Risk assessment: theoretical considerations

Cancellous bone lamellae strongly affect microcrack propagation and apparent mechanical properties: separation of patients with osteoporotic fracture from normal controls using a 2D nonlinear finite element method (biomechanical stereology)

Biomechanical stereology is proposed as a two-dimensional (2D) finite element (FE) method to estimate the ability of bone tissue to sustain damage and to separate patients with osteoporotic fracture from normal controls. Briefly, 2D nonlinear compact tension FE models were created from quantitative back scattered electron images taken of iliac crest bone specimens collected from the individuals with or without osteoporotic fracture history. The effects of bone mineral microstructure on predicted bone fracture toughness and microcrack propagation were examined. The 2D FE models were used as surrogates for the real bone tissues. The calculated microcrack propagation results and bone mechanical properties were examined as surrogates for measurements from mechanical testing of actual specimens. The results for the 2D FE simulation separated patients with osteoporotic fracture from normal controls even though only the variability in tissue mineral microstructure was used to build the models. The models were deliberately created to ignore all differences in mean mineralization. Hence, the current results support the following hypotheses: (1) that material heterogeneity is important to the separation of patients with osteoporotic fracture from normal controls; and (2) that 2D nonlinear finite element modeling can produce surrogate mechanical parameters that separate patients with fracture from normal controls.

Lebanese guidelines for osteoporosis assessment and treatment: who to test? What measures to use? When to treat?

With the demographic explosion of the population worldwide, the human, social, and economic costs of osteoporosis will continue to rise. It is estimated that the magnitude of the problem might be even larger in developing countries, including those in the Middle East. Although several organizations and countries have developed or adapted guidelines to their local needs, as of today there are no guidelines for osteoporosis assessment in the Middle East. In April 2002, a panel of osteoporosis experts met and discussed practice guidelines for osteoporosis assessment and treatment in Lebanon. The process, which involved an overview of international guidelines as well as local data on osteoporosis, resulted in a draft for Lebanese guidelines that addressed three main questions: "Who to test?" "What measures to use?" and "When to treat?". Representatives from five major Lebanese societies (Endocrinology, Rheumatology, Orthopedics, Obstetrics and Gynecology, and Radiology) subsequently reviewed, discussed, and officially endorsed the guidelines after revisions. The Lebanese guidelines were also endorsed by the Eastern Mediterranean branch of the World Health Organization.

Construction of an algorithm for quick detection of patients with low bone mineral density and its applicability in daily general practice

OBJECTIVE

To construct a quick algorithm to detect patients with low bone mineral density (BMD) and osteoporosis and determine its applicability in daily general practice.

DESIGN

Cross-sectional study in all 9107 postmenopausal women, aged 50-80, registered at 12 general practice centers.

SUBJECTS AND MEASUREMENTS

All healthy women (5303) and 25% of the remaining group (943/3804) were invited to participate. Of 6246 invited women, 4725 (76%) participated. The women were questioned (state of health, medical history, family history, and food questionnaire) and examined [weight, height, body mass index (BMI), and BMD of the lumbar spine].

STATISTICS

Multivariable, stepwise backward and forward logistic regression analyses were performed, with BMD of the lumbar spine (L2-L4, cut-off points at 0.800 g/cm(2) for osteoporosis and 0.970 g/cm(2) for low BMD) as the dependent variable. An algorithm was constructed with those variables that correlated statistically significantly and clinically relevant with the presence of both osteoporosis and low BMD.

RESULTS

The prevalence of osteoporosis was 23%, that of low BMD was 65%. Only three variables (age, BMI, and fractures) were statistically significant and clinically relevant correlated with the presence of both osteoporosis and low BMD. Age (OR 2.70 for osteoporosis and OR 1.77 for low BMD) and fractures during the past five years (OR 3.60 for osteoporosis and OR 2.85 for low BMD) were found to be the key predictors. From the algorithm the absolute risks varied from 9% to 51% for osteoporosis and from 48% to 84% for low BMD. The corresponding relative risks varied from 1.0 to 5.7 and from 1.0 to 1.8.

CONCLUSIONS

Using an algorithm with age, BMI, and fracture history subgroups at high risk could be identified. However, in whatever combination, many women with osteoporosis could not be identified. Despite the differences in methods, we found predictors for osteoporosis which were comparable with the results of other cross-sectional studies, meaning that the first selection of patients at high risk for low BMD can be done adequately by both specialists and general practitioners.

Osteoporosis for the allergist

OBJECTIVE

This review is intended to be an authoritative summary of the pathogenesis of osteoporosis, a problem that may be encountered in allergy practice. It also provides an outline for identification of subjects at high risk and directions for their appropriate evaluation, management, and prevention of the disease.

DATA SOURCES

References were obtained through a MEDLINE literature search as well as from previous reviews. Relevant articles were critically reviewed and their conclusions were included.

