Addition of right lateral decubitus positioning improves vertebral visualization with VFA in selected patients

Densitometric vertebral fracture assessment (VFA) allows detection of clinically unappreciated vertebral fracture. However, vertebral visualization using VFA can be suboptimal. In such individuals, alternative spine positioning may enhance visualization. Consistent with this, we observed that reversal of positioning (right lateral decubitus rather than standard left lateral decubitus, subsequently referred to as "reverse" positioning) improved visualization in patients with suboptimal vertebral visualization. This report describes 33 such individuals (i.e., 30 men and 3 women); their mean age and their lowest T-score (L1-L4 spine, proximal femur or 0.3 radius) was 69.9 yr and 2.2, respectively. All images were acquired using a GE Healthcare Lunar Prodigy densitometer (GE Healthcare, Madison, WI). Reverse VFA increased the number of visualized vertebrae in 82% of these patients (27 of 33; p<0.0001). Specifically, only 62% of vertebrae from T4-L5 were visualized using the standard left lateral position. Addition of either full or partial reverse VFA increased (p<0.0001) the number of visualized vertebrae to 83% (384 of 462). In this cohort, reverse positioning allowed detection of 4 additional vertebral fractures, including two in patients without previously identified fractures. We conclude that in selected patients with suboptimal vertebral visualization on VFA, addition of reverse positioning improves visualization and may enhance vertebral fracture detection.

Calcium supplement ingestion may alter lumbar spine bone mineral density measurement

Densitometry centers commonly request patients abstain from ingesting calcium supplements prior to dual-energy X-ray absorptiometry (DXA) examination to avoid interference with bone mineral density (BMD) measurement. However, it is not clear that this practice is necessary. This study assessed the impact of recent calcium supplement intake on lumbar spine BMD measurement. The phase 1 experiment demonstrated BMD differences when placing a supplement over various areas of two encapsulated phantoms. To determine whether these results were clinically relevant, the phase 2 study enrolled 36 subjects who received spine scans before and after random assignment to ingest one Citracal, OsCal or People's Choice tablet providing 315, 500, and 600 mg of elemental calcium, respectively. The phase 3 study evaluated 15 subjects that had three spine scans with repositioning between to establish BMD precision, and then ingested a calcium carbonate tablet. Post-dosing scans were performed 15 and 30 minutes after tablet ingestion. The difference in L1-L4 BMD on subsequent scans was compared with the study derived least significant change (LSC) of 0.028 g/cm(2). In phase 2, L1-L4 BMD changes outside the LSC occurred in 36% of subjects with 47% having visualized tablets. Similarly, 33% of the phase 3 subjects demonstrated changes outside the LSC after calcium ingestion and 53% of the subjects in phase 3 had tablets visualized. Visualization of calcium tablets was not associated with BMD changes. In conclusion, calcium tablet intake may affect measured L1-L4 BMD within 30 minutes of ingestion. As such, it is appropriate to request patients abstain from calcium tablet ingestion prior to a spine DXA examination.

Combination therapy for osteoporosis: considerations and controversy

Combination therapy, the simultaneous use of two pharmaceutical agents with the goal being reduction of fracture risk, is an area of substantial clinical interest. This paper summarizes the rationale, existing clinical trials data, and other considerations relevant to combination therapy for osteoporosis. Combinations of antiresorbers (eg, estrogen plus bisphosphonates) produce greater increases in bone mass than either treatment alone. Conversely, combining anabolic agents (parathyroid hormone) with bisphosphonates does not produce additive effects. None of the existing studies are large enough to determine whether combination treatment reduces fracture risk to a greater extent than use of a single agent. However, it is certain that combination treatment will increase cost and likely that it will increase side effects and reduce therapy adherence. Given the absence of demonstrated fracture reduction benefit, increased cost and likely increase in adverse events, combination therapy is not currently recommended.

