unilateral, the motion unit involved will tend to be pulled into a sustained position of action. This appears likely as each vertebral segment is "balanced" at rest in a state of physiologic equilibrium between its extremes of motion. The spine is not a stiff column of segments. The structural properties of its discs, ligaments, and cartilages are relatively plastic, flexible, elastic, and viscoelastic. We can now add to this picture the neurologic mechanism of reciprocal inhibition; viz, phasic agonist contractions are accompanied by a reciprocal decrease in action in its antagonists. For example, when flexors act, extensors relax, and vice versa. Reciprocal inhibition is usually thought of as a temporary mechanism, but is this always true?

      General Characteristics of Muscular Fixations

Muscular fixations are the most numerous type of fixation, and their potential number may appear great in any given patient. They are, however, usually minor or secondary. Although all possible muscular fixations will not necessarily exist in each patient, they are all possible and should be recorded with each patient. If no ligamentous or articular fixations are found, muscular fixations can be corrected. However, if a secondary muscular fixation is adjusted before mobilization of its primary focus, it will return quickly (in minutes) because it is an adaptation to the site of primary ligamentous or articular fixation.

      The major characteristics of perivertebral muscular fixations are as

• They are usually palpated as taut tender muscle fibers underneath hyperesthetic skin. If the overlying skin and subcutaneous tissues near the related spinous process are rolled between the skin and index finger, acute tenderness will be reported by the patient.

• They exhibit restricted mobility from the start when challenged, and the end feel exhibits a little "give" and a rubbery end block.

• They are completely released and almost immediately become nontender, relaxed, and the segment to which they are attached becomes mobile with the proper adjustment.

• They are usually secondary to another area of fixation or the result of a reflex (somatosomatic or viscerosomatic); thus, they will likely recur if the primary fixation or some other focus of irritation is not corrected.

Unilaterality and Acuteness Factors. Besides being the most numerous, muscular fixations are the most pathognomonic of overt symptoms yet the most open to change by either direct or indirect methods according to Gillet. They also are the type in which the "displacement" factor is the most visible because the spasm or hypertonicity involved is usually unilateral. This can often be seen with the axis, where unilateral hypertonicity of an obliquus capitis inferior muscle pulls the spinous of the axis laterally. This unilaterality is frequently a sign of its acute state. The more acute the condition, the less degeneration will be found in the muscle responsible and the greatest change can be observed after an adjustment either locally or through the correction of more chronic major fixations.

Remote Effects.   Muscular fixations are frequently secondary facilitated "reflex" responses to more chronic fixations elsewhere or an activated viscerosomatic reflex. If the result of a somatosomatic reflex, many of them disappear spontaneously after the correction of primary ligamentous and articular fixations. Furthermore, Gillet reports that there seems to be an important specificity between primary chronic fixations and acute muscular (reflex) fixations. This specificity is often surprising in its remote location, sometimes going from L5 to the lower cervicals without an apparent neurologic or biomechanical explanation. Another common example is an upper-cervical major fixation that produces low-back muscular fixations which, in turn, results in low-back pain and dysfunction.

      Postural Changes Related to Muscular Fixations

These secondary reflex fixations just described appear to be primarily due to hypertonicity of the short spinal muscles, but certain long muscles are sometimes involved. When they are, they produce the characteristic postural distortions and antalgic positions that are so often seen in clinical practice and measured by grids, plumb line analyses, etc. Certain methods of spinal examination use these abnormal postures to deductively reason to the causative fixation, and some therapeutic techniques work on the long muscles in an attempt to bring the body back into normal balance. Such procedures may easily lead to erroneous conclusions and misinterpretations. [See Clinical Comment 1.2]

It is possible to change human posture by working on these long muscles because it is almost always possible to provide a centripetal effect on a primary condition by influencing the secondary half of the cycle. This can often be seen in the effects of medical treatment, and it is true with many chiropractic procedures. To perpetuate this effect, however, will require a greater repetition of the therapeutic agent. It can be stated as a general rule that each time a correction has to be repeated several times within a short period, this attempt at correction is being applied to an abnormality which is secondary to another located somewhere else, originating either within the body or its immediate external environment.

Another difficulty in using gross posture as a sign of fixation is that not all fixations produce a related hypertonus of long body muscles capable of altering gross posture. This effect is a characteristic of fixations that produce irritation of the cerebrospinal nerves and far less of those which can irritate the sympathetic nerves. Specific long muscles that are involved in postural changes and fixations will be described in subsequent chapters.

Etiologic Questions.   The inquiry commonly arises: Which comes first, fixation or postural distortion? There are two general answers (possibilities) to this question:

1.   Muscular contraction can pull a vertebra out of normal resting alignment.

2.   Because the spine is forced to remain for long periods in a position of "unrest," the soft tissues of the spine will slowly adapt to the action demanded by the patient's daily activities and positions. The vertebrae involved can be considered to be "normally" misaligned as long as the reason for this malposition exists.

