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

Osteoporosis should be evaluated by bone mineral density at the combination of the lumbar spine and ipsilateral femoral neck in female patients with knee osteoarthritis scheduled for knee arthroplasty: A retrospective observational study

BACKGROUND

Knee arthroplasty is a well-established surgery with good clinical outcomes. However, periprosthetic fractures and aseptic loosening negatively impact clinical outcomes, and osteoporosis is one of the causes of such complication. Osteoporosis is usually evaluated by bone mineral density of the lumbar spine and hip using dual-energy X-ray absorptiometry (DXA). However, the prevalence of this disease in patients with knee osteoarthritis scheduled for knee arthroplasty may be underestimated due to differences in the measurement sites. This study aimed to determine the appropriate measurement site for DXA that would not miss osteoporosis in female patients with knee osteoarthritis undergoing knee arthroplasty.

METHODS

We measured bone mineral density preoperatively in the consecutive 50 female patients with knee osteoarthritis scheduled for knee arthroplasty by dual-energy X-ray absorptiometry at five sites: the lumbar spine, bilateral-total hip, and femoral neck. We then compared the prevalence of osteoporosis among the four combinations of the lumbar spine and single hip site (ipsilateral or contralateral total hip or femoral neck).

RESULTS

Osteoporosis prevalence in the combination of the lumbar spine and ipsilateral or contralateral total hip was 32%, and that in the combination of the lumbar spine and contralateral femoral neck was 44%. Notably, the disease's prevalence in the combination of the lumbar spine and ipsilateral femoral neck was 50%, which was significantly higher than that in the other combinations.

CONCLUSION

Osteoporosis should be evaluated by bone mineral density in the combination of the lumbar spine and ipsilateral femoral neck in female patients with knee osteoarthritis scheduled for knee arthroplasty.

Bone mineral density differences between femurs of scoliotic patients undergoing quantitative computed tomography analysis

PURPOSE

Scoliosis is a cause of loading imbalance between the lower limbs, which can result in BMD differences between the two femurs. We investigated the discrepancy in BMD values assessed by quantitative computed tomography (QCT) between femurs in patients with and without scoliosis, also assessing if this difference can be related to spine convexity.

METHODS

Abdominal CT examinations were retrospectively reviewed. An ''asynchronous'' calibration of CT images was performed to obtain BMD values from QCT. Scoliosis was evaluated on the antero-posterior CT localizer to calculate the Cobb angle. Differences between aBMD and vBMD of femurs were assessed in both scoliotic and non-scoliotic subjects.

RESULTS

Final study cohort consisted of 263 subjects, 225 of them without scoliosis (85.6%) and 38 with scoliosis (14.4%). No significant differences were found in the general population without scoliosis, except for vBMD at the neck. Comparison of femurs in scoliotic patients showed statistically significant differences at neck aBMD -0.028 g/cm2, p = 0.004), total femur aBMD (--0.032 g/cm2, p = 0.008) and total femur vBMD (--8.9 mg/cm3, p = 0.011), with lower BMD values on the convexity side. In 10 cases (26%) a change in the final T-score diagnosis was observed.

CONCLUSION

QCT analysis demonstrated a difference in both areal and volumetric BMD between the two femurs of scoliotic patients, in relation to the side of the scoliotic curve. If these data will be confirmed by larger studies, bilateral femoral DXA acquisition may be proposed for these patients.

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.

Comparison of the Right and Left Femur Bone Mineral Densities in Postmenopausal Women

OBJECTIVES

Bone mineral density (BMD) is measured in the hip and posteroanterior spine; moreover, according to the 2019 International Society for Clinical Densitometry guidelines, unilateral hip can be used. This study aimed to determine whether there is a difference between the BMD of both the femurs in postmenopausal women.

METHODS

A total of 343 postmenopausal women were enrolled in this study from January 1, 2010, to December 31, 2019 at a single tertiary hospital. By using the Hologic® Horizon W DXA System, the femur and spine BMD was measured; BMD was recorded in g/cm². Following regions were analyzed in both the femurs: the femur neck, the trochanter area, and total femur.

RESULTS

Mean age at imaging was 62 ± 9.7 years, and significant difference in the total BMD of both the femurs (P = 0.003) was observed. In secondary analysis, patients with osteoporosis showed significant contralateral BMD discrepancies in trochanter and total proximal femur BMD (P = 0.041 and P = 0.011, respectively). However, in women with normal BMD, no significant difference between the right and left femur BMD was observed. Furthermore, measurement of solely the unilateral hip can lead to a 16.9% of underdiagnosis in postmenopausal women.

CONCLUSIONS

In conclusion, it is necessary to check BMD in both hips, particularly in patients suspected of osteoporosis.

