Trabecular mineral content of the spine in women with hip fracture: CT measurement

Trabecular bone density of male human cervical and lumbar vertebrae

The objective of this study was to determine the bone mineral density (BMD) of cervical vertebrae and correlate with the lumbar spine. Fifty-seven young adult healthy male volunteers, ranging from 18 to 41 years of age, underwent quantitative computed tomography (QCT) scanning of C2-T1 and L2-L4 vertebrae. To account for correlations, repeated measures techniques were used to compare data as a function of spinal level and region. Linear regression methods were used (+/-95% CI) to compare data as a function of spinal level and region. The mean age and body height were 25.0 +/- 5.8 years and 181.0 +/- 7.6 cm. BMD decreased from the rostral to caudal direction along the spinal column. Grouped data indicated that the neck is the densest followed by the first thoracic vertebra and low back with mean BMD of 256.0 +/- 48.1, 194.3 +/- 44.2, and 172.2 +/- 28.4 mg/cm(3), respectively; differences were statistically significant. While BMD did not vary significantly between the three lumbar bodies, neck vertebrae demonstrated significant trends. The matrix of correlation coefficients between BMD and spinal level indicated that the relationship is strong in the lumbar (r = 0.92-0.96) and cervical (r = 0.73-0.92) spines. Data from the present study show that the trabecular bony architecture of the neck is significantly different from the low back. These quantitative BMD data from a controlled young adult healthy human male volunteer population may be valuable in establishing normative data specifically for the neck. From a trabecular bone density perspective, these results indicate that lumbar vertebrae cannot act as the best surrogates for neck vertebrae. Significant variations in densities among neck vertebrae, unlike the low back counterpart, may underscore the need to treat these bones as different structures.

Fracture site-specific deficits in bone size and volumetric density in men with spine or hip fractures

To study the structural basis of bone fragility in men, we compared bone size and volumetric bone mineral density (vBMD) of the third lumbar vertebra and femoral neck in 95 men with spine fractures, 127 men with hip fractures, and 395 healthy controls using dual-energy X-ray absorptiometry (DXA). The results were expressed in absolute terms and age-specific SD scores (mean +/- SEM). In controls, vertebral body and femoral neck width increased across age, being 0.46 +/- 0.11 SD and 0.91 +/- 0.08 SD higher in elderly men than in young men, respectively (both,p < 0.001). Men with spine fractures had reduced vertebral body width (-0.45 +/- 0.10 SD;p < 0.01) but not femoral neck width (-0.15 +/- 0.10 SD, NS). Men with hip fractures had reduced femoral neck width (-0.45 +/- 0.11 SD; p < 0.01) and vertebral body width (-0.25 +/- 0.10 SD; p < 0.05). The deficits in bone volume (BV) exaggerated the deficits in bone mineral content (BMC) by 40% at the vertebrae in men with spine fractures and by 9% at the femoral neck in men with hip fractures. vBMD deficits were greater at the vertebrae in men with spine fractures than in men with hip fractures (-1.37 +/- 0.08 SD vs.-0.70 +/- 0.10 SD, respectively; p < 0.01) but were similar at the femoral neck (-0.93 +/- 0.10 SD and -0.76 +/- 0.11 SD, respectively, NS), despite the men with spine fracture being 10 years younger. Bone fragility leading to spine or hip fractures in men may be the result of fracture site-specific deficits in bone size and vBMD that have their origins in growth, aging, or both.

An evaluation of bone loss after total hip arthroplasty for femoral head necrosis after femoral neck fracture: a quantitative CT study in 16 patients

This study was conducted to determine if bone and muscle loss is reversible in patients who had undergone total hip arthroplasty (THA) owing to necrosis of the femoral head after osteosynthesis for a displaced femoral neck fracture. The cortical bone mineral density (BMD), bone volume, bone mass, and muscle volume of the thigh and the BMD of the distal femur and proximal tibia were measured by quantitative computed tomography in 16 patients. Both extremities were measured just before reoperation. The measurements were repeated 3 and 6 months later. At reoperation, there was a mean 12% relative loss of bone mass and 23% loss of muscle volume in the middle femur on the fractured side compared with the uninjured side. In the distal femur and proximal tibia, there was a relative loss of BMD of 14% and 21% on the fractured side. Six months after reoperation, we found no change in bone mineral at any location on either side. The muscle of the thigh showed a gain in volume of 20% on the reoperated side but no change on the uninjured side. At the time of reoperation, we noted a marked bone and muscle loss on the fractured side. We failed to note any restoration of bone mineral after THA despite remobilization, which is expressed as an increase in muscle volume on the reoperated side. This study indicates that osteopenic bone has difficulties in adapting to patients' improved mobility after reoperation.

