Biomechanical Computed Tomography analysis (BCT) for clinical assessment of osteoporosis.

The surgeon general of the USA defines osteoporosis as "a skeletal disorder characterized by compromised bone strength, predisposing to an increased risk of fracture." Measuring bone strength, Biomechanical Computed Tomography analysis (BCT), namely, finite element analysis of a patient's clinical-resolution computed tomography (CT) scan, is now available in the USA as a Medicare screening benefit for osteoporosis diagnostic testing. Helping to address under-diagnosis of osteoporosis, BCT can be applied "opportunistically" to most existing CT scans that include the spine or hip regions and were previously obtained for an unrelated medical indication. For the BCT test, no modifications are required to standard clinical CT imaging protocols. The analysis provides measurements of bone strength as well as a dual-energy X-ray absorptiometry (DXA)-equivalent bone mineral density (BMD) T-score at the hip and a volumetric BMD of trabecular bone at the spine. Based on both the bone strength and BMD measurements, a physician can identify osteoporosis and assess fracture risk (high, increased, not increased), without needing confirmation by DXA. To help introduce BCT to clinicians and health care professionals, we describe in this review the currently available clinical implementation of the test (VirtuOst), its application for managing patients, and the underlying supporting evidence; we also discuss its main limitations and how its results can be interpreted clinically. Together, this body of evidence supports BCT as an accurate and convenient diagnostic test for osteoporosis in both sexes, particularly when used opportunistically for patients already with CT. Biomechanical Computed Tomography analysis (BCT) uses a patient's CT scan to measure both bone strength and bone mineral density at the hip or spine. Performing at least as well as DXA for both diagnosing osteoporosis and assessing fracture risk, BCT is particularly well-suited to "opportunistic" use for the patient without a recent DXA who is undergoing or has previously undergone CT testing (including hip or spine regions) for an unrelated medical condition.

Denosumab: a cost-effective alternative for older men with osteoporosis from a Swedish payer perspective.

OBJECTIVE: To assess the cost-effectiveness of denosumab versus other treatments in men with osteoporosis who are ≥75years old from a payer perspective in Sweden. METHODS: A lifetime cohort Markov model was developed with seven health states: well, hip fracture, vertebral fracture, other osteoporotic fracture, post-hip fracture, post-vertebral fracture, and dead. During each cycle, patients could have a fracture, remain healthy, remain in a post-fracture state or die. Background fracture risks, mortality rates, persistence rates, utilities, medical and drug costs were derived using published sources. Estimates of fracture efficacy were drawn from available studies in post-menopausal osteoporotic (PMO) women as BMD improvements have been shown to be similar across male osteoporosis (MOP) and PMO populations, and a recent clinical trial suggested that the fracture risk reduction from bisphosphonate therapy in men is similar to that seen in women in comparable studies. Lifetime expected costs and quality-adjusted life-years (QALYs) were estimated for denosumab, generic alendronate, generic risedronate, ibandronate, zoledronate, strontium ranelate and teriparatide. On average, patients in the model were 78years old, with bone mineral density T-score at the femoral neck of -2.12. Prevalent vertebral fractures were present in 23% of patients. In the base-case, the model assumed that patients would experience treatment-related effects up to 2years after discontinuation. Costs and QALYs were discounted at 3% annually. Extensive sensitivity analyses were conducted. RESULTS: Total lifetime costs for denosumab, alendronate, strontium ranelate, zoledronate, risedronate, ibandronate and teriparatide were €31,004, €33,731, €34,788, €34,796, €34,826, €35,983 and €37,461, respectively. Total QALYs were 5.23, 5.15, 5.15, 5.17, 5.13, 5.12 and 5.22, respectively. Compared to other treatments, denosumab had the lowest costs and highest QALYs. In the one-way sensitivity analyses, when compared to alendronate (next least expensive strategy), the ICER for denosumab was most sensitive to the relative risk of hip fracture on denosumab. The probability of denosumab being cost-effective compared to the other treatments at a threshold of €66,000/QALY was 96.1%. CONCLUSION: Denosumab dominated all comparators, including generic bisphosphonates, in the treatment of osteoporosis in men who were ≥75years old in Sweden.

Tools in the assessment of sarcopenia.

