Accuracy and precision of bone mineral density and bone mineral content in excised rat humeri using fan beam dual-energy X-ray absorptiometry

Effect of robotic gait training on muscle and bone characteristics in spinal cord transected rats

Osteoporosis and loss of muscle mass are secondary issues with spinal cord injury. Robotic gait training has provided evidence of increasing bone density and muscle mass, but its effect on bone strength is undetermined. The purpose of this study was to determine the effect of a 6-week robotic locomotion training program on skeletal muscle mass and bone characteristics. Twelve female Sprague-Dawley rats received a mid-thoracic spinal cord transection at 5 days old and at 3 weeks old were assigned to a Control or Trained Group. The Trained Group performed 5-min sessions on the Rat Stepper 5 days a week for 6 weeks with 90% of body weight supported. At the end of the 6 weeks, body mass was obtained and right femurs and four lower extremity muscles were harvested. Femur bone mineral density was measured with DXA and mechanical characteristics of the femur were determined via 3-point bending testing. Independent t-tests, effects sizes and percent differences were computed between the two groups (p < 0.05). The Trained Group had significantly larger normalized femur mass (p = 0.007) and normalized soleus muscle mass (p = 0.033) when compared to the Control Group. There was a medium or large effect size with the Trained Groups' femurs having larger mass, bone mineral density, rupture loads, cortical wall thickness, shaft cross sectional area, soleus mass, normalized gastrocnemius mass, and smaller shaft inner diameters compared to the Control Group. These changes may contribute to decreasing osteoporosis and fracture risk in those with spinal cord injuries.

Obesity history, physical exam, laboratory, body composition, and energy expenditure: An Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) 2022

Background

This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) on History, Physical Exam, Body Composition and Energy Expenditure is intended to provide clinicians an overview of the clinical and diagnostic evaluation of patients with pre-obesity/obesity.

Methods

The scientific information for this CPS is based upon published scientific citations, clinical perspectives of OMA authors, and peer review by the Obesity Medicine Association leadership.

Results

This CPS outlines important components of medical, dietary, and physical activity history as well as physical exams, with a focus on specific aspects unique to managing patients with pre-obesity or obesity. Patients with pre-obesity/obesity benefit from the same preventive care and general laboratory testing as those without an increase in body fat. In addition, patients with pre-obesity/obesity may benefit from adiposity-specific diagnostic testing - both generally and individually - according to patient presentation and clinical judgment. Body composition testing, such as dual energy x-ray absorptiometry, bioelectrical impedance, and other measures, each have their own advantages and disadvantages. Some patients in clinical research, and perhaps even clinical practice, may benefit from an assessment of energy expenditure. This can be achieved by several methods including direct calorimetry, indirect calorimetry, doubly labeled water, or estimated by equations. Finally, a unifying theme regarding the etiology of pre-obesity/obesity and effectiveness of treatments of obesity centers on the role of biologic and behavior efficiencies and inefficiencies, with efficiencies more often associated with increases in fat mass and inefficiencies more often associated with decreases in fat mass.

Conclusion

The Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) on History, Physical Exam, Body Composition and Energy Expenditure is one of a series of OMA CPSs designed to assist clinicians in the care of patients with the disease of pre-obesity/obesity.

Computed Tomography Osteodensitometry for Assessment of Bone Mineral Density of the Canine Head-Preliminary Results

Simple Summary

Metabolic bone disease can have disastrous consequences on canine health. Unlike in human medicine where awareness of osteoporosis and bone mineral density (BMD) disorders have led to the holistic application of osteodensitometry, application of osteodensitometry in dogs is limited. We aimed to assess the utility of quantitative computed tomography (qCT) bone mineral density (BMD) measurement of the canine calvarium using semiautomated osteodensitometry software and define host factors associated with canine BMD in a skeletally healthy population. Calvarium qCT can be used to rapidly obtain BMD measurement of dogs. Canine BMD was negatively associated with weight, whereas there was no relationship between BMD and age or sex. Many chronic canine diseases can significantly affect bone health via a variety of pathophysiological mechanisms. This efficient qCT method could facilitate rapid BMD screening in dogs undergoing CT evaluation and ultimately encourage further BMD investigation.

Abstract

Despite bone mineral density (BMD) being regularly measured in human patients, BMD studies in clinical cohorts of dogs is lacking. In order to facilitate BMD assessment and in turn better identify dogs suffering from metabolic bone disease, rapid, easy and precise computed tomography (qCT) techniques are required. In this study we aimed to assess the utility of quantitative computed tomography (qCT) bone mineral density (BMD) measurement of the canine calvarium using a semiautomated osteodensitometry software and define host factors associated with canine bone mineral density in a skeletally healthy population. Calvarial qCT at the level of the temporomandibular joints was performed on 323 dogs using a dedicated osteodensitometry calibration phantom during a clinically indicated head computed tomography (CT). Calvarial BMD was analyzed using a dedicated semiautomatic osteodensitometry software for contouring of the calvarial lamellar bone margins and BMD calculation. The mean duration of the calvarial qCT scanning was 64.6 s, and the mean duration of BMD analysis was 34 s, with a mean of two manual adjustments required for the bone margin tracing. The median BMD of all dogs in our study was 659 mg Calcium hydroxyapatite/mL. There was a negative linear correlation between BMD and body weight, but no correlation with age, sex or neutered status. Canine BMD assessment using qCT of the calvarium is a practical and fast technique that can be added to a clinical CT examination with minimal extra time requirements. Canine BMD host-dependent factors exhibit different relationships from that of humans; however, further investigation is warranted.

