[Quantitative histological study of the bone mass and cellular activity after 120-days decubitus. Trial of preventive protocols].

Bone biopsies of iliac crests, performed at the beginning and the end of a decubitus period of 120 days, were studied in 20 healthy volunteers men. The purpose of this experiment is to simulate the bony alterations of astronauts. The bony mass of all bed-ridden patients remained constant. In strictly immobilized patients, the rate of bony mineralization is decreased and the osteoclastic resorption activity is stimulated. In bed-ridden patients subjected to preventive physical exercises, the bony formation and resorption are increased. When prevention is administered with the use of a diphosphonate, the osteoid and osteoclastic parameters are decreased. When both types of prevention are administered, the osteoid parameters and the resorption activity are decreased but less markedly than in patients treated with diphosphonate alone.