Lateral vertebral assessment: a valuable technique to detect clinically significant vertebral fractures

Although many vertebral fractures are clinically silent, they are associated with increased risk for subsequent osteoporotic fractures. A substantial number of these fractures are demonstrable using instant vertebral assessment with Hologic densitometers. Whether similar recognition is possible using dual-energy lateral vertebral assessment (LVA) with GE Lunar densitometers remains uncertain. Thus, we evaluated the ability of clinicians using LVA to detect prevalent vertebral fractures. Dual-energy LVA and conventional thoracic and lumbar spine radiographs were concurrently obtained in 80 postmenopausal women. Using an established visual semiquantitative system, vertebral fractures were identified individually by two non-radiologist clinicians on LVA images, and the results were compared with spinal radiograph evaluation by an expert radiologist. Using LVA, 95% of vertebral bodies from T7 through L4 were evaluable, but a majority (66%) of vertebrae from T4 to T6 were not adequately visualized. In the LVA-evaluable vertebrae, prevalent fractures were identified in 40 vertebral bodies by radiography. In this regard, the clinicians using LVA detected 17 of 18 radiographically evident vertebral fractures of grade 2 or 3, a false negative rate of 6%. They identified 50% (11/22) of grade 1 fractures. Additionally, the vast majority of evaluable non-fractured vertebrae, (764/794, 96.2%) were correctly classified as normal by LVA. Thus, clinicians utilizing LVA correctly identified the vast majority of grade 2 or 3 vertebral compression fractures and normal vertebral bodies, although detection of grade 1 fractures was less effective. In conclusion, the low-radiation, dual-energy LVA technique provides a rapid and convenient way for clinicians to identify patients with, and without, grade 2 or 3 vertebral fractures, thereby enhancing care of osteoporotic patients.

Combination therapy for osteoporosis: considerations and controversy

Combination therapy, the simultaneous use of two pharmaceutical agents with the goal being reduction of fracture risk, is an area of substantial clinical interest. This paper summarizes the rationale, existing clinical trials data, and other considerations relevant to combination therapy for osteoporosis. Combinations of antiresorbers (eg, estrogen plus bisphosphonates) produce greater increases in bone mass than either treatment alone. Conversely, combining anabolic agents (parathyroid hormone) with bisphosphonates does not produce additive effects. None of the existing studies are large enough to determine whether combination treatment reduces fracture risk to a greater extent than use of a single agent. However, it is certain that combination treatment will increase cost and likely that it will increase side effects and reduce therapy adherence. Given the absence of demonstrated fracture reduction benefit, increased cost and likely increase in adverse events, combination therapy is not currently recommended.

Interobserver reproducibility of criteria for vertebral body exclusion

We studied reproducibility of the ISCD vertebral exclusion criteria among four interpreters. Surprisingly, agreement among interpreters was only moderate, because of differences in threshold for diagnosing focal structural defects and choice of which vertebra among a pair discordant for T-score, area, or BMC to exclude. Our results suggest that reproducibility may be improved by specifically addressing the sources of interobserver disagreement.

INTRODUCTION

Although DXA is widely used to measure vertebral BMD, its interpretation is subject to multiple confounders including osteoarthritis, aortic calcification, and scoliosis. In an attempt to standardize interpretation and minimize the impact of artifacts, the International Society for Clinical Densitometry (ISCD) established criteria for vertebral exclusion, including the presence of a focal structural defect (FSD), discrepancy of >1 SD in T-score between adjacent vertebrae, and a lack of increase in BMC or area from L1 to L4. Whereas the efforts of the ISCD represent an important advance in BMD interpretation, the interobserver reproducibility with application of these criteria is unknown. We hypothesized that there would be substantial agreement among four interpreters regarding application of the exclusion criteria and the final lumbar spine T-score.

MATERIALS AND METHODS

Each interpreter read a set of 200 lumbar DXA scans obtained on male veterans, applying the ISCD vertebral body exclusion criteria.

RESULTS

Surprisingly, agreement among interpreters was only moderate. Differences in interpretation resulted from differing thresholds for recognition of FSD and the choice of excluding the upper or lower vertebral body for the criteria requiring comparison between adjacent vertebrae.

