Age changes of spine density in posterior-anterior and lateral projections in normal women

Failure strength of human vertebrae: prediction using bone mineral density measured by DXA and bone volume by micro-CT

Significant relationships exist between areal bone mineral density (BMD) derived from dual energy X-ray absorptiometry (DXA) and bone strength. However, the predictive validity of BMD for osteoporotic vertebral fractures remains suboptimal. The diagnostic sensitivity of DXA in the lumbar spine may be improved by assessing BMD from lateral-projection scans, as these might better approximate the objective of measuring the trabecular-rich bone in the vertebral body, compared to the commonly-used posterior-anterior (PA) projections. Nowadays, X-ray micro-computed tomography (μCT) allows non-destructive three-dimensional structural characterization of entire bone segments at high resolution. In this study, human lumbar cadaver spines were examined ex situ by DXA in lateral and PA projections, as well as by μCT, with the aims (1) to investigate the ability of bone quantity measurements obtained by DXA in the lateral projection and in the PA projection, to predict variations in bone quantity measurements obtained by μCT, and (2) to assess their respective capabilities to predict whole vertebral body strength, determined experimentally. Human cadaver spines were scanned by DXA in PA projections and lateral projections. Bone mineral content (BMC) and BMD for L2 and L3 vertebrae were determined. The L2 and L3 vertebrae were then dissected and entirely scanned by μCT. Total bone volume (BV(tot)=cortical+trabecular), trabecular bone volume (BV), and trabecular bone volume fraction (BV/TV) were calculated over the entire vertebrae. The vertebral bodies were then mechanically tested to failure in compression, to determine ultimate load. The variables BV(tot), BV, and BV/TV measured by μCT were better predicted by BMC and BMD measured by lateral-projection DXA, with higher R(2) values and smaller standard errors of the estimate (R(2)=0.65-0.90, SEE=11%-18%), compared to PA-projection DXA (R(2)=0.33-0.53, SEE=22%-34%). The best predictors of ultimate load were BV(tot) and BV assessed by μCT (R(2)=0.88 and R(2)=0.81, respectively), and BMC and BMD from lateral-projection DXA (R(2)=0.82 and R(2)=0.70, respectively). Conversely, BMC and BMD from PA-projection DXA were lower predictors of ultimate load (R(2)=0.49 and R(2)=0.37, respectively). This ex vivo study highlights greater capabilities of lateral-projection DXA to predict variations in vertebral body bone quantity as measured by μCT, and to predict vertebral strength as assessed experimentally, compared to PA-projection DXA. This provides basis for further exploring the clinical application of lateral-projection DXA analysis.

Quantitative ultrasound of the calcaneus in greek women: normative data are different from the manufacturer's normal range

Quantitative ultrasound (QUS) is considered a useful method in evaluating bone status. The aim of the present study was to establish the reference data for the QUS measurements of the calcaneus in a Greek population. We measured a QUS parameter, stiffness index (SI), at the right calcaneus in 1500 women using the Achilles express Ultrasonometer (GE Lunar, Madison, WI). Participants were divided into 7 groups according to their age with a 10-yr span in each group. A progressive decline was found in the SI values after the age of 39 yr in the current study. When the SI values were compared between the age groups, high statistically significant differences were obvious, especially between 20-29 and 50- to 59-yr age groups and 60-69 and 70- to 79-yr age groups (p < 0.0005). Additionally, in the Greek normal range (GNR), the SI values of those aged 60-69 and 70-79 yr were significantly higher (81.84+/-16.14 and 77.45+/-17.65, respectively) than those in the manufacturer's normal range (MNR; 75.84+/-16.14 and 69.10+/-17.65, p < 0.005, respectively). Using the manufacturer's values, significantly fewer women were classified as normal (48% vs 67.3%), although those with T-score < or =-2.5 were more (15.7%) compared with our Greek value (1.5%), and classification of subjects into risk-of-fracture categories was significantly different (kappa: 0.459, 66.2%, p < 0.0005). Multiple regression analysis showed that weight was the most significant predictor for SI in the age groups 30-39 (beta = 0.280, p < 0.05), 40-49, 60-69, and 70-79 yr (beta = 0.185, p < 0.005; beta = 0.329, p < 0.0005; beta = 0.494, p<0.0005, respectively). Using conventional categories of risk, we report a different classification of our subjects from those proposed by the manufacturer, supporting the concept that data specific to the Greek population are necessary.