Risk of underestimation of the bone mineral density of proximal femur

Decreased bone mineral density (BMD) in the elderly increases the risk of hip fracture. Measurement of proximal femoral BMD can help us predict the risk of hip fracture, especially in the elderly. Since the BMD of proximal femur is usually measured on the unilateral side, we studied the risk of underestimation with measurement of unilateral proximal femur BMD in 266 normal Chinese women. In order to evaluate the effect of age, these subjects were divided into group A (18-59 years, n = 189) and group B (60-88 years, n = 77). BMDs of both proximal femurs were assessed with Norland 2600 dual photon absorptiometry. Using a cutoff T score of -1, the negative predictive value (NPV) in the entire group was 86.9% for femoral neck BMD and 85.7% for trochanter, and 82.2% for Ward's triangle: in group A, the NPV was 88.9% for femoral neck, 88.8% for trochanter, and 97.2% for Ward's triangle, but in group B, the NPV was 60.0% for femoral neck, 71.0% for trochanter, and 24.1% for Ward's triangle. The accuracy in the entire group was 86.1% for femoral neck, 84.2% for trochanter, and 86.3% for Ward's triangle: in group A the accuracy was 84.6% for femoral neck, 84.9% for trochanter, and 92.8% for Ward's triangle, but in group B, the accuracy was 89.6% for femoral neck, 81.7% for trochanter, and 90.0% for Ward's triangle. In general, NPV and accuracy increased at the expense of positive predictive value when the cutoff T score was changed to -2.5. This study suggested that measurement of unilateral proximal femur BMD was sufficient for screening the contralateral hip BMD in group A at a cutoff T score of -1. However, a T score of -2.5 was recommended for group B, and one should be careful in its application to Ward's triangle.

Quantitative computed tomography for spinal bone mineral measurements in chronic renal failure

The aim of this study was to assess non-invasively the status of spinal trabecular bone in patients with chronic renal failure and the influence of the disease stage. Single energy quantitative computed tomography (CT) was used in 89 patients with chronic renal failure to measure spinal trabecular bone equivalent density. 23 patients were independent of dialysis and 66 were receiving long-term haemodialysis. Spinal trabecular bone density of the patients was compared with locally determined normal ranges. Although trabecular bone mineral density (BMD) was lower (9% on average) in the patients who were not dependent on dialysis compared with the predicted mean normal values (BMDp) for age- and sex-matched normal subjects, the difference was not statistically significant. A statistically significant reduction was found in patients on dialysis (BMD/BMDp 0.75 +/- 0.16, Z-score -1.3). Osteosclerosis was found in 11 patients and they were excluded from the study. Longitudinal measurements in 42 patients on dialysis without osteosclerosis showed a 2.9% mean reduction in BMD/BMDp over a period of 8 months. All but one of the 16 haemodialysis patients with osteopenic spinal fractures had trabecular BMD values lower than the fracture threshold determined by our technique. In conclusion, end-stage chronic renal failure was associated with reduction in the spinal trabecular bone density.

Bone mineral density measurement by quantitative computed tomography in a normal Turkish population

PURPOSE

To observe the trabecular and cortical bone mineral density values of a normal Turkish population, to examine the effect of age in males, and age and duration of menopause in a female population on bone mineral density. Also to compare Turkish population bone mineral density values with the reference values in developed countries.

MATERIALS AND METHODS

Trabecular and cortical bone mineral densities were measured by the quantitative CT method in 255 (110 male and 145 female) normal cases.

RESULTS

According to the linear regression test results, loss of bone mineral density per year was 1.97 mg/ml and 2.09 mg/ml for females and 1.37 mg/ml and 1.04 mg/ml for males in the trabecular and cortical bone compartments, respectively. A 70-year-old female loses 56.7% and 31.3% of the bone mass at 20 years of age for the trabecular and cortical compartments, respectively. These ratios were 41% and 16.1% for the male population. Most loss in bone mass was observed in the premenopausal and early postmenopausal period. In the postmenopausal period, duration of menopause had more effect on bone mass than age. Loss of trabecular bone mass per year in the postmenopausal period was 2.36 mg/ml and 2.84 mg/ml with respect to age and duration of menopause, respectively.

