Bone mineral content of the lumbar spine in normal and osteoporotic women: cross-sectional and longitudinal studies.

1. Bone mineral content of the second, third and fourth lumbar vertebrae was determined in normal women and women with clinical osteoporosis by using dual-photon (153Gd) absorption. 2. A cross-sectional study of 70 normal (aged 19-88 years) showed a bone loss of 44% from the age of around 34 years throughout life. 3. Longitudinal data from 59 normal women confirmed that the vertebral bone loss started before the menopause. An accelerated bone loss amounting to nearly 6% per year was seen immediately after the menopause. The bone loss of older women was slower. 4. Mean lumbar bone mineral content of 36 women (aged 48-93 years) with recent fractures of their femoral neck after minor trauma equalled that of aged-matched normal women. Lumbar bone mineral content of the women with intratrochanteric femoral neck fractures was lower than that of the women with medial femoral neck fractures. 5. Mean lumbar bone mineral content of 72 women (aged 58-59 years) with primary osteoporosis was 41% lower than that of normal premenopausal women and 18% lower than that of age-matched controls. A weak inverse relationship between lumbar bone mineral content and the number of compression fractures was found. A weak inverse relationship between lumbar bone mineral content and the number of compression fractures was found. 6. Women with lumbar bone mineral content values below the 95% confidence limits for normal premenopausal women are at risk of future vertebral compression fractures, the fracture risk being inversely related to lumbar bone mineral content.