CONCLUSIONS

Despite their apparent simplicity, the ISCD vertebral exclusion criteria are difficult to apply consistently. In principle, appropriate refinement of the exclusion criteria may significantly improve interobserver agreement.

Recalculation of the NHANES database SD improves T-score agreement and reduces osteoporosis prevalence

In attempt to improve diagnostic agreement between manufacturers, a recent software update incorporated NHANES III data in GE Lunar densitometers. As a result, the femur neck and trochanter T-scores were lowered, and osteoporosis prevalence was increased. Use of a recalculated young-normal SD for the GE Lunar-adjusted NHANES III database improved diagnostic agreement and is recommended.

INTRODUCTION

Use of manufacturer-specific normative databases for T-score derivation leads to discordance in T-score values and differences in diagnostic classification. To address this issue, the International Committee for Standards in Bone Measurement (ICSBM) recommended the NHANES III database for femur T-score derivation. Acquired on Hologic (Hol) instruments, this database requires conversion equations for application to other DXA systems. NHANES III total femur (TF) conversions for GE Lunar (GE) have previously been available, and femoral neck (FN) and trochanter (TR) equations were reported recently. Per the ICSBM recommendation, GE Lunar incorporated these values into their female database. This should produce T-score and diagnostic agreement between Hol and GE instruments; however, this has not been evaluated.

MATERIALS AND METHODS

We compared GE femur scans in 115 postmenopausal women using software before and after the NHANES III software update. Subsequently, T-scores derived from femur scans obtained on GE and Hol densitometers were compared in a different group of 89 postmenopausal women.

RESULTS

The NHANES III software update had no effect on measured BMD (g/cm2) at any femur region. However, because of changes in values used for T-score calculation (increase in the mean young-normal BMD at the FN and TR and a reduction in SD at the TR), the T-scores were lower (mean, 0.48 and 0.68, respectively) at the FN and TR using post-NHANES III software. Consequently, this update increased femur osteoporosis prevalence in these 115 women from 7.8% to 18.3%. Comparison of GE with Hol total proximal femur T-scores revealed a minimal difference (<0.1) and equal diagnoses of osteoporosis. FN and TR differences were larger, with mean GE T-scores lower than Hol (p < 0.001) by 0.17 and 0.50, respectively, thereby introducing osteoporosis diagnostic disagreement (13 [GE] versus 9 [Hol]). Our evaluation suggested that this disparity resulted from direct application of published NHANES III SDs at the FN and TR. As such, we applied the conversion formulae to the NHANES III published Hologic data and found the FN and TR SDs were greater than assumed by GE. Using our recalculated SD to derive T-scores reduced the mean GE/Hol T-score difference to 0.03 at the FN and 0.32 at the TR and resolved osteoporosis diagnostic disagreement.

CONCLUSION

The GE NHANES III software update leads to lower FN and TR T-scores than obtained with Hol or prior GE software. Recalculation of the young-normal SD reduces this difference and is recommended. Clinicians are advised to avoid using the TR for diagnosis or, at a minimum, use caution when making treatment decisions based solely on T-score at this site.

Assay variation confounds the diagnosis of hypovitaminosis D: a call for standardization

Endemic hypovitaminosis D contributes to osteoporosis development. However, variation in 25-hydroxyvitamin D (25OHD) measurement is reported and confounds the diagnosis of vitamin D insufficiency/deficiency. This report emphasizes the marked variability observed in serum 25OHD measurements between laboratories.Initially, postmenopausal women had serum 25OHD determinations: 42 in laboratory A, 20 in laboratory B. Their mean (sem) serum 25OHD concentrations were 46 (2.1) and 21 (2.3) ng/ml in laboratories A and B, respectively. Furthermore, there was little overlap in serum 25OHD among these clinically similar individuals. Specifically, 17% of those measured in laboratory A but 90% in laboratory B were below an arbitrary threshold value of 32 ng/ml.Subsequently, serum was obtained from 10 healthy adults. Two aliquots from each individual, one of which was spiked with 20 ng/ml 25OHD, were sent to six laboratories. Substantial variability was noted between these six laboratories. The mean serum 25OHD concentration ranged from 17.1-35.6 ng/ml. Similarly, the mean increase produced by spiking with 20 ng/ml ranged from 7.7-18.0 ng/ml.In conclusion, 25OHD assays yield markedly differing results; whether an individual is found to have low or normal vitamin D status is a function of the laboratory used. If the medical community is to make progress in correcting widespread hypovitaminosis D, 25OHD measurement must be standardized.

