Bilateral measurement of femoral bone mineral density

Bilateral hip DXA Reporting: 2023 Official Positions of the International Society for Clinical Densitometry

INTRODUCTION

This position development conference (PDC) Task Force examined the use and reporting of bilateral hip bone mineral density (BMD) measurements. This was deemed appropriate as increased availability of Dual-energy X-ray Absorptiometry (DXA) technology offering bilateral hip measurement resulted in more routine clinical use. The International Society for Clinical Densitometry Official Positions accept bilateral hip BMD measurement for clinical use but currently do not include recommendations for reporting those studies.

METHODS

Four key questions regarding bilateral hip reporting were proposed by the PDC Steering Committee. Relevant literature was identified using PubMed. Questions included whether bilateral hip measurements are appropriate for diagnostic classification or monitoring, as well as which bilateral hip regions of interest should be reported for diagnosis and monitoring. Additionally, the appropriate nomenclature for bilateral hip acquisition was defined.

RESULTS

The literature review demonstrated that bilateral hip measurement is appropriate and diagnostic classification should be based on the lowest T-score at the right or left side femoral neck or total hip; the mean T-score should not be used for diagnostic purposes. Mean bilateral total hip is preferred for BMD monitoring. The terms hip, or total hip were deemed appropriate nomenclature instead of femur or total proximal femur.

CONCLUSION

Bilateral hip acquisition is clinically appropriate and reporting and nomenclature standards are offered herein when a bilateral hip study is acquired. In terms of future research, the impact of discordant hips on diagnosis and monitoring was identified as a significant knowledge gap.

Cystathionine-γ-lyase ameliorates the histone demethylase JMJD3-mediated autoimmune response in rheumatoid arthritis

Cystathionine-γ-lyase (CSE), an enzyme associated with hydrogen sulfide (H₂S) production, is an important endogenous regulator of inflammation. Jumonji domain-containing protein 3 (JMJD3) is implicated in the immune response and inflammation. Here, we investigated the potential contribution of JMJD3 to endogenous CSE-mediated inflammation in rheumatoid arthritis (RA). Upregulated CSE and JMJD3 were identified in synovial fibroblasts (SFs) from RA patients as well as in the joints of arthritic mice. Knocking down CSE augmented inflammation in IL-1β-induced SFs by increasing JMJD3 expression. In addition, CSE^-/- mice with collagen-induced arthritis (CIA) developed severe joint inflammation and bone erosion. Conversely, overexpressing CSE inhibited JMJD3 expression by the transcription factor Sp-1 and was accompanied by reduced inflammation in IL-1β-treated SFs. Furthermore, JMJD3 silencing or the administration of the JMJD3 inhibitor GSK-J4 significantly decreased the inflammatory response in IL-1β-treated SFs, mainly by controlling the methylation status of H3K27me3 at the promoter of its target genes. GSK-J4 markedly attenuated the severity of arthritis in CIA mice. In conclusion, suppressing JMJD3 expression by the transcription factor Sp-1 is likely responsible for the ability of CSE to negatively modulate the inflammatory response and reduce the progression of RA.

Densitometric study of the clavicle: bone mineral density explains the laterality of the fractures

Introduction

Epidemiological studies have shown laterality in clavicle fractures, such that the left side is more frequently fractured. The present study had the aim of evaluating whether the clavicle on the dominant side is denser and thus explaining the greater incidence of fractures on the non-dominant side.

Materials and methods

This was a descriptive study on 52 healthy patients, who were classified according to age, sex and whether the dominant or non-dominant side was affected.

Results

The participants comprised 28 women (53.8%) and 24 men (46.2%). Regarding the dominant side, 30 were right-handed (57.7%) and 22 were left-handed (42.3%). The mean age was 25 years. In this study, it could be seen that the non-dominant side had greater bone mass than the dominant side. It was also observed that the bone density was greater in the middle and distal thirds on the non-dominant side, with a statistically significant difference. In the women, the density was also greater on the non-dominant side; this difference was not significant in relation to the dominant side, but there were significant differences between the middle thirds (p < 0.001) and the distal thirds (p < 0.006).

Conclusion

Variations in bone density, toward higher and lower bone mass, may have been responsible for the fractures. According to the findings from this study, fractures occur more in the middle third of the non-dominant clavicle, as a result of greater bone mineral mass, which gives rise to lower flexibility and fractures in the region.

