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

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

Type I collagen mutation alters the strength and fatigue behavior of Mov13 cortical tissue

Despite advances in understanding the molecular basis of Osteogenesis Imperfecta, the mechanisms by which type I collagen mutations compromise whole bone function are not well understood. Previously, we have shown that a heterozygous type I collagen mutation is associated with increased brittleness of long bones from Mov13 transgenic mice, a model of the mild form of Osteogenesis Imperfecta. In the current study, we investigated tissue-level damage processes by testing the hypothesis that the fatigue properties of Mov13 tissue were significantly compromised relative to littermate controls. We also quantified tissue structure and mineral content to explain variations in the fatigue behavior. Micro-beam specimens were machined from the anterior and posterior quadrants of Mov13 and control femurs and subjected to cyclic bending at one of four stress levels. Mov13 tissue exhibited a 22–25% reduction in tissue bending strength and a similar reductions in fatigue life and the stress level at which damage was apparent. These results provided tissue-level evidence that damage accumulation mechanisms were significantly compromised in Mov13 cortical tissue. Given that significant alterations in tissue structure were observed in Mov13 femurs, the results of this study support the idea that Mov13 femurs were brittle because alterations in tissue structure associated with the mutation interfered with normal damage processes. These results provide new insight into the pathogenesis of Osteogenesis Imperfecta and are consistent with bone behaving as a damaging composite material, where damage accumulation is central to bone fracture.     

The Analysis of Bacterial Results in the Kidney Perfusion Fluid and Bone Allografts in Human Multiorgan Donors

In 19 young human multiorgan donors, we simultaneously analyzed the bacterial contamination of the kidney perfusion fluid and all retrieved bone allografts. Donor exclusion criteria were done according to the American and European Association of Tissue Banks excluding all patients with perforating wounds. The kidney perfusate revealed a contamination in 17 of 19 (89.5%) donors. Allograft testing demonstrated positive bacterial growth in 34 of 76 allografts (44.7%). Microorganisms originated from the normal skin flora and could be related to contamination during the harvesting procedure. In 5 cases we cultured identical bacterial subspecies in both cultures as a possible sign for systemic bacterial spreading during the multiorgan harvesting procedure.     

Gender specific LRP5 influences on trabecular bone structure and strength

A mutation in LRP5 (low-density lipoprotein receptor-related protein 5) has been shown to increase bone mass and density in humans and animals. Transgenic mice expressing the LRP5 mutation (G171V) demonstrate an increase in bone mass as compared to non-transgenic (NTG) littermates. This study evaluated LRP5 gene and gender-related influences on the structural and biomechanical strength properties of trabecular and cortical bone in femurs and vertebrae (L5) of 17-week-old mice. Micro-computed tomography was used to evaluate the trabecular bone structure of distal femurs and vertebrae ex vivo. Mechanical testing of the trabecular bone in the distal femur was done to determine biomechanical strength. Differences due to genotype and gender were tested using two-way ANOVA at a significance level of p<0.05. Trabecular bone structural parameters (BV/TV, trabecular thickness, number, etc.) at the distal femur, femoral neck, and vertebral body sites were greater in the transgenic as compared to the NTG mice. In addition, vertebral cortical thickness and trabecular strength parameters (ultimate and yield loads, stiffness, ultimate and yield stresses) in the distal femur were greater in the transgenic mice as compared to NTG. The increasing trends of cortical thickness were also noted in the transgenic mice as compared to NTG. Within LRP5 (G171V) mutant mice, there were significant gender-related differences in some of the trabecular bone structural parameters at all the sites (distal femur, femoral neck, and vertebral body). However, unlike trabecular structural parameters, the gender-specific differences were not found in the trabecular strength of LRP5 transgenic mice. In summary, these findings suggest that the LRP5 (G171V) mutation results in greater trabecular bone structure and strength at both the distal femurs and vertebral bodies as compared to NTG. In addition, only the trabecular structure parameters were affected by gender within the LRP5 (G171V) mutation.     

A novel approach to assess post-yield energy dissipation of bone in tension

In this study, we proposed a novel approach to assess the energy dissipation during the post-yield deformation of bone. Based on the stress-strain behavior in an incremental and cyclic loading-unloading-reloading scheme in uniaxial tension, we partitioned the post-yield energy dissipation of bone into three distinct pathways: released elastic strain energy (U(er)); irreversible energy (U(i)); and hysteresis energy (U(h)). Among them, U(er) depends on the stiffness loss, U(i) is the energy permanently consumed, and U(h) reflects changes in the viscoelastic behavior of bone in the process of post-yield deformation. As an example, bone specimens from human cadaveric femurs of middle-aged and elderly donors were tested using this approach. The results of this study indicate that there exist age-related differences in post-yield energy dissipation and modulus degradation. These results implicate that this novel approach could detect the age-related differences in energy dissipation of bone and may aid in understanding the underlying mechanisms of such changes.     

