THE VERTEBRAL COLUMN. 



479 



no normal lateral curve in the spinal column. The spine may project abnormally 

 backward, forming a kyphosis; forward, lordosis; and more or less laterally, scoliosis. 



Kyphosis. The vertebrae are supported one above another by two points of 

 contact, a posterior one, formed by the articular processes, and an anterior one, formed 

 by the bodies of the vertebrae separated by the intervertebral disks. Of these two 

 supports, that afforded by the bodies and disks is the more important. The laminae 

 and pedicles with their attached articular 1 processes are frequently fractured, but the 

 shape of the vertebral column is but little altered; even after laminectomy the spine 

 remains comparatively straight. When, however, the bodies of the vertebrae are 

 destroyed, as occurs in tuberculous disease and crushing injuries, the anterior portion 

 of the spine collapses and the parts bend, the spines projecting backward forming a 

 hump (Fig. 479). Thus the angular character of the deformity is explained by the 

 method of construction of the spine. 



Besides this angular kyphosis there is another form, due to general weakness. 

 This is seen in rachitic children ; owing to a weakness of all the tissues the normal 

 curves become increased and, as in young children, the normal spine has one long 

 general curve with its convexity posteriorly, we find this curve greatly increased, 

 forming a rachitic kyphosis. 



Lordosis. When a child is born and for some time thereafter the spine pos- 

 sesses a slight dorsal and a pelvic curve. When it sits up and begins to hold its 

 head erect and look around, the cervical curve develops. Still later when it begins 



FIG. 479. Kyphosis or angular 

 antero posterior curvature, usually 

 due to caries of the bodies of the 

 vertebrae. 



FIG. 480. Lordosis or hollow 

 back, caused by congenital luxa- 

 tion of the hips. 



FIG. 481. Scoliosis or lateral cur- 

 vature of the spine. 



to walk the lumbar curve develops. An increase in the lumbar curve, or lordosis, 

 is caused by general weakness as just described for rachitic kyphosis, or it results 

 from some disease or injury interfering with the lower extremities and thus disturbing 

 the centre of gravity. This occurs in congenital luxation of the hips (Fig. 480), in 

 which the heads of the femurs are set too far back, and also in rachitic deformities 

 of the lower extremities, hip disease, etc. Likewise, if the abdominal viscera are 

 unduly prominent, the thoracic region is carried further back to maintain the bal- 

 ance, and hence a hollow back is produced. Ankylosis of the hip in a flexed 

 position causes lordosis when the limb is brought straight down as in walking. 

 Therefore in cases of lordosis one should remember that it is a secondary condition 

 dependent on diseased conditions of' the viscera or extremities and is comparatively 

 rarely an independent affection. 



Scoliosis. A normal spine is either absolutely straight or very slightly convex 

 to the right in the dorsal region, probably due to the increased use of the right hand. 

 While scoliosis is called lateral curvature of the spine, it is not a simple lateral 

 bending, but is a complex distortion (Fig. 481). R. W. Lovett has shown that a 

 flexible straight rod can be bent in one plane either anteroposteriorly or laterally, but 



