Part 14

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.