This review provides a framework for the development of an operational definition of sarcopenia and of the potential end points that might be adopted in clinical trials among older adults. While the clinical relevance of sarcopenia is widely recognized, there is currently no universally accepted definition of the disorder. The development of interventions to alter the natural history of sarcopenia also requires consensus on the most appropriate end points for determining outcomes of clinical importance which might be utilized in intervention studies. We review current approaches to the definition of sarcopenia and the methods used for the assessment of various aspects of physical function in older people. The potential end points of muscle mass, muscle strength, muscle power, and muscle fatigue, as well as the relationships between them, are explored with reference to the availability and practicality of the available methods for measuring these end points in clinical trials. Based on current evidence, none of the four potential outcomes in question is sufficiently comprehensive to recommend as a uniform single outcome in randomized clinical trials. We propose that sarcopenia may be optimally defined (for the purposes of clinical trial inclusion criteria as well as epidemiological studies) using a combination of measures of muscle mass and physical performance. The choice of outcome measures for clinical trials in sarcopenia is more difficult; co-primary outcomes, tailored to the specific intervention in question, may be the best way forward in this difficult but clinically important area.

Cost-effectiveness of bone densitometry among Caucasian women and men without a prior fracture according to age and body weight.

UNLABELLED: We used a microsimulation model to estimate the threshold body weights at which screening bone densitometry is cost-effective. Among women aged 55-65 years and men aged 55-75 years without a prior fracture, body weight can be used to identify those for whom bone densitometry is cost-effective. INTRODUCTION: Bone densitometry may be more cost-effective for those with lower body weight since the prevalence of osteoporosis is higher for those with low body weight. Our purpose was to estimate weight thresholds below which bone densitometry is cost-effective for women and men without a prior clinical fracture at ages 55, 60, 65, 75, and 80 years. METHODS: We used a microsimulation model to estimate the costs and health benefits of bone densitometry and 5 years of fracture prevention therapy for those without prior fracture but with femoral neck osteoporosis (T-score ≤ -2.5) and a 10-year hip fracture risk of ≥3%. Threshold pre-test probabilities of low BMD warranting drug therapy at which bone densitometry is cost-effective were calculated. Corresponding body weight thresholds were estimated using data from the Study of Osteoporotic Fractures (SOF), the Osteoporotic Fractures in Men (MrOS) study, and the National Health and Nutrition Examination Survey (NHANES) for 2005-2006. RESULTS: Assuming a willingness to pay of $75,000 per quality adjusted life year (QALY) and drug cost of $500/year, body weight thresholds below which bone densitometry is cost-effective for those without a prior fracture were 74, 90, and 100 kg, respectively, for women aged 55, 65, and 80 years; and were 67, 101, and 108 kg, respectively, for men aged 55, 75, and 80 years. CONCLUSIONS: For women aged 55-65 years and men aged 55-75 years without a prior fracture, body weight can be used to select those for whom bone densitometry is cost-effective.

Correlates for a low ankle-brachial index in elderly Chinese.

This study examines the prevalence of atherosclerosis (using ankle-brachial index (ABI) value <0.9) and associated socioeconomic and lifestyle factors in elderly Chinese, adjusting for presence of cardiovascular diseases and body mass index, in a cross-sectional survey of 1999 men and 1999 women aged 65 years and over living in the community. A questionnaire containing information regarding socioeconomic status, medical history and lifestyle factors was administered. Measurement included height, weight, percentage body fat using dual-energy X-ray absorptiometry and ABI. The Hong Kong population (2000) age adjusted prevalence of ABI <0.9 was 5.3% for men and 11.0% for women. In multivariate analysis, old age, female gender, presence of cardiovascular diseases, cognitive impairment, prolonged 6 m walk, smoking habit and alcohol intake were positively associated with ABI <0.9, while negative associations were observed with Vitamin C intake >100 mg per day, with the lowest OR for the range 141-190 mg (OR 0.4). Physical activity level, and self rated higher social standing in the community, while significant in univariate analysis, were not included as independent significant factors in the multivariate model. Lifestyle factors and the female gender were independent risk factors for atherosclerosis in the elderly Chinese population.

The role of collagen abnormalities in ultrasound and densitometry assessment: In vivo evidence.

There is little information concerning how the mutation of collagen affects bone mineralization and the assessment of bone properties. To estimate these influences, we performed ultrasonic assessments of the calcaneus and bone mineral density (BMD) measurements of the hip and lumbar spine. Females with diseases related to the mutation of collagen [Ehlers-Danlos syndrome (EDS) type III and systemic sclerosis (SSc)] participated in this study. We compared the broadband ultrasound attenuation (BUA and UBI-4), the average transit time through the heel (TTH), and a multiple factor index (UBI-4T) with control subjects matched on age, race, and menstrual status. Both groups of patients had BMD of the spine (L2-L4) within the normal range for their age and sex (for EDS: n = 23, 1.14 +/- 0. 14 g/cm2 and z-score = 0.37; for SSc: n = 15, 0.98 +/- 0.15 g/cm2 and z-score = 0.20). EDS and SSc subjects had lower BMD of the femoral neck (FN) compared with controls (for EDS: 0.91 +/- 0.13 g/cm2, z-score = -0.41, P = 0.025; for SSc 0.67 +/- 0.13 g/cm2, z-score = -0.92, P = 0.006). Subjects with EDS and SSc also had lower BUA values (P = 0.051-0.001) compared with controls. After adjusting for body weight, height, and the level of physical activity, the difference in FN BMD between EDS or SSc and controls became marginal (EDS: P = 0.072; SSc: P = 0.086). However, the significant difference for BUA between subjects and controls remained for EDS (P = 0.008), and disappeared for SSc (0.70) after adjusting for weight, height, level of physical activity, and BMD. These results suggest that the abnormalities of collagen may impact on bone mass measurements differently depending on skeletal site, modality of the assessment, and the source and nature of collagen defects. To determine whether collagen properties influence QUS, proper models in vivo and in vitro should be used.