Establishing a Total Hip T-Score Threshold to Measure Contralateral Hip Bone Mineral Density: Avoiding Missed Diagnosis of Osteoporosis

Bone mineral density (BMD) of the hip is routinely measured unilaterally, but can differ between left and right. This study aimed to establish total hip T-score thresholds for measuring contralateral hip BMD, to avoid missing the diagnosis of osteoporosis. In 4914 participants (2709 females) in the Busselton Healthy Ageing Study, BMD of both hips and lumbar spine (L1-L4) was measured by dual-energy x-ray absorptiometry (DXA) using a GE Lunar Prodigy Pro densitometer. Least significant change (LSC) was calculated according to International Society for Clinical Densitometry recommendations. For participants whose left-right total hip BMD difference exceeded LSC, the 95th percentile of the difference in T-score was calculated, then added to -2.5 (the cut-off for osteoporosis) to derive T-score thresholds for measuring contralateral hip to avoid a missed diagnosis in 95% of individuals. Participant mean age (±SD) was 57.4 ± 5.8 years; total hip T-score was 0.7 ± 0.1 in males and -0.2 ± 1.1 in females. Left and right total hip BMD were highly correlated (r = 0.943 for males, 0.959 for females), but in 56.2% of males and 50.0% of females, the left-right difference exceeded the LSC of 0.026 g/cm². In these participants, the 95th percentile of difference in T-score between two hips was 0.872 in males and 0.742 in females. This gave T-score thresholds for measuring contralateral total hip BMD of -1.6 (males) and -1.8 (females). When total hip T-score is between -1.6 and -2.5 (males), or between -1.8 and -2.5 (females), measuring contralateral hip BMD could avoid a missed diagnosis of osteoporosis.

Novel press-fit technique of patellar bone plug in anterior cruciate ligament reconstruction is comparable to interference screw fixation

PURPOSE

Conventional press-fit technique for anterior cruciate ligament reconstruction (ACLR) is performed with extraction drilling of the femoral bone tunnel and manual shaping of the patellar bone plug. However, the disadvantages of this technique include variation in bone plug size and, thus, the strength of the press-fit fixation, bone loss with debris distribution within the knee joint, potential heat necrosis, and metal wear debris due to abrasion of the guide wire. To overcome these disadvantages, a novel technique involving punching of the femoral bone tunnel and standardized compression of the bone plug was introduced. In this study, the fixation strength and apparent stiffness were tested and compared to that of the gold-standard interference screw fixation technique in three flexion angle configurations (0°/45°/90°) in a porcine model. We hypothesized that the newly developed standardized press fit fixation would not be inferior to the gold standard method.

METHODS

Sixty skeletally mature porcine knees (30 pairs) were used. Full-thickness central third patellar tendon strips were harvested, including a patellar bone cylinder of 9.5 mm in diameter. The specimens were randomly assigned to 10 pairs per loading angle (0°, 45°, 90°). One side of each pair was prepared with the press-fit technique, and the contra-lateral side was prepared with interference screw fixation. Equivalent numbers of left- and right-sided samples were used for both fixation systems. A three-way multifactor ANOVA was carried out to check for the influence of (a) fixation type, (b) flexion angle, and (c) side of the bone pair.

RESULTS

The primary fixation strength of femoral press-fit graft fixation with punched tunnels and standardized bone plug compression did not differ significantly from that of interference screw fixation (p = 0.51), which had mean loads to failure of 422.4 ± 134.6 N and 445.4 ± 135.8 N, respectively. The flexion angle had a significant influence on the maximal load to failure (p = 0.01). Load values were highest in 45° flexion for both fixations. The anatomical side R/L was not a statistically significant factor (p = 0.79).

CONCLUSION

The primary fixation strength of femoral press-fit graft fixation with punched femoral tunnels and standardized bone plug compression is equivalent to that of interference screw fixation in a porcine model. Therefore, the procedure represents an effective method for ACL reconstruction with patellar or quadriceps tendon autografts including a patellar bone plug.

Dual Hip DXA. Is it Time to Change Standard Protocol?

Previous studies have examined the utility of bilateral DXA hip bone mineral density (BMD) scans. While most studies demonstrate an advantage of bilateral hip scanning, the studies have been limited by size, or have not included simultaneous lumbar spine scans. To analyse the utility of dual hip scans in a clinical environment, a large retrospective study was performed of DXA BMD of both hips, and lumbar spine, in 17,169 individuals assessed at one centre over 10 years. There was no clinically significant difference in the population mean femoral neck BMD of the left vs the right leg (0.878 vs 0.881g/cm2) or total proximal femoral BMD of the left vs the right leg (0.920 vs 0.919g/cm2). There were however discrepancies in individuals between hip t-scores. For the total hip 1,977 (11.5 %) and 147 (0.9 %) of subjects had absolute t score differences ≥ 0.50 or ≥ 1.00. respectively. For the femoral neck 3,320 (19.3%) and 337 (2.0%) of subjects had absolute t score differences ≥ 0.50 or ≥ 1.00. respectively. Of the total 17,169 individuals there were 2,776 subjects with osteoporosis (T≤ -2.5) using the lumbar spine and right hip, compared to 2,834 subjects using the lumbar spine and left hip. Using the lumbar spine and both hips identified 3,214 individuals with osteoporosis. Diagnosis based on use of the lumbar spine and right hip BMD, or lumbar spine and left hip BMD, therefore failed to identify 15.8%, or 13.4%, of osteoporotic subjects respectively. Additional scanning time required was assessed in 40 subjects prospectively. Performing lumbar spine and both hips, compared to lumbar spine and one hip, required an average additional scan time of 55 seconds. The recommendation of best practise for DXA BMD measurements should be reviewed to consider lumbar spine and dual hip DXA as standard of care.