Clinical utility of spine bone density in elderly women

It is common clinical practice to obtain a bone density measurement at both the hip and spine to evaluate osteoporosis. With aging, degenerative changes in the lumbar spine may elevate the bone mineral density (BMD) results giving false assurances that the fracture risk at the spine is low. We examined the association of spine osteoarthritis and bone mineral density in 1082 community-dwelling ambulatory older women aged 50-96 years who participated in a 1992-1996 osteoporosis research clinic visit. The BMD was measured at the hip and posteroanterior (PA) and lateral lumbar spine using dual energy X-ray absorptiometry (DXA). Spine osteoarthritis was identified on the PA lumbar spine DXA images by a musculoskeletal radiologist. Forty percent of women had evidence of spine osteoarthritis (OA). Women with spine OA had a mean age of 77.4 yr (95% confidence interval [CI]: 76.5-78.2), were significantly older than women without spine OA (mean age, 66.8 yr; 95% CI: 65.9-67.7), and were more likely to have prevalent radiographic fractures (14.2% vs. 9.5%; p<0.05). Age-adjusted BMD at the femoral neck, total hip, PA spine, and lateral spine was significantly higher in women with spine OA. Women with spine OA were more likely to have osteoporosis by the World Health Organization classification at the femoral neck and total hip than those without spine OA, but less likely based on the PA spine (14.4% vs. 24.5%). Despite higher BMD levels, women with OA of the lumbar spine had higher prevalence of osteoporosis at the hip and more radiographic vertebral fractures. In elderly women 65 yr and older who are likely to have spine OA, the DXA measurement of the spine may not be useful in assessing fracture risk, and DXA of the hip is recommended for identification of osteoporosis.

Ten-year prediction of osteoporosis from baseline bone mineral density: development of prognostic thresholds in healthy postmenopausal women. The Danish Osteoporosis Prevention Study

Osteopenia is common in healthy women examined in the first year or two following menopause. Short-term fracture risk is low, but we lack algorithms to assess long-term risk of osteoporosis. Because bone loss proceeds at only a few percent per year, we speculated that baseline bone mineral density (BMD) would predict a large proportion of 10-year BMD and be useful for deriving predictive thresholds. We aimed to identify prognostic thresholds associated with less than 10% risk of osteoporosis by 10 years in the individual participant, in order to allow rational osteodensitometry and intervention. We analyzed dual energy X-ray absorptometry (DXA) of the lumbar spine (LS) and femoral neck (FN) from 872 women, who participated in the non-HRT arms of the Danish Osteoporosis Prevention Study and had remained on no HRT, bisphosphonates or raloxifene since inclusion 10 years ago. We defined development of a T -score below -2.5 at the LS and/or FN or incident fracture as end-point, and we derived prognostic thresholds for baseline BMD, defining 90% NPV (negative predictive value) and 90% sensitivity, respectively. Seventy-six percent of the variation in BMD of the LS at 10 years was predicted by baseline BMD. In an individual participant, a baseline BMD T -score above -1.4 (FN or LS, whichever was lower) was associated with a 10-year risk of less than 10% of developing osteoporotic BMD or fracture. This covered 69% of the population. By contrast, participants with T -scores below -1.4 had a 56% risk of fracture or low BMD within 10 years. At the population level, baseline T -score cutoffs below 0 at the LS (68% of the population), 0 at the FN (72%) or -0.6 (62%) at the lower of the two sites capture 90% of the population that developed osteoporosis during the following 10 years. A BMD measurement, performed in the first two years following menopause, is a strong long-term predictor of BMD in healthy women. The association is strong enough to provide robust prognostic thresholds, which can be used to divide the population into two prognostic classes at menopause.