Effect of a formalin-based fixation method on bone mineral content in human ex-vivo specimens

OBJECTIVE

Histopathology of formalin-fixated human ex-vivo specimens may be used as reference standard for evaluation of diagnostic index tests like CBCT or MRI. The aim was to estimate changes in bone mineral content (BMC) over time in human ex-vivo bone specimens fixated in a formalin-based solution for 24 h followed by storage in an alcohol-based medium for six months, assessed by dual-energy X-ray absorptiometry (DXA).

METHODOLOGY

Bone specimens (n = 19) from human ex-vivo mandibles donated for science were included. BMC was measured by DXA before fixation (D₀), after 24 h of immersion fixation in a formalin-based solution (D₁), and hereafter every 30 days (M₁-M₆) during storage in a 30% ethanol-based storage medium for 6 months. Changes in BMC from D₀ to D₁ and from D₀ to M₆ were calculated and mean change in BMC estimated.

RESULTS

Mean change in BMC from D₀ to D₁ was -0.73% (95% CI -1.75%; 0.29%), and from D₀ to M₆ -1.19% (95% CI -2.14%; -0.23%).

CONCLUSIONS

No changes in BMC of ex-vivo human bone specimens were found after 24 h formalin-based immersion fixation. After six months storage in an ethanol-based medium, BMC mean loss of 1% was detected. In this range, changes in BMC are not clinically relevant.

Precision of the Hologic DXA in the Assessment of Visceral Adipose Tissue

INTRODUCTION

Visceral fat, also known as visceral adipose tissue (VAT), has been the focus of intensive research over the past several yr, as ground breaking studies have investigated its possible role in predicting long-term cardiac dysfunction, hypertension, and diabetes. Historically, magnetic resonance imaging and computed tomography were the instruments of choice for visceral fat quantification. However, with the introduction of visceral fat assessment software for Dual-energy X-ray Absorptiometry (DXA) scanners, DXA's use for VAT assessment has become increasingly common. To effectively utilize DXA in future VAT research studies, information about their precision and accuracy must be known. This study provides novel information regarding the precision of the Hologic Horizon DXA scanner in the assessment of VAT.

METHODS

Sixty individuals (32.7 ± 17.1 yr, 51% male, 40% with body mass index (BMI) > 25 kg/m²) above the age of 16 years were recruited to participate in this study. Subjects found to be pregnant, have a lumbar vertebral compression fracture, nonremovable metal implants in the abdomen, or scoliosis/lordosis/kyphosis were excluded from the study. All subjects underwent 3 consecutive whole body scans on a Hologic Horizon A DXA scanner.

RESULTS

VAT mass ranged from 102 g to 1454 g. VAT precision improved with increasing BMI (p = 0.025): coefficient of variation (%CV) was 15.2% for underweight subjects (n = 2), 7.1% for healthy subjects (n = 34), 6.4% for overweight subjects (n = 18), and 4.7% for obese subjects (n = 6).

CONCLUSIONS

VAT measurement by Hologic DXA displays a satisfactory level of precision in individuals with a BMI of >18.5 kg/m². Precision was found to be higher in those with the greatest risk of cardio-metabolic dysfunction (individuals with high VAT). Due to its low cost, brief examination time, noninvasiveness, and limited radiation exposure, DXA may be considered the tool of choice for VAT determination in future studies.

Trabecular bone score (TBS): Method and applications

Trabecular bone score (TBS) is a texture index derived from standard lumbar spine dual energy X-ray absorptiometry (DXA) images and provides information about the underlying bone independent of the bone mineral density (BMD). Several salient observations have emerged. Numerous studies have examined the relationship between TBS and fracture risk and have shown that lower TBS values are associated with increased risk for major osteoporotic fracture in postmenopausal women and older men, with this result being independent of BMD values and other clinical risk factors. Therefore, despite being derived from standard DXA images, the information contained in TBS is independent and complementary to the information provided by BMD and the FRAX® tool. A procedure to generate TBS-adjusted FRAX probabilities has become available with the resultant predicted fracture risks shown to be more accurate than the standard FRAX tool. With these developments, TBS has emerged as a clinical tool for improved fracture risk prediction and guiding decisions regarding treatment initiation, particularly for patients with FRAX probabilities around an intervention threshold. In this article, we review the development, validation, clinical application, and limitations of TBS.