Prevalence of osteoporosis and osteopenia in an apparently healthy Indian population - a cross-sectional retrospective study

OBJECTIVES

An understanding of bone mineral density (BMD) pattern in a population is crucial for prevention and diagnosis of osteoporosis and management of its complications in later life. This study aimed to screen the bone health status and factors associated with osteoporosis in an apparently healthy Indian population.

METHODS

A retrospective review of medical records was done in a tertiary-care hospital for the subjects who had undergone preventive health-check-ups that included BMD measurements at femur-neck, total-femur, and lumbar-spine.

RESULTS

We evaluated 524 subjects (age, 50.0 ± 12.4 years) including 41.2% female and 58.8% male subjects. Osteoporosis was present in 6.9% subjects (female, 11.1%; male, 4.2%) and osteopenia in 34% subjects (female, 40.3%; male, 29.9%). Absolute BMD was higher in male subjects (P < 0.001) compared to female subjects at all bone sites. Prevalence of osteoporosis increased with age in female subjects, but not in male subjects. Osteoporosis rates in the age-groups of 30-39, 40-49, 50-59, 60-69, and ≥70 years were 3%, 3.4%, 14.3%, 18.6%, and 36.4%, respectively in female subjects while prevalence in male subjects was 0%, 4%, 6.5%, 4.3%, and 5.6%, respectively, at lumbar spine. Height (r = 0.234-0.358), weight (r = 0.305-0.388), body mass index (r = 0.143-0.285) and physical activity (r = 0.136-0.153) were positively; and alkaline phosphatase (r = -0.133 to -0.203) was negatively correlated with BMD (all P < 0.01) at all sites. These parameters retained significant correlation after controlling for age and sex. No correlation of serum 25-hydroxy-vitamin-D and calcium was noted with BMD (P > 0.05) at any site.

CONCLUSIONS

Further data on absolute BMD, T scores, and prevalence rates of osteoporosis/osteopenia on multiple bone sites have been presented in this article.

Association of incident hip fracture with the estimated femoral strength by finite element analysis of DXA scans in the Osteoporotic Fractures in Men (MrOS) study

Finite element model can estimate bone strength better than BMD. This study used such a model to determine its association with hip fracture risk and found that the strength estimate provided limited improvement over the hip BMDs in predicting femoral neck (FN) fracture risk only.

INTRODUCTION

Bone fractures occur only when it is loaded beyond its ultimate strength. The goal of this study was to determine the association of femoral strength, as estimated by finite element (FE) analysis of DXA scans, with incident hip fracture as a single condition or with femoral neck (FN) and trochanter (TR) fractures separately in older men.

METHODS

This prospective case-cohort study included 91 FN and 64 TR fracture cases and a random sample of 500 men (14 had a hip fracture) from the Osteoporotic Fractures in Men study during a mean ± SD follow-up of 7.7 ± 2.2 years. We analysed the baseline DXA scans of the hip using a validated plane-stress, linear-elastic FE model of the proximal femur and estimated the femoral strength during a sideways fall.

RESULTS

The estimated strength was significantly (P < 0.05) associated with hip fracture independent of the TR and total hip (TH) BMDs but not FN BMD, and combining the strength with BMD did not improve the hip fracture prediction. The strength estimate was associated with FN fractures independent of the FN, TR and TH BMDs; the age-BMI-BMD adjusted hazard ratio (95% CI) per SD decrease of the strength was 1.68 (1.07-2.64), 2.38 (1.57, 3.61) and 2.04 (1.34, 3.11), respectively. This association with FN fracture was as strong as FN BMD (Harrell's C index for the strength 0.81 vs. FN BMD 0.81) and stronger than TR and TH BMDs (0.8 vs. 0.78 and 0.81 vs. 0.79). The strength's association with TR fracture was not independent of hip BMD.

CONCLUSIONS

Although the strength estimate provided additional information over the hip BMDs, its improvement in predictive ability over the hip BMDs was confined to FN fracture only and limited.

