Definition

A vertebral subluxation is a displacement, less than a dislocation, in which the chief element is the partial loss of normal apposition of the articular surfaces of the subluxated vertebra with those of the vertebra above or below, or both. Or, Vertebral subluxation is a permanent partial dislocation.

How Produced

Subluxations are primarily caused by trauma—falls, blows, strains, etc., being the chief factors. Hereditary weakness in structure of some part predisposes by rendering that portion more easily displaced.

Subluxations are never hereditary but may be congenital through violent or instrumental delivery into the world or may appear hereditary because they occur shortly after birth through the effect of light jars upon the hereditarily weakened segments of the spinal column.

They are always the result of concussions of forces; never of forces acting entirely within the organism. They result from the contact of the body with its environment.

It has been said that muscular action in response to peripheral irritation may produce subluxation. The laws of reflex action render this impossible. Given a normally aligned vertebra, and consequently normal nerves and a normal reflex arc in that segment, the ventral horn cells respond to a slight peripheral stimulus by exciting muscular contraction on the same side with the irritation. If the irritation be sufficiently increased, the response occurs on both sides but most strongly on the side from which the irritation comes. Greater irritation merely serves to cause greater distribution of the responsive action. (See any standard physiology on reflex action.) In no case will the difference between the contractions of muscles on the two sides be sufficient to displace a normally aligned vertebra. Nature has provided against that contingency.

Given a subluxated vertebra causing nerve impingement and thus interruption of the normal action of the reflex arc, irritation may result in greater contraction upon the opposite side than upon the side of the irritation. This is an abnormal condition and accounts for the increase of previously existing subluxations under pain or peripheral irritation. But in every instance trauma must and does precede and cause subluxation.

Reaction of Secondary Causes

Once produced, however, a subluxation may not cause noticeable effect until it has been increased in degree by the reaction of forces within the body such as poisons, general fever, etc. Thus germs, dietetic errors, exposure to sudden temperature changes, waste of energy through abnormal mental activities, as hate, fear, worry, etc., or through physical excess—in fact, all the secondary causes of disease may appear to have produced a subluxation. In fact, they have merely accentuated that which already existed and have done so through the muscular contractions which they induced.

General thinning of intervertebral substance through a condition of disturbed metabolism itself produced through the agency of some one serious subluxation, may narrow all the foramina and increase impingement of nerves at any point where a slight subluxation previously existed. An irritated nerve may become swollen and the nerve impinged at the foramen.

Law Governing Location

So definite is the law governing the effect of force applied to a given portion of the body upon an associated vertebral segment that the skilled Chiropractor who has studied vertebrate segmentation thoroughly may determine, from the history of a fall or injury, the vertebra which would tend to be subluxated by that injury and the tissues controlled from that part. The rule is this:

Force applied to any body segment tends to subluxate the segmentally associated vertebra. This subluxation tends to produce disease throughout the area of distribution of the subjacent pair of spinal nerves.

The task of explaining this law seems hopeless unless the student is familiar with human embryology and the life history of the vertebrata, as well all the details of human anatomy. To such a student the law will be self-evident, so interwoven with the threads of higher organization as practically to form its pattern.

In simple terms we might offer this general statement. Any force applied to the body with sufficient violence will produce subluxation of the vertebra above the spinal nerves supplying the injured area. Thus, the brachial plexus controls the arm and shoulder and connects with the spine by way of the 5, 6, 7, 8, Cervical and 1 Dorsal nerves. Any force striking the arm or shoulder tends to produce subluxation of the sixth or seventh Cervical or first Dorsal vertebra so that all permanent disease conditions resulting will be found in the arm or shoulder or nearby tissues of the neck.

This theme presents a magnificent field for individual study and research but is, per se, beyond the limitations set for this work.

Effect of Subluxations

Slight subluxations may exist, because of the adaptation of surrounding parts and the slight play within the intervertebral foramen, without producing noticeable effect. They always, however, evidence a tendency to disease.

The majority of subluxations do produce disease, to some degree, and do so by impinging nerves. Impingement may be either by pressure against a nerve or ganglion or by constriction of a nerve where it passes through an intervertebral foramen; the former occurs in the case of the Cervical sympathetic, the sub-occipital nerves, and the sacral nerves; the latter is the commoner form in Dorsal and Lumbar regions of the spine. Probably the most positive constriction of a nerve which can occur within the body is to be found in rotation of Lumbar vertebrae; the body of the rotated vertebra encroaches upon the inferior nerve on the side opposite to the direction taken by the spinous process.

