Each vertebra except the Atlas is composed of a body and an arch; the arch is made up of two pedicles, short, thick plates of bone extending outward and backward from the postero-lateral surface of the body nearer its upper than its lower border, two laminae, thin plates of bone extending backward and inward from their union with the pedicles and joining behind to form the spinous process, and has projecting from it seven processes, two transverse, one spinous, and four articular, two of which are superior and two inferior. The foramen enclosed by the body, pedicles, and laminae is called the neural or vertebral foramen and the canal formed by the connection of these foramina and completed by the ligaments which unite the arches is called the neural, vertebral, or spinal canal. It contains the spinal cord with its membranes and the roots of the spinal nerves. By means of the four articular processes each true vertebra except the first articulates with its fellows above and below.
The body of the vertebra is its largest portion and is joined to its fellows by fibrocartilaginous disks which are sufficiently elastic to permit some torsion and compression. Nine sets of ligaments, including the intervertebral substance just mentioned, bind the vertebrae firmly together. Many muscles are attached to the spinal column.
The intervertebral foramina are openings at the sides of the vertebrae, formed by the notching of apposed pedicles. These openings are surrounded by bone, cartilage, and ligaments and vary in shape in different sections of the spine. They permit the exit of the spinal nerves and their sheaths, the re-entrance of some nerve fibres into the neural canal, and the passage of blood-vessels to and from the cord. The entire philosophy of Chiropractic focuses at the intervertebral foramen because there we find the primary cause of all pathological changes in the body.
The spinous and transverse processes merit particular description since they are the levers by which vertebrae are adjusted and nerve impingements at the intervertebral foramina corrected. But it will be found easiest to describe these processes separately in different sections of the spine and before proceeding to this description, a brief picture of the peculiar vertebrae will be presented.
The Atlas is a bony ring composed of two arches, an anterior and a posterior, separated in the recent state by a transverse ligament. Its body is detached and appears as a tooth-like projection upward from the body of the Axis, the odontoid process, which articulates with the anterior arch of the Atlas and around which the Atlas rotates, a ring around a pivot. The Atlas supports the head upon its lateral masses, two wedge shaped bodies between the anterior and posterior arches, thinner internally than externally. It has no spinous process but merely a tubercle where the laminae join, so that it can be palpated only from the sides upon the tips of its long transverses. The first Cervical, or suboccipital, nerves emerge by a groove above the pedicles instead of through a foramen.
The Axis, or second Cervical, is distinguished by its large, strong spinous process, which is bifid at its tip, by its superior articular processes which rest upon body, pedicles, and transverses, and by its odontoid process, upreared from the body.
The Seventh Cervical, or Vertebral Prominens, usually has a large spinous process, presents no foramina in its transverse processes, or only one, the left, and shows no facets on body or transverse for the rib articulation, as do the Dorsals.
The Sacrum is the largest vertebra; is curved with its convexity backward; is commonly made up of five fused segments; has only rudimentary spinous and transverse processes except the first; and shows sixteen openings, eight anterior and eight posterior, or four on either side of the median line in front and the same number and arrangement behind. These openings permit the exit of the anterior and posterior primary divisions of the sacral nerves separately.
The Coccyx, usually composed of four fused segments, is a triangular bone which articulates with the Sacrum above and is free at its distal extremity. Its portion of the neural canal is open posteriorly and contains merely the thread-like termination of the cord membranes. It is frequently ankylosed to the Sacrum, sometimes in an abnormal position so as to impinge the single pair of coccygeal nerves.
The different regions of the spine show decided differences in structure, though all resemble each other. The Cervicals are smallest, the Dorsals next in size, and the Lumbars largest and strongest of the movable vertebrae. The Dorsals have facets and demi-facets for the articulation of the twelve pairs of ribs with their bodies and intervertebral substance, as well as oval facets upon the anterior aspect of their transverses for articulation with the tubercles of the ribs.
The spinous processes are smallest and usually bifurcated down to and including the fifth. The sixth may show a plain bifurcation, or on any Cervical the bifurcation may be so small as to be imperceptible to touch. The spinous process of the second overlies that of the third so as to make the latter very difficult of detection. Indeed, all cervical spinous processes down to the sixth are harder to palpate than those in other regions, owing to the anterior cervical curve. The processes lie in a groove between prominent muscle ridges.
Dorsal spinous processes are usually single, although the last four, three, two, or one may show plain bifurcation in certain individuals. They are somewhat pointed and overlap, except the lower ones, the obliquity being greatest in the mid-dorsal region and least at the first and last dorsals.
Lumbar vertebrae have broad, flat-tipped spinous processes much larger than the others. The last Dorsal may sometimes appear like a Lumbar in shape, so that the change in shape commonly supposed to mark a division between Dorsals and Lumbars is not always an infallible guide.
The transverse processes in the cervical region are very short and lie close in front of the articular processes. They are pierced by foramina for the vertebral artery and vein, except the seventh, which may have one foramen or none. They are difficult of access for palpation because of their shortness and the amount of overlying muscle, but may be reached from the front and side by drawing back the sternomastoid. They increase in length from the second to the seventh.
In the dorsal region the transverses are larger and stronger and more constant in size, shape, and direction, serving to support rib articulations. They extend in a curved direction outward, backward, and slightly upward from the union of laminae and pedicles and terminate in a large subcutaneous club-shaped extremity which may be readily palpated. The eleventh and twelfth dorsal transverses do not articulate with the ribs and must therefore be used with caution or not at all as levers for adjustment. The dorsal transverses are located on a higher level than the spinous processes. In the case of the upper three dorsals the transverse lies in a plane which would cross the mid-spinal line between its own and the next superior spinous. In the mid-dorsal region the transverse is even with the spinous of the vertebra above, though the relation may vary slightly. The lower dorsals return to the same relation as the upper.
The transverse processes of the Lumbars are relatively light compared with the general structure of the vertebrae and are found just even with the interspace between their own and the adjacent superior spinous process. They vary greatly in size, length and strength and may be used as levers for adjustment only when they are large enough to be clearly palpable through the muscle mass which separates them from the body surface.
Preparation of Patient
In all cases where a complete spinal examination is intended the preparation is essentially the same. Have patient arrange clothing so that the spine is exposed to the touch throughout. Avoid bands of cloth across the spine, as these interfere with the necessary continuous gliding movement of the fingers. Advise the patient, if a female, to wear waist or dressing sack, reversed, and have skirts loosened at the waist. If a man, he should strip to the waist and wear coat or coat shirt reversed.
Position of Patient
This varies widely according to circumstances but for general purposes use position:
(A) Place patient on stool, feet even on floor and body in an easy, relaxed position. This may be modified by asking him to