III. Static Scoliosis.—Thequality in.the lengths of the legs causes a distortion of the pelvis and the spine. flowerer, to hold the trunk vertically above the pelvis the patient must distort the spine into a scoliotic curve. A difference in the length of the legs is observed in con genital dislocation of the hip, in diseases of the hip-, knee- or ankle-joint, in paralyses, and in other marked deformities of the leg. Differences of from 1 to 3 em. in the length of the legs occur without any apparent cause. Until the eighteenth year such differences may disappear or at least become less.
IV. Habit Scolioses.—The exciting cause in the great majority of seolioses is the habitual assumption of a posture in which the spine, for a longer period, takes on a lateral curvature. This attitude may be purely passive; for example, when a child sleeps during the night regularly on one side and uses a large pillow the spine always assumes the same lateral curve (Fig. 81). But the lateral curvature may likewise be pro duced by active muscular action. It happens in all unequal, unilateral exercise, i.e., working as cabinet maker, playing the violin, playing lawn tennis or carrying school books on one side only (Fig. S2). When in pain, as from a furuncle, or pleurisy or rheumatism, patients are induced to bend the spine so as to form a lateral curvature in attempt;ng to get relief. Faulty posture in writing may be looked upon as a combination of the active and passive factors ing lateral curvature of the spine. That, fortunately, only a small ber of these scolioses develop as a result of faulty attitude, we must attribute to a further fact which of itself causes a deformity of the spine. It has been surmised that rachitis even in the later school period ens the bones, making them pliable and yielding to faulty terming the disease rachilis but the present material is not cient to warrant a definite opinion.
One point, however, seems to be evident as a result of clinical experience, namely, that to the other causes an especial flexibility of muscles and ligaments and an abnormal softness of the bones must be added to trans form an occasionally occurring lateral curvature of the spine into a true scoliotie deformity.
V. Scolioscs Reselling from Other Causes.—Rachitis and habit arc in nearly all eases the predisposing and exciting causes of scoliosis. A very few cases are based on other ailments. Occasionally pleurisy and empyema may produce scoliosis as a result of the accompanying con traction of the lungs. In such cases the convexity is directed toward the sound side (empyemic scoliosis). Finally, paralysis of one erector spine muscle now and then may be the cause of a spinal scoliosis. The con vexity in such paralytic scoliosis is, as a rule, not directed toward the diseased side, as may be presumed, but generally turns toward the sound side. To overcome the deficient action of the paralyzed erector
spline muscle the patient bends the trunk toward the opposite side, the force of gravity and the support of the other sound erector spina. holding it in balanced suspension over the Pathological Anatomy The pathological anatomy of scoliosis has been most diligently studied by our most famous authors, Albert, Nicoladotti, Lorenz, floffa, Sehulthess, and others, but we are still far from solving this very inter esting as well as difficult problem.
It is manifest that in a scoliosis of short duration only trifling devia tions from the normal anatomy of the spine are found, while very marked scolioses of long duration produce pronounced changes in form and lime tion of the spine. In general, the following rule may be applied to the soft tissues and osseous vertebne: every part located 011 the concave side is shortened; every part located on the convex side is lengthened. Details may he lime considered only as they pertain to practical clinical conditions. Chief consideration must be given to the form of the thorax in a ease of scoliosis. Vertebrae and ribs are pressed together on the concave side, whereas on the convex side the ribs spread apart, thus enlarging the intcrvetehral spaces. At the same time the curvature of the ribs undergoes a change. On the convexed side the ribs arc deflected toward the front in the region of the posterior angle, thus producing the characteristic form of the posterior costal angle. Toward the front they become fairly straight. Just the opposite condition prevails on the con cave side of the trunk. The ribs are exceptionally straight posteriorly and display a somewhat pronounced deflection near the sternum at the articulation of bone A. nd cartilage, forming the so-called anterior costal hump (Fig. S3). As a result the space for the development of the lung on the convex side is materially diminished. Therefore, in marked scolioses the principal work in breathing is performed by the lung which is located on the concave side. The diminished exchange of air favors apical tuberculous infiltration in scoliotic patients. Mosse found among one hundred children fifty-three cases of infiltration of the apex. In dorso-scolioses the apical affection was found mostly on the convex side. The heart is often found to be hypertrophied on account of strain. Dis placements have also been observed in marked cases of scolioses. The aorta follows the scoliotic curvature, while the msophagus is displaced, or it may be kinked, only in marked deformities, thus offering an obstacle to passing a stomach-tube. Intercostal neuralgias, finally, are of great practical interest. They occur mostly on the concave side and are excited by the pressure on the nerves exerted by the compressed ribs. Neuralgias also appear on the convex side.