CONCLUSIONS

Quantitative CT is a valuable method to determine bone mass because it allows to detect bone mass of trabecular and cortical bone separately. Loss in trabecular bone was found to be higher than in cortical bone for both sexes, while overall bone loss was higher in females. Rate of loss increases in the menopause period. Duration of menopause had more effect on bone mass than age. Bone mineral density values in Turkey were similar to reference values of western countries.

Bone mineral content of the spine and proximal femur in female patients with hip fracture

Measurement of bone density in the spine and hip by quantitative computed tomography (QCT) and dual photon absorptiometry (DPA) was performed in 36 women with hip fracture. Hip density by DPA was determined at three anatomic subregions of the hip. Comparison to normals revealed an average decrease in hip bone density by 15% below controls. Spine density measurements were not significantly different from that of controls. Correlations of hip and spine densities varied by hip subregion. This study demonstrated that bone density measurement methods and measurement at one axial site may not accurately reflect bone density at appendicular subregions.

In-vitro relationships between vertebral body density, size, and compressive strength the elderly thoracolumbar spine

The bone density of thoracolumbar vertebral columns (T1-L2) from 12 individuals having a mean age of 73 years was examined using quantitative computed tomography and dual energy X-ray absorptiometry. Spinal units, comprising three vertebrae, from different regions were then tested for compressive strength in a materials test device. Results showed segmental variations in trabecular and integral bone density of the vertebral bodies and their capacity for load bearing. Failure strength increased craniocaudally, whereas failure stress (load/cross-sectional area) decreased. Vertebral compressive strength was moderately correlated with bone mineral density as assessed with dual energy X-ray absorptiometry. In contrast, trabecular bone density determined from quantitative computed tomography was a poor predictor of compressive strength, as was bone mineral content. Use of an integral measure of bone density may provide a more practical guide to bone fragility.

The assessment of vertebral bone macroarchitecture with X-ray computed tomography

On a macroscopic scale, the structural characteristics of whole bone are likely dependent on the distribution of typically applied loads to the bone surface, the full bone shape, the thickness of the cortex at the various surface positions, and the distribution of cancellous bone material. X-ray computed tomography is presently the best available method for assessing the macroarchitecture of bone in-vivo. Fine detail, three-dimensional CT methods are available to measure regional bone mineral density (rBMD) in contiguously spaced small volumes and have been applied to the assessment of macroarchitecture in vertebrae. The more detailed rBMD methods produce radiation exposures to the subject similar to lumbar radiography and substantially higher than traditional QCT. The cancellous bone within lumbar vertebral bodies has been found in cross-sectional studies to have increased density in the inferior, posterior and lateral regions. Notably, regions with higher density at age 40 have a larger decline with age. The vertebral body cortex declines with age at a slower rate than observed for cancellous bone; however, the decline with age of cortical bone appears to vary substantially amongst subjects. The amount of cortical bone in the anterior portion of the body is less than in the lateral portion, which may explain previous discrepancies in assessing the fraction of vertebral body bone in the cortex.

Fracture risk as determined by prospective and retrospective study designs

Both retrospectively and prospectively designed studies consistently show low bone mass and/or bone mineral content (BMC) to be risk factor for low-trauma fractures in postmenopausal women. Along with the reports of such studies there has been concern expressed that BMC measurements overlap between fracture groups, i.e., some women with high BMC develop fractures and some women with low BMC do not. In these commonly used epidemiologic study designs, BMC does not discriminate between those who have and have not experienced the untoward event at some level of the exposure factor. The ability to discriminate is more properly determined by the sensitivity and specificity of the measured value. To contrast the concepts of risk and sensitivity, a nested case-control study was conducted within a 24-year cohort study of women at risk for osteoporosis. We found that for each 1.0 decrement of BMC z-scores, the adjusted relative risk for the prospective study design was 1.67, while the odds ratio obtained from the most recent BMC z-score measurements was 1.87. A receiver operating characteristic (ROC) curve, calculated from the nested case-control study data, showed that BMC z-scores, measured after low-trauma fracture, have both low sensitivity and low specificity to detect existing fracture status.