In vivo intrarater and interrater precision of measuring apparent bone mineral density in vertebral subregions using supine lateral dual-energy x-ray absorptiometry

Analysis of apparent bone mineral density (BMD) in the lumbar spine is commonly based on anteroposterior (AP) scanning using dual-energy X-ray absorptiometry (DXA). Although not widely used, clinically important information can also be derived from lateral scanning. Vertebral bone density, and therefore strength, can may vary in different subregions of the vertebral body. Therefore, subregional BMD measurements might be informative about fracture risk. However, the intrarater and interrater precision of in vivo subregional BMD assessments from lateral DXA remains unknown. Ten normal, young (mean: 24 yr) and 10 older (mean: 63 yr) individuals with low BMD were scanned on one occasion using an AP/lateral sequence. Each lateral scan was reanalyzed six times at L2 by three raters to determine the intrarater and interrater precision in selecting seven regions of interest (subregions). Precision was expressed using percentage coefficients of variation (% CV) and intraclass correlation coefficients (ICC). Intrarater precision ranged from ICC(1,1) 0.971 to 0.996 (% CV: 0.50-3.68) for the young cohort and ICC(1,1) 0.934 to 0.993 (% CV: 1.46-5.30) for the older cohort. Interrater precision ranged from ICC(2,1) 0.804 to 0.915 (% CV: 1.11-2.35) for the young cohort and ICC(2,1) 0.912 to 0.984 (% CV: 1.85-4.32) for the older cohort. Scanning a subgroup of participants twice with repositioning was used to assess short-term in vivo precision. At L2, short-term in vivo precision ranged from ICC(1,1) 0.867 to 0.962 (% CV: 3.38-9.61), at L3 from ICC(1,1) 0.961 to 0.988 (% CV: 2.02-5.57) and using an L2/L3 combination from ICC(1,1) 0.942 to 0.980 (% CV: 2.04-4.61). This study demonstrated moderate to high precision for subregional analysis of apparent BMD in the lumbar spine using lateral DXA in vivo.

Material changes in osteoporotic human cancellous bone following infiltration with acrylic bone cement for a vertebral cement augmentation

Bone cement infiltration can be effective at mechanically augmenting osteoporotic vertebrae. While most published literature describes the gain in mechanical strength of augmented vertebrae, we report the first measurements of viscoelastic material changes of cancellous bone due to cement infiltration. We infiltrated cancellous core specimen harvested from osteoporotic cadaveric spines with acrylic bone cement. Bone specimen before and after cement infiltration were subjected to identical quasi-static and relaxation loading in confined and free compression. Testing data were fitted to a linear viscoelastic model of compressible material and the model parameters for cement, native cancellous bone, and cancellous bone infiltrated (composite) with cement were identified. The fitting demonstrated that the linear viscoelastic model presented in this paper accurately describes the mechanical behaviour of cement and bone, before and after infiltration. Although the composite specimen did not completely adopt the properties of bulk bone cement, the stiffening of cancellous bone due to cement infiltration is considerable. The composite was, for example, 8.5 times stiffer than native bone. The local stiffening of cancellous bone in patients may alter the load transfer of the augmented motion segment and may be the cause of subsequent fractures in the vertebrae adjacent to the ones infiltrated with cement. The material model and parameters in this paper, together with an adequate finite-element model, can be helpful to investigate the load shift, the mechanism for subsequent fractures, and filling patterns for ideal cement infiltration.

Data driven attempt to create a clinical algorithm for identification of women with rheumatoid arthritis at high risk of osteoporosis

OBJECTIVES

To examine relations between osteoporosis and low bone mass and demographic and clinical variables in patients with rheumatoid arthritis (RA), in an attempt to develop a data driven clinical tool for identification of patients at high risk of osteoporosis.

METHODS

All patients were recruited from a county based register and were examined cross sectionally with a variety of clinical and health status measures as well as bone density measures (anteroposterior spine L2-4, total hip, and femoral neck). Associations between osteoporosis (T score < or = -2.5SD) and low bone mass (T score < or = -1SD), on the one hand, and demographic and clinical measures, on the other, were examined bivariately and by logistic regression analyses.