A novel microRNA regulates osteoclast differentiation via targeting protein inhibitor of activated STAT3 (PIAS3)

MicroRNAs (miRNAs) involve in the regulation of a wide range of physiological processes. Recent studies suggested that miRNAs might play a role in osteoclast differentiation. Here, we identify a new miRNA (miR-9718) in primary mouse osteoclasts that promotes osteoclast differentiation by repressing protein inhibitor of activated STAT3 (PIAS3) at the post-transcriptional level. MiR-9718 was found to be transcribed during osteoclastogenesis, which was induced by macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). Overexpression of miR-9718 in RAW 264.7 cells promoted M-CSF and RANKL-induced osteoclastogenesis, whereas inhibition of miR-9718 attenuated it. PIAS3 was predicted to be a target of miR-9718. Luciferase reporter gene validated the prediction. Transfection of pre-miR-9718 in RAW 264.7 cells induced by both M-CSF and RANKL inhibited expression of PIAS3 protein, while the mRNA levels of PIAS3 were not attenuated. In vivo, our study showed that silencing of miR-9718 using a specific antagomir inhibited bone resorption and increased bone mass in mice receiving ovariectomy (OVX) and in sham-operated control mice. Thus, our study showed that miR-9718 played an important role in osteoclast differentiation via targeting PIAS3 both in vitro and in vivo.

miR-148a regulates osteoclastogenesis by targeting V-maf musculoaponeurotic fibrosarcoma oncogene homolog B

MicroRNAs (miRNAs) play crucial roles in bone metabolism. In the present study, we found that miR-148a is dramatically upregulated during osteoclastic differentiation of circulating CD14+ peripheral blood mononuclear cells (PBMCs) induced by macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL). Overexpression of miR-148a in CD14+ PBMCs promoted osteoclastogenesis, whereas inhibition of miR-148a attenuated osteoclastogenesis. V-maf musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB) is a transcription factor negatively regulating RANKL-induced osteoclastogenesis. miR-148a directly targeted MAFB mRNA by binding to the 3' untranslated region (3'UTR) and repressed MAFB protein expression. In vivo, our study showed that silencing of miR-148a using a specific antagomir-inhibited bone resorption and increased bone mass in mice receiving ovariectomy (OVX) and in sham-operated control mice. Furthermore, our results showed that miR-148a levels significantly increased in CD14+ PBMCs from lupus patients and resulted in enhanced osteoclastogenesis, which contributed to the lower bone mineral density (BMD) in lupus patients compared with normal controls. Thus, our study provides a new insight into the roles of miRNAs in osteoclastogenesis, and contributes to a new therapeutic pathway for osteoporosis.

Differences in bone mineral density between the right and left hips in postmenopausal women

Bone mineral density (BMD) using dual energy radiography absorptiometry are commonly used for the diagnosis of osteoporosis. It is usually measured at the spine and also at one hip joint. Controversy still exists regarding the use of bilateral hip scanning. We analyzed the difference of BMD at bilateral hips in 384 postmenopausal women, retrospectively. The concordance and discordance rates of the lowest T-score and BMD between both hips were evaluated. The BMDs of the femoral neck and trochanter were significantly different between both hips (P < 0.05). There were also discrepancies between the lowest T-scores of both hips (P < 0.05). The discordance rates were about 30%. Due to significant differences in BMD between both hips at the femoral neck and trochanter and high discordance rate, bilateral hip measurements using DEXA are recommended to avoid underestimating osteoporosis.

Underestimated fracture probability in patients with unilateral hip osteoarthritis as calculated by FRAX

Osteoporosis (OP) and osteoarthritis (OA) are age-related diseases often considered to be mutually exclusive. We previously found that 25% of women with advanced OA had occult OP and that femoral neck (FN) bone mineral density (BMD) T-scores were significantly higher for osteoarthritic vs contralateral hips. The FRAX calculator incorporates clinical risk factors and FN BMD T-score to estimate 10-yr total fracture probability and hip fracture probability. In 35 women and men aged 41 yr or older with unilateral hip OA scheduled for hip replacement, we tested whether FRAX fracture probability is underestimated when using data for the OA rather than the contralateral hip. There were between-hip differences for FN BMD T-score (p<0.0001), total fracture probability (p =0.0004), and hip fracture probability (p =0.0009). Use of FN BMD T-scores resulted in OP treatment recommendations for 0% and 11% of subjects compared with 11% and 17% for total fracture probability and hip fracture probability, respectively. In 6-11% of subjects in this series, the FRAX calculator underestimated fracture probability with data for the OA hip. With the increased use of FRAX in clinical use, these data suggest that measurement of BMD at the contralateral hip may yield higher calculated FRAX total and hip fracture probabilities.

