Radial and spinal bone mineral density in a patient population

WHOLE BODY AND REGIONAL BONE MINERAL CONTENT AND DENSITY IN WOMEN AGED 20-75 YEARS

Background

Dual-energy X-ray absorptiometry (DXA) allows measurement of whole body (WB) and regional bone mineral content (BMC) and density (BMD).

Objective

To measure WB and regional bone area, BMC and BMD (arms, legs, ribs and pelvis) in women of different ages.

Subjects and Methods

140 women participated (age range 20-75 yrs). Three subgroups were built: 20-44 yr (30 premenopausal women), 45-59 (80 women), and 60-75 (30 women). WB DXA was performed on a Hologic QDR 4500 A bone densitometer (Hologic Inc., Bedford MA). WB BMD T-scores were calculated by using the manufacturer-provided and the NHANES 1999-2004 reference databases, while the WB BMC Z-scores - based on the latter. Statistical analysis was performed on an IBM SPSS Statistics 19.0 for Windows platform (Chicago, IL).

Results

WB BMC and BMD Z-scores were consistently lower than the reference databases showing a difference of about 0.4 - 0.5 SD. The arms, legs and ribs lost more BMC after the age of 50-55, while the pelvis - much earlier. The total decreases in BMC were highest in the pelvis (26.36 %), followed by the arms (16.81 %) and whole body (15.91 %), while the bone area decreased mostly in the pelvis (13.23 %).

Conclusion

The age-related declines in regional BMC, bone areas and BMD follow different patterns in appendicular and axial bones.

Classification of osteoporosis in the elderly is dependent on site-specific analysis

Vertebral osteoporosis accounts for over 500,000 spinal fractures annually, the majority of which occur in older women. Despite these statistics, data regarding the rate of spinal bone loss in this population are conflicting. Moreover, the site of skeletal evaluation may significantly alter classification of osteoporosis in this age group. To examine trabecular-rich spinal bone loss with a measurement less affected by age-related artifacts than the AP spine, we measured lateral lumbar spine bone density (BMD) using dual-energy X-ray absorptiometry in 120 healthy, ambulatory, community-dwelling women 65 years of age and older (mean 70 +/- 5 years, range 65-88). We also examined cortical-rich sites in the forearm and total body along with AP spine and femoral BMD to assess the impact of site specificity using the World Health Organization (WHO) classification of osteoporosis. Significant losses in BMD were observed at the lateral spine (-1.1%/year, P < 0.01), forearm (-0. 77%/year, P </= 0.01), total hip (-0.75%/year, P </= 0.01), femoral neck (-0.70%/year, P </= 0.05), and trochanter (-0.78%/year, P </= 0. 01), but not the AP spine. Using the WHO criteria, lateral spine BMD determinations classified 66% of women with osteoporosis in contrast to 29% using the AP projection. Osteoporosis was diagnosed in 55% of women using measurements of the femoral neck, 43% using the total radius, and 19% using the total body. We conclude that elderly women lose bone at trabecular- and cortical-rich sites (lateral spine and total radius, respectively) in addition to sustaining significant age-related bone loss at mixed cortical/trabecular sites such as the hip. Classification of osteoporosis in this age group more than doubles using lateral versus AP spinal projections, supporting the necessity of developing more uniform agreement on site-specific analyses.

A paradigm for skeletal strength homeostasis

This article integrates engineering principles with skeletal biology to describe skeletal strength homeostasis. Skeletal strength revolves around its perceived mechanical usage. Mass, geometric properties, and fatigue damage burden are the principle determinants of structural strength. Bone cells form sensor and effector systems that monitor usage and adjust strength and stiffness by changing mass, geometric properties, and fatigue damage burden. The bone lining cell-osteocyte complex is the sensor; the bone modeling and remodeling systems are the effectors. Deformation and fatigue damage in bone are the signals received by the sensor. Accumulated energy in the sensor's cytoskeleton determines the rate at which the sensor sends messages to the effectors. The activity of both effector systems is proportional to the rate of incoming messages. Modeling raises bone strength and stiffness by improving geometric properties as it adds bone where customary deformation is greatest. Remodeling improves bone strength by replacing fatigue-damaged areas without mass changes. Bone removed during modeling and remodeling comes from sites where the impact on bone strength and stiffness is least. Hormones and agents alter the rigidity of the cytoskeleton and, thus, its capacity to deform and store energy. Osteopenic agents make it more rigid, causing detection of fewer deformations and transmission of fewer loading signals to the effector. Osteotropic agents decrease the rigidity of the cytoskeleton, causing detection of more strain events and transmission of more loading signals to the effector. Agent treatment thus establishes false conditions of disuse or hyperuse.

