Discriminative ability of dual-energy X-ray absorptiometry site selection in identifying patients with osteoporotic fractures.

Dual-energy X-ray absorptiometry (DXA) is the gold standard method for measurement of bone mineral density (BMD). The aims of the current study are to compare the ability of BMD measurements to identify subjects with vertebral fractures (VF), when the lumbar spine (LS), hip or both sites are measured. 460 subjects aged 73+/-5.2 years participated in the study. Thoraco-lumbar spine radiographs were obtained and analyzed for the presence of VF using the visual semi-quantitative assessment. BMD of the LS and the left femur were measured by DXA. Eighteen men (12%) and 56 women (20%) had at least one VF. 16% of scans at the LS were unreadable because of the presence of degenerative changes. In both genders, BMD of the hip showed better ability than LS BMD in detecting subjects with osteoporosis. BMD and T-score values at the hip, but not the LS, were lower in subjects with VF than those without (p<0.05). Femoral neck BMD showed the highest OR for each S.D. decrease in BMD for identifying subjects with VF, and the best predictability for prevalent VF using ROC. Fracture risk prediction did not increase by adding the spine to the hip measurement. In conclusion, hip BMD was the only and best skeletal site needed to detect subjects with osteoporosis and showed the strongest relationship with prevalent vertebral fractures in elderly subjects.

Vertebral fracture risk and impact of database selection on identifying elderly Lebanese with osteoporosis.

The International Osteoporosis Foundation recommends using a universal database i.e. the NHANES database for the diagnosis of osteoporosis. Population-based databases for T-score calculation are still debated in terms of clinical and public health relevance. The current study aimed at estimating the prevalence of vertebral fractures in the Lebanese elderly, determining BMD-fracture relationship, and assessing the effect of database selection on osteoporosis prevalence and fracture risk assessment. Apparently healthy subjects were randomly selected from the Greater Beirut area - one-third of the Lebanese population at large - using a multilevel cluster technique. Subjects with medical conditions likely to affect bone metabolism i.e. history of major chronic disease, intake of medications that affect bone metabolism were excluded. Presence of vertebral fracture was estimated by a semi-quantitative assessment. Bone density was measured by central DXA. Clinical risk factors included age, gender, height, weight, body mass index, smoking, exercise, falls, previous fragility fracture and family history of fragility fracture. Impact of database selection was assessed by: (1) Comparison of sensitivity and specificity for prevalent vertebral fractures of the T-score

Hypovitaminosis D osteopathy: is it mediated through PTH, lean mass, or is it a direct effect?

Hypovitaminosis D is increasing worldwide and is associated with low bone mass. The effects of hypovitaminosis D on bone might be direct or mediated through decreased muscle mass and function and/or secondary hyperparathyroidism. This study systematically investigated the relative contribution of lean mass, PTH, and the direct effect of vitamin D as predictors of vitamin D mediated osteopathy in elderly individuals. 460 ambulatory subjects aged 65-85 years had their bone mass and lean body mass measured by a dual-energy X-ray absorptiometry. Serum calcium, phosphorus and alkaline phosphatase, intact parathyroid hormone (PTH) and 25-hydroxyvitamin D (25 OHD) were also measured. Serum 25 OHD correlated with lean body mass in men, r = 0.24, P = 0.002, but not in women; and with bone mass at all skeletal sites in men, r = 0.20-0.30, P < 0.02. Correlations were also noted at all skeletal sites in women except for the spine, r = 0.13-0.18, P < 0.04. In both genders, BMD at sites enriched in cortical bone was 0.4-0.7 SD lower in the group with the lowest vitamin D tertile than that in the group in the highest tertile. After controlling for PTH, the magnitude of the correlations between BMD and 25 OHD remained significant in both genders. After controlling for lean body mass, the magnitude of these correlations did not change in women and decreased but remained significant in men. After adjustment for age and height, both lean body mass and PTH had significant independent contributions to BMD variance at all skeletal sites. After adjustment for age, height, lean mass, and PTH, 25 OHD did not have any significant residual contribution to BMD variance except at the trochanter in men. This study demonstrates that vitamin D osteopathy in the elderly is in large part mediated through lean mass in men and through PTH levels in both genders, with a greater contribution of PTH in women than in men. There was little demonstrable independent relation between serum 25 OHD and bone mass.

Hypomagnesemia associated with chondrocalcinosis: a cross-sectional study.

OBJECTIVE: To determine an association between magnesium (Mg) depletion and chondrocalcinosis, which has been reported but not investigated in a cross-sectional study. METHODS: Prevalence of chondrocalcinosis was investigated in 144 individuals: 72 patients receiving home parenteral nutrition (HPN) compared with 72 age- and sex-matched controls. Presence of chondrocalcinosis was assessed by knee radiographs. Blood serum and globular Mg levels and 24-hour urinary Mg content were compared. RESULTS: Mean +/- SD age for both patients and controls was 51 +/- 17 years, and 51% in both groups were women. Mean duration of HPN was 6.4 years. Prevalence of chondrocalcinosis was markedly higher in patients receiving HPN than controls (16.6% versus 2.7%; P = 0.006, odds ratio [OR] 7.0, 95% confidence interval [95% CI] 1.45-66.1). Mean +/- SD serum and globular Mg levels were significantly lower in patients than controls (serum: 0.75 +/- 0.09 mmoles/liter versus 0.81 +/- 0.08 mmoles/liter, P = 0.0006; globular Mg: 1.8 +/- 0.31 mmoles/liter versus 2.0 +/- 0.35 mmoles/liter, P = 0.0003). Twenty-four-hour urinary Mg level was lower in patients than controls (mean +/- SD 3.85 +/- 1.50 mmoles versus 5.37 +/- 3.71 mmoles; P = 0.001). Prevalence of chondrocalcinosis was significantly higher in patients with a low serum Mg level (OR 13.5, 95% CI 2.76-127.3, P < 0.0001), with a similarly high but not significant occurrence of chondrocalcinosis in patients with a low globular Mg level (OR 4.09, 95% CI 0.603-20.26, P = 0.08) and in patients with a low 24-hour urinary Mg level (OR 3.9, 95% CI 0.77-16.34, P = 0.05). CONCLUSION: Long-lasting Mg depletion is strongly associated with chondrocalcinosis.

Hypomagnesemia and chondrocalcinosis in short bowel syndrome.

Chondrocalcinosis is a result of deposition of calcium pyrophosphate dihydrate (CPPD) crystals in cartilage and fibrocartilage. Chondrocalcinosis is usually sporadic but has also been associated with a variety of metabolic diseases including hypomagnesemia. Reported cases of hypomagnesemia associated chondrocalcinosis were mostly due to renal genetic disorders such as Bartter's or Gitelman's syndrome. We describe 3 patients with chronic hypomagnesemia induced by short bowel syndrome who developed symptomatic chondrocalcinosis. CPPD crystals were identified by polarizing light microscopy in one patient. The underlying intestinal pathology was radiation enteritis in 2 patients and mesenteric arterial thrombosis in the third. Our observations strengthen the hypothesis of a role for magnesium in CPPD crystal deposition disease.