Quantitative computed tomography: comparative study using different scanners with two calibration phantoms

To assess computed tomography (CT) scanners in vertebral quantitative computed tomography (QCT) measurement, five cadaveric vertebrae fixed in a water phantom were measured using 16 CT scanners of 10 different models using two types (CaCO3 and K2HPO4) of reference phantom. Although the same reference phantoms were used, the QCT values varied markedly depending on the CT scanner employed. The differences in QCT values were greater in the equivalent amount of CaCO3 than in that of K2HPO4. The largest difference between CT scanners was 40 mg/cm3 in the equivalent amount of CaCO3 and 28 mg/cm3 in that of K2HPO4. These differences were reflected among CT scanners by different slopes and intercepts of the reference lines of CaCO3, K2HPO4 and ash density depending on the CT scanner used. However, good correlations (r greater than 0.97) were observed for the QCT values obtained by various CT scanners. These results show that QCT values on one machine can be compared more closely with those of another machine if conversion formulae, determined by using materials equivalent to human vertebral bone, are employed.

Incidence of hip fractures in the elderly: a cross-national analysis

This paper reviews international data on incidence rates of hip fracture in persons 50 years of age and older, based on a bibliographic search of articles published since 1960. Incidence rates are higher in white populations than in black, Asian, and Hispanic populations. In both sexes and in all ethnic groups and geographic areas, incidence rates increase markedly with age. The steep increase with age, however, occurs later in black, Asiatic and Hispanic populations than in whites. The ratio of female to male incidence rates is higher than 1.0 in whites, while in blacks and Asians it has often been the reverse, with higher rates among men. In recent years in Hong Kong incidence rates in females have increased more rapidly than incidence rates in males, so that now the incidence rates in females are higher than those in males. In addition to the study in Hong Kong, most studies in Northern Europe and North America show an increase in age-adjusted hip fracture incidence rates over time over the past few decades. Methodological differences among the various studies (including differences in the definition of hip fracture, in case ascertainment, and in the selection and sample size of the study population) necessitate cautious interpretation of the findings of this report.

Quantitative computed tomography for bone mineral measurement: technical aspects, dosimetry, normal data and clinical applications

A single KVp quantitative CT (QCT) technique was used for measuring the spinal trabecular bone density. The trabecular bone equivalent density (TBED) was expressed as the density of a K2HPO4 solution that exhibits a linear attenuation coefficient identical to that of trabecular bone. A field non-uniformity correcting factor was obtained from experiments on phantoms. The effective equivalent dose of the whole examination (four sections and a scout view) is 370 muSv. The in vivo short-term precision (reproducibility coefficient of variation) ranges from 1.4% to 4.1% depending on the TBED values of the normal subjects. The TBED was measured in 206 normal Greeks aged 30-69 years. Average TBED decreased with increasing age for both sexes. Analysis considering separately each vertebra showed a tendency to a caudal spinal TBED reduction. No correlation was found between the TBED values and the body habitus, milk consumption, smoking habits in men, and number of full-term pregnancies. A significant difference (p less than 0.01) was found between the TBED values of the normals and those of 50 women suffering from post-menopausal osteoporosis, 37 alcoholic men, and 12 gastrectomized men (Billroth II). Quantitative CT has been established as a method of measuring TBED in health and disease, and the results from this study confirm these applications.

Bone mineral density in patients with cervical and trochanteric fractures of the proximal femur

The bone mineral density (BMD) of the proximal femur, spine and radius shaft was determined in 75 women with atraumatic fractures of the proximal femur (FXf) (average age: 70.1 +/- 9.6 years) and 51 controls of similar age. Fractures were classified as either cervical (n = 36) or trochanteric (n = 39) on the basis of radiographic and surgical finding. The BMD of spine and proximal femur was determined by dual-photon absorptiometry (Lunar DP3) and the BMD of the radius shaft by single photon absorptiometry. The BMD of patients with FXf was significantly decreased over all skeletal sites compared to controls of similar age. No significant correlation was found between age and the BMD of the femoral neck in patients with FXf. Patients with trochanteric FXf were older and thinner (average: age, 72.9 +/- 9.4 years; weight, 53.1 +/- 7.8 kg) compared with patients with cervical fractures (age, 67.2 +/- 8.9 years; weight, 59.3 +/- 8.3 kg). Likewise the BMD of trochanteric FXf was lower at all measured sites: femoral neck, 0.548 +/- 0.066 g/cm2 vs 0.624 +/- 0.055 g/cm2 (P less than 0.001); L2-L4, 0.799 +/- 0.115 g/cm2 vs 0.925 +/- 0.106 g/cm2 (P less than 0.001); radius shaft, 0.454 +/- 0.057 g/cm2 vs 0.502 +/- 0.083 g/cm2 (P less than 0.05). Of the patients with trochanteric fractures 66% had concomitant vertebral fractures, while this occurred in only 28% of the patients with cervical fractures (P (Fisher) = 0.0007). In summary, females with trochanteric FXf are older, thinner, have less bone mass in all measured sites and suffer with a significantly greater frequency of vertebral fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphometric analysis of vertebrae and intervertebral discs as a basis of disc replacement

