RAREFYING DISEASE OF THE SKELETON 417 



TABLE V. Urinary Indices of Physiologic Aging 

 OF Bone and Osteoporosis 



Accelerated Changes of Aging in Osteoporotics 



The distinguishing feature of patients with severe osteoporosis, 

 described in Table II, as compared with patients of comparable age 

 without osteoporosis, was bone failure or collapse of the vertebral 

 bodies of dorsal and lumbar spine. Figure 12 illustrates the relation 

 between the reduction in bone mass and the age. The number of 

 osteoporotic patients was too small for statistical evaluation, but suf- 

 ficient to suggest a relationship to aging. The shape of the curve that 

 describes the rapid rate of reduction of bone mass with time in 

 osteoporotics, and the more gradual decline that describes the rate 

 of normal or physiologic aging, indicated that the disease is most 

 active during the period from 50 to 65, and mav progress, but rarely 

 arises, after age 75. The various tissue (Table IV) and urinarv (Table 

 V) indices of change in bone structure and metabolism that have 

 been estimated and attributed to physiologic aging were also found 

 in patients with osteoporosis. The large amount of tissue with empty 

 lacunae and the patches of necrotic bone suggested bone circulatory 

 insujQficiency in osteoporotics to a greater degree than in nonosteo- 

 porotic aged persons (Table VI). Spontaneous fracture or bone 

 failure occurs in the spine, the ribs, and the neck of the femur, 

 where the cortex is thin and the necrotic osteoporotic bone is revas- 