Differential effects of glucocorticoids on cortical appendicular and cortical vertebral bone mineral content

The susceptibility to glucocorticoid-induced bone loss may vary in different parts of the skeleton. We studied 62 patients with rheumatoid arthritis, 26 of whom were on low-dose glucocorticoid treatment. Bone mineral content (BMC) in the forearm was measured by single photon absorptiometry at a cortical, diaphyseal, and at a mixed cortical and trabecular, metaphyseal site. Lumbar BMC was measured by dual energy computed tomography in a trabecular and a cortical region of interest. The presence of vertebral deformities was evaluated on lateral spine radiographs. After correction for possibly confounding variables, prednisone therapy significantly influenced BMC at both the trabecular (-22.0%, 95% confidence interval -36.0% to -8.1%) and cortical (-24.8%, 95% confidence interval -39.3% to -10.3%) lumbar site. A significant effect was also seen at the metaphyseal (-15.7%, 95% confidence interval -27.1% to -4.2%), but not the diaphyseal (-3.9%, 95% confidence interval -14.1% to 6.4%) site in the forearm. Correlations between peripheral and vertebral BMC were moderate at best. The diaphyseal to metaphyseal BMC ratio did not identify patients with vertebral osteoporosis. It is concluded that the anterior cortical rim of the vertebral body is more susceptible to the effects of glucocorticoids than the cortical bone in the forearm, and that measurements of trabecular and anterior cortical vertebral BMC are essential in the management of patients with possible glucocorticoid-associated osteoporosis.

Bone mass of spine and forearm in osteoporosis and in German normals: influences of sex, age and anthropometric parameters

We measured forearm bone mineral density (BMD) using single photon absorptiometry (SPA) and bone mineral content (BMC) and BMD of lumbar spine by dual photon absorptiometry (DPA). The population consisted of 463 bone healthy subjects, 346 females and 117 males aged 20-85 years. Any underlying bone disease or other diseases known to affect bone mass were excluded by physical examination, thoracic and lumbar radiographs and laboratory screening. Patients with osteoarthritis of lumbar spine were excluded as well as patients taking drugs known to affect bone mass. All bone mass values declined with age. Body height also declined with age by 1.2 cm and 1.8 cm per 10 years (-0.7% and -1%) in females and males respectively. Main effects of age, body height, -surface, -weight and -mass index on bone mass were calculated using multiple regression models. In males and females lumbar BMC measured in gHA depended primarily on body height and secondarily on age. Spinal BMD as measured in g cm-2 was primarily dependent on age and then on height. In females forearm BMD depended primarily on age and then on body surface, in males on body surface only. Using receiver operating characteristic (ROC) analysis the ROC area increased from 0.81-0.85 (n.s.) including body height into spinal BMD values leading to a higher sensitivity of measurements of spinal bone mass in recognizing 58 patients with spinal postmenopausal osteoporosis. Including body surface into forearm BMD measurements ROC area increased from 0.66-0.69 (P = 0.055).(ABSTRACT TRUNCATED AT 250 WORDS)

Osteopenia in men with a history of delayed puberty

BACKGROUND AND METHODS

The effect of delayed puberty on peak bone mineral density in men is unknown. To determine whether such a delay reduces normal peak bone density and leads to osteopenia during adulthood, we measured radial bone mineral density by single-photon absorptiometry and spinal bone mineral density by dual-energy x-ray absorptiometry in 23 men who had a history of constitutionally delayed puberty and 21 men who underwent normal puberty. Their mean ages were 26 and 24 years, respectively. The groups were matched for other factors known to affect bone mass.

RESULTS

The mean (+/- SD) radial bone mineral density was significantly lower in the men with a history of delayed puberty than in the normal men (0.73 +/- 0.07 vs. 0.80 +/- 0.05 g per square centimeter; P less than 0.0002). Spinal bone mineral density was also significantly lower in the men with delayed puberty than in the normal men (1.03 +/- 0.10 vs. 1.13 +/- 0.11 g per square centimeter; P less than 0.003). Radial bone density was at least 1 SD below the mean value for the normal men in 15 of the 23 men with a history of delayed puberty, and spinal bone density was similarly decreased in 10 of the 23.

CONCLUSIONS

Adult men with a history of constitutionally delayed puberty have decreased radial and spinal bone mineral density. These findings suggest that the timing of puberty is an important determinant of peak bone density in men. Because the peak bone mineral density achieved during young adulthood is a major determinant of bone density in later life, men in whom puberty was delayed may be at increased risk for osteoporotic fractures when they are older.