The first type (1 above) takes in all traumatic subluxations in which one or more muscles react to the trauma by a vigorous defensive contraction (nociceptive reflex). If this contraction exceeds an individual's limits, a noxious nerve-muscle cycle can be established that tends to remain until a counter- acting force (eg, adjustment) interrupts the cycle. This type of fixation-mal-placement syndrome would also include situations resulting from a feedback mechanism from a unilateral peripheral irritation (eg, a viscerospinal reflex), including those of the upper cervical area from excessive mentalemotional stimulation, visual fatigue, and other reflex fixations. As these fixations are of a muscular nature, they are usually unilateral, or predominantly so, and acute.

The second type of fixation-subluxation (2 above) is of the spinal balance class, including any vertebral articulation that would be forced to adapt itself to:

(1) a short leg,

(2) malformed vertebrae,

(3) the imbalancing effect of acute subluxations,

(4) poor posture caused by unusual working conditions, and

(5) unilateral imbalancing "specialized" movements in work.

In all these conditions, we would have what could be called "microtraumatism," the most typical being the anatomical short-leg syndrome in which the associated lumbar scoliosis is a normal adaptation as long as the scoliosis is flexible to the degree that the spine will straighten in the sitting and recumbent positions. On this subject, Faye mentions that Lynton G. Giles has shown that a leg length difference of approximately 15 mm is necessary before appreciable adaptation occurs.

Thus, we have two possible etiologies:

(1) the fixation comes first, or

(2) the "displacement" is the primary element.

Both types may sometimes be found in the same area, in which case it is more often the acute type that adds itself to the chronic type. In the chronic type, states Faye, degenerative changes within the three-joint complex of the motion unit must be present for true displacement to exist.

      DR. FAYE'S CLINICAL COMMENT #1.2

Most patients have more than one major ligamentous or articular fixation. We try to adjust the most fixated (least "springy") motion unit first. As the muscular fixations spontaneously normalize, a second or third motion unit is adjusted to influence other muscular fixations. As the biomechanics improve and there are less aberrant joint insults to the spine and locomotor system, the inflamed joints begin to heal.

      Effects of Adjustive Therapy

If two spinal motion segments are in a state of "malposition" because of unilateral hypertonicity or spasm of one or more intervertebral muscles, the structures to which the involved muscles have their origin and insertion will be drawn towards one another during most types of adjustments. Thus, a dynamic thrust that has as its objective "realignment" of the segments will obviously stretch the contracted muscles (increase the distance between muscle origin and insertion). It is probably for this that a chiropractic dynamic thrust, as contrasted to a simple slow pull or push, has proved to be more successful in practice.

While Gillet does not propose that this hypothesis offers a complete ex- planation, he does believe that it answers more questions than others projected in the past. In addition, this explanation is only rational for those muscular fixations that remain in a state of prolonged abnormal function and which are not associated with myodegeneration. He also adds that for some still unknown reason, other fixations (possibly those in which we have two or more hypertonic muscles between adjacent vertebrae) sometimes do undergo the usual degenerative process in a fixation-subluxation syndrome.


Ligamentous (Class II) Fixations

One early physiologic change seen with chronically fixated vertebral articulations is the shortening of ligaments. This is true because ligaments always tend to adapt themselves to the range of motion used. That is, they will shorten to the degree necessary to remove any slack. Thus, in complete or multimuscular fixations, the associated ligaments and related soft tissues will have distinctively shortened. The type of thrust used here must be one designed to lengthen ligamentous tissues (eg, repeated nontraumatic traction on the insertions of the involved ligaments). Total multimuscular and multiligamentous fixations are frequently found at the sacroiliac joints and the occipital-atlantal area and are associated with the thoracic spine.

The most pertinent characteristics of ligamentous fixations, which are often major fixations, are that they are usually:

• The reflection of a degenerating chronic muscular fixation or the effect of ligament trauma.

• Overlaid with atrophied subcutaneous tissues.

• Palpated as an abrupt, hard block within the normal range of motion that exhibits no end play.

• Bilateral (with one side tighter than the other) or else are in the median line.

• Improved only slightly immediately after each corrective treatment.

      Shortening of Capsular Ligaments

Gillet and associates have found few spinal fixations that can be explained by shortening of the capsular ligaments, although practically all the other spinal ligaments seem to be involved in fixations.

When apophyseal capsular shortening occurs, one might think that it would result in an articular-like fixation. However, this has not been found to be true: there is still a certain amount of torsion possible. This is especially evident in the extraspinal joints; eg, when there are many fixations in the feet involving the calcaneus, tarsals, and metatarsals. Similar fixations can frequently be found in the proximal articulation of the fibula with the tibia, in sternoclavicular and acromioclavicular joints, and among the metacarpals. Such extraspinal fixations can have noxious effects either locally or in the spine (reflex fixation). These manifestations will be described in Chapters 8 and 9.