Assessment of the bilateral asymmetry of human femurs based on physical, densitometric, and structural rigidity characteristics

The purpose of this study was to perform a comprehensive geometric, densitometric, biomechanical, and statistical analysis of paired femurs for an adult population over a wide age range using three imaging modalities to quantify the departure from symmetry in size, bone mineral density, and cross-sectional structural rigidities. Femur measurements were obtained from 20 pairs of cadaveric femurs. Dimensions of these anatomic sites were measured using calipers directly on the bone and plain radiographs. Dual energy X-ray absorptiometry was used to measure bone mineral density. Bone mineral content and axial and bending rigidities were determined from the CT imaging. No differences were observed between the geometric measurements, DXA based bone mineral density and axial and bending rigidities of left and right femurs (P>0.05 for all cases). Left and right proximal femurs are not significantly different based on geometric, densitometric, and structural rigidity measurements. However, absolute left-right differences for individual patients can be substantial. When using the contralateral femur as a control, the number of femur pairs required to assess significant changes in anatomic dimensions and structural properties induced by a tumor, infection, fracture, or implanted device can range from 3 to 165 pairs depending on the desired effect size or sensitivity (5% or 10% difference). This information is important both for femoral arthroplasty implant design and the use of the contralateral femur as an intra-subject control for clinical assessment and research studies. In addition, our statistical analysis provides sample size estimates for planning future orthopedic research studies.

Discordance in femoral neck bone density in subjects with unilateral hip osteoarthritis

Osteoarthritis (OA) is a common disease that increases in incidence with age and currently affects an estimated 27 million Americans. To determine whether site-specific hip bone mineral density (BMD) measures are confounded by the presence of OA, we measured bilateral hip BMD by dual X-ray absorptiometry in 34 subjects (19 women and 15 men) scheduled for hip replacement for confirmed advanced unilateral hip OA. The femoral neck (FN) BMD (p=0.035) and T-score (p=0.017) for the hip with OA was higher than those of the contralateral hip. There was a difference in osteoporosis classification depending on which hip was considered: for 11 of the 34 subjects (32%), the FN T-score was normal for OA hip, but the contralateral hip was classified as osteopenic (T-score between -1.0 and -2.5). For 1 subject, the FN T-score was normal for OA hip, but the contralateral hip was classified as osteoporotic (T-score below -2.5). Discordance was also present for trochanter values and not for total hip values. These data indicate that advanced hip OA can be associated with a higher bone density at the FN and trochanter but not at total hip and that the discrepancy between hips at the FN may have an impact on patient treatment decisions.

Slight abduction/adduction deviations in femur positioning for dual-energy X-ray absorptiometry are inconsequential

Straight femur alignment during dual-energy X-ray absorptiometry (DXA) acquisition is assumed to help ensure accurate bone mineral density (BMD) measurement. Use of bilateral femur positioners may not result in straight femur alignment. To assess the effect of a bilateral femur positioner on DXA results, we compared a standard fixed-width bilateral femur positioner with an adjustable-width positioner that allowed for straight femur alignment. BMD values obtained from the adjustable-width bilateral femur positioner were highly correlated (R(2)=0.98-0.99) with those obtained using a fixed-width positioner. The mean bias in BMD between the fixed- and adjustable-width positioner was low (-0.001 to +0.006g/cm(2)) at all proximal femur regions of interest. In this study, the use of a fixed-width bilateral femur positioner and associated deviations in femur alignment have little consequence on BMD measurement.

A novel microRNA targeting HDAC5 regulates osteoblast differentiation in mice and contributes to primary osteoporosis in humans

MicroRNAs (miRNAs) interfere with translation of specific target mRNAs and are thought to thereby regulate many cellular processes. Recent studies have suggested that miRNAs might play a role in osteoblast differentiation and bone formation. Here, we identify a new miRNA (miR-2861) in primary mouse osteoblasts that promotes osteoblast differentiation by repressing histone deacetylase 5 (HDAC5) expression at the post-transcriptional level. miR-2861 was found to be transcribed in ST2 stromal cells during bone morphogenetic protein 2-induced (BMP2-induced) osteogenesis, and overexpression of miR-2861 enhanced BMP2-induced osteoblastogenesis, whereas inhibition of miR-2861 expression attenuated it. HDAC5, an enhancer of runt-related transcription factor 2 (Runx2) degradation, was confirmed to be a target of miR-2861. In vivo silencing of miR-2861 in mice reduced Runx2 protein expression, inhibited bone formation, and decreased bone mass. Importantly, miR-2861 was found to be conserved in humans, and a homozygous mutation in pre-miR-2861 that blocked expression of miR-2861 was shown to cause primary osteoporosis in 2 related adolescents. Consistent with the mouse data, HDAC5 levels were increased and Runx2 levels decreased in bone samples from the 2 affected individuals. Thus, our studies show that miR-2861 plays an important physiological role in osteoblast differentiation and contributes to osteoporosis via its effect on osteoblasts.