Dietary Conjugated Linoleic Acid Does Not Adversely Affect Bone Mass in Obese fa/fa or Lean Zucker Rats

Conjugated linoleic acid (CLA) elevates body ash in healthy animals. The objective of the present study was to determine if single or mixed CLA isomers improve bone mass in an obese and hyperinsulinemic state. Male (n = 120) lean and obese fa/fa Zucker rats (age, 6 weeks) were randomized to 8 weeks on a control diet or to 0.4% (w/w) cis-9, trans-11 CLA (Group 1); 0.4% (w/w) trans-10, cis-12 CLA (Group 2); 0.4% (w/w) cis-9, trans-11 CLA and 0.4% (w/w) trans-10, cis-12 CLA (Group 3); 0.4% (w/w) cis-9, trans-11 CLA, 0.4% (w/w) trans-10, cis-12 CLA, and traces of other CLA isomers (Group 4); and 0.4% (w/w) cis-9, trans-11 CLA, 0.4% (w/w) trans-10, cis-12 CLA, and 0.3% (w/w) other CLA isomers (Group 5). Bone area (BA), bone mineral content (BMC), and bone mineral density (BMD) of the whole body, spine, and femur were measured at baseline (6 weeks) and at 14 weeks of age. Effects of genotype, diet, and genotype × diet interactions were assessed using factorial analysis of variance. At 6 and 14 weeks, whole-body BA and BMC were lower in lean rats compared with fa/fa rats. Similarly, at 14 weeks, fa/fa rats had a higher spine and femur BMD despite a lower femur weight. The fa/fa rats in Groups 4 and 5 had higher adjusted whole-body BMC compared with Group 3, but not with Group 1, Group 2, or the control. In lean rats, Group 3 had a greater adjusted whole-body BMC than Groups 1 and 2, but not Group 4, Group 5, or the control. Thus, commercially available CLA mixtures and single CLA isomers do not affect bone mass in a hyperinsulinemic, obese state.

Guidelines for Dual Energy X-Ray Absorptiometry Analysis of Trabecular Bone-Rich Regions in Mice: Improved Precision, Accuracy, and Sensitivity for Assessing Longitudinal Bone Changes

Trabecular bone is frequently studied in osteoporosis research because changes in trabecular bone are the most common cause of osteoporotic fractures. Dual energy X-ray absorptiometry (DXA) analysis specific to trabecular bone-rich regions is crucial to longitudinal osteoporosis research. The purpose of this study is to define a novel method for accurately analyzing trabecular bone-rich regions in mice via DXA. This method will be utilized to analyze scans obtained from the International Space Station in an upcoming study of microgravity-induced bone loss. Thirty 12-week-old BALB/c mice were studied. The novel method was developed by preanalyzing trabecular bone-rich sites in the distal femur, proximal tibia, and lumbar vertebrae via high-resolution X-ray imaging followed by DXA and micro-computed tomography (micro-CT) analyses. The key DXA steps described by the novel method were (1) proper mouse positioning, (2) region of interest (ROI) sizing, and (3) ROI positioning. The precision of the new method was assessed by reliability tests and a 14-week longitudinal study. The bone mineral content (BMC) data from DXA was then compared to the BMC data from micro-CT to assess accuracy. Bone mineral density (BMD) intra-class correlation coefficients of the new method ranging from 0.743 to 0.945 and Levene's test showing that there was significantly lower variances of data generated by new method both verified its consistency. By new method, a Bland-Altman plot displayed good agreement between DXA BMC and micro-CT BMC for all sites and they were strongly correlated at the distal femur and proximal tibia (r=0.846, p<0.01; r=0.879, p<0.01, respectively). The results suggest that the novel method for site-specific analysis of trabecular bone-rich regions in mice via DXA yields more precise, accurate, and repeatable BMD measurements than the conventional method.

ASSESSMENT OF OSTEOPOROTIC FEMORAL FRACTURE RISK: FINITE ELEMENT METHOD AS A POTENTIAL REPLACEMENT FOR CURRENT CLINICAL TECHNIQUES

Femoral fracture risk prediction is a necessary step preceding effective pharmacological intervention or pre-operative planning. Current clinical methods for fracture risk prediction rely on 2D imaging methods and have limited predictive value. Researchers are therefore trying to find improved methods for fracture prediction. During last few decades, many studies have focused on integration of 3D imaging techniques and the finite element (FE) method to improve the accuracy of fracture assessment techniques. In this paper, we review the recent advances in FE and other techniques for predicting the risk of femoral fractures. Based on a number of selected studies, the different steps that are involved in generation of patient-specific FE models are reviewed with particular emphasis on the fracture criteria. The inaccuracies that might arise due to the imperfections of the involved steps are also discussed. It is concluded that compared to image- and geometry-based techniques, FE is a more promising approach for prediction of fracture loads. However, certain technological advancements in FE modeling protocols are required before FE modeling can be recruited in clinical settings.