      Musculotendinous Fixations Resembling Ligamentous Fixations

In certain purely muscular fixations, the spastic or hypertonic muscles involved tend to degenerate and become fibrotic. For all practical purposes, such fibrotic muscles resemble ligaments in function and structure. As most of the deep spinal muscles are underlaid and/or overlaid with ligaments, it is often difficult to determine which structure is responsible for the fixation. Fortunately, the type and direction of a corrective thrust is nearly the same, and even the amount of demonstrable change that can be expected from a fibrosed muscle or a shortened ligament is the same. Thus, from a clinical viewpoint, a fibrotic muscle fixation can be classed as a ligamentous fixa- tion. Gillet believes that this type of fixation is the most common but not the most irritative.

Several authors have described the shortening or tension found in certain fascia and tendons as being responsible for the restriction of joint motion, either by themselves or by hindering the action of their associated muscles. One example of this is the fascia lata in fixations of the proximal femur. The Belgium researchers, however, have not been able to confirm this as yet.

      Muscular vs Ligamentous Postadjustment Effects

While the adjustive technique need be modified only slightly with either muscular or ligamentous fixations, the postadjustive reaction is quite different. In muscular fixations, an immediate near-normal range of motion should be expected. In ligamentous fixations, however, the immediate gain in mobility is only slight with each treatment. This does not mean, however, that the increased movements during everyday activities between office visits are not another important factor in restoring mobility. [See Clinical Comment 1.3]

      DR. FAYE'S CLINICAL COMMENT #1.3

During this phase of treatment, stretching exercises at home should be recommended to the patient. A 30-second stretch into the fixation, just short of inducing pain, is my suggestion. This stretching should be repeated two or three times a day. The last few seconds of the stretch is done while exhaling.

      The Intervertebral Discs

Gillet gives no more importance to the intervertebral disc (IVD) in the production of spinal fixations than any other ligamentous structure. He believes the integrity of the IVD is generally more of a passive factor than an active factor. A few exceptions to this general rule will be described in subsequent chapters, but motion palpation studies have not confirmed that true IVD lesions are as common as generally accepted in the medical community and to a great extent within our own profession. Faye states that disc degeneration, with its internal disruption and posterior joint gapping, causes more hypermobility and instability.


Articular (Class III) Fixations

True articular or total fixations are common manifestations in the human spine, and they have been the subject of several studies that arrive at conflicting conclusions. Regardless of cause, they appear to be the result of intra-articular joint "gluing" similar to that seen in adhesive capsulitis and multiple ligamentous shortenings. Overt pathology does not appear to be related as the fixation is eventually made mobile by repeated chiropractic adjustments.

In any total articular fixation, one lateral pair of articulations (inferior and superior facets) of the bilateral posterior articulations may be the seat of fixation and the other not. The contralateral pair may be normal initially, but as the inferior and superior zygapophyses become more immobilized because of the fixation of their contralateral counterparts, they also become functionally incapable of motion. In time, the pathologic effects of disuse can be expected in the initially normal pair of articulations.

In total fixations in which the fixative element is the product of degeneration of the interarticular and periarticular soft tissues, with the probable development of "adhesions," the major corrective effect of the chiropractic adjustment is produced by the forced opening of the apposed facets.

Gillet points out that this type of unilateral total fixation can be demonstrated when reflex-fixations are searched for and found. This procedure will be described in a following chapter. It should be mentioned, however, that total unilateral fixations in the spine function differently than total unilateral fixations in the sacroiliac joints. In total unilateral fixation of a sacroiliac joint, the contralateral articulation is not restricted in movement and typically adapts by becoming hypermobile and acutely overstressed in a prolonged attempt to serve the role of both joints.

This reciprocity of immobility and hypermobility is found in all types of fixations. In total fixations found between vertebrae, Illi states that the adaptive hyperkinesis takes place in the articulation above and below, or in the opposite articulations exceptionally. In partial fixations, it takes place on the still mobile side of segments unilaterally fixated (Figs. 1.6 and 1.7).

In summary, the major characteristics of articular (total) fixations are that they:

• Are motion palpated as being completely immobile in all directions and asymptomatic.

• Are painful when challenged by the palpator.

• Progress to ankylosis; thus, irreversible in the terminal stage.

Articular fixations, which are always considered major faults, should usually be corrected first, and ligamentous fixations should be given priority consideration over muscular fixations because the latter are often secondary (compensatory, reflexively produced). [See Clinical Comment 1.4]

      DR. FAYE'S CLINICAL COMMENT #1.4

I have found it a clinical advantage to adjust one major at one office visit. However, I attempt multiple adjustments in different ranges of motion in the motion unit selected. Some will produce audible releases, others will effect only a mobilization.