Quantitative trait loci for tibial bone strength in C57BL/6J and C3H/HeJ inbred strains of mice

Three-point bending technology has been widely used in the measurement of bone strength. Quantitative trait loci (QTLs) for bone strength have been identified using mouse femurs. In this study, we investigate the use of mouse tibiae in identification of QTLs that regulate bone strength. Mouse tibiae were from a F₂ population derived from C57BL/6J (B6) and C3H/HeJ (C3H). Three-point bending was measured using ISO 4049, with the support width adjustable to accommodate specimen sizes outside the scope of ISO 4049. The strain rate is selectable from 0.05 to 500 mm per min. All stress strain diagrams are recorded and retrieved in digital electronic form. Genome scan was performed in The Jackson Laboratory (TJL). QTL mapping was conducted using Map Manager QTX software. Data show that (i) both elastic modulus (stiffness) and maximum loading (strength) value appear as normal distributions, suggesting that multiple genetic factors control the bone strength; (ii) 11 QTLs, accounting for 90% of variation for strength, have been detected. More than half QTLs of three-point bending are located on the same locations of bone density earlier identified from mouse femurs; (iii) a major QTL of femoral and vertebral bone mineral density (BMD) was not detected for bone strength of tibiae; (iv) the QTL on chromosome 4 has extremely high LOD score of 31.8 and represents 60% of the variation of bone strength; and (v) four QTLs of stiffness (chromosomes 2, 11, 15 and 19) have been identified.     

Structural properties of a new design of composite replicate femurs and tibias

The purpose of this study was to compare the structural properties of a new vs. established design of composite replicate femurs and tibias. The new design has a cortical bone analog consisting of short-glass-fiber-reinforced (SGFR) epoxy, rather than the fiberglass-fabric-reinforced (FFR) epoxy in the currently available design. The hypothesis was that this new cortical bone analog would improve the uniformity of structural properties between specimens, while having mean stiffness values in the range of natural human bones. The composite replicate bones were tested under bending, axial, and torsional loads. In general, the new SGFR bones were significantly less stiff than the FFR bones, although both bone designs reasonably approximated the structural stiffnesses of natural human bones. With the exceptions of the FFR bone axial tests, the highest variability between specimens was 6.1%. The new SGFR bones had similar variability in structural properties when compared to the FFR bones under bending and torsional loading, but had significantly less variability under axial loading. Differences in epiphyseal geometry between the FFR and SGFR bones, and subsequent seating in the testing fixtures, may account for some of the differences in structural properties; axial stiffness was especially dependent on bone alignment. Stiffness variabilities for the composite replicate bones were much smaller than those seen with natural human bones. Axial strain distribution along the proximal-medial SGFR femur had a similar shape to what was observed on natural human femurs by other investigators, but was considerably less stiff in the more proximal locations.     

A preliminary biomechanical study of cyclic preconditioning effects on canine cadaveric whole femurs

Biomechanical preconditioning of biological specimens by cyclic loading is routinely done presumably to stabilize properties prior to the main phase of a study. However, no prior studies have actually measured these effects for whole bone of any kind. The aim of this study, therefore, was to quantify these effects for whole bones. Fourteen matched pairs of fresh-frozen intact cadaveric canine femurs were sinusoidally loaded in 4-point bending from 50?N to 300?N at 1?Hz for 25 cycles. All femurs were tested in both anteroposterior (AP) and mediolateral (ML) bending planes. Bending stiffness (i.e., slope of the force-vs-displacement curve) and linearity R(2) (i.e., coefficient of determination) of each loading cycle were measured and compared statistically to determine the effect of limb side, cycle number, and bending plane. Stiffnesses rose from 809.7 to 867.7?N/mm (AP, left), 847.3 to 915.6?N/mm (AP, right), 829.2 to 892.5?N/mm (AP, combined), 538.7 to 580.4?N/mm (ML, left), 568.9 to 613.8?N/mm (ML, right), and 553.8 to 597.1?N/mm (ML, combined). Linearity R(2) rose from 0.96 to 0.99 (AP, left), 0.97 to 0.99 (AP, right), 0.96 to 0.99 (AP, combined), 0.95 to 0.98 (ML, left), 0.94 to 0.98 (ML, right), and 0.95 to 0.98 (ML, combined). Stiffness and linearity R(2) versus cycle number were well-described by exponential curves whose values leveled off, respectively, starting at 12 and 5 cycles. For stiffness, there were no statistical differences for left versus right femurs (p?=?0.166), but there were effects due to cycle number (p?相似文献   