Effect of the bilateral hip bone density measurement on clinical practice in elderly subjects

OBJECTIVES

The aim of this study was to determine whether the addition of the measurement of bilateral hip bone mineral density (BMD) has an impact on indications for osteoporosis (OP) treatment in community-dwelling elderly individuals, based on criteria from the National Osteoporosis Foundation (NOF).

METHODS

In total, 605 consecutive community-dwelling elderly individuals who were 65 years and older were evaluated. Dual energy X-ray absorptiometry was used to determine the lowest T-score in the lumbar spine+unilateral hip, the bilateral hips, and the lumbar spine+bilateral hips. Risk factors associated with the lowest T-score in these three conditions were applied to indicate treatment in accordance with NOF criteria. McNemar's test was used to assess the difference of adding bilateral hip BMD measurements.

RESULTS

There was a significant difference in the frequency of pharmacological indication using NOF criteria together with the lowest T-score for the three tests (72.8% for lumbar spine+bilateral hips and 71.2% for lumbar spine+unilateral hip; p=0.002). A higher frequency of treatment indication was also observed for lumbar spine+unilateral hip (71.2%) compared to bilateral hips (61.1%) (p<0.001). The discrepancies in treatment appeared to be more evident in women when analyzed by gender distribution.

CONCLUSION

Our finding supports the theory that evaluation of the bilateral hips with the lumbar spine seems to be more sensitive measure for identifying patients with an osteoporosis treatment indication. Furthermore, despite the well-known artifact in the lumbar spine, this site should not be excluded when determining the indication for OP treatment in elderly people.

Comparison of the effects of genistein and zoledronic acid on the bone loss in OPG-deficient mice

Using osteoprotegerin (OPG)-knockout mice, we demonstrated that in vivo the effects of both genistein and 17beta-estradiol (E2) on bone metabolism were completely abolished. In contrast, zoledronic acid could effectively suppress bone resorption and prevent bone loss.

INTRODUCTION

The anti-resorptive effects of E2 on bone metabolism are considered to be mediated via modulation of the osteoblast-derived paracrine factor OPG. Recently, the phytoestrogen genistein was found to suppress bone resorption by enhancing osteoblastic production of OPG. However, the mechanism underlying the in vivo effects of E2 and genistein on bone is not entirely understood, and a central question in this regard is whether E2 regulates bone metabolism via an OPG-dependent pathway.

METHODS

After mating heterozygous (OPG+/-) mice, homozygous (OPG-/-) and wild-type (WT) with a mixed C57BL/6J x 129/SV background were obtained. The study involved 6-week-old female OPG-/- (n=40) and WT mice (n=8). The OPG-/- mice were randomly divided into 5 groups (n=8 per group) as follows: (1) genistein-treated mice (Gen) that were subcutaneously injected with genistein at a maximal dose (0.8 mg/day); (2) E2-treated mice (E2) that were subcutaneously injected with E2 at a dose (0.03 microg/day); (3) DMSO control mice (DMSO) that were subcutaneously injected with a mixture of dimethylsulfoxide (DMSO) and polyethyleneglycol-300; (4) zoledronic acid-treated mice (Zol) that were subcutaneously injected with zoledronic acid at a dose of (150 microg/kg) twice per week; and (5) H2O control mice that were subcutaneously injected with sterilized water twice per week. The doses of genistein, estrogen and zoledronic acid were selected based on the results of dose-response effect of agents on bone versus uterus in OPG-/- mice. The mice were sacrificed 6 weeks after this intervention. The microarchitecture of the trabecular and cortical bone was assessed by performing microcomputed tomography (micro-CT) for the right proximal tibia. The bone mineral density (BMD) of the left femur was measured by dual-energy X-ray absorptiometry (DXA). The biomechanical parameters of the right femur were determined by a three-point bend testing. Serum levels of bone alkaline phosphatase (B-ALP), tartarate-resistant acid phosphatase-5b (TRACP-5b), and receptor activator of nuclear factor kappaB ligand (RANKL) were determined by performing ELISA.

