Technic and Practice of Chiropractic

by Joy Maxwell Loban

The spinal column is composed of twenty-six segments called vertebrae, twenty-four movable and two fixed. The movable vertebrae are divided for convenience in study into three sections. There are seven Cervical vertebrae, twelve Dorsal, and five Lumbar in the normal individual. The number of Dorsals or Lumbars may vary by one in a rare case. These variations occur in about one spinal column in each five hundred and are usually in the Lumbar region, which may contain four or six vertebrae. A prominent first sacral spinous process may be mistaken for an extra Lumbar.

Five vertebrae have special names. The first Cervical is called Atlas; the second Cervical, Axis; the seventh Cervical is commonly known as Vertebra Prominens on account of its long and large spinous process, although this long process belongs to the sixth Cervical or first Dorsal instead in 35% of all cases; the large, irregularly fusiform vertebra just below the Lumbars and between the ilia is called the Sacrum; and the smaller one below it, the Coccyx. The latter is occasionally missing.

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.