240 VITAMIN D GROUP 



of gravity on the soft structure. After a few months the child begins to 

 spend much of his time in the sitting position. The pelvis must now support 

 the weight of the head and trunk, and as a result of this new stress a dorsal 

 kyphosis appears. When the child stands up, and later when he begins to 

 walk, the strain on the spine changes again. Now the dorsal kyphosis 

 changes to a sharp lumbar lordosis, and the spine pushes forward at the 

 promontory of the sacrum, thus further decreasing the anterior-posterior 

 diameter of the pelvis. In the severest cases, the head of the femur may 

 push up the acetabulum, thus further encroaching upon the pelvic space. 



In the period during which the child begins to sit up, various deformities 

 of the long bones may develop. The severely ricketic child sits cross-legged 

 and supports the weight of his body by extending his hands to the 

 table or floor. In this position the upper of the two crossed legs is bent by 

 gravity as it extends over the lower shin which acts as a fulcrum. At the 

 same time the wrists against which the weight of the body rests may also 

 bend. This pressure against soft and rapidly growing bones results in bend- 

 ing deformities. Occasionally, the bending may progress to actual angula- 

 tion of the epiphyses which is then bent towards the diaphysis. As the 

 growth of the diaphysis in the original axis continues, however, the bend 

 is accentuated. The process of growth may carry the bend some distance 

 from the epiphysis so that its real nature may not be easily recognized. 

 Such deformities occur, particularly at the lower ends of the tibiae and 

 fibulae, and in the lower ends of the radius and ulna. They occur particu- 

 larly when the rickets is severe at about the age of 2 years, when growth 

 in these areas is particularly rapid. Bending deformities may also be due 

 to fractures which occur chiefly in the severer forms of the disease. In 

 addition to the actual bone involvement, there is great relaxation of the 

 tendons in rickets, and this looseness seems to initiate or accentuate many 

 of the deformities. 



To summarize, curvatures of the shaft may result from bending of 

 softened bone, tilting and dislocation of the epiphysis, and as a result of 

 fractures. Posture may suffer from tendon relaxation. The typical deformi- 

 ties of the lower extremities which occur as a result of these forces are 

 bowlegs (genu varum), knock-knees (genu valgum), and saber shin de- 

 formity. The curvatures of the arms are much less marked than those in 

 the leg. Ovitward bowing of the humerus and exaggeration of the normal 

 curvatures of the radius and the ulna may be seen. 



The type of rickets we have been describing is the moderately severe 

 type. Park has pointed out that rickets may vary in degree. Both he and 

 Follis have described cases in adults and in children in which the only 

 evidence of the disease is a slight to moderate increase in the osteoid seam 

 around the trabeculae. This may be limited even to one aspect or side of 