Use of the lowest vertebral body T-score to diagnose lumbar osteoporosis in men: is "cherry picking" appropriate?

In this study, we hypothesized that use of the lowest T-score among four lumbar vertebral bodies would lessen the impact of degenerative arthritis and other artifacts on diagnostic categorization at this site and increase study sensitivity, classifying more men with prior fracture as osteoporotic than the other two methods of lumbar spine analysis. Bone density studies of 533 male veterans measured between January and October 2002 were reviewed to determine diagnostic classification using the L1-L4 average, International Society for Clinical Densitometry (ISCD)-determined, and lowest lumbar vertebral body T-score. We calculated sensitivity and specificity of the three methods of spine analysis, using spine osteoporosis to indicate a positive test and prior fracture as the true indicator of osteoporosis. The lowest lumbar T-score performed with similar sensitivity and specificity to that of the lowest hip or wrist T-score in the ability to classify men with prior fracture as osteoporotic, whereas the average L1-L4 and ISCD-determined T-scores performed with lower sensitivity, but better specificity. In conclusion, this retrospective study suggests that use of the lowest vertebral body T-score among men increases diagnostic sensitivity of lumbar spine bone mass measurement. Prospective studies are needed to determine which of these three methods of lumbar spine analysis best predicts future fragility fracture in men and women.

Are Wisconsin physicians knowledgeable about male osteoporosis?

It is unknown if recent research defining the relatively frequent occurrence and pathophysiology of male osteoporosis has been conveyed to clinicians. To assess if physicians have incorporated such information, 5646 licensed Wisconsin physicians received a 1-page survey consisting of 14 statements regarding general knowledge, diagnosis, and treatment of osteoporosis in men. Twenty-six percent (1488) responded; 69% (1033) were family physicians or internists, 7% (106) orthopedic surgeons, and 5% (63) endocrinologists or rheumatologists. Of these physicians, 61% to 78% recognized that osteoporosis is not rare in men. Most (68%-97%) agreed that low-trauma fracture or corticosteroid therapy initiation are indications for bone mass measurement. Treating osteoporosis at a T-score of -2.5 was accepted by 79% to 89% of responders. Overall these physicians: (1) recognize osteoporosis as an important disease in men; (2) accept corticosteroid therapy and prior low-trauma fracture as indications for bone mass measurement; and (3) utilize T-scores in treatment decisions. These data suggest that knowledge regarding male osteoporosis has been conveyed to practicing physicians. Evaluation of methods by which physicians will translate this knowledge into action, thereby optimizing patient care, are needed.

Bone loss detection in rats using a mouse densitometer

Estrogen-depletion bone-loss studies often use ovariectomized (ovx) rats and measure bone mineral density in vivo or ex vivo using DXA. Recently, a portable densitometer (PIXImus) was developed for mouse research; however, its use in rats is unclear. This study compared the ability of PIXImus and a standard densitometer (DPXL) to detect ovx-induced bone loss in rats both in vivo and ex vivo. Additionally, instrument accuracy was assessed by comparing measured bone mass with ash weight. Finally, the use of two distal femur regions of interest (ROI) to detect ovx-induced bone loss was evaluated. Twenty-three 6-month-old nulliparous female Sprague-Dawley rats were randomly assigned to sham or ovx groups. Distal femur bone mineral density was assessed at baseline and at 1 and 2 months postoperatively, using a PIXImus and DPXL densitometer. At 3 months postoperatively, all animals were killed, and ex vivo femur scans obtained. Distal femur bone loss was demonstrable by 1 month post-ovx using either densitometer. With the PIXImus, a 4-mm ROI demonstrated greater bone loss (p < 0.05) than an 8-mm ROI. Using the 4-mm ROI, similar amounts of bone loss were detected by the PIXImus and DPXL: 22.2% and 22.4%, respectively, at 2 months post-ovx. Total femur bone mineral content was overestimated by the PIXImus but highly correlated with the DPXL measurement (r = 0.988) and ash weight (r = 0.998). Given its comparability to standard DXA plus its rapid scan speed and portability, the PIXImus is useful in evaluating ovx-induced osteopenia in rats.