The Singh Index does not correlate with bone mineral density (BMD) measured with dual energy X-ray absorptiometry (DXA) or peripheral quantitative computed tomography (pQCT)

The Singh Index (SI), a classification system by which the severity of osteoporosis is assessed based on plain radiographs, is a renowned, simple and inexpensive form of evaluating osteoporosis. The aim of this study was to evaluate the correlation between the SI and bone mineral density (BMD) as measured by dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). The SI was evaluated in 128 cadaveric femora (64 patients, mean age 66.7 years, range 24-89 years) by three independent observers, all blinded to plain radiographs. BMD was also analysed by means of DXA and pQCT in the cadaveric femora. The mean interrater correlation was found to be 0.629. The correlation of the mean BMD measured by DXA (DXA-BMD) and SI was found to be poor, with r = 0.49. The corresponding sensitivity of 45.2 % and specificity of 92.3 % were even poor. The BMD measured by pQCT (pQCT-BMD) also revealed a poor correlation with SI, such that r = 0.337 and r = 0.428 for the trochanteric and neck regions, respectively. Due to the poor correlation of the SI with BMD and the poorer interrater correlation, the SI should be rejected as a tool for evaluating osteoporosis. The SI was found to be too imprecise and is therefore unsuitable for diagnosing osteoporosis and osteopenia.

Effect of endodontic cement on bone mineral density using serial dual-energy x-ray absorptiometry

INTRODUCTION

Materials with new compositions were tested in order to develop dental materials with better properties. Calcium silicate-based cements, including white mineral trioxide aggregate (WMTA), may improve osteopromotion because of their composition. Nano-modified cements may help researchers produce ideal root-end filling materials. Serial dual-energy x-ray absorptiometry measurement was used to evaluate the effects of particle size and the addition of tricalcium aluminate (C3A) to a type of mineral trioxide aggregate-based cement on bone mineral density and the surrounding tissues in the mandible of rabbits.

METHODS

Forty mature male rabbits (N = 40) were anesthetized, and a bone defect measuring 7 × 1 × 1 mm was created on the semimandible. The rabbits were divided into 2 groups, which were subdivided into 5 subgroups with 4 animals each based on the defect filled by the following: Nano-WMTA (patent application #13/211.880), WMTA (as standard), WMTA without C3A, Nano-WMTA + 2% Nano-C3A (Fujindonjnan Industrial Co, Ltd, Fujindonjnan Xiamen, China), and a control group. Twenty and forty days postoperatively, the animals were sacrificed, and the semimandibles were removed for DXA measurement.

RESULTS

The Kruskal-Wallis test followed by the Mann-Whitney U test showed significant differences between the groups at a significance level of P < .05. P values calculated by the Kruskal-Wallis test were .002 for bone mineral density at both intervals and P20 day = .004 and P40 day = .005 for bone mineral content.

CONCLUSIONS

This study showed that bone regeneration was enhanced by reducing the particle size (nano-modified) and C3A mixture. This may relate to the existence of an external supply of minerals and a larger surface area of nano-modified material, which may lead to faster release rate of Ca(2+), inducing bone formation. Adding Nano-C3A to Nano-WMTA may improve bone regeneration properties.

DXA and pQCT predict pertrochanteric and not femoral neck fracture load in a human side-impact fracture model

The validity of dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) measurements as predictors of pertrochanteric and femoral neck fracture loads was compared in an experimental simulation of a fall on the greater trochanter. 65 proximal femora were harvested from patients at autopsy. All specimens were scanned with use of DXA for areal bone mineral density and pQCT for volumetric densities at selected sites of the proximal femur. A three-point bending test simulating a side-impact was performed to determine fracture load and resulted in 16 femoral neck and 49 pertrochanteric fractures. Regression analysis revealed that DXA BMD trochanter was the best variable at predicting fracture load of pertrochanteric fractures with an adjusted R(2) of 0.824 (p < 0.0001). There was no correlation between densitometric parameters and the fracture load of femoral neck fractures. A significant correlation further was found between body weight, height, femoral head diameter, and neck length on the one side and fracture load on the other side, irrespective of the fracture type. Clinically, the DXA BMD trochanter should be favored and integrated routinely as well as biometric and geometric parameters, particularly in elderly people with known osteoporosis at risk for falls.

Characterization of Salvia miltiorrhiza ethanol extract as an anti-osteoporotic agent

BACKGROUND

Salvia miltiorrhiza (SM) has long been used as a traditional oriental medicine for cardiovascular disease. Accumulating evidence also indicates that SM has anti-osteoporotic effects. This study was conducted to examine the SM-induced anti-osteoporotic effect and its possible mechanisms with various doses of SM.

METHODS

We studied Sprague-Dawley female rats aged 12 weeks, divided into six groups: sham-operated control (SHAM), OVX rats supplemented with SM (1, 3, 10 and 30 mg/kg) orally for 8 weeks. At the end of the experiment, blood samples were collected and biochemistry analysis was performed. Specimens from both tibia and liver were processed for light microscopic examination. DEXA and μ-CT analyses of the tibia were also performed.