Screening Post-menopausal Women for Bone Mineral Level by Bioelectrical Impedance Spectroscopy of Dominant Arm

Dominant arm bioimpedance spectroscopy (BIS) and lumbar and hip dual energy X-ray absorptiometry (DXA) measurements were conducted simultaneously on 48 post-menopausal women, aged between 43 and 86 years, with no hip or arm fracture history at Department of Radiology of Istanbul University Cerrahpasa Hospital. According to lumbar DXA results, 21 women were classified as normal, 22 as osteopenia and 5 as osteoporosis; whereas hip DXA results classified 30 women as normal, 15 as osteopenia and 3 as osteoporosis. Only 26 participants had identical lumbar and hip bone mineral density (BMD) diagnostic results. Dominant arm characteristic frequencies of normal subjects were statistically significantly different from osteoporotic subjects based on both lumbar (p < 0.005) and hip classification groups (p < 0.001). Hip and lumbar spine DXA BMD values were significantly correlated (r = 0.55, p < 0.005). The dominant arm BIS characteristic frequency, considered as the single predictor in earlier diagnosis of osteoporosis, was found negatively correlated with DXA measurements for both hip and lumbar spine regions. The Spearman rank correlation coefficient of BIS values with the hip DXA values (r = -0.53, p < 0.001) was higher than that of lumbar spine (r = -0.37, p < 0.001). In receiver operating characteristic (ROC) curve analysis, the best discrimination of dominant arm characteristic frequency was made between normal and osteoporotic subjects based on the hip subgroups (p < 0.001). Both lumbar bone mineral content (BMC) (r = -0.47, p < 0.001) and hip BMC (r = -0.4340, p < 0.005) were statistically significantly correlated with dominant arm characteristic frequency.

Vertical ground reaction force during standing and walking: Are they related to bone mineral density left-right asymmetries?

Osteoporosis is a systemic skeletal disease that is characterized by reduced bone mass, deterioration of bone tissue and skeletal fragility. The purpose of the current study was to determine whether asymmetrical femur bone mineral density (BMD) is associated with asymmetrical gait and standing. We compared measures of gait and standing asymmetry in subjects with (n=38) and without (n=11) significant left-right differences in BMD. Participants walked for 72m at their comfortable speed and stood quietly for 60s while outfitted with pressure-sensitive insoles. Based on the pressure measurements, indices of standing and gait asymmetry were determined. Gait Asymmetry (GA) indices of maximum ground reaction force (GRF) and stance time were significantly higher in the asymmetrical BMD group, compared to the symmetrical group (p<0.03). During quiet standing, maximal GRF was twice as high in those with BMD asymmetry, compared to those without, although this difference was not statistically significant (p=0.10). These preliminary findings indicate that femur BMD asymmetry and gait asymmetry are interrelated in otherwise healthy adults. Nutrition, metabolism and lifestyle are known contributors to BMD; typically, they affect bone health symmetrically. We suggest, therefore, that the BMD asymmetry may be due to previous changes in the loading pattern during walking that might have led to asymmetric bone deterioration. Future larger scale and prospective studies are needed to identify the mechanisms underlying the relationship between standing, gait and BMD and to explore whether gait training and exercises that target gait symmetry might help to reduce BMD asymmetry.

SIDE TO SIDE DIFFERENCES BETWEEN DOMINANT AND NON-DOMINANT ARM'S BONE DENSITY AND ISOMETRIC HANDGRIP STRENGTH IN MALES AND FEMALES AGED 40-65 YEARS OLD

OBJECTIVE

This observational, cross-sectional study, investigates and compares the differences of BMD, T-score, Z-score and isometric strength between dominant (D) versus non-dominant (ND) arms of 162 subjects aged 40-65 in a developing, low income country (Kosova).

MATERIAL AND METHODS

Bone Mineral Density (BMD), T-score and Z-score at distal forearm regions of both arms (measured by DXA scan), together with the Handgrip Isometric Strength (HIS) (by handgrip) were evaluated in a total subjects (53 Males and 109 Females). Additionally, General Healthcare Status Questionnaire together with self-administrated International Physical Activity Questionnaire (IPAQ) were filled.

RESULTS

Significant differences (p<0.05) between arms were found in BMD, T-score, and Z-score in total subjects and in females, whereas not significant differences (p>0.05) were observed in Males BMD comparing to significantly higher results (p<0.05) in T-score and Z-score. Significant differences (p<0.05) were also found in total subjects and in females handgrip, but not (p>0.05) in males. When comparing the total subject's BMD, T-score, Z-score and Handgrip based on the PA levels (1 to 3 according to IPAQ scoring) no significant differences (p>0.05) were found between PA1, as well as PA3 whereas significantly differences (p<0.05) were found in D arms of PA2 level.

CONCLUSION

The study analyses side-to-side differences in bone density and muscular force between D and ND arms amongst a population which is frequently exposed to diagnostic screenings for age related osteomuscular conditions (aged 40-60), and demonstrates that these differences should be in consideration amongst clinicians, but not in the way it is done right now.