An overlying fat panniculus affects femur bone mass measurement

Dual-energy X-ray absorptiometry (DXA) is currently the gold standard technique for osteoporosis diagnosis. However, DXA has limitations, including artifacts, such as degenerative disease or metallic foreign bodies, that may confound bone mineral density (BMD) results. Because fat folds overlying the proximal femur may alter soft-tissue density in a nonuniform manner, this may be a currently unappreciated confounder of proximal femur BMD measurement. This possibility was evaluated in 127 patients (52 women/75 men) referred for routine BMD measurement who were identified as having a fat panniculus overlying their proximal femur scan area. Presence of a fat panniculus within the scan field was confirmed by visual assessment of images obtained utilizing a GE Lunar Expert-XL. Subsequently, these individuals were rescanned while retracting their fat panniculus away from the femur scan area without other repositioning between scans. In 49% of the men, and 56% of the women, either the femoral neck, trochanter, or total femur BMD differed by more than the least significant change at our facility. No pattern was observed to predict whether BMD would increase or decrease upon fat retraction. Subsequently, 30 patients were scanned using the standard and retracted technique twice, with repositioning between scans to establish precision. Retracted and standard precision was similar. In conclusion, an overlying fat panniculus may alter proximal femur BMD measurement, which would be expected to impair the ability to accurately diagnose low bone mass and monitor osteoporosis therapy. When a fat panniculus overlays the proximal femur scan area, its retraction should be part of routine densitometric practice.

Osteoporosis in men

Osteoporosis is often considered a disease of women. However, the lifetime risk of osteoporotic fracture in men is as high as 1 in 4. Furthermore, approximately 30% of hip fractures occur in males. Additionally, morbidity and mortality following osteoporotic fractures appears to be greater in men than women. Thus, it is appropriate that increased attention be paid to this problem in men. Recently, indications for bone mass measurement in men have been published. They include prior low trauma fracture, hypogonadism, and corticosteroid treatment, among others. Additionally, a consensus recommendation that osteoporosis be diagnosed at a T-score of -2.5 or below will soon be published. In men presenting with low bone mass or osteoporotic fractures, secondary causes of bone loss will be found in up to two thirds. The most common secondary causes are corticosteroid use, alcohol abuse, hypogonadism, and idiopathic hypercalciuria. Thus, laboratory evaluation is indicated in osteoporotic men. Finally pharmacologic agents to treat osteoporosis have recently been approved in men. This review highlights current understanding of epidemiology, pathophysiology, diagnosis, and treatment of osteoporosis in men.

Vitamin K supplementation does not affect ovariectomy-induced bone loss in rats

Vitamin K may be important in bone metabolism. Notably, high-dose menaquinone-4 (menatetrenone, MK4) has been reported to reduce ovariectomy (ovx)-induced bone loss in rats and to decrease osteoporotic fracture in postmenopausal women. However, it is unclear whether these beneficial effects reflect a physiologic effect of vitamin K, or indicate direct pharmacologic activity of MK4. To further evaluate this, 60 6-month-old nulliparous Sprague-Dawley rats were randomized by distal femur bone mineral density (BMD) in a 3:1 ratio to ovx or sham groups. The sham and one ovx group's diet contained 1% calcium and 1300 microg/kg of vitamin K1, phylloquinone. Diets of the other two ovx groups were supplemented with 882 mg phylloquinone or MK4 per kilogram chow. Distal femur bone mineral density (DFBMD) in an 8 mm region of interest was measured at baseline, 1 and 3 months postoperatively, utilizing dual-energy X-ray absorptiometry (DXA). All animals were killed at 3 months, their right femurs excised, ex vivo BMD measured by DXA, and biomechanical testing performed. No effect of phylloquinone or MK4 supplementation on ovx-induced bone loss was observed. Specifically, DFBMD declined 10.5%, 9.2%, and 11.2% at 1 month and 14.4%, 10.6%, and 13.9% at 3 months in the ovx control, high phylloquinone, and high MK4 groups, respectively. In addition, serum osteocalcin was elevated by ovx; this was not altered by phylloquinone or MK4. Finally, femoral biomechanical properties were not affected by phylloquinone or MK4. To conclude, in this study, neither high-dose phylloquinone nor MK4 reduced the ovx-associated increase in bone turnover or decline in DFBMD.