RESULTS

DXA analysis revealed that the total BMD of the femur was not significantly altered in the Gen, E2, H2O, and DMSO groups. The three-point bending test revealed no significant differences in the biomechanical parameters, including ultimate loading, ultimate stress, stiff index, and elastic modulus, and micro-CT analysis revealed that the microarchitectural parameters of the trabecular bone (vBMD, tBMD, BVF, BSF, SMI, Tb.N, Conn.D, Tb.Sp, and Tb.Th) and cortical bone (Ct.Th, Mm, In.Pm, Ot.Pm, Ma.Ar, Ct.Ar, Tt.Ar, Ct.BMD, and Ct.BMC) did not differ among the groups. Genistein and E2 treatment did not alter the serum TRACP-5b, B-ALP, or RANKL levels. However, in addition to increasing the bone mass, zoledronic acid could effectively improve biomechanical parameters and could completely prevent deterioration of the bone architecture in the OPG-/- mice.

CONCLUSIONS

The effects of genistein and E2 on bone metabolism in vivo were lost completely in OPG-deficient mice, suggesting that the effect of these agents on bone metabolism seems to be entirely dependent on OPG. In contrast, zoledronic acid could effectively suppress bone resorption and completely prevent the bone loss in the OPG-/- mice--an effect that is likely to be independent of the OPG pathway.

The prevalence of significant left-right differences in hip bone mineral density

INTRODUCTION

We determined the prevalence of left-right differences in hip bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) and the resultant consequence, namely: the frequency at which patients would be classified differently if lumbar spine and only one hip (rather than both hips) were measured.

METHODS

This was a retrospective DXA scan reanalysis of 3012 white women >or=50 yrs who had scans of both hips using Hologic DXA systems. The difference between left and right hips was considered significant if it exceeded the least significant change (LSC) for any of three hip subregions (total hip, femoral neck, trochanter). The number of women with osteoporosis in both hips, the left hip only, or the right hip only was determined by lowest T-score from total hip, femoral neck, or trochanter.

RESULTS

Despite high left-right correlations of subregion BMD, significant left-right differences in BMD were common: the difference exceeded the LSC for 47% of women at total hip, 31% at femoral neck, and 56% at trochanter. Left-right differences in BMD that exceeded the LSC affected the percent agreement of left-right hip classification: for all women irrespective of spine status, there was 77% classification (diagnostic) agreement in hip pairs in which the left-right hip BMD difference exceeded the LSC versus 87% agreement in which LSC was not exceeded (significant difference in proportions, P<0.0001). The greatest risk of different classification would occur in women with normal spines as the diagnosis might be determined by hip T-scores. Using L1-4 lumbar spine T-scores, 1229 women were normal at the spine. Twenty-four (2%) were osteoporotic at both hips. However, 12 women (1%) were osteoporotic only in the left hip (significantly different from zero, P<0.001) and 11 (1%) only in the right hip (P<0.001); of these 23 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 16 (70% of those with osteoporosis in only one hip). Using L1-4 lumbar spine T-scores, 1159 women were osteopenic at the spine. Of these, 126 (11%) were osteoporotic at both hips, 54 (5%) only in the left hip (P<0.001), and 42 (4%) only in the right hip (P<0.001); of these 96 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 56 (58% of those with osteoporosis in only one hip).

CONCLUSIONS

A statistically significant number of women with osteoporosis are potentially classified differently when scanning only one hip as a result of the high prevalence of left-right differences in BMD. Although the percentages are low, the total number of women affected may be large. From a public health perspective, the practice of scanning both hips could potentially identify more women with osteoporosis and may help prevent future hip fractures.

Comparison of the femoral neck bone density, quantitative ultrasound and bone density of the heel between dominant and non-dominant side

Our study was initiated to evaluate whether there are differences between the two sides, depending on hand dominance, in densitometry values and quantitative ultrasound parameters (QUS) of the lower limb. One hundred and six women and 44 men were involved. The hand dominance was determined by interview. The bone mineral density (BMD) of the left and the right femoral necks and the calcanei were measured by dual-energy X-ray absorptiometry (DXA). The QUS examination consisted of measuring the attenuation (BUA), the speed of the ultrasound (SOS) and quantitative ultrasound index (QUI) transversing the left and right calcanei. The density of the neck of femur of the non-dominant side did not differ from that of the dominant side. On the other hand, BMD, BUA and the QUI of the calcaneus were higher on the non-dominant side in both genders (p<0.05 for each parameter). No similar differences were seen for the SOS values. Our study has confirmed the side-to-side differences of the calcaneus in both genders, lower values were found on the dominant side. No similar differences were seen on the femur. The AUC values seemed to be higher on the dominant side, however, these differences were not strictly significant. In the case of peripheral site (heel) measurements, the practical significance of our observations is that they raise the possibility of performing peripheral DXA and QUS examinations of the calcaneus on the dominant side of the patient according to handedness.

