[Bone histomorphometric study in involuted fractured osteoporosis treated with 1-ethane-1-hydroxybiphosphonate (etidronate) during one year].

The efficacy of the biphosphonate etidronate has recently been demonstrated versus the vertebral fracture rate in fractured involuted osteoporosis in the literature. However, it would appear that the increase in bone mass (measured from the calcium density) may alone account for these results. The authors undertook a histomorphometrie study in 20 patients with a group mean age of 55 years presenting recent vertebral fracture in the context of osteoporosis, in order to assess the cell changes which may affect bone quality. This factor remains the only one which can account for the reduced number of fractures. The patients received treatment with phosphorus (1,500 mg/d) for 3 days followed by etidronate (400 mg/d) for 14 days every 90 days. A permanent daily intake of 50 mg of calcium and 400 IU of vitamin D was also administered. Each patient underwent bone biopsy of the iliac wing before and after one year of treatment (4 cycles). No change in the bone mass or architectural parameters was observed. However, general slowing of the bone remodeling was found, affecting the natality and activity of the osteoforming and osteoresorbing cells. However, this remodeling which is traditionally uncoupled in osteoporosis was once more coupled. This results in a slowing of bone loss, ageing of the bone present and no change in the architecture. Thus, the diphosphonates appear to have a beneficial effect on the quality of bone rather than on its quantity. This represents a novel approach to the treatment of osteoporosis.