[The effect of immobilization on the number and function of osteoblasts]

The influence of immobilisation on the number and function of osteoblasts was determined by morphological examination of normal rabbit bone and that that had been inactivated through surgery. Contrary to earlier supposition, after inactivation not only the osteoclasts but also the osteoblasts increase distinctly. Even retardation of the parathyroid gland by magnesium does not lead to decrease of the osseous structure. Therefore, it can be concluded that disuse osteoporosis is normally produced in its first weeks by a considerable activity decrease of even more osteoblasts and less by increased function of osteoclasts. The increase in number of osteoblasts and their decreased activity after immobilisation indicate that the mechanical stimulus gives the essential impulse for full osteoblast function.