RESULTS

SM treatment significantly ameliorated the decrease in BMD and trabecular bone mass according to DEXA and trabecular bone architecture analysis of trabecular bone structural parameters by μ-CT scanning. In serum biochemical analysis, SM decreased the released TRAP-5b, an osteoclast activation marker and oxidative stress parameters including MDA and NO induced by OVX.

CONCLUSIONS

The preventive effect of SM was presumably due to its anti-oxidative stress partly via modulation of osteoclast maturation and number. In current study, SM appears to be a promising osteoporosis therapeutic natural product.

Bone mineral analysis through dual energy X-ray absorptiometry in laboratory animals

To determine how to eliminate species difference in animal bone experiment, bone mineral content (BMC) was measured using dual energy X-ray absorptiometry (DXA) on the femurs of laboratory mice (Mus musculus) and rats (Rattus norvegicus), and common marmosets (Callithrix jacchus). Measures were taken on femurs in situ, detached from the body, skinned and defleshed, or dried completely. When the BMC of the bone measured in the intact limb attached to the trunk was set at 100%, the actual BMC of the dry bone was 58.7 +/- 11.5% in mice and 103.2 +/- 3.2% in rats. Similarly, the bone area (Area) and bone mineral density (BMD) of the dried femur was significantly lower in the mouse femurs than intact limb. Thus, soft limb tissue such as skin and muscle modified the BMC, Area, and BMD only in mouse but not in those from rats or marmosets. The bone mineral ratio (BMR; BMC divided by dry bone weight) was nearest to the human bone value in the rat femurs, whereas the mouse femur BMR was the most different. The BMR was proved to be a practical index in evaluating bone characteristics in laboratory animals, but the mouse femur might not be suitable as an animal model for research into the aging of human bone.

Correcting fan-beam magnification in clinical densitometry scans of growing subjects

As children grow, body and limb girths increase. For serial densitometric measurements, growth increases the distance between the bone region of interest and X-ray source over time, thereby increasing fan-beam magnification. To isolate bone accrual from magnification error in growing subjects, we developed a correction method based on waist girth, a common anthropometric measure. This correction was applied to dual-energy X-ray absorptiometry output obtained in a cohort of premenarcheal gymnasts and nongymnasts. After correcting for magnification, results for projected area and bone mineral content (BMC) increased by 0.4-1.1% at the lumbar spine and 8-16% at the femoral neck, decreasing areal bone mineral density (aBMD) by 0.4-2.3% at both sites. The effects of magnification correction were similar in magnitude to BMC and aBMD gains previously reported in longitudinal studies of normoactive children. Because of body size differences, the effect of correction for BMC and aBMD was 10-20% greater in nongymnasts than in gymnasts, which increased the observed aBMD differential between gymnasts and nongymnasts. Fan-beam magnification distorts true changes in bone mineral measures in growing premenarcheal girls and, therefore, may obscure additional activity-related changes during growth. Our correction technique may enhance detection of skeletal adaptation, particularly in pediatric populations.

Erste Erfahrungen mit einem Flächendetektor-Volumen-CT (fpVCT) in der experimentellen Osteoporosediagnostik am Kleintiermodell

BACKGROUND

Flat-panel volumetric computed tomography (fpVCT) is a new, noninvasive CT imaging modality with increased isotropic resolution. Technical details, potential applications, and our initial experience with a fpVCT prototype scanner in the imaging of osteoporosis in a rat model are presented.

METHODS

To date, 21 rats have been investigated in vivo with fpVCT. Pharmacologic effects on bone mineral density (BMD) and structure were of special interest. Image evaluation focussed on the second lumbar vertebra and the left femoral bone. To validate measurement results, BMD values calculated with fpVCT were correlated with results of BMD measurements from ashing of the second lumbar vertebra and femoral bones.

RESULTS

Our initial results show that fpVCT is capable of detecting differences in BMD between ovariectomized rats treated with estradiol and a control group with high statistical significance (p<0.05), corresponding to ashing as the gold standard.

CONCLUSIONS

In a rat model, fpVCT imaging is especially useful in longitudinal in vivo investigations of BMD measures. Spatial resolution of up to 150 microm allows imaging of the trabecular structure only in human cadaveric bones.

New imaging technologies in the diagnosis of osteoporosis

In the context of osteoporosis, bone quality--which encompasses trabecular and cortical micro-architecture, mass, and tissue mechanical & compositional properties--plays an important and as yet undiscovered role. Non-invasive assessment of bone quality has recently received considerable attention, as bone density alone has not been able to predict existing or future osteoporotic fractures, or to explain therapeutic effects of emerging treatments. The goal of this review, therefore, is to present imaging modalities and related analysis methods capable of assessing bone quality for improved diagnosis and care of osteoporotic individuals. The techniques described include quantitative ultrasound, quantitative computed tomography, peripheral quantitative tomography, micro computed tomography, magnetic resonance, radiographic texture analysis, as well as finite element analysis based on the above-mentioned imaging modalities. The performance of these techniques in predicting osteoporotic fracture and assessing strength indices are discussed.

