Etiologically two questions~ are to be considered, viz.: Is the rachitie asymmetry primary, and the scoliosis only secondary? May not the asym metry be due to shortening of one of the lower limbs, and the scoliosis again be simply secondary ? Leopold believes that scoliosis is the original lesion, the pelvic deformity resulting in consequence. That does not mean, he explains, that there are not pelves in which arrest of development nd atrophy of the sacrum may cause secondary deviation of the vertebrm ind consequent modifications in their form. Scoliosis and shortening of :be leg produce the same results, that is to say, unequal distribution of dm weight of the trunk, so that more pressure is thrown upon one side A the pelvis than upon the other. Primary scoliosis causes more marked deformity than shortening of the lower extremity. Rickets is most apt to cause curvature in the dorsal region; the spine bends towards the right in the majority of cases, the lumbar curve being merely compensatory. As the latter becomes more marked, the pressure increases until the last lumbar vertebrm are sometimes in contact with the posterior surface of the corresponding ilium; the deformity in this case is due directly to the pressure transmitted to the ilium through the spine, and in part, also, to the deviation of the sacrum, which shares in the lumbar curvature. Muscular contraction also influences the deformity. A number of power ful muscles are attached to the pelvis, and, in consequence of the deviation of the vertebral column, these act in a new direction, thus exaggerating the abnormal condition (so as to cause rotation of the ilium around its antero-posterior axis.) Schroeder does not admit the influence of scoliotic deviation of the spine, except in those cases (which he thinks are the rule) in which the sacrum shares in the compensatory lordosis. He affirms that the promontory is displaced towards one side of the pelvis, and that the iliac bone on the side corresponding to the scoliosis is turned upward, inwards, and back wards, at the same time being straightened, especially in the neighborhood of the cotyloid cavity, while the tuberosity of the ischium is deflected out wards, and the pubic arch is widened. The symphysis is slightly bent on the side opposite to the scoliosis, the line of the innominate bone on the contracted side is a little less curved than normal, while the sacro-cotyloid distance is much shortened. When the scoliosis is exaggerated, the coty loid cavity may approach so near to the promontory, that the pelvis as sumes to some extent the shape of the pseudo-osteomalacic type.
C. Kyphosis.—Kyphotie Pelves.
Kyphosis is characterized by anterior deviation of the vertebral column, which may include a large part of the spine, or may be quite circum scribed (true angular curvature), and confined to the dorso-lumbar, lum bar, or lumbo-sacral region. It may be due to localized diseases (caries, tuberculosis, etc.), or to rachitis, hence the following vareties of deform ity: 1. The pure kyphotic pelvis. 2. The kypho-scoliotic. 3. The kypho scolio-rachitic. When Pott's disease occurs during childhood (especially in the dorsal lumbar and lumbo-sacral regions), the pelvic deformity is most marked a. Pure Kyplumis.
Herbiniaux (1785) was the first to clearly describe the deformity; Schroeder, Spiegelberg, Leopold, and others, have since studied it.
A. Dorso-lumbar Kyphosis. this condition there is marked in crease in tho transverse measurement of the superior strait, as compared with that of the inferior. It seems as if the iliac bones had revolved about an axis passing through the centres of the cotyloid cavities. The spine has a posterior curvature, the angle of which is almost 90°. (Fig. 59.) The upper part of the sacrum is carried upwards and backwards, its an terior surface forming with the last 'lumbar vertebrae a slight convexity; the lower sacral vertebrae unite with the coccyx to form a concavity. The
anterior surface forms only a slight curve, as seen in profile. Its posterior aspect is nearly flat, as viewed longitudinally, and occupies a higher plane than the anterior. The sacrum is concave transversely, and the aloe project forwards strongly. . The coccyx is revolved around a trans verse axis, and is directed backwards in such a way that the iliac foss arc separated one from the other, while the ischial tuberosities, on the con trary, are nearer together than usual. The pubic arch is narrowed and the angle is more acute than normal. The ilia are more elongated from before backwards, the lines of the ossa innominata are less curved, and the cotyloid cavities are situated more laterally, and incline downwards more than in the normal pelvis. The iliac foss are flat, anterior inferior spines well developed, and the S-shape of the crests has nearly disappeared.
The pubic rami form an acute angle at their junction, they incline sharply backward; the ischial tuberosities are approximated.
B. Lumbo-sacral Kyphosts.—The principal changes are seen in the sa crum. It is diminished in size, the anterior borders of the auricular sur faces project in front of the corresponding surfaces of the ilia; the verse axis of the bone is shortened at the level of the upper foramina, and the concavity is more shallow, the former themselves are smaller and are separated by irregular intervals. The sacruin has a marked wedge-shape, especially at its lower end; instead of being largest at the level of the superior strait, its greatest breadth is at the first pair of foramina.
The deformities of the ilium and pubic bone are similar to those in the dorsal-lumbar variety, but are more marked. The pelvis is funnel-shaped, by reason of the increased size of the false pelvis and superior strait, and the transverse contraction of the inferior strait.
b. Complicated Kyphosis.
Kyphosis rarely exists alone; it is usually associated with scoliosis or rachitis, or it may accompany sacroiliac synostosis, luxation of the femur, etc. We shall describe, with Leopold, the non-rachitic kypho-scoliotic, and the kypho-scolio-rachitic pelves.
1. The non-Rath Kypho-scoliotic Pelvis. (Figs. 62 and 63. )—When kyphosis and scoliosis are located in the lower dorsal region, kyphosis is the more active factor, but it only affects the sacrum; scoliosis, on the other hand, only causes pelvic deformity when there is a lumbar com pensatory curve. When the two lesions are situated lower down, they both influence the deformity, the character of the deformity depending upon the predominating factor.
2. The Kypho-scolio-Racbitic Pelvis. (Figs. 64 and 65.)—Rickets and kyphosis act in precisely opposite directions, so that the deformity is often the resultant of two forces; the condition is often very complex, being modified by the different periods at which each of the forces began to act (before ossification was complete). Leopold mentions the follow ing features as characteristic of such pelves: The conjugate diameter of the brim is increased if the pelvis approaches the pure kyphotic type, varying from 3.2 to 4.8 inches, while in the scoliotic it does not exceed 3.4 inches. The conjugate of the outlet is absolutely shortened (being at least in. less than normal). The sacrum is increased in length and is more elevated than in the rachitic pelvis. The distance between the anterior superior iliac spines is relatively increased, being equal to or greater than that between the crests. The transverse diameter of the brim is relatively greater, while that of the outlet is shorter; the oblique diameters are lengthened, as compared with those of the scolio-rachitic pelvis, and, in consequence of asymmetry of the pelvis, are unequal. The sacro-cotyloid distances are relatively increased, according to the amount of unilateral pressure.