The effect of measurement of the contralateral hip if the spine is not included in the bone mineral density analysis

The aim of this study was to determine if measurement of the contralateral femora has an effect on osteoporosis diagnosis and treatment classification if the spine is not included in the bone mineral density (BMD) scan. The method used was the T-score discordance from the dual femur BMD scans of 537 women (mean age: 61.2 yr; standard deviation: 10.5; age range: 32-90 yr) who were evaluated to determine if inclusion of the contralateral hip in the BMD study made a difference in clinical diagnosis and treatment classification when the spine was not included in the BMD scan. Clinical diagnosis and treatment classification was based on the lowest T-score at each hip of three femur sites: the neck, the trochanter, and the total femur. The results of the diagnosis classification (i.e., normal, osteopenia, and osteoporosis) differed in the right versus the left femora in 28% of subjects at one or more sites, and in 14%, 15%, and 10% of subjects at the neck, trochanter, and total femur, respectively. Diagnosis discordance increased in subjects who were aged 65 yr and older. Treatment classification (T>or=-1.5; T<-1.5; T<-2.0) differed in the right versus the left femora in 33% of subjects at one or more sites, and in 18%, 14%, and 12% of subjects at the neck, trochanter, and total femur, respectively. Treatment discordance increased in subjects age 65 yr and older. Using the lowest T-score for clinical diagnosis classification, when the contralateral hip was considered, a clinical difference in diagnosis from normal-->osteopenia occurred in 3.9% of subjects, and from osteopenia-->osteoporosis in 1.3% of subjects. A clinical difference in treatment category from T>or=-1.5-->T<-1.5 occurred in 2.7% of subjects, and from T>or=-2-->T<-2 in 2.7% of subjects. In conclusion, inclusion of the bilateral hip in the BMD study made a clinical difference in diagnosis classification in 5.2% of subjects and in treatment classification in 5.4% of subjects. T-score differences between the contralateral hips increased with age. In the subgroup of subjects age 65 yr and older, a clinical difference in classification to a more severe diagnosis or treatment category occurred in 5.35% and 7.25% of subjects, respectively.

Reduced hip bone mineral density is related to physical fitness and leg lean mass in ambulatory individuals with chronic stroke

Following a stroke, the reduced level of physical activity and functional use of the paretic leg may lead to bone loss and muscle atrophy. These factors and the high incidence of falls may contribute to hip fractures in the stroke population. This study was the first to examine total proximal femur bone mineral content (BMC) and bone mineral density (BMD) and their relationship to stroke-specific impairments in ambulatory individuals with chronic stroke (onset >1 year). We utilized dual-energy X-ray absorptiometry (DXA) to acquire proximal femur and total body scans on 58 (23 women) community-dwelling individuals with chronic stroke. We reported total proximal femur BMC (g) and BMD (g/cm2) derived from the proximal femur scans, and lean mass (g) and fat mass (g) for each leg derived from the total body scans. Each subject was evaluated for ambulatory capacity (Six-Minute Walk Test), knee extension strength (hand-held dynamometry), physical fitness [maximal oxygen uptake (VO2max)] and spasticity (Modified Ashworth Scale). Results showed that the paretic leg had significantly lower proximal femur BMD, lean mass and percent lean mass, but higher fat mass than the non-paretic leg for both men and women. Proximal femur BMD of the paretic leg was significantly related to ambulatory capacity (r=0.33, P=0.011), muscle strength (r=0.39, P=0.002), physical fitness (r=0.57, P<0.001), but not related to spasticity (r=-0.23, P=0.080). Multiple regression analysis showed that lean mass in the paretic leg was a major predictor (r2=0.371, P<0.001) of the paretic proximal femur BMD. VO2max was a significant predictor of both paretic proximal femur BMD (r2=0.325, P<0.001) and lean mass in the paretic leg (r2=0.700, P<0.001). Further study is required to determine whether increasing physical fitness and lean mass are important to improve hip bone health in chronic stroke.