Left-right differences in the proximal femur's strength of post-menopausal women: a multicentric finite element study

The strength of both femurs was estimated in 198 post-menopausal women through subject-specific finite element models. Important random differences between contralateral femurs were found in a significant number of subjects, pointing to the usefulness of further studies to understand if strength-based classification of patients at risk of fracture can be affected by laterality issues.

INTRODUCTION

Significant, although small, differences exist in mineral density and anatomy of contralateral proximal femurs. These differences, and their combined effect, may result in a side difference in femurs' strength. However, this has never been tested on a large sample of a homogenous population.

METHODS

The strength of both femurs was estimated in 198 post-menopausal women through CT-derived finite element models, built using a validated procedure, in sideways fall conditions. The impact of the resulting asymmetry on the classification of subjects at risk of fracture was analysed.

RESULTS

The small difference observed between sides (the right femur on average 4 % stronger than the left) was statistically significant but mechanically negligible. In contrast, higher random differences (absolute difference between sides with respect to mean value) were found: on average close to 15 % (compared to 9.2 % for areal bone mineral density (aBMD) alone), with high scatter among the subjects. When using a threshold-based classification, the right and left femurs were discordant up to over 20 % of cases (K always lower than 0.60) but the left femur was concordant (mean K = 0.84) with the minimum strength between right and left.

CONCLUSION

Considering both femurs may be important when trying to classify subjects at risk of failure with strength estimates. Future studies including fracture assessment would be necessary to quantify the real impact.

Prediction of incident hip fracture with the estimated femoral strength by finite element analysis of DXA Scans in the study of osteoporotic fractures

A bone fractures only when loaded beyond its strength. The purpose of this study was to determine the association of femoral strength, as estimated by finite element (FE) analysis of dual-energy X-ray absorptiometry (DXA) scans, with incident hip fracture in comparison to hip bone mineral density (BMD), Fracture Risk Assessment Tool (FRAX), and hip structure analysis (HSA) variables. This prospective case-cohort study included a random sample of 1941 women and 668 incident hip fracture cases (295 in the random sample) during a mean ± SD follow-up of 12.8 ± 5.7 years from the Study of Osteoporotic Fractures (n = 7860 community-dwelling women ≥67 years of age). We analyzed the baseline DXA scans (Hologic 1000) of the hip using a validated plane-stress, linear-elastic finite element (FE) model of the proximal femur and estimated the femoral strength during a simulated sideways fall. Cox regression accounting for the case-cohort design assessed the association of estimated femoral strength with hip fracture. The age-body mass index (BMI)-adjusted hazard ratio (HR) per SD decrease for estimated strength (2.21; 95% CI, 1.95-2.50) was greater than that for total hip (TH) BMD (1.86; 95% CI, 1.67-2.08; p < 0.05), FN BMD (2.04; 95% CI, 1.79-2.32; p > 0.05), FRAX scores (range, 1.32-1.68; p < 0.0005), and many HSA variables (range, 1.13-2.43; p < 0.005), and the association was still significant (p < 0.05) after further adjustment for hip BMD or FRAX scores. The association of estimated strength with incident hip fracture was strong (Harrell's C index 0.770), significantly better than TH BMD (0.759; p < 0.05) and FRAX scores (0.711-0.743; p < 0.0001), but not FN BMD (0.762; p > 0.05). Similar findings were obtained for intracapsular and extracapsular fractures. In conclusion, the estimated femoral strength from FE analysis of DXA scans is an independent predictor and performs at least as well as FN BMD in predicting incident hip fracture in postmenopausal women.

The assessment of bone mineral content and density of the lumbar spine and proximal femur in US submariners

The submarine environment is unique in that there is limited space and no sunlight, which may negatively affect skeletal health and lead to accelerated bone loss, osteoporosis, and fractures.

INTRODUCTION

The primary purpose of this study was to determine whether there was an association with submarine service, specifically time spent at sea, and bone mineral content (BMC) and bone mineral density (BMD) of the lumbar spine and dual proximal femur (total hip and femoral neck) measured by DXA.

METHODS

This is a cross-sectional study of 462 submariners 20-91 years old. Variables included in the analysis were age, height, race, alcohol intake, tobacco use, fracture history, conditions, and medications known to cause bone loss and osteoporosis and submarine service.

RESULTS

Of the submarine service predictors, only serving onboard a diesel submarine was determined to be independently associated with a reduction in BMD of the total hip and femur neck, while no submarine service predictor increased the odds of having low BMD. In submariners 50+ years old, the age-adjusted prevalence of osteopenia was 15.7 % (lumbar spine) and 40.4 % (femur neck), while the prevalence of osteoporosis was 4.8 % (lumbar spine) and 4.2 % (femur neck), rates that did not differ from NHANES 2005-2008. In submariners <50 years old, 3.1 % was below the expected range for age. The proportion of submariners 50+ years old that met the FRAX criteria for pharmacological treatment was 12 %.