Femoral Strength after Induced Lesions in Rats (Rattus norvegicus)

Rats are a common model for the study of bone healing, with the cranium, femur, and tibia being the bones studied most frequently. This study examines noncritical-sized lesions that would allow rats to continue to bear weight without the need for fixation but that are sufficiently large to enable characterization of the healing process. We compared the femoral bone strength associated with 3 lesion sizes selected for use in future studies. Sprague–Dawley rats (age, 10 to 16 wk) were used to assess the ultimate breaking strength, stress, and break force of normal, unmanipulated femurs. We then created lesions of 3 different sizes in the mid- to distal diaphysis of the left and right femurs and characterized the associated decreases in bone strength. Femurs (n= 85) for this study were collected through tissue sharing from rats used in other acute surgical procedures and were tested by using a 3-point bending flexural materials-testing machine. Our hypothesis was that, as a model for bone healing, 3 induced lesions of different sizes would show incremental and proportional decreases in femoral strength, with the intermediate-sized (1.5-mm) lesion demonstrating a decrease of 20% to 40%. A lesion of 1.5 mm yielded a decrease in strength of 17% for both the left and right femurs. The strength of left femurs carrying intermediate lesions was significantly less than that of control, uninjured femur bones. In addition to providing validation for our own future bone-healing project, these data are a useful baseline for other investigators studying bone healing in a rat femur model.Rodents, particularly rats, represent a reliable and affordable model for conducting basic research involving the skeleton.² Although biomechanical techniques for testing bone strength have been well documented, few studies define the theory, methods, and experimental procedures for evaluating the fracture toughness of bone (fracture resistance), especially whole-bone testing in small animals.¹⁰ This said, femurs are still the ideal rat and mouse bones to use to evaluate the fracture toughness properties in small-animal model studies.^4,10 Bending tests are useful to assess the mechanical properties of bones from rodents and other small animals.¹⁵ Even though this method of testing is referred to as a ‘bending test,’ the material (in this case, bone) is actually fractured to assess fracture toughness or breaking. For bending tests, long bones are loaded mainly in bending or compression during normal movement of the animals and are subject to both intrinsic and extrinsic large bending forces.^4,14 In rodents, locomotion results in alternating tension and compression on the cortex of weight-supporting bones during the gait cycle, with no limit on the magnitude or direction in which these forces can be exerted.⁸ This makes testing of bending, compression, torsion or any combination of methods potentially applicable. Therefore we chose to conduct 3-point bending testing on rat femurs. Bones were stressed to the point of fracture and the values required were recorded for computer-assisted analysis.In the testing of bone, the fundamental structural properties of greatest importance are stiffness, strength, and toughness.^8,10 Measured and calculated values of importance are peak force (ultimate breaking strength), fatigue resistance, stress, strain, break force, and energy to break. We chose to collect and compare peak force (measured data) as well as stress and break force (both calculated data). We made these choices because the most important biomechanical property from a clinical point of view is the peak force, which corresponds to the ability of a patient''s leg to resist high loading before a fracture or irreversible deformation occurs.Strength can be tested as tension, compression, bending, or shear.^8,10 Strength as a material parameter is defined as the ultimate stress at which failure occurs, but strength is defined structurally as the ultimate load (or force) when failure of the system occurs.⁸ In the current study, we tested the strength of rat femurs via 3-point bending. We hypothesized that the 1.5-mm lesion, which involved 39% of the bone circumference, would yield a 20% to 40% decrease in strength. In addition, the femurs with induced lesions showed a consistent decrease in strength, with larger lesions associated with lower peak force on both the right and left sides.     

