Ageing and osteoporosis, in particular spinal osteoporosis

Assessment of bone mineral density in postmenopausal and senile osteoporosis using quantitative CT

The authors analyzed bone mineral density in 213 patients from January 1988 to September 1989. Bone mineral density of the vertebral body in the osteoporosis group of patients was compared with that in the normal group to investigate the correlation between bone mineral density and age distribution, and to estimate fracture threshold in the osteoporosis group. It was found that men, by linear regression, lose an average of 0.91% of bone per year, and women, by cubic regression, lose an average of 1.14% per year, accelerating at menopause. In the osteoporotic group, bone mineral density of men decreased an average of 29.7% compared with the non-osteoporotic group; that of women decreased an average of 29.9%. There was no difference between sexes. The fracture threshold of the osteoporotic patient was estimated to be about 90 mg/cm3.

Skeletal mass in postmenopausal women

The techniques of photon absorptiometry of the radius and total body neutron activation analysis were used for the determination of bone mineral content and total body calcium, respectively. The subjects consisted of 71 normal women who were 1-5 yr postmenopausal and 44 osteoporotic women who had crush fractures of the dorsal spine. Both bone mineral content and total body calcium were corrected for age and body size by using the ratio of observed values to those predicted from previously derived equations. Discrimant analysis involving both osteoporotic and normal postmenopausal women resulted in the successful assignment of 81% of the 115 subjects to their correct group. Statistical analyses of the distribution of the bone mass of the postmenopausal women yielded no evidence to support the hypothesis that a subgroup exists with bone mass levels markedly different from the remainder of the women.

Quantitative radiology: radiogrammetry of cortical bone

Based on personal experience and data in the literature, an overview is given of radiogrammetry of cortical bone of the second metacarpal. There is a within- and between-observer error which amounts respectively to 1.2 and 1.5% for the outer diameter and 4.8 and 6.4% for the inner diameter. The systematic + or-- trend between observers indicates that one observer working according to certain defined rules obtains the most reliable results. There is a large variability in amount of bone within one age and sex group which is partly due to skeletal size differences, are insufficient since skeletal size differences still exist. The variability is reduced when the data are divided into strata of skeletal size. Since cortical area shows the best correlation with outer diameter within each age group and since cortical area represents best the ash content of the bones the values of this index are most suited to be grouped according to outer diameter. In differentiating pathological from physiological bone loss this procedure is an improvement on the previously published indices of amount of bone. When comparing different populations this method has advantages since skeletal size differences are eliminated. Comparing seven populations it was found that populations living in the United States of America have more bone for a given skeletal size than populations in Europe or Nigeria. Bone loss with age is a general phenomenon but differences in rate of loss are observed between the sexes and between ethnic different populations. The decrease of bone mass is faster after the age of 50 years in woman than in men. Blacks living in the United States loose less bone with age than whites. Radiogrammetry of cortical bone in groups gives useful information on bond remodelling during ageing and in pathological conditions. At an individual level, however, it is difficult to evaluate changes on a short term basis with radiogrammetry. Radiogrammetry of cortical bone is a simple and reproducible method which measures bone mass indirectly. Changes in cortical width show a high degree of correlation with the changes in mass of cortical bones but trabecular bone is not measured. This is a serious handicap, since most of the metabolic diseases of the skeleton affect trabecular bone to a greater extent than cortical. Nevertheless the measurement of cortical thickness certainly has added to the knowledge of changes in bone mass in ageing and in disease.

The relationship between oestrogen status and bone loss in post-menopausal women

The relationships between the rate of change of metacarpal cortical width, urinary hydroxyproline/creatinine ratio, net absorption of calcium and maturation value of vaginal smear have been examined in normal post-menopausal women and crush fracture cases. Rapid bone loss, high bone resorption and low calcium absorption are shown to be associated with poor oestrogen status, with crush fracture cases presenting an exaggerated view of the normal post-menopausal situation.