Under these terms are included certain deviations from normal relationships of the vertebræ, both in their superposition in the median line and in their rotation on each other, by which are produced lateral curvatures, with more or less rotary displacement. Of these deformities there is a rare congenital form which is due to fetal, or rather intra-uterine, rickets, but practically all rotary lateral curvatures are acquired. One-half of such cases begin before the twelfth year of life. It may also come on during adult life, as the result of bad postural habits, exclusive use of the right hand, etc. Altogether it occurs in about 1 per cent. of females and in a smaller percentage of males. Scoliosis being not a disease but rather a process of irregular growth, cannot be said to have a symptomatology. It is known rather by signs. Only in the advanced stage can it produce symptoms. It is rarely seen in its incipiency by either the surgeon or the physician. Not until parents have noticed distortions of the spine are these children usually taken to their medical advisers. Exception, however, should be made to this in respect to certain gymnasia and athletic training schools, where trainers are quick to notice irregularities of this kind. The abnormal curves thus produced are at first flexible, but later become fixed. In rapidly growing girls who take but little exercise there may be some muscle weakness, which may cause fatigue or even actual soreness. Pain is rarely present. The rate and extent of deformity are not subject to any rule. Spontaneous cessation ensues in practically every case, i. e., a stage of convalescence and arrest, at a time when the deformity may be but slight, or perhaps hideous.
The nervous phenomena attending lateral curvature, like the discomforts attaching to it, are mainly due to the increasing strains and stresses that are imposed on certain structures as the deformity occurs and increases. Of these, muscles and ligaments suffer most, especially those uniting the thorax and spine. Pressure effects on nerves and tissues may be produced by distorted ribs and vertebræ or by final displacement of viscera. The conditions which lead up to spinal curvature are attended often by neurasthenic and neurotic features, both mental and physical. As deformity increases impairment of function of thoracic as well as of the upper abdominal viscera will occur, and such patients are usually thin and anemic, rather than fat.
To mere lateral distortion is added, in every pronounced case, more or less rotation of the entire trunk. The curvature consists of one primary curve, with one or two secondary curvatures, according to the location of the first. If the primary curve be located in the mid-dorsal region there will occur compensatory curvature above and below in order that the head may still be kept in the line of the centre of gravity above the pelvis. Such secondary alterations are of much less import than the primary. The most common of the mid-dorsal curvatures, which occurs in nearly four-fifths of the cases, has its convexity to the right. While the right shoulder seems higher its scapula will be more pronounced and carried backward, the back and the chest below it will be more rounded, and in front the breast on the opposite side more prominent. The whole trunk in marked cases becomes so warped that the arm on one side will hang free while the other touches the pelvis; thus the back loses its symmetry either in the erect or stooping position. In the lumbar region there is compensatory curvature to the opposite side, which makes one hip and flank more prominent. By virtue of the rotation of such a warped spinal column there result certain anterolateral curvatures that may later become pronounced. While such changes are going on in the upper part of the trunk there is sufficient rotation of the lumbar segment to lead to tilting of the pelvis, with consequent limp, or a peculiarity of gait.
The degree of torsion of the spinal column is the best index of the real severity of a given case, and to it are due the most disfiguring features of the deformity. Torsion may even precede curvature, causing a prominence of one shoulder or hip as the first visible evidence of its existence.
Those forms of lateral curvature due to rickets occur most often in the dorsal region, and as frequently in boys as in girls. In most of these cases the constitutional condition will be indicated by other significant features. Another form much less frequent, yet well known, is the result of inequality of the length in the limbs, so that patients stand ordinarily with tilted pelves; hence, the limbs should be carefully measured in every instance. A truly paralytic form of scoliosis is also known, which is of the infantile type and due to some form of infantile palsy. Again, scoliosis is produced by shrinkage of tissues and contraction of old exudates occurring within the thorax and following chronic disease, as when the ribs on one side are drawn down after an old pleurisy or empyema. Extrinsic causes of lateral curvature are met with among several occupations when one side of the body is used more than the other, or when the individual habitually stands in an unsymmetrical position. In addition to this, the habitual right-hand habit, which seems instinctive, and which the majority of people exhibit, leads to excessive use of the right side of the body, with overdevelopment and consequent warping of the upper part of the skeleton. The young should be taught the use of the left hand as well as the right, i. e., to become ambidextrous.
The foreign surgeons have given the term ischias scoliotica to a form of lateral curvature involving rather the lower part of the spine and occurring usually in adults or elderly people, which is accompanied by more or less acute pain, usually assuming the type of sciatica. Its etiology is obscure, as is implied by the synonym scoliosis neuropathica. It is not a frequent malady, but usually chronic and refractory. It is best dealt with by fixation or immobilization.
Etiology.
—Predisposing causes of scoliosis may be both constitutional and inherited. They include general debility, rickets—with its accompanying osseous instability and liability to abnormal curvature—the consequences of various diseases of childhood, and anything which greatly lowers vitality. The actual causes include congenital or acquired defects, such as differences in the lengths of the limbs or other skeletal asymmetries; acquired abnormal position of the head due to defective vision, with its natural sequences; results of intrathoracic disease, such as empyema; faulty attitudes and bad developmental habits, such as those assumed often in school and elsewhere in sitting at a desk or standing in bad position, or at work in various ways. To these should be added the right-hand habit already mentioned. These may all be summed up as among the causes of asymmetrical growth and deformity, occurring as the result of ignorance or inattention, and allowed to go on indefinitely or until it is too late to correct the malposition. Theories of paralysis of individual muscles or certain muscle groups have been advanced, as well as of contractures, but usually these are effects which have been mistaken for causes. The bones have been blamed, but their changes are secondary results of pressure, save perhaps in some cases of rickets. The structures of the thorax have relatively considerable superimposed weight to carry, and both lateral halves of the thorax should be developed symmetrically in order to distribute this weight evenly. Nothing so influences skeletal development as exercise; thus even to assume and maintain the normal erect attitude requires a certain amount of muscular effort, and if each side be not given an equal task one will develop at the expense of the other, and thus lateral curvature is sure to result.
It is important to impress this on parents, teachers, nurses, dressmakers, and all who have a part in the care of the young, in order that they may realize the importance of ensuring symmetrical growth and of preventing the right-hand habit. It is to be expected that after deformity has occurred there may result a series of perversions of function in nerves, as well as in viscera; thus, respiration and circulation may be interfered with, the liver may be compressed, while, of course, autopsy will show all sorts of distortion of bone, among other pathological changes.