Raman and mechanical properties correlate at whole bone- and tissue-levels in a genetic mouse model

The fracture resistance of bone arises from the composition, orientation, and distribution of the primary constituents at each hierarchical level of organization. Therefore, to establish the relevance of Raman spectroscopy (RS) in identifying differences between strong or tough bone and weak or brittle bone, we investigated whether Raman-derived properties could explain the variance in biomechanical properties at both the whole bone and the tissue-level, and do so independently of traditional measurements of mineralization. We harvested femurs from wild-type mice and mice lacking matrix metalloproteinase 2 because the mutant mice have a known reduction in mineralization. Next, RS quantified compositional properties directly from the intact diaphysis followed by micro-computed tomography to quantify mineralization density (Ct.TMD). Correlations were then tested for significance between these properties and the biomechanical properties as determined by the three-point bending test on the same femurs. Harvested tibia were embedded in plastic, sectioned transversely, and polished in order to acquire average Raman properties per specimen that were then correlated with average nanoindentation properties per specimen. Dividing the ν(1) phosphate by the proline peak intensity provided the strongest correlation between the mineral-to-collagen ratio and the biomechanical properties (whole bone modulus, strength, and post-yield deflection plus nanoindentation modulus). Moreover, the linear combination of ν(1) phosphate/proline and Ct.TMD provided the best explanation of the variance in strength between the genotypes, and it alone was the best explanatory variable for brittleness. Causal relationships between Raman and fracture resistance need to be investigated, but Raman has the potential to assess fracture risk.     

A surrogate long-bone model with osteoporotic material properties for biomechanical testing of fracture implants

In vitro comparative testing of fracture fixation implants is limited by the highly variable material properties of cadaveric bone. Bone surrogate specimens are often employed to avoid this confounding variable. Although validated surrogate models of normal bone (NB) exist, no validated bone model simulating weak, osteoporotic bone (OPB) is available. This study presents an osteoporotic long-bone model designed to match the lower cumulative range of mechanical properties found in large series of cadaveric femora reported in the literature. Five key structural properties were identified from the literature: torsional rigidity and strength, bending rigidity and strength, and screw pull-out strength. An OPB surrogate was designed to meet the low range for each of these parameters, and was mechanically tested. For comparison, the same parameters were determined for surrogates of NB. The OPB surrogate had a torsional rigidity and torsional strength within the lower 2% and 16%, respectively, of the literature based cumulative range reported for cadaveric femurs. Its bending rigidity and bending strength was within the lower 11% and 8% of the literature-based range, respectively. Its pull-out strength was within the lower 2% to 16% of the literature based range. With all five structural properties being within the lower 16% of the cumulative range reported for native femurs, the OPB surrogate reflected the diminished structural properties seen in osteoporotic femora. In comparison, surrogates of NB demonstrated structural properties within 23-118% of the literature-based range. These results support the need and utility of the OPB surrogate for comparative testing of implants for fixation of femoral shaft fractures in OPB.     

Strain shielding in distal femur after patellofemoral arthroplasty under different activity conditions

Strain shielding, a mechanical effect occurring in structures combining stiff with more flexible materials, is considered to lead to a reduction of density in bone surrounding the implant. This effect can be related to the weakness of the implant fixation, which can promote implant loosening. Several studies describe a significant decrease in postoperative bone mineral density adjacent to joint implants, which can compromise their long-term fixation. The aim of the present study was to quantify the strain shielding effect on the distal femur after patellofemoral arthroplasty. For this purpose three activities of daily living were considered: level walking, stair climbing and deep bending at different angles of knee flexion. To determine the strain shielding effect, cortical bone strains were measured experimentally with triaxial strain gauges in synthetic femurs before and after patellofemoral arthroplasty for each of the different daily activities. The results showed that the patellofemoral arthroplasty in general reduced the strains in the medial and distal regions of the femur when deep bending activity occurred, consequently, strain shielding in these regions, with strain decreases of ?72.0% and ?67.5% were measured. On the other side, higher values of strain were found in the anterior region after patellofemoral replacement for this activity with an increase of +182.0%. The occurrence of strain shielding seems to be more significant when the angle of knee flexion and applied load increases. Strain shielding and over-loading may have relevant effects on bone remodeling surrounding the patellofemoral implant, suggesting a potential effect of later bone resorption in the medial and distal femur regions in case of regular deep bending activity.     

Antler stiffness in moose (Alces alces): Correlated evolution of bone function and material properties?