Bony Restrictions

Bony outgrowths may be obvious, but if they are near the periphery of a joint, they may be recognized only by the sudden arrest of an otherwise free motion. In true ankylosis, there is no mobility whatever and adjacent joints are often hypermobile in compensation. Roentgenography is usually necessary for diagnosis.

During physical examination, bony outgrowths within a joint are sometimes recognized by the sudden arrest of an otherwise free joint motion at a certain point. That is, an abrupt hard halt in motion usually signifies bone-to-bone contact, signifying that further movement should not be conducted. Such an approximation will be felt before the end of normal motion occurs when hypertrophic bone growth (eg, an osteophyte, a malunited fracture, or myositis ossificans) has developed. If force that is continued beyond the point of a bony block is painless, neuropathic arthropathy is likely.

True bony ankylosis is one type of total fixation. It has been Gillet's experience that ankylosis is invariably the result of a local bone disease process or severe trauma and practically never correctable by adjustive therapy. On the other hand, he feels that a fibrous type of pseudoankylosis is far more frequent, especially in the midthoracic area during middle age or in the elderly. This is likely the result of a general degeneration of the perivertebral muscles and ligaments. Although this fibrous condition can be manipulated, it takes months or years to produce a pale picture of normal motion. Gillet also states, "Unfortunately, as long as it exists, the rest of the spine will never remain free from recurrent fixations." [See Clinical Comment 1.5]

Muscle spasm is distinguished from bony outgrowth as a cause of limited joint motion by several features. Bony outgrowths allow perfectly free motion up to a certain point, after which motion is arrested suddenly, completely, and without great pain. Muscular spasm, on the contrary, checks motion slightly from the onset. Resistance and pain gradually increase until the examiner's efforts are arrested at some point.

      DR. FAYE'S CLINICAL COMMENT #1.5

It has been my clinical experience that if chronic changes are present the gross ranges of motion can be restored to the spine with repeated mild adjustments directed to the least fixated areas. Gradually, over a long period of time (often 12-16 months), the doctor can adjust the most fixated areas. The change of flexibility is greatly appreciated by the older patient. I see these patients twice a week for 1-2 years and have recorded many remarkable improvements in range of motion.

The Mechanisms of Equilibrium

Most practitioners will agree that many patients will present with one lower limb anatomically shorter than the other limb. Although the term short leg is used to describe this phenomenon, the length of all structures contributing to the structural distance between the head of the femur and the floor is being considered. Thus, more structures can contribute to this "shortness" than just the weight-bearing tibia of the leg; viz, the pelvis, femur, ankle, and foot.

When a short leg exists, the crests of the pelvis will not be level and the superimposed spine will try to adapt through various curvatures in an attempt to keep the eyes level and at the same time keep various body parts balanced relative to the body's line of gravity. This usually occurs in the same manner as the biomechanical adaptation of a person walking on the side of a hill.

All people do not adapt to walking on a horizontally slanted surface in the same manner, nor do all people adapt to a short leg in the same manner. Some spines will regain an equilibrium imbalance due to a short leg within a few lumbar segments (eg, L3), while others will not achieve this until the upper cervical area is reached. The reasons for this variance may be structural, functional, or just habitual.

Cabot, the famous diagnostician, constantly admonished his students that "to recognize the abnormal, one must be completely familiar with the normal and its many variations." Several mechanisms will be described in this section that are normal responses to the commonly seen anatomical short leg.

      The "Flatfoot" Factor

Some authorities consider a unilateral flattened longitudinal arch in the foot to be one factor that will cause a measurable lowering of one femur. Gillet feels that this is true in a way, but not in the oversimplified manner that is often given in explanation. When the Belgium researchers measured the influence of the height of the arch on the total length of a lower extremity, they found it to be not more than 1 mm. As anatomical short legs usually have a discrepancy of at least 5 mm, it is obvious that other causes must be found.

It has been the experience of Gillet that a fallen arch frequently appears on the side of the long leg. After adding a heel lift on the short side, the fallen arch may spontaneously correct itself within a few days to become near normal. He offers the following possible explanations for this phenomenon.

Flatfoot.   The flattening of the arch (pes planus or valgus) on the long extremity could be a natural adaptation process to diminish the leg of the relatively long leg. If we examine pelvic equilibrium, it will be found that the long extremity has rotated externally because of movement of the related ilium, when the weight of the body during gait falls abnormally at an angle over the arch of the foot (forcing it downward). When such a mechanism occurs, it would appear to be contraindicated to attempt to raise the compensatory fallen arch with an arch support.

Foot Eversion.   Another mechanism, which in a way is part of the one described above, is foot eversion. This usually occurs simultaneously on the side of the fallen arch and also tends to bring the head of the femur (and the structures supported) a little closer to the ground. Gillet contends that the wearing of a wedge-shaped heel in such a case could aggravate the situation because it would hinder intrinsic adaptation mechanisms from shortening the long extremity, thus forcing the pelvis and superimposed spine to distort further. Such foot eversion (toe-out, ankle pronation) is also part of other adaptive mechanisms.