CONCLUSIONS

Intermittent periods of submergence that can range from a few days to 3+ months do not appear to compromise skeletal health differently than the general population.

DIFFERENCES BETWEEN CONTRALATERAL BONES OF THE HUMAN LOWER LIMBS: A MULTISCALE INVESTIGATION

This study addressed side asymmetry between human lower limb long bones.

A multiscale approach was taken to investigate differences between contralateral femurs, tibias and fibulas, at body-level (total-body CT-scans, anatomical dissection), organ-level (volume and moments of areas; structural stiffness and strain distribution in bending and torsions) and tissue-level (mineral density, elastic modulus, hardness).

Because of the large amount of measurements taken, the study was limited to two donors. However, high statistical power within the same donor was achieved thanks to a large number of highly-repeatable measurements. Muscle cross-sections suggested that both donors were right-legged. The right bones had higher structural stiffness (up to +115%, statistically significant, except for the tibia). The right bones also experienced generally lower strain than the contralateral ones (up to -25%, statistically significant). The right bones had larger volume (up to +16%) and moments of area (up to +116%, statistically significant in most cases) than the left ones. Difference in tissue density between contralateral bones (< 7%) was not statistically significant in most cases. Also the differences found in elastic modulus of the femur cortical tissue (2–5%) were not statistically significant. Similarly, tissue hardness in the right bones was only marginally higher than in the contralateral ones (+1% to +4%, not statistically significant). Therefore, it seems that structural differences between contralateral bones associated with laterality are mainly explained by differences in bone quantity (volume) and organization (area moments). Bone tissue quality (density, hardness) seems to give a marginal contribution to structural side asymmetry.

Asymmetrical hip bone density in multiple sclerosis

As multiple sclerosis (MS) may affect one leg more than the other, we predicted that bone mineral density (BMD) would be lower in the limb self-identified as more affected. Therefore, the purpose of this study was to determine whether ambulatory individuals with MS displaying moderate-to-severe lower-extremity paresis exhibit asymmetrical femoral neck BMD. Dual-energy x-ray absorptiometry was used to assess proximal femoral neck BMD. Lower BMD was observed in the proximal femoral neck of the more paretic limb (P = .001) in a group (N = 23) of ambulatory individuals with relapsing-remitting MS (RRMS). Our preliminary findings suggest that bilateral hip screening may be important in the early detection of compromised bone health in ambulatory individuals with RRMS. Further research is warranted to fully characterize the factors and mechanisms associated with bone loss and identify effective strategies for optimizing bone health in people with MS.

Unilateral vs bilateral hip bone mineral density measurement for the diagnosis of osteoporosis

It has not been established whether unilateral or bilateral hip dual-energy X-ray absorptiometry (DXA) is preferable for the diagnosis of osteoporosis. We investigated the discordance in DXA measurements in bilateral hips to determine whether unilateral DXA is valid for osteoporosis diagnosis. The subjects were 2964 Japanese patients without a previous diagnosis of primary osteoporosis. We measured bilateral femoral bone mineral density (BMD) and calculated indices, related to the unilateral results, for predicting contralateral hip osteoporosis. A likelihood ratio (LR) of a negative test (LR [-]) of less than 0.2 was considered to exclude the diagnosis. In the normal spinal BMD group, the sensitivity of unilateral DXA for women was 27-73% and LR (-) was 0.28-0.73; the sensitivity for men was 0-50% and LR (-) was 0.51-1.00; the diagnosis of contralateral osteoporosis was not excluded. Sensitivity increased and LR (-) increased with worsening spinal BMD status; however, LR (-) did not meet the cutoff for exclusion. We could exclude unilateral hip osteoporosis, in women only, by performing contralateral femoral DXA; this necessitated lowering the T-score cutoff from -2.5 to -2.0. Unilateral femoral DXA is not useful for excluding the diagnosis of contralateral hip osteoporosis.

Bone mineral density differences between femurs of scoliotic patients undergoing dual-energy X-ray absorptiometry

AIM

To investigate whether a difference exists in the bone mineral density (BMD) between femurs in scoliotic patients undergoing dual-energy X-ray absorptiometry (DXA) and whether this difference is related to spine convexity.

MATERIALS AND METHODS

Of 1080 consecutive patients who underwent DXA, 127 had lumbar scoliosis seen at DXA. Further, after excluding 30 patients with previous osteoporotic fractures, metallic/image artefacts, soft-tissue calcifications, the BMD differences between femurs of 97 scoliotic patients (94 females; mean age 67 ± 11 years) were analysed. Femurs were classified as ipsilateral or contralateral to the spine convexity. Least significant change was used as a threshold of measurement precision. Differences between femoral neck BMD in respect of and regardless of spine convexity were calculated for each patient. Student's t-test and Wilcoxon's signed-rank test were used to assess significance.