Relationships between quantitative histological measurements and noninvasive assessments of bone mass

We performed a comprehensive analysis of the relationships between histologic indices in the iliac crest (cancellous bone volume, trabecular structural indices, cortical width, and core width) and bone density in the spine, hip, and wrist in 81 patients with various metabolic bone diseases including osteoporosis, osteomalacia, hyperparathyroidism, and Paget's disease. In the whole group, all of the histologic indices correlated significantly with bone mineral density (BMD) of the spine and the three regions of the hip (r = 0.28-0.73), with the exception of cortical width which correlated with the hip but not the spine (r = 0.21). There was no relationship between the histologic variables and either the distal or proximal radius. When the osteoporotic subgroup was considered separately, the relationships between BMD and both cancellous bone volume and the structural indices (trabecular number, separation, and thickness) were lost. In contrast, cortical width correlated more strongly with both spine and hip BMD. The relationship between core width and the spine was lost but persisted in the hip region. In female osteoporotic patients alone, only cortical width remained significantly correlated with spine or hip BMD. We conclude that the relationships between bone densities in the axial and peripheral regions and histomorphometric variables in iliac crest are not constant. In addition, cancellous bone volume and the trabecular structural indices relate well to noninvasive axial BMD measurements only in a heterogenous group with a large variance in both parameters. In the more homogeneous group with osteoporosis, cortical width appears to be a more powerful predictor of BMD at the important sites of osteoporotic fracture.

Osteoporosis associated with rheumatoid arthritis: pathogenesis and management

Rheumatoid arthritis is associated with both localized and generalized osteoporosis. Localized osteoporosis can be considered to be caused by local disease mechanisms, including the generation of factors from activation of the cytokine pathway. The etiology of generalized osteoporosis has been difficult to elucidate, particularly because of the lack of sensitive techniques to measure bone mineral density. The introduction of single- and dual-photon absorptiometry and quantitative computed tomography has allowed more accurate assessment of bone mineral density. In general, bone mineral density loss at appendicular sites does not correlate well with axial bone density loss. Corticosteroid treatment exaggerates the development of osteoporosis in up to 40% of patients with rheumatoid arthritis. Sex hormone status, physical activity, disease duration, and functional class are all significant predictors for the development of osteoporosis. Current therapy for prevention and treatment is based largely on theoretical considerations. Physical activity should be encouraged once acute joint inflammation has settled. Postmenopausal women and amenorrheic premenopausal women will benefit from cyclical estrogen replacement. Patients with low serum 1,25-dihydroxy vitamin D3 levels, and males with low serum testosterone levels, are candidates for replacement therapy with the appropriate hormones. In patients who are receiving corticosteroids the dose should be limited, and oral calcium supplements are of benefit. The use of the newer corticosteroid deflazacort, and disease-modifying immunosuppressive drugs, are discussed. Other therapeutic options which should be considered, although published trials are scarce, are calcitonin and the diphosphonates. Further studies are awaited concerning the optimum prevention and treatment of osteoporosis associated with rheumatoid arthritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationships among bone densitometry sites in normal young women

Interrelations among skeletal sites were examined in a population of up to 300 normal young white women aged 20-40 years. Measurements were done on the radius shaft, ultradistal radius, and ultradistal ulna using single-photon absorptiometry (SPA) and on the lumbar spine, proximal humerus, and proximal femur using dual-photon-absorptiometry (DPA). Because of the narrow range of intrapopulation variance in these normal young women, the intercorrelations among skeletal sites were not very high; the average correlation (r) was 0.43 for bone mineral content (BMC) and 0.45 for bone mineral density (BMD). The results at any one site predicted values at other sites with a standard error of estimate (SEE) of approximately 11% for BMD and 17% for BMC. Even in this relatively homogeneous sample, measurements at a single skeletal site could not be extrapolated to indicate skeletal status at other sites. BMC, and to a lesser extent BMD, were influenced by body size much as has been observed in both men and postmenopausal women. Bone results are preferably expressed as BMD, because (a) intrapopulation variability is lower (10% versus 15% for the lumbar spine), (b) intercorrelations among skeletal sites, and even among adjacent vertebrae, are higher for BMD, and (c) the influence of body size on BMD is lower (the average r for weight and BMD was 0.26 versus 0.33 for BMC).

