Pharmacological interventions for the prevention of vertebral and nonvertebral fractures in women with postmenopausal osteoporosis: does site-specificity exist?

Diet, nutrition and the prevention of osteoporosis

Objective:

To review the evidence on diet and nutrition relating to osteoporosis and provide recommendations for preventing osteoporosis, in particular, osteopototic fracture.

Approach:

Firstly, to review the definition, diagnosis and epidemiology of osteoporosis, to discuss the difficulties in using bone mineral density to define osteoporosis risk in a world-wide context and to propose that fragility fracture should be considered as the disease endpoint. Secondly, to provide an overview of the scientific data, the strengths and weaknesses of the evidence and the conceptual difficulties in interpreting studies linking diet, nutrition and osteoporosis. The following were considered: calcium, vitamin D, phosphorus, magnesium, protein and fluorine. Other potential dietary influences on bone health were also discussed, including vitamins, trace elements, electrolytes, acid–base balance, phyto-oestrogens, vegetarianism and lactose intolerance.

Conclusions:

There is insufficient knowledge linking bone mineral status, growth rates or bone turnover in children and adolescents to long-term benefits in old age for these indices to be used as markers of osteoporotic disease risk. For adults, the evidence of a link between intakes of any dietary component and fracture risk is not sufficiently secure to make firm recommendations, with the exception of calcium and vitamin D. For other aspects of the diet, accumulating evidence suggests that current healthy-eating advice to decrease sodium intake, to increase potassium intake, and to consume more fresh fruits and vegetables is unlikely to be detrimental to bone health and may be beneficial.

Vertebral morphometric X-ray absorptiometry in women with Colles' fracture

Colles' fracture (CF) in younger postmenopausal women is associated with low bone mineral density (BMD) and with an increased risk of other osteoporotic fractures; however, the prevalence of vertebral deformities has been not studied in CF patients. Vertebral morphometry (MXA) using dual-energy X-ray absorptiometry (DXA) is a research tool developed to evaluate the presence of vertebral deformities, but its clinical use is still limited. The goals of this work were to know the prevalence of vertebral deformities in women with CF, to study the morphometric characteristics of height ratios, and to determine the correlation between MXA findings and BMD. MXA was evaluated within an incident case-control study in which 58 women with a recent CF and 83 population-based control women were enrolled. Anterior (Ha), middle (Hm), and posterior (Hp) heights were measured, and wedge (Ha/Hp) and mid-wedge (Hm/Hp) ratios were calculated. A vertebral deformity was defined when at least one ratio fell 3 SD below the reference mean of that ratio at any vertebral level. The mean age of cases was 65.8 yr and in controls 58.7 (p < 0.05). Morphometric vertebral deformities were found in 19% of cases against 11% of controls (nonsignificant). The cases had a lower mid-wedge ratio than controls at each vertebral level (p < 0.05), while wedge ratio results did not show significant results. When the sample was stratified by age, CF showed a trend to be associated with vertebral deformity only in the younger (<65 yr) group. A low but significant coefficient of correlation was found between mid-wedge ratio and BMD, mainly at hip level. By using MXA we found that younger Colles' fracture cases were likely to have more vertebral deformities than healthy controls of the same age range.

Long-term treatment with sodium warfarin results in decreased femoral bone strength and cancellous bone volume in rats

The issue of whether long-term sodium warfarin therapy results in decreased bone density is controversial. To address this question, we randomized rats to once daily subcutaneous injections of either sodium warfarin (0.20 or 0.25 mg/kg) or saline for 28 days and monitored the effects on bone, both biomechanically and by histomorphometric analysis. In addition, the anticoagulant status of both saline- and warfarin-treated rats were monitored throughout the course of the experiment by measuring the prothrombin time, expressed as international normalized ratios (INRs). Rats treated with 0.25 mg/kg warfarin demonstrated INRs of approximately 2.6, while rats treated with either 0.20 mg/kg warfarin or saline were found to have INRs of 1.3 and 1.0, respectively. Biomechanical testing of the right femur of rats treated with 0.25 mg/kg warfarin demonstrated that warfarin caused an 8% reduction in bone strength as measured by maximum tolerated load. A similar reduction in the biomechanical parameters of energy to break (P<.0001) and force at break point (P<.005) was also observed. Histomorphometric analysis of the left femur of warfarin-treated rats revealed a 17% reduction in cancellous bone volume. This was accompanied by a 60% decrease in osteoblast surface, as well as an 80% reduction in osteoid surface. In contrast, warfarin treatment had the opposite effect on osteoclast surface, which was 35% higher following warfarin treatment. Based on these observations, we conclude that clinically relevant doses of warfarin decrease femoral bone strength and cancellous bone volume, both by decreasing the rate of bone formation and increasing the rate of bone resorption.

Different effects of antiresorptive therapies on vertebral and nonvertebral fractures in postmenopausal osteoporosis

In postmenopausal osteoporosis, controlled clinical trials with antiresorptive therapies have shown consistent effects on vertebral fracture incidence while their effects on nonvertebral fractures, especially at the hip, have been reported with some agents, but not others. These discrepancies stress the differences in the pathogenesis of vertebral and nonvertebral fractures as discussed below, and the need to further investigate the mechanisms of action of various antiresorptive agents.