      Other Efforts to Achieve Equilibrium with an Anatomical Short Leg

The Trochanter Phenomenon.   The trochanter phenomenon, a term coined by Illi, refers to the lateral sway of the whole pelvis towards the side of the short leg. Gillet explains that this mechanism would not be able to influence pelvic level if the lower extremities were simply straight vertical structures and if the feet were placed exactly beneath the heads of the femurs because this would constitute a parallelogram in which the upper horizontal arm would always be parallel to the floor. The influence of lateral sway is achieved because the femoral head projects at an angle from the surgical neck and, as the femur is usually slanted exteriorly, each femur slants to a different degree during lateral sway. This makes one femur shift slightly superior on the long side and the other slightly inferior on the short side.

Compensatory Sacroiliac Rotational Misalignment.   The next articulations that try to align themselves in an abnormal fashion to achieve equilibrium in a short-leg syndrome are the sacroiliac joints. Even with the compensatory trochanter phenomenon, the whole pelvis will still be tilted downwards on the side of the short leg so the ilia attempt to rotate anteriorly and superiorly on the low side to lift its articulation with the sacrum and rotate posteriorly and inferiorly on the high side to lower its articulation (Fig. 1.8). This is possible because the sacroiliac joints lie somewhat posteriorly in relation to the head of the femur. This motion permits another gain of 1 2 mm, but unfortunately, it is achieved at the expense of other joints.

Compensatory Sacral Tilt.   Intrinsic adaptive mechanisms also attempt to tip the sacrum itself into a position normally seen during lateral bending; ie, upward on the short-leg side and downward on the long-leg side in order to provide a more stable base for the spinal column.

Compensatory Inferior-Superior Sacroiliac.   At times, in addition to the iliac rotation and sacral tilting described, inferior translation of the sacrum on the ilium on the long side and superior translation of the ilium on the side of the short leg may be found as an aid to sacral leveling.

Compensatory Lumbar Rotation.   The area where postural deformation and compensation is greatest is within the lower lumbar region. The vertebral bodies and IVDs of the lumbar vertebrae are thicker anteriorly than they are posteriorly, exhibiting the shape of a wedge. During adaptation to a short leg, the lower lumbars rotate posteriorly on the shortened side in an attempt to compensate for the slanted sacral base. Unfortunately, this rotation produces a prolonged deformation of the lower lumbar IVFs that tends to encroach on the nerve roots on the side of posteriority and add tension on the nerve roots on the contralateral side. Although the sacrum also tries to rotate to adapt to the position of the rotated L5, the attempt is in vain because the sacrum is held in a vise-like grip by the ilia assisted by the strong sacroiliac ligaments and superimposed body weight. The lumbar vertebrae above L5 also rotate and laterally bend in accordance to their respective base of support. In a typical spine, it is rare to find levelness achieved below the interface of the disc of L2 and the superior surface of L3.

Compensatory Thoracic Rotation.   The mechanisms of pelvic sway and lumbar rotation described above attempt to swing L3 sideward for 1 3 cm, but this cannot be tolerated because it places greater weight on that side. The long muscles of the legs and lower back are forced to remain tensed to restrain this sway from increasing. So it is at this point that equilibratory forces begin to return the spine toward the median line, which it usually reaches in the region of the lower thoracic spine, to distribute body weight more equal bilaterally. While the perimeters of the lumbar vertebrae may appear to have rotated considerably, it should be noted that the vertebral canal has only distorted slightly because each vertebra has rotated only slightly in relationship to its adjacent vertebrae: the spine is not only designed for segmental motion, it is also designed for protection of the contents of the vertebral canal. Furthermore, if the lumbar spine is normally flexible, the lower thoracic vertebrae are progressively less so because of their attachment to the thoracic cage. The necessary counterrotation of the thoracic vertebrae, in compensation to the contralateral lower lumbar rotation, is usually complete by the level of T8, at which point the vertebrae thereafter rest on a relatively level plane. Another curve is then produced to return the spine to the midline near the level of C7 or C6.

Although the compensatory shifting mechanisms described above are slight, each in its own way attempts to contribute a benefit to the overall adaptation to an anatomical short leg (Fig. 1.9). It should also be noted that the mechanisms described and their effects are the ideal and the result of an extremity deficit likely acquired at birth or during childhood when the spine was supple enough to regain balance easily and completely. Such ideal adaptation could also be achieved during puberty or early adulthood if the spine is supple enough.