Comparison between radial bone mineral density measured by single photon absorptiometry and histomorphometric bone mass parameters measured on iliac crest biopsies

Bone mineral density (BMD) measured by single photon absorptiometry (SPA) with a Moolsgard 1100 device on the distal and proximal part of the radius was compared with histomorphometric parameters measured on iliac crest biopsies in 37 patients suffering from various bone disorders. In the whole population, a good correlation was observed between the cancellous bone volume (Cn-BV/TV) measured on iliac crest biopsies and BMD from both the proximal part of the radius (r = 0.76, p less than 0.001) and the distal part of the radius (r = 0.73, p less than 0.001). Significant, although weaker correlations, were also found between the cortical width and the BMD from the distal part (r = 0.37, p less than 0.001) and the proximal part (r = 0.44, p less than 0.001) of the radius. In the 14 untreated osteoporotic patients, only a significant Spearman correlation was observed between the iliac Cn-BV/TV and the proximal radial BMD (r' = 0.69, p less than 0.05). It is thus not clear, whether radial proximal BMD correctly indicates cortical bone density in osteoporotic patients or not. The large internal variability of each of the two investigated methods and the small group of osteoporotic patients might explain the lack of correlation between the two methods in this group.

Does a single local absorptiometric bone measurement indicate the overall skeletal status? Implications for osteoporosis and osteoarthritis of the hip

Regional bone mineral content (BMC) and density (BMD) (head, arms, chest, spine, pelvis, legs) of a total body dual photon 153Gd absorptiometry (DPA) scan were measured in 20 healthy postmenopausal women, 27 postmenopausal women with hip fracture, and 17 postmenopausal women with osteoarthritis of the hip. In addition, local BMC and BMD were measured in the proximal and distal regions of the distal forearm (BMCprox, BMDprox, BMCdist, BMDdist) by single photon absorptiometry (SPA); and in the lumbar spine (BMCL2-L4 and BMDL2-L4) by 153Gd DPA. The overall impression was a reduction of bone mass in hip fracture patients compared with healthy controls and an increase in the bone mass of osteoarthritic patients. These results were valid using both regional values of the total body scan, and local forearm and lumbar spine measurements, and statistically significant using one-way analysis of variance. There were, however, also significant within-group between-region differences (one-way analysis of variance), showing that the bone mass of the pelvis and legs in hip fracture patients was more reduced than in the remaining skeleton; in osteoarthritic patients it was not increased but rather unchanged or slightly reduced. The differences between the level of the three local measurements (BMDprox BMDdist BMDL2-L4), on the one hand, and the level of the six regional BMD values, on the other hand, were investigated by the two-way analysis of variance: local measurements = rows; regional values = columns. This analysis showed that none of the three local measurements was statistically better than the other two in predicting the overall level of skeletal bone mass as judged by the six regional values. We conclude that serious osteoporotic bone loss has a generalized nature, however, with a tendency towards lower values in the regions affected by fracture (viz: low bone mass in the legs of femoral neck fracture patients). Osteoarthritis may be associated with a high bone mass in most areas, but low values in the affected regions. Local lumbar spine measurement of bone mass by DPA is not superior to local forearm measurement of bone mass by SPA in predicting the nature of overall osteoporotic or osteoarthritic bone change.

Monitoring skeletal response to estrogen

Estrogen replacement therapy at accepted doses is not fully effective in preventing bone loss and fractures in postmenopausal women. Bone densitometry is useful for monitoring estrogen replacement therapy to assess dose, foster compliance, and check for secondary bone loss. The most appropriate site for bone loss monitoring is probably the spine because it shows larger decreases at the menopause than appendicular sites, it shows larger increases with therapy, and it has clinical import in terms of fracture. Both dual-photon absorptiometry (or dual-energy x-ray absorptiometry) and computed tomography are the preferred monitoring methods. The precision of these densitometry methods is generally adequate to permit interim decisions with regard to continuing therapy, as well as conclusive decisions on therapeutic efficacy after 1 to 2 years of monitoring. Judicious use of densitometry in combination with biochemical determinations can enhance therapeutic control and provide both patient and physician confidence in long-term estrogen replacement therapy.

Bone mineral density and fracture in postmenopausal women

This retrospective study examined bone mineral density (BMD) for discrimination of female patients with fractures. Bone densitometry was done in 146 patients over the age of 50 years at radius, lumbar spine, and proximal femur sites using single and dual photon absorptiometry. The patients were divided into three groups: (A) no osteoporotic fractures (n = 92); (B) mild spine fractures with greater than 15% compression (n = 38); and (C) hip fractures (n = 16). Groups B and C did not differ significantly from each other in BMD, but these groups differed significantly from group A for spine and femur BMD. No significant differences between groups were found for the radius. Receiver operating characteristic (ROC) analysis showed that the BMD of the proximal femur had the highest diagnostic sensitivity for both spine and femur fractures; the radius had the lowest overall sensitivity, and the spine was intermediate.