Densitometric diagnosis of osteoporosis in men: effect of measurement site and normative database

Controversy exists regarding which sites to measure, and the appropriate reference database to use, for densitometric diagnosis of osteoporosis in men. While hip and spine bone mineral density (BMD) measurement is routine, spinal osteoarthritis often elevates measured BMD in older men. Additionally, the use of male reference data is standard practice; however, recent reports suggest that a female database may be more appropriate. This study evaluated the effect of sites measured, and normative database utilized, on the densitometric diagnosis of osteoporosis in men. Spine, femur, and ultradistal radial BMD T-scores were determined in 595 male veterans using the GE Lunar male normative database. Subsequently, World Health Organization diagnostic criteria were applied, identifying 282 men with osteoporosis (T-score </= 2.5). The combination of femoral (lowest of neck or total) with the ultradistal radius site was more sensitive (p < 0.0001) for diagnosing osteoporosis than femur plus lumbar spine. When scans from 129 subjects with documented fractures were analyzed using female normative data, fewer (p < 0.0001) met an arbitrary threshold for receiving pharmacologic osteoporosis therapy. In conclusion, BMD measurement at only the spine and hip leads to underdiagnosis of osteoporosis in men. This situation will be exacerbated by utilization of a female normative database; more men with prior fracture may be categorized as not meeting a pharmaceutical intervention threshold.

Diet- or warfarin-induced vitamin K insufficiency elevates circulating undercarboxylated osteocalcin without altering skeletal status in growing female rats

To further characterize the skeletal role of vitamin K (K), markers of bone turnover, density, and strength were evaluated in rats with diet- or warfarin (W)-induced K insufficiency. One hundred two, 7-week-old, female rats were randomly assigned to low K (phylloquinone [K1], 20 microg/kg diet), control K (K1, 1300 microg/kg diet), low-dose W (W, 1.5 mg/kg control diet), or high-dose W plus K (W/K1, 10/100 mg/kg diet). Femur bone mineral content (BMC) and bone mineral density (BMD), plasma prothrombin time (PT) and prothrombin concentration (PC), and serum total alkaline phosphatase (ALP) and skeletal alkaline phosphatase (sALP) were measured at baseline and days 20, 40, 60, and 80. Serum total osteocalcin (OC) and undercarboxylated osteocalcin (ucOC) and femur length (FL) were measured at baseline and day 80. Left femur OC was measured and biomechanical testing of the right femur and third lumbar vertebral body was performed at day 80. Low dietary K elevated circulating ucOC (17% higher than control; p < 0.0001) at day 80. Furthermore, in both W groups, essentially all circulating OC was undercarboxylated and femur OC was lower than control (p < 0.0001). However, there was no change in femur percent ucOC, suggesting deposition of less newly synthesized OC. No between group differences were observed in PT, ALP, sALP, FL, BMC, BMD, or bone strength. In conclusion, skeletal K insufficiency can be induced by W or diet manipulation. This does not hinder peak bone mass attainment in female rats; however, W causes less newly synthesized OC to be deposited in bone.

Hypervitaminosis A and bone

Animal, human, and in vitro data all indicate that excess vitamin A stimulates bone resorption and inhibits bone formation. This combination would be expected to produce bone loss and to contribute to osteoporosis development and may occur with relatively low vitamin A intake. It is possible that unappreciated hypervitaminosis A contributes to osteoporosis pathogenesis.

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.