RESULTS

394 patients with a mean age of 54.8 years were examined. The percentages having osteoporosis/low bone mass were 16.8/45.8, 14.7/54.5 and 14.7/55.5 in spine L2-4, total hip, and femoral neck, respectively. Osteoporosis and low bone mass were bivariately related to age, body mass index (BMI), disease duration, disease process measures, presence of deformed joints, physical disability, current use of corticosteroids, and history of non-vertebral fracture. In multivariate analyses, age >60 years, low BMI, and current use of corticosteroids were consistently related to osteoporosis and to low bone mass at all sites. The presence of deformed joints was associated with osteoporosis at the total hip, and a history of previous non-vertebral fracture with osteoporosis at the femoral neck. The Modified Health Assessment Questionnaire (MHAQ) > or = 1.5 and non-vertebral fracture were also independently associated with low bone mass at the hip. The logistic regression analyses models could, however, only predict osteoporosis with a sensitivity of about 50-60% and a specificity of 80-90% at the various measurement sites, and low bone mass with a sensitivity and specificity of about 70%.

CONCLUSION

Consideration of demographic and disease markers may be of some help in predicting presence of osteoporosis or low bone mass, but a combination of markers cannot be used as a clinical tool with sufficient sensitivity and specificity for the identification of osteoporosis or low bone mass in patients with RA.

Central region-of-interest analysis of lumbar spine densitometry demonstrates lower bone mass in older rhesus monkeys

Osteoarthritis (OA) spuriously elevates spine bone mineral density (BMD) as measured by dual-energy X-ray absorptiometry (DXA). This study documents spinal OA prevalence in adult female rhesus monkeys, and evaluates a custom central region-of-interest (CROI) analysis technique designed to minimize OA effects on BMD measurement. Lumbar spine radiographs were obtained on 71 animals, age 10-37 years. OA degree was blindly scored as none, minimal, or moderate/severe. Moderate/severe OA was not observed before age 19, but was present in 66% of older animals. Subsequently, lumbar spine (L2-4) BMD was determined by standard DXA analysis and manual placement of 0.92 cm2 CROIs in two groups of female rhesus monkeys. One group (eight control, eight postovariectomy, ages 10-19 years) was assessed longitudinally, the second (n = 90, ages 10-37) cross-sectionally. Measured bone loss following ovariectomy (8.1% standard analysis, 11.5 % CROI) was comparable with both techniques. By contrast, CROI demonstrated lower bone mass with age (p < 0.0001), whereas only a trend (p = 0.06) was observed with standard analysis. When World Health Organization criteria were applied, 42% of animals > or = age 19 years were classified as osteopenic/osteoporotic by standard analysis compared with 67% by CROI. All "normal" animals reclassified as osteopenic/osteoporotic by CROI had OA. In conclusion, female rhesus monkeys often develop spinal OA with advancing age. CROI analysis demonstrated lower bone density in older monkeys and was as sensitive to estrogen-depletion bone loss as standard methodology. This suggests that alternative analysis techniques, such as CROI, may be more appropriate to evaluate bone density in nonhuman primates, and potentially in people.

The effect of aging on bone mineral metabolism and bone mass in Native American women

OBJECTIVE

To examine the effect of age on mineral metabolism and bone mineral density (BMD) of the hip and spine in Native American women.

DESIGN

A cross-sectional study.

SETTING

The Sac and Fox Nation in rural Oklahoma

MEASUREMENTS

Serum measurements were made of 25 hydroxyvitamin D (25OHD), osteocalcin, and immunoreactive parathyroid hormone. Bone mineral density of the hip and spine was assessed by dual energy X-ray absorptiometry.

PARTICIPANTS

A total of 77 Native American women aged 19 to 85 years.