Maladaptation Attempts.   During the aging process, connective tissues tend to lose their youthful degree of flexibility, elasticity, viscoelasticity, and plasticity. The rib cage especially tends to become tough and tight, and the spine is forced to use whatever compensatory mechanisms are available. When the forces of adaptability are meager, we may see the unfortunate picture of a cervical spine that has had to distort itself to a great degree to "catch up" the lost balance which stopped at the lower thoracic spine. Fortunately, like the lumbar vertebrae and discs, the cervical segments are also wedge shaped and this helps considerably. There is also the biologic necessity to maintain, if possible, level eyes. This sometimes forces a high degree of lateral flexion at the occipitoatlantal articulations with all the danger of nerve compression and/or irritation that we know is possible in this highly vulnerable area of the spine.

The spine is always subject to the trauma of daily living (stumbles, jars, falls, blows, strains, chronic biomechanical microtrauma, psychic tension, etc), and it is disturbing to see the spine of a patient in which the mechanisms of adaptation are continually being overtaxed and overthrown by fixation-subluxations. These deficiencies add to the noxious process and introduce new causes of imbalance that force adaptive reserves to start new efforts at several stages. It is this poorly adaptable spine that we see so frequently within our respective practices. But let us not forget that even a perfectly rebalanced spine can and will, sooner or later, become functionally inadequate as mechanisms of rebalancing lose their ideal properties.

Adding the Factor of Fixation.   We should not insist that all the compensations described are seen only in the standing position and disappear in positions that eliminate the basic factor of imbalance such as the influence of an anatomical short leg. Ideally, they should not exist in the sitting and recumbent postures. However, such adaptive forces necessary in the erect position will, little by little, tend to become fixed and remain in the state of compensation regardless of the position assumed, whether it serves a beneficial purpose or not. In the situation of adaptation to a short leg, such fixation is especially true in an individual whose occupation requires prolonged hours of standing, for it is in the standing position that the involved muscles, ligaments, and cartilages have been forced to change their architecture. The ligaments especially on the concave side of a spinal curve tend to shorten and those on the convex side of the curve stretch to conform to the demands upon them. Then, and only then, will the lumbar curve, the sacral adaptation, the iliac rotation, the thoracic counterrotation, the trochanter phenomenon, and the flattened longitudinal arch become static, fixated. As such, they must not be "replaced" but mobilized. Thereafter, the role of the doctor of chiropractic changes from therapeutic to preventive. And unless the reason for the focal imbalance is found and corrected (eg, a short leg), all the fixations associated will recur.

Testing a Patient's Spinopelvic Adaptability.   The following test will demonstrate to the student of dynamic chiropractic a patient's ability to adjust to imbalancing factors: First, position the patient in front of a plumb line and dot the back with a skin pencil where the vertical line falls. Second, place a piece of wood or a book about 2-cm thick under a patient's foot. Observe the changes of the plumb line relative to the patient's spine and pelvis, and mark with a different color the points at which the line crosses the patient's cervicals, thoracics, lumbars, and sacrum or buttocks. Then place the block or book under the other foot of the patient and mark the patient again with a different color. If this test is first conducted with many supple spines, the examiner is likely to be astonished to see how much imbalancing a normal spine can withstand. Sometimes, it does not appear to react with any difficulty to even a 3 cm foot raise. Then compare this to the reactions viewed with typical adult patients. Some spines will not be able to adapt to even 1 cm of change, and some changes witnessed will be abnormal. Although this test will not be of benefit in localizing the specific sites of fixations, it will show the diverse changes that can take place within an individual's spine that are due to imbalancing influences.

The Mechanisms of Irritation

Gillet's studies continually verified several major characteristics of fixations, one being that the pathogenicity of a fixation varies inversely to the degree of fixation existing. In a unilateral nontotal fixation, for example, signs of irritation will be found on the movable (contralateral) side of the vertebra and not on the side of fixation. In a partial bilateral fixation in which some movement occurs on the A-P plane, the signs of irritation will be bilateral and often of the same degree on both sides. In a total fixation, there are rarely any signs of irritation at the level of the involved segments with one notable exception: the occipitoatlantal articulation.

Another finding of Gillet was that if the area of the spine in fixation was actively or passively flexed or rotated several times, skin temperature readings tend to immediately increase and then decrease upon rest. This supports the hypothesis that the site of fixation, especially if degeneration has occurred, will exhibit signs and symptoms of hypofunction (eg, anesthesia, paresthesia, vasodilation, stasis). This would explain why a total fixation (eg, an ankylosed articulation) is not painful but important clinically because of the extraordinary motion it forces on adjacent mobile articulations in the kinematic chain and by the secondary fixations it produces.

When a unilateral fixation exists that allows some contralateral movement, that motion will occur around an abnormal axis which, if forced, causes a distinct pivoting-type of aberrant joint separation rather than the normal translatory gliding or sliding of the articulating surfaces. Oblique x-ray films of the spine, for example, will reveal reduced facet mobility on the side of fixation and separation of the facets contralaterally which will widen further when the patient's spine is forced into flexion or rotation.