RESULTS

Fifty-nine of 97 patients (61%) had left-sided scoliosis. Osteoporosis was found in 32/97 patients (33%), osteopenia in 54/97 (56%), and 11/97 (11%) had a normal T-score. Of 97 patients, 46 (47%) had ipsilateral BMD < contralateral BMD. Regardless of spine convexity, 66/97 patients (68%) had different BMD values between femurs. Among them, variation of densitometric diagnosis was seen in 29/66 patients (44%), and in 29/97 patients overall (30%).

CONCLUSION

Differences in the femoral neck BMD exist between femurs of scoliotic patients undergoing DXA. Thus, bilateral femoral DXA acquisition is recommended.

Prevalence and Risk Factors of Discordance between Left- and Right-Hip Bone Mineral Density Using DXA

To determine the prevalence of significant left-right differences in hip bone mineral density (BMD), and the impact of this difference on osteoporosis diagnosis, we measured bilateral proximal femora using dual energy X-ray absorptiometry (DXA) in 3481 subjects (608 males, 2873 females). The difference between left and right hip was considered significant if it exceeded the smallest detectable difference (SDD) for any of the three hip subregions. Contralateral femoral BMD was highly correlated at all measuring sites (r = 0.92-0.95). However, significant left-right differences in BMD were common: the difference exceeded the SDD for 54% of patients at total hip, 52.1% at femoral neck, and 57.7% at trochanter. The prevalence of left-right differences was greater in participants >65 years. For 1169 participants with normal spines, 22 (1.9%) had discordant left-right hips in which one hip was osteoporotic; for 1349 patients with osteopenic spines, 94 (7%) had osteoporosis in one hip. Participants with BMI < 20 kg/m(2) were more likely to show major T-score discordance (osteoporosis in one hip and normal BMD in the other). Multiple regression analysis showed that the only significant statically parameter that persists after adjusting for all potential confounding parameters were age over 65 years.

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.

Asymmetries in hip mineralization in mobile cellular phone users

A number of potential effects of mobile cellular phones on human health have been pinpointed, but the question of whether they affect bone mineralization has rarely been addressed. This study assessed differences in bone mineralization in the right and left hip of healthy male adult volunteers who were either nonusers of mobile phones (n=24) or users who carried the phone close to the right hip, for at least 1 year (n=24). Dual-energy x-ray absorptiometry (GE Lunar Prodigy) was performed in dual femur mode for each subject. Right and left hip bone mineral density (BMD) and bone mineral content (BMC) were compared. No difference in mean BMDs and BMCs between groups was found. Nonusers had higher BMC in the right femoral neck (P=0.0044), a difference absent in mobile phone users (P=0.028 for the right-left difference in nonusers vs users). Mobile phone users, but not nonusers, had lower BMD at the right trochanter (P=0.027) and lower BMC at the right trochanter (P=0.014) and right total hip (P=0.039). Linear regression showed a correlation between estimated cumulative hours carrying a cell phone on the right hip and differences between right and left trochanter BMD (r=0.434; P=0.034). The different asymmetries between right and left hip dual-energy x-ray absorptiometry values in nonusers and mobile phone users suggest that these devices may adversely affect bone mineralization.

Structural asymmetry between the hips and its relation to experimental fracture type

Experimental analysis with paired femurs provides the opportunity to study within-person differences in fracture type and associated structural side differences. We hypothesized that different fracture types in the hips of a subject are associated with structural asymmetry. Bone mineral density (BMD) and structural measurements of paired cadaver femurs (32 females, 24 males) were performed before mechanical testing in a side-impact configuration. Fractures were classified (cervical or trochanteric) and differences in structural parameters, BMD, and failure load were evaluated between the left and right hips as well as between experimental fracture types. We observed larger dimensions (P < 0.05-0.01), thicker cortices (P < 0.05-0.001), and a smaller femoral shaft diameter (FSD) (P < 0.01) in the left hip than in the right. Seventeen pairs (30.4%) had trochanteric fractures on one side and cervical on the contralateral side. The asymmetric trochanteric fracture side had a higher head/neck diameter ratio (HD/ND) (P < 0.05) and a trend toward a lower neck-shaft angle (NSA) (P = 0.066) than its collateral cervical side in females and a lower HD and higher FSD (P < 0.05) in males. In females, asymmetric fracture cases displayed lower NSA (P < 0.001) and HD/ND (P < 0.01) than symmetric cervical ones. In males, asymmetric fracture cases showed larger dimensions than the other groups (P < 0.05-0.01). BMD increased from symmetric cervical to asymmetric and then to symmetric trochanteric cases (P < 0.05-0.01), with the experimental failure load showing a similar trend. In conclusion, intrasubject structural asymmetry is associated with asymmetric fracture types. Asymmetry should be considered when using the opposite side as control in clinical 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.