Either variety of impingement produces disease, morbid structure or function, by irritation of the nerve: light impingement irritates, heavy impingement partially or completely paralyzes, the nerve.

VARIETIES OF SUBLUXATION

According to the abnormal relations between vertebrae subluxations may be variously described as rotated, tipped, anteriorly, posteriorly, or laterally displaced. They commonly combine two or more of these forms, so that the purely rotary or the entirely lateral subluxation is uncommon.

Rotation

Every vertebra has a vertical axis around which it tends to rotate. This axis is not always the center of mass but depends upon the arrangement of mass, the fixity of cartilages, ligaments, and muscles, which tend to hold some parts of the vertebra more fixed than others, and the apposition of articular processes, which tends to prevent movement in certain directions.

The axis of rotation of the first Cervical is the center of the odontoid process of the second Cervical, which articulates with the transverse ligament and anterior arch of the first. A frequent subluxation of the Atlas is a rotation around this process so that the one transverse is permanently posterior to its normal position and the other correspondingly anterior.

The axis of rotation of the Cervicals below the Atlas is in the extreme anterior portion of their bodies. This part remains relatively fixed in rotatory subluxation while the tip of the spinous process describes the greatest arc.

In the Dorsals the axis of rotation lies in the posterior portion of the centrum near the neural canal. When the spinous process appears laterally displaced in rotation the anterior portion of the body is slightly displaced in the opposite direction, twisting and straining the fibres of the intervertebral disk.

In the Lumbar region rotation is the commonest form of subluxation, the axis of rotation being laterally movable upon a transverse line between the articular processes in the beginning and shifting, as soon as the vertebra leaves its normal relations, to the junction of the articular process with that of the adjacent vertebra on the side toward which the spinous process is moving. Thus, in rotation of the vertebra so that the spinous is to the right, the axis will be found on the right side, the superior articular process of the next vertebra serving as a support on which the inferior articular process of the rotating vertebra may turn. The processes are so firmly locked that unless the whole vertebra be quite posterior little lateral movement of the spinous process is possible without marked rotation. The body describes the greatest arc because it is further removed from the center of rotation than is the tip of the spinous.

Tipping

This is a subluxation in which the one transverse process is, or appears to be, superior or inferior to the other. It occurs frequently to the Atlas in combination with lateral subluxation. In fact, the shape of the occipito-atlantal articulations is such that, if the remaining Cervicals maintain their proper relation to each other, the Atlas cannot be laterally displaced without a certain amount of tipping. It will be relatively superior on the prominent side and the head will be tipped toward that side; that is toward the side of the lateral displacement. Thus, on account of the wedge-shaped lateral masses, if the whole Atlas be to the right of its normal position the right side will be superior and the head tipped toward the right. This is only true when the vertebrae below maintain a normal interrelation.

Approximation

This is a name applied to that condition in which, on account of changes in the intervertebral disks due to subluxation interfering with metabolic processes, the bodies or spinous processes of vertebrae are crowded too closely together.

Occasionally a spine is found in which, on palpation, the spinous processes are found to be crowded together in groups, sometimes of two or three, sometimes of five or six; no two interspaces appear equal, a very wide one being succeeded by one or two which are almost inappreciable; the variation in width of the interspaces does not correspond to the known normal variation in those regions where the changing obliquity of spinous processes should modify the relative width of successive spaces. We expect, for instance, to find a wider space between third and fourth Dorsals than between second and third; if we do not find this difference it is doubtless due to cartilage change and the vertebrae are approximated.

In case of general thinning of intervertebral substance unequally divided between different sections of the spine the record will show that almost every vertebra is listed either S or I, and if a system of underscoring is used that these two directions are frequently indicated as most noticeable.

A study of the spine will make clear the fact that if the cartilage between any two Dorsal vertebrae be thinned in front the bodies of the vertebrae will be closer together and the spinous processes more widely separated; the spinous process of the upper vertebra will be crowded against the one superior to it and that of the lower against the one inferior to it. These spinous processes are said to be approximated.

The correction of S or I subluxations, then, depends upon correction of disturbed nutritive processes.

Lateral Displacements

According to the usage of earlier writers on subluxations this term (lateral displacement) included rotation of the vertebra as well as those changes in position in which the whole or nearly all of the vertebra deviates sidewise from its normal position. Since the introduction of the term “rotation” into the description of subluxations, the meaning of the term “lateral displacement” is much more restricted. It refers now to a condition which probably occurs in the strictest sense only in the Cervical region, most frequently with the first and second Cervical, the two being subluxated together.