Dual-energy x-ray absorptiometry measurement and accuracy of bone mineral after unilateral total hip arthroplasty

The standard technique for monitoring bone mineral in hip arthroplasty has been dual-energy x-ray absorptiometry (DEXA). The accuracy of DEXA in the cortical bone adjacent to femoral components has not been established. This study evaluated bone mineral in the cortical bone adjacent to the femoral component comparing DEXA and ashing. Seven pairs of human femora from postmortem donors with unilateral hip implants were examined. Twenty-eight ashed core specimens from both the medial and lateral sides were taken. Cortical bone loss was seen to be greater in the proximal and medial regions of the implanted femora. Dual-energy x-ray absorptiometry failed to show an acceptable level of accuracy compared with ash data (r = 0.56; P = .002). It did show relative patterns of bone loss. Bone loss was consistent with implant-induced stress shielding.

Marginal Zinc Deficiency Exacerbates Bone Lead Accumulation and High Dietary Zinc Attenuates Lead Accumulation at the Expense of Bone Density in Growing Rats

Environmental lead exposure is associated with reduced bone growth and quality, which may predispose to osteoporosis. Zinc supplementation may reduce lead accumulation; however, effects on bone development have not been addressed. Our objective was to investigate the effects of marginal zinc (MZ) and supplemental zinc (SZ) intakes on bone lead deposition and skeletal development in lead-exposed rats. In a factorial design, weanling Sprague-Dawley rats were assigned to MZ (8 mg/kg diet); zinc-adequate control (CT; 30 mg/kg); zinc-adequate, diet-restricted (DR; 30 mg/kg); or SZ (300 mg/kg) groups, with and without lead acetate-containing drinking water (200 mg Pb/l) for 3 weeks. Excised femurs were analyzed for bone mineral density (BMD) by dual-energy x-ray absorptiometry, morphometry, and mineral content. MZ had higher femur lead and lower femur zinc concentrations and impaired skeletal growth and mineralization than CT. DR inhibited growth but did not result in higher femur lead concentrations than CT. SZ had higher femur zinc and lower femur lead concentrations than the other treatments. DR and SZ had impaired BMD versus CT and MZ. Lead also retarded skeletal growth and impaired BMD, but an interaction between lead and MZ was only found for femoral knee width, which was lower in MZ exposed to lead. In summary, while MZ deficiency exacerbated bone lead concentration, it generally did not intensify lead toxicity. SZ was protective against bone lead but was detrimental to BMD, suggesting that the optimal level of SZ to reduce lead absorption, while supporting growth and bone development, requires further investigation.

Dual-Energy X-Ray Absorptiometry Analysis of Implants in Rat Tibiae

Dual energy x-ray absorptiometry (DXA) was evaluated for its ability to measure changes in bone mineral density in isolated rat tibiae. This technique is available for in vivo use to potentially augment or replace some aspects of conventional histomorphometric techniques used for the evaluation of metallic implant-to-bone interfaces. Known quantities of hydroxyapatite powder, representing various bone densities, were measured using DXA in a series of 3 experiments: (1) the hydroxyapatite powder was placed within a plastic tube, (2) the hydroxyapatite was placed within an excised rat tibia, and (3) hydroxyapatite powder was placed within a rat tibia with soft tissue overlying it. Statistical analysis (analysis of variance) showed significant differences in bone mineral density among groups that varied by only 5% hydroxyapatite density within the plastic tubes. The system detected hydroxyapatite changes of 20% within the tibiae with and without overlying soft tissue (P < 0.05). These data were consistent and linear (R > 0.90). Although DXA analysis has been widely used in clinical and research applications for detection of osteoporosis, its use for documenting bone growth around implants has not been widely reported. The use of such a technique could have substantial benefits for both the clinical and research arenas. These data show that DXA analysis to identify bone density changes adjacent to implants has significant applications in small animal research models.

Effect of orthotopic small bowel transplantation on mineral metabolism in an experimental model

BACKGROUND

Numerous experimental models have been described for investigation of short bowel syndrome. The aim of this study was to examine the effect of orthotopic small bowel transplantation (OSBT) on universal metabolism in an inbred rat model, with particular emphasis on mineral metabolism.

METHODS

Jejunoileal resection and syngeneic OSBT was performed in 12-week-old male Lewis rats. Metabolic studies were performed over the following 16 weeks. Bones were analysed by physicochemical methods, dual X-ray absorptiometry, biomechanical procedures and histomorphometry. Biochemical markers of bone turnover were also measured.

RESULTS

Jejunoileal resection induced severe short bowel syndrome with profoundly reduced food efficiency, bone size, fracturing energy and bone mineral content, but no cancellous bone osteopenia. After OSBT rats showed normal growth; bones were of normal size, and bone mineral content and fracturing energy were similar to those in sham-operated controls. However, tibial, but not vertebral, cancellous bone osteopenia was found after transplantation.