Although there is a tendency of many within chiropractic to narrow their practices to the treatment of musculoskeletal disorders, Gillet strongly believes that a subluxation complex is involved in many functional disorders of the viscera. He also proposes that many of these disorders are due more to faults in autonomic innervation than to irritation or compression of the cerebrospinal nerves. The question then arises why a subluxation should affect the smaller sympathetic and parasympathetic nerves without seemingly producing greater harm to the extremely larger motor and sensory nerves. He answers this by calling attention to the position of the vertebra in fixation, whose motion may be blocked either within or beyond the normal range of motion. The latter occurs when an articulation is forced into a compensatory movement that it would not normally take.

This type of subluxation was frequently described in pioneer chiropractic literature. In has been absent in more recent years because it has not conformed to the data about normal vertebral motion. Gillet contends, however, that when such abnormal motion is forced to occur, the facets are displaced, the intervertebral foramen is abnormally closed, the IVF contents are impinged, and processes leading to neurologic, circulatory, and osseous degeneration in this area are formed that involve the most vulnerable tissues first. If occurring in the thoracic spine, for example, we could have visceral symptoms but no intercostal neuralgia associated. This could be called a pathologic subluxation in contrast to the physiologic subluxation in which motion is restricted within the normal range of motion. In the latter, we would expect to find minimal compression on or stretching of the involved IVF contents. Fixations producing sympathetic abnormalities appear to produce far less secondary contractions in the long spinal muscles and, therefore, far less postural distortion.


Potential Effects of the Summation of Irritation

It has been perplexing to many chiropractors of a narrow school of thought why doctors of chiropractic using widely divergent techniques, medical doctors, doctors of osteopathy, physiotherapists, Christian Science practitioners, etc, frequently obtain comparable results on seemingly the same types of cases. Typical rationalizations either deny the allegations of others or attribute the benefits achieved to suggestion or a placebo effect. Our competitors have done the same when the benefits to our form of chiropractic are described. Obviously, there are several factors at work during a healing process that can be activated either directly or indirectly through a wide variety of approaches.

      Individual Responses to Adverse Conditions

Every practitioner who has been in practice for several years has seen patients with frightful compensations that exhibit little handicap and few symptoms. There are also those patients in whom only minor, recently acquired fixation-subluxations produce grotesque manifestations. In each situation, the fixation-subluxations found may be either a cause or an effect of some other disturbing focus.

We have previously described how an articular correction made in any part of the spine (or anywhere in the skeletal system) has an influence on the neuromusculoskeletal system as a whole. This is especially true with partial muscular-type fixations. Thus, the correction of an atlas fixation will have an affect on the sacrum and possibly as distal as the feet, and the correction of a metatarsal or sacral fixation will have an affect on the atlas. This fact does not mean that one fixation is necessarily the cause of the remote effect; it just means that it can be one factor within the causal picture.

There is, however, far more to consider in the analysis of the cause of disease than articular fixations and their correction. The effects of pathogenic microbes, parasites, toxins, poisons, excessive heat or cold, malnutrition, poor habits, physical and psychologic stress, etc, should not be overlooked. Any one of these factors can produce illness in itself, but more frequently each plays a variable contributing share or predisposing role in the health status of the patient at hand. See Table 1.2.

Type of
Stress      Examples                                              
Mental      Anger                          Divorce
            Anxiety                        Emotional overexertion
            Changes in lifestyle           Frustration
            Changes in sex life            Loss of a job
            Constant tension               Loss of social status
            Death of a loved one           Mental exhaustion
            Depression                     Phobias

Physical    Biomechanical microtrauma      Insufficient rest or sleep
            Changes in environmen          Obesity
            Dislocation                    Overexertion, prolonged
            Fixation-subluxations          Postural imbalance
            Fracture                       Sprain
            Homeostatic malfunction        Strain
            Inadequate exercise            Structural distortion
            Inherited impairments          Surgery

Thermal     Abrupt temperature changes     Frostbite
            Burns                          Heatstroke
            Dehydration                    Temperature extremes

Chemical    Caustic chemical contact       Food additives
            Chemical depressants           Herbicides
            Chemical stimulants            Malnutrition
            Denourished foods              Pesticides
            Drugs                          Poisoning
            Endotoxins                     Pollution
            Environmental anoxia           Radiation
            Exhaust fumes                  Toxicosis

Gillet believes that the pathogenicity of any agent or act that is detrimental to health is summed with others present until they accumulate to the point where the reserve forces and defenses (eg, neurologic, hormonal, immunologic) of the body become overpowered. He proposes that each individual has a certain hereditary or acquired health-index (ie, a threshold of dysfunction).