RESULTS

Serum 25 hydroxyvitamin D was related inversely to age (r = -0.32; P < .05) and was less than 15 ng/mL in 7% of the subjects. Serum osteocalcin was higher (P < .001) in postmenopausal than in premenopausal subjects. In postmenopausal subjects, serum osteocalcin was related to age (r = .59, P < .001). BMD was lower (P < .001) in postmenopausal than in premenopausal subjects. There was no evidence of bone loss before age 50 in either the femur or the spine. Age (r > or = -0.48, P < .001) and body mass index (BMI) (r > or = 0.41, P < .005) were independent determinants of both femoral and lumbar BMD. Serum 25OHD was a significant independent determinant of both lumbar (r = .26, P < .05) and femoral (r = .41, P < .01) BMD. Age, BMI, and serum 25OHD together accounted for 70% of the variance in BMD at these sites. The use of t scores indicated femoral bone density was higher (P < .05) in premenopausal Native American women, and lower (P < 0.05) in postmenopausal subjects, compared with white women.

CONCLUSIONS

In Native American women, there is a reduction in bone density and a sustained increase in bone turnover postmenopausally. BMI and serum 25OHD are significant determinants of BMD. Peak BMD may be higher, and the postmenopausal rate of bone loss greater, than that in white women.

Instrumental diagnosis of osteoporosis

Considerable progress in the development of methods for assessing the skeleton now makes it possible to detect osteoporosis non-invasively and early. There is a variety of techniques available at present: single-photon (SPA) and single X-ray absorptiometry (SXA), dual-photon (DPA) and dual X-ray absorptiometry (DXA), quantitative computed tomography (QCT), radiographic absorptiometry (RA), and quantitative ultrasound (QUS), and their development has certainly been driven by the need to overcome the inherent shortcomings of plain radiography for this purpose. Both SPA and SXA methods make a quantitative assessment of the bone mineral content (BMC) or density (BMD) at peripheral sites of the skeleton possible. Single energy measurements are not possible at sites with variable soft tissue thickness and composition, i.e., the axial skeleton. For these purposes, DPA and DXA techniques were introduced. The main advantages of an X-ray system over a radionuclide system are shortened examination time, greater accuracy and precision limited to higher resolution, and removal of errors due to source decay correction. Low radiation dose, availability, capacity to evaluate multiple sites, and ease of use have made DXA the most widely used technique for measuring bone mineral density. QCT can determine the true volumetric density of trabecular or cortical bone in three dimensions at any skeletal site. Recently developed new computer-assisted methods have improved RA precision, thus providing a simple and inexpensive technique for screening of bone mineral status of large populations. QUS was reported to provide information regarding the structural characteristics of bone, which may be relevant to the appearance of osteoporotic fractures; indeed, some studies suggest a relationship between QUS and bone strength beyond that which can be explained by BMD. Recent experimental studies suggested that magnetic resonance might also constitute a promising tool for assessing osteoporosis.

How often does lateral spine DXA detect low bone mass in patients with both normal PA spine and hip?

The clinical utility of lateral bone mineral density (BMD) measurement for the diagnosis of osteoporosis remains controversial. Since both posterior-anterior (PA) spine and hip scans are universally performed, the true clinical utility of lateral dual-energy X-ray absorptiometry (DXA) should lie in its ability to detect low bone mass independent of both PA spine and hip. We examined lateral, PA and hip BMDs in 2134 referred Caucasian females aged 25-89 using the Hologic 2000. Compared only to PA scans, the additional percentages of women with very low BMD (T-score below -2.5 utilizing the National Health and Nutrition Examination Survey [NHANES] III normative database) on lateral were 7.3, 16.4, 28.2, 33.7, and 26.2% for age groups 25-49, 50-59, 60-69, 70-79, and 80-89, respectively. When the results from both PA and total hip measurements were combined, lower but still significant percentages were found: 5.4, 14.9, 24.4, 26.6, and 17.8% for age groups 25-49, 50-59, 60-69, 70-79, and 80-89, respectively. Utilizing the original Hologic normative database, the additional yield in women with a nonosteoporotic PA spine and femoral neck was quite low: 4.6, 8.5, 13.3, 10.0, and 2.5% for women age 25-49, 50-59, 60-69, 70-79, and 80-89, respectively. Thus, the lateral scans now add more additional patients into the very low BMD category. Whether the relationship to future fracture risk of low BMD and T-scores on lateral is similar to that of PA spine remains to be established.