The material properties of bone can vary considerably among skeletal elements from different parts of the body that serve different functions. However, functional demands placed on a specific type of skeletal element also can vary at a variety of scales, such as between different parts of the element, among individuals of a species, and across species. Variation in bone material properties might be correlated with differing functional demands at any of these scales. In this study we performed three-point bending tests on bone specimens extracted from antlers of moose (Alces alces) to test for three types of variation in bone material stiffness (Young's modulus): within the antler structure, between populations of moose, and between moose and other deer species. Because superficial portions of the antler are exposed to greater bending stress and strain than deeper portions, and because the antler beam (the basal shaft that attaches to the skull) is subjected to greater bending moments than more distal parts of the antler, we predicted that superficial bone and bone from the beam would be stiffer than bone from other parts of the antler. Instead, we identified no significant differences in these comparisons. There were also no significant differences in antler stiffness between moose from Michigan and the Yukon, even though the rapid growth required of antlers from northern latitudes like the Yukon has the potential to compromise bone material properties. However, moose have significantly stiffer antlers (11.6 +/- 0.45 GPa, mean +/- SE) than any other deer in the odocoileine lineage. Moreover, phylogenetic reconstructions of the evolution of antler stiffness in deer indicate a strong potential that high antler stiffness is a derived feature of moose. The unusual palmate shape of moose antlers likely subjects their antler beams to higher bending moments than found in other odocoileines, a factor that may have contributed to the evolutionary divergence of moose antler stiffness from that of other members of this clade. Although similarities in the mineral composition of bone across species likely limit the overall range of phylogenetic variation in bone material properties, our results demonstrate that evolutionary diversity in bone material properties can show correspondence with phylogenetic differences in mechanical or ecological demands on skeletal elements.     

Reactive oxygen species on bone mineral density and mechanics in Cu,Zn superoxide dismutase (Sod1) knockout mice

Reactive oxygen species (ROS) play a role in a number of degenerative conditions including osteoporosis. Mice deficient in Cu,Zn-superoxide dismutase (Sod1) (Sod1^−/− mice) have elevated oxidative stress and decreased muscle mass and strength compared to wild-type mice (WT) and appear to have an accelerated muscular aging phenotype. Thus, Sod1^−/− mice may be a good model for evaluating the effects of free radical generation on diseases associated with aging. In this experiment, we tested the hypothesis that the structural integrity of bone as measured by bending stiffness (EI; N/mm²) and strength (MPa) is diminished in Sod1^−/− compared to WT mice. Femurs were obtained from male and female WT and Sod1^−/− mice at 8 months of age and three-point bending tests were used to determine bending stiffness and strength. Bones were also analyzed for bone mineral density (BMD; mg/cc) using micro-computed tomography. Femurs were approximately equal in length across all groups, and there were no significant differences in BMD or EI with respect to gender in either genotype. Although male and female mice demonstrated similar properties within each genotype, Sod1^−/− mice exhibited lower BMD and EI of femurs from both males and females compared with gender matched WT mice. Strength of femurs was also lower in Sod1^−/− mice compared to WT as well as between genders. These data indicate that increased oxidative stress, due to the deficiency of Sod1 is associated with decreased bone stiffness and strength and Sod1^−/− mice may represent an appropriate model for studying disease processes in aging bone.     

Cortical screw pullout strength and effective shear stress in synthetic third generation composite femurs

BACKGROUND: The use of artificial bone analogs in biomechanical testing of orthopaedic fracture fixation devices has increased, particularly due to the recent development of commercially available femurs such as the third generation composite femur that closely reproduce the bulk mechanical behavior of human cadaveric and/or fresh whole bone. The purpose of this investigation was to measure bone screw pullout forces in composite femurs and determine whether results are comparable to cadaver data from previous literature. METHOD OF APPROACH: The pullout strengths of 3.5 and 4.5 mm standard bicortical screws inserted into synthetic third generation composite femurs were measured and compared to existing adult human cadaveric and animal data from the literature. RESULTS: For 3.5 mm screws, the measured extraction shear stress in synthetic femurs (23.70-33.99 MPa) was in the range of adult human femurs and tibias (24.4-38.8 MPa). For 4.5 mm screws, the measured values in synthetic femurs (26.04-34.76 MPa) were also similar to adult human specimens (15.9-38.9 MPa). Synthetic femur results for extraction stress showed no statistically significant site-to-site effect for 3.5 and 4.5 mm screws, with one exception. Overall, the 4.5 mm screws showed statistically higher stress required for extraction than 3.5 mm screws. CONCLUSIONS: The third generation composite femurs provide a satisfactory biomechanical analog to human long-bones at the screw-bone interface. However, it is not known whether these femurs perform similarly to human bone during physiological screw "toggling."     

