Epidemiology of postmenopausal spinal and long bone fractures. A unifying approach to postmenopausal osteoporosis.

The incidence of spontaneous postmenopausal fractures and their relationship to menopausal age and bone mass were determined in a representative sample of 70-year-old Danish women. Two hundred and eighty-five women (1.2% of all women in that age group) were examined by case history, by 125I photon absorptiometry in both forearms (BMC), by metacarpal index (CA/TA), and by lateral radiographs of the spine. Twenty-four per cent of the participants had sustained single fractures, and 20% multiple fractures. Nineteen per cent had fractures of the lower forearm, 5% of the proximal humerus, 4% of the hip, and 5% crush fractures of the spine. These comprise Group I fractures, the most definite expressions of osteoporosis. The remaining other long bone fractures (7%) and spinal wedge fractures (18%) comprise Group II fractures. Group I cases were characterized by an earlier onset of the menopause and a definite decrease in bone mass, as judged from BMC and CA/TA, as compared with the nonfracture group. Group II cases did not display this distinction. Of Group I cases, those with multifractures differed from those with single fractures by having a five-year earlier occurrence of first fracture, a further decrease in bone mass, and a slightly raised serum alkaline phosphatase level. Serum calcium and phosphate levels were the same in all groups.