Dual energy X ray absorptiometry of ex vivo HcB/Dem mouse long bones: left are denser than right

Dual energy X ray absorptiometry (DXA) has become a popular analytical technique in mice and other small animals. Comparative study of bone properties at different anatomical sites is an active area of study in model organisms. Such investigations require that site-specific data be generated and interpreted. There are no published data addressing the degree to which contralateral mouse bones resemble each other in the absence of an experimental intervention, nor are there data addressing the correlation of bone densitometry measurements between anatomically distant sites. To address these gaps in our knowledge, we used DXA to compare excised mouse femora and humeri. At the population level, left bones were slightly but significantly denser than right bones, with an overall adjusted bone mineral density (BMD) difference of 0.7 +/- 0.3 and 0.5 +/- 0.2 mg/cm2 at the femur and humerus, respectively. At the level of bone pairs from a single animal, absolute adjusted BMD disparities between the right and left sides were 2.3 +/- 1.9 mg/cm2 at the femur and 1.7 +/- 1.4 mg/cm2 at the humerus. Correlation coefficients between left and right sides were 0.78 for adjusted BMD at both sites. The correlation coefficient between side-averaged femoral and humeral BMD was 0.81, but ranged between 0.70 and 0.75 when limited to ipsilateral or contralateral femur-humerus pairs. Our findings suggest the desirability of randomizing limbs for treatment in studies using contralateral limb controls. These observations may represent the densitometric manifestation of behavioral and neuroanatomical lateralization in laboratory mice.

Reproducibility and side differences of mechanical tests for determining the structural strength of the proximal femur

In this experimental study, we evaluated the reproducibility error of mechanical strength tests of the proximal femur when simulating a fall on the trochanter. Based on side differences in femoral failure loads in 55 pairs of femora, we estimated the upper limit of the precision error to be 15% for the side impact test, whereas the intersubject variability was >40%.

INTRODUCTION

Mechanical tests are commonly used as the gold standard for determining one of the main functions of bones, that is, to provide mechanical strength. However, it is unknown what magnitude of error is associated with these tests. Here we investigate the precision error and side difference of a side impact test of the proximal femur.

MATERIALS AND METHODS

BMC was measured using DXA in 54 pairs of femora from donors 79.0 +/- 10.6 years of age. Bones were tested to failure, simulating a fall on the greater trochanter.

RESULTS

Failure loads were 3951 +/- 1659N (CV% = 42%) on the right and 3900 +/- 1652N (CV% = 42%) on the left (no significant side difference). The average random difference of femoral BMC was 7 +/- 7% and that of femoral failure loads was 17 +/- 12%. The correlation between BMC and failure load was 79% (r2), but the association between side differences in failure load with those in BMC was only 4%. When confining the analysis to pairs with less than 5% differences in BMC (n = 31), side differences in failure loads were 15 +/- 13%. When correcting failure loads for side differences of BMC, the difference was 16 +/- 15%

CONCLUSIONS

These results suggest that the upper limit of the precision error for femoral strength tests is approximately 15% in a side impact configuration. Given the large intersubject variability of failure loads, this test provides an efficient tool for determining the structural strength of the proximal femur in a fall.

Does the combination of two BMD measurements improve fracture discrimination?

Combining information from different types of BMD measurement should improve the evaluation of patients' risk of fracture. This study used a bivariate gaussian model to examine the effect of combining two different BMD measurements. The results show that, in practice, there is little benefit unless the measurements are completely unrelated.

INTRODUCTION

Intuitively, the combination of information from two or more different types of bone densitometry investigation should improve our ability to identify patients at high risk of fracture. However, the best way to combine measurements and the resulting gain in fracture discrimination are not known.

MATERIALS AND METHODS

In this study, we used a bivariate gaussian model to investigate the effect of combining two different types of bone densitometry measurements. The measurements had individual relative risk values RR1 and RR2 and a correlation coefficient r between their Z-scores. Different approaches to the combination of the two measurements were compared by calculating the area under the curve (AUC) for the receiver operating characteristic (ROC) curve, which was obtained by plotting the percentage of fracture patients against the percentage of the whole population with a Z-score below some chosen threshold. ROC curves were calculated for three cases: (1) one type of measurement only; (2) two different types of measurements combined using their mean Z-score weighted according to the theoretical optimum weighting factors predicted by the bivariate gaussian model; and (3) two different types of measurements combined using the conventional World Health Organization (WHO) approach, where one or other measurement is below a set threshold. The theoretical model was tested using measurements of speed of sound (SOS) in the radius, phalanx, and metatarsal in patients with vertebral and Colles' fractures.

RESULTS

Results were calculated for RR values of 1.5, 2.0, and 2.5 and r = 0, 0.5, and 0.7. Although a significant improvement in fracture discrimination was obtained when r = 0 and RR1 = RR2, the improvements obtained when r > or = 0.5 or RR1 double dagger RR2 were relatively modest. Slightly better fracture discrimination was obtained using the weighted mean Z-score approach compared with the WHO approach, although the differences were small. The results of the in vivo study in Colles' and vertebral fracture patients showed close agreement with the predictions of the bivariate gaussian model.