We have already stated that the most important fact to be determined regarding the Atlas is its lateral displacement, since this produces the greatest impingement of nerves. Lateral displacement of any other Cervical can best be judged by examination of the transverse processes, since by palpation of the spinous process alone it is quite impossible to distinguish between lateral and rotary subluxation.

In the Dorsal and Lumbar regions the R or L used to describe the position of the spinous process most often indicates rotation of the vertebra. While it is perfectly proper thus to describe the subluxation on a record, in the determining of the form of adjustment to be used the position of the whole vertebra must be considered.

Anterior Subluxations

Forward displacements may occur anywhere in the spine. In the case of the first Cervical they are usually, though not always, forward displacements of only one side—rotation—though the whole Atlas may be anterior if the Axis has moved with it or is tipped so that the spinous process is much superior. This is rare.

Any Cervical may be anterior; usually a series are anterior (if any) amounting to an increase in the Cervical curve—a lordosis. This condition may be corrected by transverse adjustments given from the front and side.

A Dorsal vertebra is only relatively anterior, the adjacent ones being relatively posterior, and the only possible correction at present is the adjustment of the posterior ones. A Lumbar cannot be anterior unless those below it are also anterior, on account of the locking of articulations. Discovery of anterior Lumbars is quite common. The fifth Lumbar may be subluxated anteriorly by slipping forward on the Sacrum; it must be superior at the same time, on account of the shape of the articulating surfaces which face downward and forward. The spinous process is crowded closely against the fourth while the body of the fifth is too widely separated from that of the fourth.

Posterior Subluxations

There are many Chiropractors who have always considered the posterior subluxation more than any other, not because it produces greater nerve impingement than others but because it is easiest to detect; it intrudes itself upon the attention of the unskilled examiner most persistently. Nor should its importance be underestimated, though we now realize that in some instances a rotated or anterior vertebra may cause more nerve impingement than a posterior one.

The posterior subluxation in the lower Dorsals and Lumbars is the easiest variety to adjust; in this region a posterior displacement of one vertebra tends to bring with that one the next adjacent superior one, the sharpest deviation occurring between the posterior one and the one below it.

Any vertebra may be posterior: the Atlas is rarely so as a whole, and never unless the Axis is also displaced backward; the Cervical and Dorsal regions present frequent variations of this sort, which must not, however, be confused with long, prominent, or overdeveloped spinous processes; the Sacrum may be posterior to the ilium on one side, or to both ilia.

Occipital Subluxations

Mention should be made here of a form of subluxation not strictly vertebral—displacement between the condyles of the occipital bone and the lateral masses of the Atlas. This occurs when the head has been moved too violently upon the Atlas so as to cause an immediate nerve irritation and muscle tension sufficient to hold it in its abnormal position. The Cervicals may be quite normal below the Atlas though this, of course, is not the rule. Correction of occipital subluxations is made by applying force to the Atlas and to the skull, sometimes by holding Atlas and rotating the skull.

Age of Subluxations

The relative age of subluxations may be determined, within rather wide limits, it is true, by a study of the form of the spinous process. Newly acquired subluxations are sharply defined, having noticeable edges on the spinous process. In time they tend to become rounded and blunt and appear to cover more surface, just as the mountain range which, when first upheaved, is sharp and rugged, gradually rounds into regular curves through the work of the elements.

In this way Nature protects the subluxated vertebra from further contact with the environment surrounding man, the rounded process offering less opportunity for a blow or shock to affect it.

Changes in Shape

Bone diseases such as rachitis osteomalacia, etc., and especially Potts’ Disease, or spinal caries, make marked changes in the shape of vertebrae. Also a subluxated vertebra may gradually assume a shape suited to the abnormal position it occupies, the commonest change being the assumption of a wedge shape by the centrum. This is a great obstacle to adjustment, as the abnormal shape of the vertebra makes it tend to settle after each movement into the old abnormal position.

There are few spines without some more or less misshapen vertebrae.

Ankylosis also makes great changes in the shape of vertebrae. There are two kinds of ankylosis—true and false. The first is a deposit of bone cells upon bone, often the formation of a bridgelike structure to hold contiguous vertebrae together. This may bind any portions of the vertebrae but most commonly holds the bodies, in which case it can only be appreciated by detecting the lack of movement between normally separable vertebrae. False ankylosis occurs with fever in bone and consists in an exudation of bone substance which sometimes produces remarkable distortions of shape.

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