      Neural Stimulation vs Irritation

The physiologists of Europe make a subtle differentiation between biologic stimulation and irritation. They consider stimulation to be any circumstance that sets up a normal action or response in a tissue or function. Thus, the sight and smell of tempting food to a hungry person does not irritate the optic and olfactory nerves, higher CNS centers, or the salivary glands; rather, the visual image and odor just stimulate certain tissues to act in a normal manner that is beneficial to an individual's health and well being. It is usually a subtle yet precise reaction, adapted to the needs of the moment. In contrast, any situation that is dangerous to the life or integrity of a body is considered to be irritative to the tissues responding. It is usually a more violent reaction such as when drawing the hand away from a hot or otherwise dangerous object, but it may be subtle such as during the development of antibodies to fight an invasion. Unfortunately, this differentiation between stimulation and irritation is not made in North America: here biologic stimulation and irritation are considered to be synonymous.

      The Physiologic Stress Factor in Illness

We are indebted to Hans Selye for his descriptions of the nonspecific mechanisms that the body initiates to defend itself against danger and stress (Fig. 1.10). Unfortunately, he did not differentiate between normal and abnormal defensive reactions in time or degree. We can, however, divide diseases into two categories for study in which:

(1) the symptoms are overanxious reactions of the body to rid itself of a new or chronic irritation; and

(2) the manifestations reflect degeneration of diseased tissues.

According to this classification, a majority of symptoms belong to the first category. Normal defensive reactions (eg, fever, tachycardia, hypertension) may become so poorly integrated or out of control that the overreaction progresses to an action that kills the individual.

In this context, we can consider a subluxation complex as being one possible effect of an excessive normal defensive mechanism. Gillet hypothesizes that the deep short muscles of the spine were the slowest to adapt to the upright biped posture, therefore in a constant state of alert readiness or preparedness for danger. In this functional state, he believes that an overreaction to a threat of danger is likely and that, once the danger has passed, a noxious self-perpetuating nerve-muscle cycle manifesting as contraction can be established.

From another viewpoint, Gillet believes that subclinical subluxations may so pre-irritate spinal nerves and lower their firing threshold that a minor peripheral irritation will produce reactions far out of proportion to the extent or severity of the lesion. In such a case, either peripheral or spinal therapy would likely be beneficial at least temporarily until the summation factor of circumstances detrimental to neurologic, musculoskeletal, circulatory, glandular, or psychic health arise again.

Let us suppose that an individual has a health index that is capable of withstanding a moderate degree of debilitating factors before dysfunction appears in the most vulnerable tissues. If smoking, drinking too much, infrequently exercising, chronic worry, having poor nutritional habits, and the irritation from subclinical subluxations deplete his or her reserves to just below the threshold of dysfunction, it would not require much additional stress (in whatever manner) to so overtax his systems reserves that one or more vital organs fail. A chill, unaccustomed exertion, a fright, loss of a job, or a mild infection may be all that is necessary for functional collapse to occur. Conversely, correcting existing subluxations and offering logical counsel regarding rest, diet, and exercise, even if wise counsel is followed only partially, may be all that is necessary to have the patient become symptom free and feeling well.

The same principles can be applied strictly from a spinal-health viewpoint. If a patient's health index is being depleted from cervical, pelvic, and some extraspinal fixation-subluxations and manifesting as neuromusculoskeletal complaints in tissues with a low threshold to stress, correction of any one or more of these factors may be enough to make the patient symptom free and feeling well.

In discussing this concept with students, Gillet admonishes that "truth is always complex; all generalizations are false, including this one."

      The Hereditary Factor

Patients who are born into families whose members have lived long lives for generations often appear to come into this world with an intrinsic genetic makeup for longevity in spite of some adversities that would lead to the early death of another. Many extremely heavy drinkers and smokers who overeat and avoid exercise long outlive their doctors who neither drink or smoke, are careful in their diet, and exercise frequently. Population statistics are useless in predicting the actions and reactions of an individual. We must learn to deal with the patient and circumstances at hand not on our subjective expectations, regardless of how valid they might be when related to humanity as a whole.

      The Psychic Factor

When a patient enters a doctor's office, he or she does so for two reasons: the disorder existing and the disorder feared. Both must be treated and treated with skill, compassion, thoroughness, and confidence. Also, it should not be forgotten that:

(1) the patient's faith in the doctor's ability/honesty and

(2) psychotherapeutic suggestion designed to enhance the patient's hope in achieving rational goals are two therapeutic components in every act of healing, whether it be chiropractic, medical, or whatever.

Although women appear to have a higher threshold for pain than men, Gillet points out that nature appears to also have provided them with a compensatory lower threshold for worry. It is likely for this that females seem to suffer with cancer phobia more than males.

     Motion                          Coordinate
     Flexion                          + X
     Extension                          X
     Right rotation                     Y
     Left rotation                    + Y
     Right lateral flexion            + Z
     Left lateral flexion               Z