In this study measurements were obtained from 359 vertebrae and 215 intervertebral discs in an attempt to classify discs by their size. At the cervical and thoracic levels, this attempt was unproductive because of extensive variations. In the lumbar spine, discs were allocated to six size-matched groups and to two height-matched groups. The breadth of marginal rims were also measured with a view to provide surgeons operating on the spine with precise data on disc morphology to facilitate disc replacement.

Regional bone mineral in healthy and osteoporotic women: a cross-sectional study

Regional bone mineral content and density (BMC and BMD) was measured in six regions (head, arms, chest, spine, pelvis, and legs) using dual photon 153Gd absorptiometry (DPA) in 128 healthy women aged 21-77 years, and in 45 women presenting with Colles' fracture (mean age 65 years), 46 women with vertebral crush or wedge fracture (mean age 68 years), and 27 women with femoral neck-fracture (mean age 74 years). The age-related normal bone loss was generalized, uniformly distributed, and best described by a combination of a premenopausal linear and a postmenopausal exponential regression in all six regions. Looking at BMD, the overall expected bone loss from age 20 to age 80 was approximately 20% in all the regions. When the fracture patients were examined, we found also generalized bone deficit as the prominent feature, amounting to about 20% of the premenopausal level for Colles' and spinal fractures, and about 25% for femoral neck-fracture. However, there was a regional bias in the fracture patients, as the Colles' and spinal fracture patients had a preferential reduction in spinal and pelvic BMD, whereas the patients with femoral neck-fracture had a preferential reduction in pelvic and leg BMD. We conclude that age-related and osteoporotic bone loss is generalized. Furthermore, we propose that regional differences in osteoporotic bone loss are brought about by a simple biological variability of the range of (i) relative amount of trabecular and cortical bone, (ii) rate of loss in the two types of bone tissue, and (iii) time of onset of trabecular relative to cortical bone loss.

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.

Quantification of bone mineral content using dual-photon absorptiometry in a normal Japanese population

The bone mineral content of lumbar spine and/or total body were quantified in 217 healthy Japanese (86 males and 131 females) using a Dichromatic Bone Densitometer (Norland Corp., Model 2600). The bone mineral density of the third lumbar vertebra (L3 BMD) decreased significantly after age 20 in males (r = -0.417, p less than 0.0002), with acceleration of the decrease after age 50 (r = -0.621, p less than 0.00002). A significant correlation was found between L3 BMD and age after age 40 (r = -0.747, p less than 0.0001) in females. L3 BMD correlated with both the body height (r = 0.335, p less than 0.0001) and the body weight (r = 0.340, p less than 0.0001). Total bone mineral content from the second to fourth lumbar vertebrae correlated significantly with total body bone mineral (r = 0.880, p less than 0.00001) in these normal subjects. Lumbar spine bone mineral as measured by dual-photon absorptiometry is lower in Japan than the bone mass in the United States, although not lower than in other parts of the world.

Advances in noninvasive bone measurement

Several noninvasive measurement methods are used for evaluation of metabolic disease. Single-photon (125I) scans of the peripheral skeleton are useful in some diseases but are ineffective in osteoporosis (even on the distal radius or os calcis) because they cannot predict spinal or femoral density. Also, peripheral measurements show high percentages of false negatives, that is many patients with fractures have normal peripheral density. Dual-photon (153Gd) scans of the spine, femur, and total skeleton are precise and accurate (2% error) and provide direct measurements of bone strength at fracture sites. This gives the best discrimination of abnormality and the most sensitive monitoring. Quantitative computed computed tomography (QCT) allows measurement of the spine but not the critical proximal femur area. QCT has a large accuracy error because (a) the limited area measured (under 5 cm3) fails to represent the total vertebral body, (b) technical errors, and (c) variable fat and osteoid influence the results.