犬完整骨及骨水泥重建骨缺损微波灭活后的生物力学研究

目的:研究微波消融(microwave ablation)对结构正常及缺损后骨水泥修复重建的犬骨生物力学性能的影响.方法:取成年犬股骨12对,随机分为完整组和重建组,再随机选取每对股骨的一侧作为对照组,另一侧为实验组,试验由此分为四组:完整对照组,完整微波组,重建对照组,重建微波组.然后将每根股骨制作成两个不同的骨标本,分别长3 cm和6 cm.两种微波组的标本均进行微波灭活,两种重建组的标本均制备成缺损模型并行骨水泥修复重建.然后分别对3、6 cm两种标本行压缩和三点弯曲试验.结果:完整对照组与完整微波组之间,重建对照组与重建微波组之间的最大压缩力、最大压缩位移、最大弯曲力及最大挠度等均无显著性差异.结论:微波消融对结构正常的犬骨的生物力学性能无明显影响,且不会加剧对重建犬骨的力学强度的破坏.     

Structural behaviour and strain distribution of the long bones of the human lower limbs

Although stiffness and strength of lower limb bones have been investigated in the past, information is not complete. While the femur has been extensively investigated, little information is available about the strain distribution in the tibia, and the fibula has not been tested in vitro. This study aimed at improving the understanding of the biomechanics of lower limb bones by: (i) measuring the stiffness and strain distributions of the different low limb bones; (ii) assessing the effect of viscoelasticity in whole bones within a physiological range of strain-rates; (iii) assessing the difference in the behaviour in relation to opposite directions of bending and torsion. The structural stiffness and strain distribution of paired femurs, tibias and fibulas from two donors were measured. Each region investigated of each bone was instrumented with 8–16 triaxial strain gauges (over 600 grids in total). Each bone was subjected to 6–12 different loading configurations. Tests were replicated at two different loading speeds covering the physiological range of strain-rates. Viscoelasticity did not have any pronounced effect on the structural stiffness and strain distribution, in the physiological range of loading rates explored in this study. The stiffness and strain distribution varied greatly between bone segments, but also between directions of loading. Different stiffness and strain distributions were observed when opposite directions of torque or opposite directions of bending (in the same plane) were applied. To our knowledge, this study represents the most extensive collection of whole-bone biomechanical properties of lower limb bones.     

Biochemical analysis of the bone of SHC rats with spontaneous hypercholesterolemia and renal dysfunction.

Spontaneously hypercholesterolemic (SHC) rats exhibit severe abnormalities in renal function and bone metabolism at old ages, in addition to hypercholesterolemia. SHC rats were also found to show endocrine abnormalities such as hyperthyroidism from young ages. In this study, biochemical and microdensitometric analyses were carried out using femurs to characterize further the abnormality in bone metabolism: whether biochemical markers of the bone may be affected by these abnormalities. At 6 weeks of age, the ashed weight and calcium content of the dried femurs were slightly lower in SHC rats than in age-matched Sprague-Dawley (SD) rats. None of the markers of microdensitometric analysis was changed. At 24 weeks of age, the ashed weight of dried femurs and the density of the marrow region of femurs were lower in the SHC rats. The results indicate that SHC rats exhibit severe abnormality in bone metabolism leading to biochemical changes in the bone at old ages whereas changes in bone markers were minimal at young ages before the onset of severe renal dysfunction.     

Variation of trabecular architecture in proximal femur of postmenopausal women

This investigation of microstructure in the human proximal femur probes the relationship between the parameters of the FRAX index of fracture risk and the parameters of bone microstructure. The specificity of fracture sites at the proximal femur raises the question of whether trabecular parameters are site-specific during post-menopause, before occurrence of fragility fracture. The donated proximal femurs of sixteen post-menopausal women in the sixth and seventh decades of life, free of metabolic pathologies and therapeutic interventions that could have altered the bone tissue, constituted the material of the study. We assessed bone mineral density of the proximal femurs by dual energy X-ray absorptiometry and then sectioned the femurs through the center of the femoral head and along the femoral neck axis. For each proximal femur, morphometry of trabeculae was conducted on the plane of the section divided into conventional regions and sub-regions consistent with the previously identified trabecular families that provide regions of relatively homogeneous microstructure. Mean trabecular width and percent bone area were calculated at such sites. Our findings indicate that each of mean trabecular width and percent bone area vary within each proximal femur independently from each other, with dependence on site. Both trabecular parameters show significant differences between pairs of sites. We speculate that a high FRAX index at the hip corresponds to a reduced percent bone area among sites that gives a more homogeneous and less site-specific quality to the proximal femur. This phenomenon may render the local tissue less able to carry out the expected mechanical function.