Osteoporosis and normality: how to express the bone mineral content of lumbar vertebrae

Abstract

Bone mineral content of the 2nd, 3rd and 4th lumbar vertebrae (lumbar BMC) was measured in 70 normal women (aged 19-88 yr) and 72 postmenopausal women (aged 58-89 yr) with primary osteoporosis by dual-photon (153Gd) absorptiometry. Interindividual variation of lumbar BMC was 26.7% in normal women. This figure could be reduced to 13.9% if lumbar BMC was normalized to age (or years after the menopause), body height, body weight and vertebral size according to multiple regression analysis. The reduction thus obtained of the interindividual variation in normal postmenopausal women was statistically insignificant, and it appeared that other variables were of importance to lumbar BMC of older women. Mean lumber BMC of the osteoporotic women was 41% lower than that of normal premenopausal women. Separation between normal and osteoporotic individuals became less clear if lumber BMC was normalized as mentioned. Spinal osteoporosis is predominantly a condition of normal, small, old women with diminutive vertebrae and early menopause. Lumber BMC should be expressed as the total mineral mass of the bones measured, the normal range being BMC of healthy premenopausal women. Normalization to age, body height, body weight and vertebral size seems to be rather speculative.