The prevalence of significant left-right hip bone mineral density differences among black and white women

SUMMARY

In a cross-sectional retrospective study, we examined the prevalence of significant opposite hip bone mineral density difference among white and black women. Left-right hip bone mineral density difference was a common finding in both races, raising the possibility that osteoporosis can be missed if only one hip is imaged.

INTRODUCTION

We examined the prevalence of significant left-right hip bone mineral density (BMD) difference among black and white female subjects and its implications on the diagnosis of osteoporosis.

METHODS

This was a retrospective review of dual energy X-ray absorptiometry (DXA) data in black and white subjects age 50 years and older. One thousand four hundred seventy-seven scans obtained using a GE Lunar Prodigy scanner in dual hip mode were analyzed (24% black, 76% white). Significant left-right hip BMD difference was considered present when the subregion least significant change (LSC) was exceeded. Its prevalence was determined, along with consequences on the diagnosis of osteoporosis.

RESULTS

Significant differences in BMD were common in both races; the LSC was exceeded in 47% of the patients at the total hip, 37% at the femoral neck, and 53% at the trochanter. Diagnostic agreement was lower when the LSC was exceeded than when it was not. The LSC was exceeded in a statistically significant number of black and white patients with normal or osteopenic spines and unilateral hip osteoporosis.

CONCLUSIONS

Significant left-right hip BMD difference is a common finding among black and white women and can result in osteoporosis being missed if only one hip is imaged.

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.

Bone mineral density measurement at both spine and hip for diagnosing osteoporosis in Japanese patients

In Japan, spinal dual-energy X-ray absorptiometry (DXA) has been commonly performed for diagnosing osteoporosis but scanning the proximal femur is not done widely. The latest Japanese guidelines for prevention and treatment of osteoporosis, revised in 2006, recommend bone mineral density (BMD) measurement at both spine and hip for diagnosing osteoporosis, although there have been no reports that proved the necessity of those measurements. One thousand forty-one women and 485 men with clinical suspicion of osteoporosis were enrolled in this study, and DXA was performed at both spine and hip. The proportions of the patients who had inconsistency between diagnosis of osteoporosis from spinal DXA and that of hip were estimated. As a result, 22% of women and 15% of men had an inconsistency with the diagnosis of osteoporosis using DXA at each measurement site. There was inconsistency in diagnosing osteoporosis using DXA at the spine and proximal femur measurement sites. Because spine and femoral DXA measurements complement each other in the diagnosis of osteoporosis, BMD measurement at both spine and hip should be performed for all Japanese patients who are suspected osteoporosis, regardless of age and sex.

DXA scanning in clinical practice

Dual-energy X-ray absorptiometry (DXA) is recognized as the reference method to measure bone mineral density (BMD) with acceptable accuracy errors and good precision and reproducibility. The World Health Organization (WHO) has established DXA as the best densitometric technique for assessing BMD in postmenopausal women and based the definitions of osteopenia and osteoporosis on its results. DXA allows accurate diagnosis of osteoporosis, estimation of fracture risk and monitoring of patients undergoing treatment. However, when DXA studies are performed incorrectly, it can lead to major mistakes in diagnosis and therapy. This article reviews the fundamentals of positioning, scan analysis and interpretation of DXA in clinical practice.

Effect of precision error on T-scores and the diagnostic classification of bone status

We quantified confidence intervals (CIs) for T-scores for the lumbar spine and hip and determined the practical effect (impact on diagnosis) of variability around the T-score cutpoint of -2.5. Using precision data from the literature for GE Lunar Prodigy dual-energy X-ray absorptiometry (DXA) systems, the 95% CI for the T-score was +/-0.23 at the lumbar spine (L1-L4), +/- 0.20 at the total hip, and +/-0.41 at the femoral neck. Thus, T-score variations of +/-0.23 or less at the spine, +/-0.20 at the total hip, and +/-0.41 at the femoral neck are not statistically significant. When diagnosing osteoporosis, T-scores in the interval -2.3 to -2.7 for spine or total hip (after rounding to conform to guidelines from the International Society for Clinical Densitometry) and -2.1 to -2.9 for femoral neck are not statistically different from -2.5. Better precision values resulted in smaller 95% CIs. This concept was applied to actual clinical data using Hologic DXA systems. The study cohort comprised 2388 white women with either normal or osteopenic spines in whom the densitometric diagnosis of osteoporosis would be determined by hip T-scores. When evaluating actual patient T-scores in the range -2.5+/-95% CI, we found that the diagnosis was indeterminate in approximately 12% of women when T-scores for femoral neck were used and in 4% of women when T-scores for total hip were used, with uncertainty as to whether the classification was osteopenia or osteoporosis. We conclude that precision influences the variability around T-scores and that this variability affects the reliability of diagnostic classification.