Relationship between bone mineral content and frequency of postmenopausal fractures.

To elucidate the relationship between bone mineral content (BMC) and the frequency of postmenopausal fractures, we performed an epidemiologic investigation in a representative sample of 70-year-old women. Anamnestic data concerning postmenopausal fractures due to minor trauma were recorded and lateral X-rays of the spine were taken for evaluation of spinal fractures. BMC was measured by 125I photon absorptiometry. The 285 women studied were allocated into quintiles according to their BMC value. In 77 women, there were 131 definite osteoporotic fractures (i.e., spinal crush, and fracture of the hip, proximal humerus, and distal forearm), and in 48 women, there were 162 other non-violent fractures (i.e., spinal wedge and other long bone fractures). The frequencies of osteoporotic fractures varied inversely with the mean BMC values for each quintile (r = 0.959, p less than 0.01). The difference in frequency of osteoporotic fractures between the first and fifth quintiles was highly significant (p less than 0.001). In contrast, other non-violent fractures appeared to be unrelated to BMC. It is concluded that low BMC levels predispose to osteoporotic fractures.