RESULTS

Osteoporosis is a relatively common disease that is associated with significant morbidity and mortality. The management and prevention of osteoporosis have been improved by an increased awareness of the magnitude of the problem, a better understanding of the pathogenesis, development of a better technique for assessment of bone mineral density, and the availability of specific medications. With the increase in human life-span and the increasing use of glucocorticosteroids for a wide variety of diseases, the incidence of osteoporosis has been on the rise.

CONCLUSION

Glucocorticosteroids are the most common medications that cause or contribute to the pathogenesis of osteoporosis and have been widely used in allergy practice. It is important for physicians to appreciate the current basic understanding of osteoporosis and to be able to identify patients at high risk for this serious disorder, and to initiate appropriate intervention at a sufficiently early time to be effective. Medications for treatment and prevention of osteoporosis include: calcium, vitamin D, estrogen, bisphosphonates, calcitonin, and others are reviewed in this article.

Physician characteristics associated with the use of bone densitometry

To determine physician characteristics associated with the use of bone densitometry (BD), we conducted a cross-sectional survey of primary care practitioners in an urban community hospital. Participants were internists, geriatricians, and family practitioners. Seventy-two percent of the physicians never used BD. There was no association between physician or practice characteristics and BD use. Bone densitometry users were more likely than nonusers to treat their patients with osteoporosis or at risk of developing it. Self-reported barriers to use included cost, unfamiliarity with guidelines, uncertainty with clinical applicability, minimal impact on treatment decisions, and availability. In conclusion, although it has been shown that osteoporotic women who are aware of their BD results are more likely to accept treatment, further attention should be paid to primary care practitioners' attitudes, knowledge, and behavior regarding the use of BD in the management of osteoporosis.

Altered loading patterns and femoral bone mineral density in children with unilateral Legg-Calvé-Perthes disease

Maximization of bone accrual during the growing years is thought to be an important factor in minimizing fracture risk in old age. Mechanical loading through physical activity has been recommended as a modality for the conservation of bone mineral in adults; however, few studies have evaluated the impact of different loading regimes in growing children. The purpose of this study was to compare bone mineral density (BMD) in weight-bearing and non-weight-bearing limbs in 17 children with unilateral Legg Calvé Perthes Disease (LCPD). Children with this condition have an altered weight-bearing pattern whereby there is increased mechanical loading on the noninvolved normal hip and reduced loading on the involved painful hip. Thus, these children provide a unique opportunity to study the impact of differential mechanical loading on BMD during the growing years while controlling for genetic disposition. BMD at four regions of the proximal femur (trochanter, intertrochanter, femoral neck, total of the regions) was measured using dual energy x-ray absorptiometry (DXA), and the values were compared between the involved and noninvolved sides of the children with LCPD. The BMD of the both sides also were compared with normative values based on both chronological and skeletal age data. A significantly higher BMD was found on the noninvolved side over the involved side for all regions (P < 0.01 and percentage differences of 12-15%) except at the femoral neck (percentage difference of 3.9%). The BMD (at all regions) of the noninvolved side also was significantly greater (P < 0.01) than either the chronological or skeletal age based norms for all sites except the trochanter. The results support the concept that mechanical loading of the skeleton during the growing years is an important factor in BMD accrual.

Osteoporotic fractures: background and prevention strategies

OBJECTIVES

To review current knowledge of the epidemiology, pathogenesis, prevention and treatment of osteoporosis, with particular reference to issues related to the menopause.

METHODS

Peer-reviewed publications were assessed.

RESULTS

Much international variation exists in the prevalence of osteoporosis and the incidence of fracture. Risk fractures for osteoporosis are numerous. The menopause and other causes of hypogonadism in both women and men strongly predispose to osteoporosis. Various endocrinopathies, especially glucocorticoid excess, also are important. The contribution of family history may be explained by one or more genetic markers. Poor vitamin D and calcium nutrition, smoking, high alcohol consumption and inactivity increase risk. Reduced bone mass is a major risk factor for fracture, although the magnitude of that risk may vary between populations. In addition, bone fragility, length of the femoral neck (for hip fracture), history of prior fracture (for vertebral fracture) and falls affect fracture risk. Useful methods for measuring bone density are available for both epidemiologic surveillance and for clinical practice. Dual energy x-ray absorptiometry is the most desirable method in clinical care settings. Some risk factors can be modified for prevention of osteoporosis. Postmenopausal bone loss can be inhibited with estrogen or estrogen plus progestin therapy. Bone loss in the elderly may be moderated with calcium and vitamin D supplementation. Maintenance of muscle tone and strength through exercise may reduce falls. CONCLUSIONS. Osteoporosis is a large and growing health problem in many countries. Prevention of osteoporosis is a high priority, especially because treatment of the established disease remains sub-optimal. Prevention requires immediate, intermediate-term and long-term strategies. First line therapy for established osteoporosis in women in many countries is estrogen or estrogen plus progestin, calcium and vitamin D. Prospects for improved prevention of osteoporotic fractures are encouraging.