[Histomorphometry. Method for evaluating the bone mass].

The histomorphometric analysis of a non-decalcified trans-iliac bone biopsy allows the bone mass to be evaluated histologically and, more especially, enables the bone mass to be divided into its cortical and trabecular compartments. The parameters usually measured are the trabecular bone volume (TBV), the total bone density and the cortical thickness. The inter-sample variation for the TBV can be as high as 29 per cent for a given osteoporotic subject, but is only 10 per cent and 7 per cent respectively for groups of 10 and 20 subjects. This variation can be considered to be significant in larger groups with successive biopsies. There is a physiological bone loss with age, but the intensity and the profile of this decrease in the TBV is different in men and women. In cases of osteoporosis with vertebral compression, the TBV appears to be the most discriminating parameter between osteoporotic subjects and controls of the same age and sex and was always found to be less than 16 per cent in a series of 154 osteoporotic patients with at least one vertebral compression. Apart from the evaluation of the quantity of bone present, histomorphometry also allows trabecular osteoporosis to be differentiated from cortical osteoporosis and allows a histological definition of the type of osteoporosis in terms of the parameters reflecting bone remodelling (area of resorption, number of osteoclasts, area of osteoid osteoblastic apposition rate, etc...).