Serum osteocalcin and bone mineral density at various skeletal sites: a study performed with three different assays

The purposes of this study were threefold: (1) to compare values obtained by three conventional radioimmunoassays for serum bone-gla-protein (BGP) in a population of normal women, (2) to study the relationship between serum BGP and bone mineral density (BMD) measured at four different skeletal sites (lumbar spine, proximal femur, proximal and ultradistal radius), and (3) to compare the results obtained by the three assays with conventional markers of bone turnover. Ninety-seven normal women (age range 25 to 75 years, mean +/- 1 SD = 54.3 +/- 10.9 years) were studied. Three independent assays were used to measure serum osteocalcin levels: a heterologous radioimmunoassay (RIA) (A) (Incstar Co., Stillwater, Minn.), a homologous RIA (B) (Nichols Institute, San Juan Capistrano, Calif.), and a two-site immunoradiometric assay (C) (Cis Biointernational, Gif-sur-Yvette, France). Mean +/- SD values of serum osteocalcin in the group as a whole were 4.05 +/- 1.37 microg/L by assay A, 6.03 +/- 2.90 microg/L by assay B, and 22.67 +/- 7.52 microg/L by assay C. Serum osteocalcin levels increased linearly with age; however, no correlation between serum BGP (whatever the assay used) and age was observed when only postmenopausal women were taken into account. When the effect of age was held constant by means of partial correlation analysis, only serum BGP levels measured by assays B and C were still inversely related with lumbar spine and ultradistal radius BMD; the latter assay was also weakly correlated with Ward's triangle BMD. After all the biochemical and clinical variables taken into consideration were introduced in a multiple regression equation, serum BGP still represented an important predictor of ultradistal radius and lumbar spine BMD only. Regarding relationships with other markers of bone turnover, the assay C in general showed the highest r values. In conclusion, our results indicate that commercially available BGP assays differ analytically and clinically; furthermore for the first time they show the existence of an inverse correlation between serum osteocalcin levels (which reflects bone turnover at the time of examination) and bone mass (which at a given time represents the balance of all previous metabolic events), after the influence of aging is excluded.

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 longitudinal study of supine lateral DXA of the lumbar spine: a comparison with posteroanterior spine, hip and total-body DXA

We report a study to assess whether supine lateral dual-energy X-ray absorptiometry (DXA) scans of the lumbar spine provide better data for monitoring response to treatment than alternative measurement sites such as the posteroanterior (PA) spine, hip and total body. The study population was 152 women enrolled in a placebo-controlled clinical trial of cyclical etidronate therapy. All subjects were 1-10 years after the menopause with bone mineral density (BMD) between 0 and -2 SD of age-matched normal women. Paired PA and lateral spine, left hip and total-body DXA scans were performed at baseline, 1 year and 2 years on a Hologic QDR-2000. One hundred and thirty-one subjects completed the study. Mean percentage change from baseline at 2 years in the treated (n = 61) and control (n = 70) groups was calculated for vertebral body, width-adjusted (WA) vertebral body, mid-vertebral body and WA mid-vertebral body BMD measurement on the lateral scans and compared with the percentage changes in PA spine, femoral neck, trochanter, Ward's triangle and total-body BMD. The long-term precision for each BMD measurement site was obtained by linear regression analysis in subjects taking placebo. Overall treatment effect, defined as the difference in the percentage change in BMD in the two treatment groups at 2 years, was divided by long-term precision to give an index of the ability of each site to monitor response to treatment. Results (and standard errors) normalized to the ratio of treatment effect/ precision for PA spine BMD were as follows: PA spine, 1.00; vertebral body, 0.89 (0.14); WA vertebral body, 0.78 (0.14); mid-vertebral body, 0.65 (0.14); WA mid-vertebral body, 0.60 (0.13); femoral neck, 0.35 (0.15); trochanter, 0.45 (0.15); Ward's triangle, 0.59 (0.22); total body, 0.52 (0.19). Although treatment effect was larger for lateral than for PA spine BMD, this advantage was offset by the greater precision errors. PA spine BMD remains the optimum measurement for longitudinal studies in recently postmenopausal women.