Precision and discriminatory ability of calcaneal bone assessment technologies.

To determine if measuring skeletal status at the calcaneus is a potentially valuable technique for diagnosing osteoporosis, we examined five calcaneal assessment techniques in 53 young normal women and 108 postmenopausal women with osteoporosis and compared these measurements to dual-energy X-ray absorptiometry (DEXA) at the calcaneus, hip, and spine. The five instruments, including single-energy X-ray absorptiometry (SEXA) and four quantitative ultrasound (QUS) instruments, were evaluated for precision, ability to discriminate osteoporotic from young normal subjects, and correlation to the other instruments. The coefficient of variation (%CV) for instrument, positioning, interobserver, and short-term precision of the five calcaneal instruments ranged from 1.34-7.76%, 1.63-7.00%, 1.84-9.44%, and 1.99-7.04%, respectively. The %CVs for positioning, interobserver, and short-term precision were similar for calcaneal DEXA, calcaneal SEXA, and stiffness (as measured by Achilles). The %CVs for instruments precision were similar between calcaneal DEXA and SEXA. The ability of the five calcaneal instruments to discriminate osteoporotic from young normal subjects was similar based on the analysis of area under the receiver operating characteristic curves (range 0.88-0.93) and equivalent to DEXA of the calcaneus and hip (0.88-0.93). The correlations between the measurements of five calcaneal instruments were strong (0.80 < or = r < or = 0.91, p < 0.001). These data suggest that although the precision is variable, the calcaneal QUS and SEXA instruments can discriminate between osteoporotic patients and young normal controls and appear to be a useful technique for assessment of osteoporosis.

Calcium, vitamin D, and parathyroid hormone status in young white and black women: association with racial differences in bone mass.

The etiology of the racial disparity in bone mass and fracture rate is unknown. Since the PTH-vitamin D endocrine system is a major regulator of calcium metabolism and bone turnover, this cross-sectional study examined the relationship of radial and lumbar bone density to vitamin D metabolite and PTH concentrations and to calcium intake and excretion in 67 white and 70 black highly comparable, healthy, premenopausal women. Bone density at both radial and lumbar sites was higher in blacks than in whites. Serum 25-hydroxyvitamin D was slightly but not statistically significantly (P = 0.08), lower in blacks than in whites, but there were no racial differences in 1,25-dihydroxyvitamin D, PTH, or renal tubular maximum for reabsorption of phosphate. The mean 25-hydroxyvitamin D concentration in blacks was well within the normal range and was not associated with evidence of secondary hyperparathyroidism. There were no correlations of bone density to vitamin D or PTH concentrations. Although there were no racial differences in dietary intake of calcium and vitamin D or in sodium excretion, 24-h urinary calcium excretion was significantly lower in blacks than in whites, and calcium excretion was inversely associated with radial bone density. In contrast to previous reports, in healthy, normal weight, premenopausal black women there is no evidence of vitamin D deficiency or secondary hyperparathyroidism, suggesting that factors other than the vitamin D-PTH axis are responsible for racial differences in bone mass.

Marked disparity between trabecular and cortical bone loss with age in healthy men. Measurement by vertebral computed tomography and radial photon absorptiometry.

To define age-related changes in bone mineral content in normal men, we measured radial (proximal and distal) and vertebral bone mineral content in 62 men aged 30 to 92 years. Radial bone mineral content (largely cortical bone) was measured by single photon absorptiometry, and trabecular vertebral content (T12, L1 to L3) by computed tomography. Radial bone mineral content fell gradually (2% to 3.4% per decade) with age, but vertebral trabecular content fell more rapidly (12% per decade). Body size was not associated with the rate of bone loss from the distal radial and vertebral sites, but men with lower surface areas lost bone more rapidly at the predominantly cortical proximal radial site. The fact that radial cortical bone mineral content falls much less rapidly than vertebral trabecular content with age and is also associated with surface area indicates that trabecular and cortical bone compartments may be independently modulated. Age-related bone loss should not be considered a homogeneous process.