Sensitivity of dual-photon absorptiometry in spinal osteoporosis

Lumbar spine bone mass and density were measured with Dual photon absorptiometry (DPA) in 60 patients with crush fractures and 60 age-matched normal women. Short-term reproducibility of bone mineral density (BMD) was 1.3% in normal women and 2.5% in osteoporotic women; long-term reproducibility in normal women was 2.2%. The reproducibility of bone mineral content (BMC) seemed to be poorer than that of BMD. In this study, aortic calcifications had no effect on BMD, and one or two crush fractures in the L2-L4 region increased BMD by an average of 3% (0-10%). Lumbar spine DPA provided high sensitivity for these younger crush fracture osteoporotic patients (x = 65 years). The sensitivity at 95% specificity was 74% for BMD and 73% for BMC. This sensitivity is substantially better than that reported for DPA instruments giving higher variances or for quantitative computed tomography.

Bone density of the radius, spine, and proximal femur in osteoporosis

Bone mineral density (BMD) was measured in 140 normal young women (aged 20 to 39 years) and in 423 consecutive women over age 40 referred for evaluation of osteoporosis. Lumbar spine and proximal femur BMD was measured using dual-photon absorptiometry (153Gd), whereas the radius shaft measurement used single-photon absorptiometry (125I). There were 324 older women with no fractures, of which 278 aged 60 to 80 years served as age-matched controls. There were 99 women with fractures including 32 with vertebral and 22 with hip fractures. Subsequently, another 25 women with hip fractures had BMD measured in another laboratory; their mean BMD was within 2% of that of the original series. The mean age in both the nonfracture and fracture groups was 70 +/- 5 years. The BMD in the age-matched controls was 20% to 25% below that of normal young women for the radius, spine, and femur, but the Ward's triangle region of the femur showed even greater loss (35%). The mean BMD at all sites in the crush fracture cases was about 10% to 15% below that of age-matched controls. Spinal abnormality was best discriminated by spine and femoral measurements (Z score about 0.9). In women with hip fractures, the BMD was 10% below that of age-matched controls for the radius and the spine, and the BMD for the femoral sites was about 25% to 30% below that of age-matched control (Z score about 1.6). Femoral densities gave the best discrimination of hip fracture cases and even reflected spinal osteopenia. In contrast, neither the spine nor the radius reflected the full extent of femoral osteopenia in hip fracture.

Quantitative computed tomography in assessment of osteoporosis

Computed tomography (CT) has been widely investigated and applied in recent years as a means for noninvasive quantitative bone mineral determination. The usefulness of computed tomography for measurement of bone mineral lies in its ability to provide a quantitative image and, thereby, measure trabecular, cortical, or integral bone, centrally or peripherally. For measuring the spine, the potential advantages of quantitative computed tomography (QCT) over dual-photon absorptiometry (DPA) are its capability for precise three-dimensional anatomic localization providing a direct density measurement, and its capability for spatial separation of highly responsive cancellous bone from less responsive compact bone. Currently, QCT vertebral mineral determination has been implemented at over 800 sites encompassing a wide geographic distribution and a wide array of commercial scanners. With a world-wide distribution of approximately 8,000 advanced CT body scanners, the capability now exists for widespread application of vertebral bone mineral determination by quantitative computed tomography. These QCT techniques for vertebral mineral determination have been used to study skeletal changes in osteoporosis and other metabolic bone diseases. Longitudinal and cross-sectional bone mass measurements have been obtained at the University of California at San Francisco (UCSF) in over 3,000 patients seen clinically or on research protocols. The results presented here illustrate the use of QCT spinal mineral measurement in the delineation of normal age-related bone loss, in the evaluation of estrogen effects on bone, in the assessment of fracture threshold and risk, and in the study of the effects of various exercise regimens on bone mineral and the determination of relationships to other techniques of bone mineral measurement. The laboratory and clinical results presented herein indicate that QCT provides a reliable means to evaluate and monitor the many forms of osteoporosis and the various interventions aimed at ameliorating this condition. The greatest advantages of spinal QCT for noninvasive bone mineral measurement lie in the high precision of the technique, the high sensitivity of the vertebral trabecular measurement site, and the potential for widespread application.