CONCLUSION

OSBT with portal venous drainage achieves almost optimal mineral and bone metabolism. In the absence of immunosuppressive therapy, OSBT does not appear to have major untoward side-effects on bone in rats.

(n-3) fatty acids reduce the release of prostaglandin E2 from bone but do not affect bone mass in obese (fa/fa) and lean Zucker rats

Childhood obesity is prevalent and linked to the development of Type 2 diabetes mellitus (DM) and poor bone health. Some PUFA enhance bone mass and thus may improve bone health in obese children. The study objective was to determine the effects of dietary (n-6) compared with (n-3) essential PUFA and long-chain PUFA (LCPUFA) on bone in an obese and insulin-resistant state. Male fa/fa (n = 48) and lean Zucker rats (n = 48) were fed diets containing safflower oil [SO, high (n-6) PUFA], flaxseed oil [FXO, high (n-3) PUFA], or menhaden oil [MO, high (n-3) LCPUFA] for 9 wk. Measurements included the following: femur bone area (BA), mineral content (BMC), density (BMD), morphometry and ex vivo release of prostaglandin E(2) (PGE(2)); plasma osteocalcin and C-terminal telopeptides of type I collagen. Differences among groups were detected using 2-way ANOVA. Genotype effects in the fa/fa rats included lower femoral weight, length, BA, and BMC, as well as femoral head and proximal epiphysis widths compared with the lean rats, but BMD was not affected. Femur BA, BMC, and BMD did not differ among the dietary groups, but diaphysis width was elevated in the MO group and PGE(2) release was reduced by the FXO and MO diets. No genotype x diet interactions were observed. These data indicate that the fa/fa Zucker rat is at risk for low bone mass and that dietary (n-3) FA effectively reduce PGE(2) release. Whether reduced PGE(2) will support optimal peak bone mass during childhood and conserve bone mass with aging warrants investigation.

Low levels of dietary arachidonic and docosahexaenoic acids improve bone mass in neonatal piglets, but higher levels provide no benefit

In piglets, feeding arachidonic acid (AA) and docosahexaenoic acid (DHA) in a 5:1 ratio leads to elevated bone mass, but the optimal total quantity requires clarification. We studied bone mass and modeling of piglets that were randomized to receive 1 of 4 formulas for 15 d: control formula or the same formula with various levels of AA:DHA (0.5:0.1 g, 1.0:0.2 g or 2.0:0.4 g AA:DHA/100 g of fat). Measurements included: bone area (BA), mineral content (BMC), and density (BMD) of whole body, lumbar spine, and excised femurs; biomarkers of bone modeling were plasma osteocalcin and urinary cross-linked N-telopeptides of type 1 collagen (NTx), tibial ex vivo release of prostaglandin E(2) (PGE(2)), plasma insulin-like growth factor-1 (IGF-1), and tissue fatty acids. Main effects were identified using ANOVA and post hoc Bonferroni t tests. In supplemented piglets, relations among liver fatty acid proportions and bone mass were assessed using Pearson correlations. Whole body (P = 0.028) and lumbar spine (P = 0.043) BMD were higher in the group supplemented with 0.5:0.1 g AA:DHA/100 g of fat than in controls. Tissue AA and DHA increased in proportion to diet levels. Liver eicosapentaenoic acid (EPA) correlated positively (r > or = 0.38, P < or = 0.05) with whole body and femur BMC and BMD and lumbar spine BMC. Liver AA:EPA ratio correlated negatively (r > or = -0.039, P < or = 0.05) with whole body, femur, and lumbar spine BMC plus whole body and femur BMD. Dietary 1.0:0.2 g AA:DHA/100 g reduced NTx relative to 2.0:0.4 g AA:DHA/100 g of fat (P = 0.039). The diets did not affect the other biochemical variables measured. Low levels of dietary AA:DHA (0.5:0.1 g/100 g of fat) elevate bone mass, but higher amounts are not beneficial.

The effect of dietary n-3 long-chain polyunsaturated fatty acids on femur mineral density and biomarkers of bone metabolism in healthy, diabetic and dietary-restricted growing rats

INTRODUCTION

Dietary fish oil promotes bone formation in healthy states, but its effect during insulin deficiency or nutrient restriction is unclear.

METHODS

Eighty weanling male rats were randomized to receive an injection of streptozotocin to induce insulin deficiency (diabetes) or saline (control) and a diet containing soy oil or corn + fish oil for 35 days. Half of the saline-injected rats were randomized to 20% dietary restriction. Measurements were growth, biomarkers of bone metabolism and femur bone mass.

RESULTS

Density of femur was elevated in the corn + fish group and reduced in the diabetes group. Plasma osteocalcin and bone prostaglandin E2 (PGE2) were reduced by the corn + fish diet. N-telopeptide, IGF-1, bone PGE2 and urinary Ca were highest and calcitriol lowest in the diabetes group.