CONCLUSION

In practice, from a theoretical point of view, there is unlikely to be any benefit from combining information from different types of bone densitometry measurements unless they are completely unrelated.

Evaluation of calcaneus bone densitometry against hip and spine for diagnosis of osteoporosis

Dual X-ray absorptiometry (DXA) is now widely available as a method for assessing bone density. However, the place of peripheral bone densitometry in clinical practice for diagnosis of osteoporosis is not yet clear. To examine the potential use in our district general hospital setting, we compared calcaneus measurements with conventional DXA of the hip and spine in 100 patients referred for assessment following identification of risk factors for osteoporosis. Measurements were made on both heels and the results were found to be similar but not completely interchangeable. Use of receiver operating characteristic curves confirmed that a threshold T-score of -1.6 could be used to identify many of the high risk subjects. However, there was only moderate agreement between fracture risk classifications derived from heel T-scores, and diagnostic classification (osteoporosis/osteopenia/normal) derived from axial DXA. The specificity of heel measurements was high, but sensitivity was poorer. Heel measurements could therefore be valuable in some circumstances for finding patients for whom treatment of osteoporosis would be appropriate, such as in a population with a low prevalence of osteoporosis. They may also be of value in a population with a high prevalence of disease, particularly if there were no alternative means of bone densitometry. However, with an intermediate prevalence, the relatively high risk of false negative values would mean that false reassurance could be given to many of those classed as "low risk". This could be a major drawback in clinical practice if heel densitometry were used as the initial investigation and axial measurements were also available, since they would give conflicting results for a substantial proportion of these patients.

Improving femoral bone density measurements

Femoral bone density measurements are clinically important because of their strong relationship with hip fracture. However, current densitometers have not improved upon femoral densitometry since the introduction of dual-energy X-ray absorptiometry (DXA) systems. Recently, several advances in DXA measurement of the proximal femur have been proposed by various published studies. These advances can be added to existing DXA systems, while maintaining the conventional femoral regions of interest. Both upper neck bone mineral density (BMD) and hip axis length have been reported to be associated with hip fractures. With newer technology that enables a rapid assessment of both hips, bilateral femur measurements are now clinically practical and are of importance in those with T-scores approaching, yet not reaching, diagnostic or therapeutic thresholds. Bilateral femur measurements also reduce precision error compared to a single femur measurement, yielding precision errors less than observed at the spine. With this decrease in precision error, monitoring of bone changes is now possible at the femur with the utility comparable to the spine.

Bilateral variation in calcaneal broadband ultrasound attenuation. Part II: as measured by three bone densitometers employing ultrasound or X-ray

In previous study, we found a bilateral difference in broadband ultrasound attenuation (BUA) of the calcaneus, using the McCue Cubaclinical II device. The purpose of the present study was to determine whether a calcaneal bilateral difference (greater than that that would be expected from the coefficient of variation) was also found by other instruments and their technologies. Twenty-four subjects (ages 22-81) were each scanned by the same operator using three devices: the Cubaclinical (ultrasound [US], BUA), the Lunar Achilles plus (US, BUA and stiffness index), and the Pixi (dual X-ray absorptiometry, bone mineral density). To allow for the different variables used by the three devices, the following computation was applied to the data for comparison purposes (left - right) / (right). Analysis of variance showed no significant difference. We conclude that the three devices do not differ in their ability to detect a proportional difference between right and left calcanei. In an additional investigation, using the Cubaclinical, 23 subjects were scanned. The direction of the US wave between emitter and receiver transducers was reversed to determine the effect, if any, on bilateral BUA readings. In this case, the direction of the US wave was not influential.

Bilateral variation in calcaneal broadband ultrasound attenuation: part I

A total of 1412 women of various ethnic origins ages 20-80 yr were tested for bilateral calcaneal broad-band ultrasound attenuation (BUA) with the McCue Cubaclinical ultrasound bone densitometer. A significant difference was found between nondominant and dominant measures (p < 0.0001). The magnitude of calcaneal BUA was not related to dominance. The difference was of a significant degree to have resulted in differing predictions of fracture risk depending on the side used in assessment. Forty-eight subjects (3%) would have been considered at risk of osteoporotic fracture based on the nondominant measure, whereas only 21 subjects (1.5%) would have been considered to be at risk based on the dominant measure. In concurrence with other studies, we conclude that it is essential to carry out bilateral measurements of the os calcis to avoid misleading implications for prediction of fracture risk.