CONCLUSIONS

These data suggest that the benefit of a diet high in n-3 long-chain polyunsaturated fatty acid is most advantageous to long bone density in healthy states.

Effect of different masticatory functional and mechanical demands on the structural adaptation of the mandibular alveolar bone in young growing rats

The influence of masticatory functional and mechanical demands on the structural adaptation of the alveolar bone has not been investigated in both animals and humans. The effect of two experimental factors, the insertion of a bite-opening appliance and the alteration of food consistency, was investigated in young growing rats, with a particular emphasis on three-dimensional (3D) bone microstructure. Thirty-six male albino rats were divided into two equal groups, fed with either the standard hard diet or soft diet, at the age of 4 weeks. After 2 weeks, half of the animals in both groups had their upper molars fitted with an upper posterior bite block, an appliance similar to those used in clinical orthodontics. The remaining animals served as a control. After another 4 weeks, the animals were sacrificed, and their left hemimandibles were excised. Bone mineral density (BMD) and bone microstructure parameters of the alveolar process were subsequently measured, using dual-energy X-ray absorptiometry (DXA) and micro-computed tomography (micro-CT). The alveolar process width was also measured. Both experimental factors led to significant shape and structure modification of the mandibular alveolar bone in the growing rat. The bite block applied a continuous light force, which was associated with an inhibition of alveolar process vertical growth and a significant increase of cortical thickness. Soft diet and the consequent reduction of the intermittent forces applied to the alveolar bone during mastication resulted in a reduction of bone mineral density, accompanied by decreased trabecular bone volume and thickness. This rat model could prove to be a useful tool for the in vivo investigation of the role of muscular forces on the shape and structure adaptation of bone.

Accuracy and precision of PIXImus densitometry for ex vivo mouse long bones: comparison of technique and software version

Many densitometric studies in mice assess bone mineral density (BMD) at specified regions of interest, often using ex vivo specimens. In the present study, we sought to determine the precision and accuracy of ex vivo densitometry of mouse bones, comparing two software versions and two data acquisition techniques. The newer software allows manual adjustment of the threshold value for bone, improving the ability to analyze bone edges correctly. Root mean square standard deviations were 2-3 mg/cm2, with coefficients of variation ranging between 3% and 5% for femora and humeri and between 6% and 7% for radii. The regression coefficients for bone mineral content as a function of ash mass were near 1 for femora and humeri, but considerably lower for radii. Coefficients of determination were inversely related to bone size, with R2 values exceeding 0.9 at the femur, 0.8 at the humerus, and ranging between 0.3 and 0.6 at the radius. We found that our instrument has a position artifact, with BMD and bone mineral content dependent on the specimen's coordinates in the scanned field. Our findings establish the limitations of ex vivo densitometry with the PIXImus and support our recommendation that investigators seek position artifacts in their instruments.

Roles of periosteum, dura, and adjacent bone on healing of cranial osteonecrosis

It has been reported that large cranial osteonecrotic areas can heal. It was hypothesized that optimal healing is possible by the synchronized contribution of the osteogenic structures (periosteum, dura, and adjacent bone) that envelop the necrotic cranium. This hypothesis was tested by preserving or isolating the contribution of these osteogenic tissues. A total of 37 4-old-month rats were included in the study. Twelve animals were killed immediately, and cranial bone samples were taken and processed for examination (from 6 animals as fresh samples [Group A] and from the rest as autoclaved samples [Group B]). Group B was created to test if the bone was completely nonviable. In Group C (n = 25), cranial bone disks 8 mm in diameter were taken from 4-month-old rats, autoclaved, and put back onto the defect area. This group was further divided into the four Subgroups C1 through C4 (n = 7 in C3; n = 6 in C1, C2, and C4). Dura mater was isolated from the overlying bone disk with a polytetrafluoroethylene sheet in Subgroups C1 and C2, whereas the bone contacted the dura in the rest. The bone samples were covered with healthy periosteum in Subgroups C1 and C3 and with skin in Subgroups C3 and C4. These animals were killed after a healing period of 12 weeks, and the relevant bone disks were obtained. Surrounding healthy bone was also harvested from the same animals after they were killed to create Group D. The data of Group A and D were compared with those of the experimental group to comment on the degree of bone healing in the latter group. Quantitative and qualitative assessment was performed by mammography, bone densitometry, computed tomography, and histological examinations to find out the density and cellular content (osteocytes and vessels) of the samples. Examination of Group B samples showed nonviable tissue with a preserved microstructure. Analysis of other samples showed that both the periosteum and, mainly, the dura play an important role in cranial bone healing. The periosteal reaction was observed to be more evident when the dura was not separated. Cellular repopulation was more evident when both structures contributed to the healing process. Newly formed bone progressed centripetally; however, adjacent bone without the support of the dura and periosteum was capable of producing limited neovascularization and bone formation.