Bone Elasticity Research Articles

Microimplant Assisted Rapid Palatal Expansion: A Comprehensive Review

Maxillary transverse deficiency routinely requires expansion of the palate. In prepubertal patients, Rapid Maxillary Expansion (RME) is a reliable treatment modality. However, in skeletally mature patients due to progressively interdigitated mid palatal suture, decreased elasticity of bone and increased stiffness of the osseous articulations of the maxilla with the adjoining bones, palatal expansion becomes challenging. Patients are frequently suggested to opt for more invasive procedures, like the Surgically Assisted Rapid Palatal Expansion (SARPE). The quest for minimally invasive expansion appliances with pure orthopaedic movement led researchers to incorporate mini-implants with conventional RME. Microimplant Assisted Rapid Palatal Expansion (MARPE) maximises skeletal expansion and minimises dentoalveolar undesirable effects and obviates the need for orthognathic surgery. This comprehensive review aims to discuss MARPE as an effective, non surgical, minimally invasive treatment modality for skeletally mature patients with maxillary transverse insufficiency. Furthermore, various designs of MARPE with different placement sites, lengths, and numbers of miniscrews along with the latest technological advancements to improve diagnosis and treatment planning using CBCT and intraoral scan, as well as the use of Computer-Aided Design/Computer-Aided Manufacturing (CAD-CAM) technology to custom fabricate three dimensional (3D) miniscrew insertion surgical guide, 3D laser-printed metallic mini-implant to enhance implant placement accuracy and comfort were discussed along with the clinical significance and limitations of the MARPE. Maxillary Skeletal Expander (MSE) is a unique lineage of MARPE when combined with facemask results in distraction osteogenesis like movement of midface and forms a promising basis for non surgical orthopaedic treatment modality for skeletal class III mature patients. Bone-anchored maxillary expansion appliances provide better vertical control, especially beneficial for hyperdivergent skeletal pattern patients. MARPE significantly increases transverse widths of the nasal floor, nasopharyngeal volume and significantly lowers mean nasal airway resistance thereby facilitating nasal breathing. MARPE results in greater orthopaedic expansion and safety, with fewer undesirable effects and high success rates.

Bone elasticity and ultrasound velocity are affected by subtle changes in the organic matrix.

The mechanical competence of bone can be studied through the measurement of the components of its material elasticity, a property which can vary both in magnitude and in dependence upon orientation (anisotropy). While it is known that the elasticity is largely determined by the mineral constituents of the bone matrix, it is nonetheless clear that it must be also dependent upon the remaining constituents of bone material. In this work, the influence of organic components on the elasticity is explored by altering specific constituents of the bone matrix to varying degrees. This study addresses two questions: first, are the resulting changes in elasticity strongly or weakly dependent upon direction, and second, are they substantially dependent upon the nature and magnitude of the induced matrix alteration? To answer these questions, we performed different chemical manipulations of the bone matrix and measured the changes in elasticity and velocity using the technique of ultrasound critical angle reflectometry. Altering the properties of the organic matrix resulted in substantial and complex changes in the elasticity of bone. The observed changes were strongly dependent upon direction, could not be explained by changes in density alone, and varied strongly with the specific chemical treatment of the matrix. Immersion in urea selectively affected protein components of the organic matrix and resulted in reversible changes in velocity and elasticity, while removal of collagen caused anisotropic decreases and removal of all organic matter caused a collapse of all components of the elasticity. In conclusion, this study confirms that the organic matrix exerts a profound influence on the elasticity and indicates that the measurement of elastic properties at multiple directions is necessary in the assessment of bone mechanical competence.

Implant Placement Using Alveolar Ridge Split in Atrophic Maxillary Alveolar Bone

If the volume of the horizontal alveolar bone is insufficient during the implant procedure, it is difficult to establish a fixture of the required diameter without surgical procedures such as block bone graft, lateral bone graft, and ridge split. Among them, alveolar ridge split is known as an effective technique to increase the volume of the horizontal alveolar bone using maxillary bone elasticity. The theoretical background of this technique is to provide a basis for maintaining the implant with the expectation that new bone will form when the implant and bone graft material are operated, forming a space surrounded by the bone and periosteum. In two cases reported herein, there was no postoperative inflammatory reaction and normal healing was observed. Since then, the follow-up radiograph has shown good outcomes, and ongoing progress is being observed. Alveolar ridge split and bone graft are effective techniques for horizontal alveolar augmentation. In these cases, it was actually possible to form a stable alveolar ridge for implant placement through a successful procedure in the maxillary edentulous region.

Prolonged Hyperglycemia Reduces Elasticity of Type II Diabetic Rat Bone.

An increase in bone fracture risk has been reported in patients with diabetes. To evaluate an early effect of glucose intolerance on bone homeostasis, we have characterized bones from spontaneously diabetic torii (SDT) rats, an animal model of type 2 diabetes in comparison with Sprague Dawley (SD) rats as healthy control. Focusing on early effects of diabetes on bone elasticity, longitudinal wave velocities of animal bones were first determined by a micro-Brillouin scattering technique in a non-destructive way. Wave velocities in the cortical and cancellous bones in the tibias of the SDT and SD rats were compared. In a pre-diabetic stage at approximately 10weeks of age, there seems no significant difference in wave velocities in bones from age-matched SDT and SD rats. By contrast, after the onset of diabetes at approximately 20weeks of age, the mean velocities of bones from SDT rats were lower than those of SD rat. In addition, the X-ray CT showed that the bone amounts of SDT rats were smaller than those of SD rats in an early diabetic stage at 20weeks of age. The current study demonstrated that the wave velocity decreased in bones of SDT rats in the early stages of diabetes. While a decrease of bone strength in an early stage of diabetes can be partially explained from decreases in bone amount as well as bone elasticity, further studies will be needed in understanding a detailed mechanism of bone deterioration due to diabetes.

Synthesis of nanostructured biomaterials by high-pressure torsion: Effect of niobium content on microstructure and mechanical properties of Ti-Nb alloys

Titanium-niobium alloys with the bcc structure (β-Ti-Nb) are recently investigated for their potential use in biomedical applications; however, improvement of their mechanical properties (particularly hardness and elastic modulus) is still a challenge. In this study, nanostructured Ti-Nb alloys with different Nb contents were successfully synthesized by mechanical alloying of elemental powders via high-pressure torsion (HPT). The HPT process led to the homogenous mixture of the two elements and the formation of nanograined β phase. Examination of mechanical properties by nanoindentation and microhardness measurements revealed that all synthesized alloys exhibited high hardness and good plasticity; however, the best combination of low elastic modulus and high hardness was obtained for the sample with 25 at% Nb: E = 39 ± 11 GPa (close to the elasticity of human bone) and Hv = 3.7 ± 0.1 GPa (comparable to the hardest Ti-based biomaterials). The current results confirm the potential of HPT to synthesize nanograined Ti-Nb alloys for future biomedical applications.

Second harmonic generation characterization of collagen in whole bone.

Bone is a unique biological composite material made up of a highly structured collagen mesh matrix and mineral deposits. Although mineral provides stiffness, collagen's secondary organization provides a critical role in bone elasticity. Here, we performed polarimetric analysis of bone collagen fibers using second harmonic generation (SHG) imaging to evaluate lamella sheets and collagen fiber integrity in intact cranial bone. Our polarimetric data was fitted to a model accounting for diattenuation, polarization cross-talk, and birefringence. We compared our data to the fitted model and found no significant difference between our polarimetric observation and the representation of these scattering properties up to 70 µm deep. We also observed a loss of resolution as we imaged up to 70 µm deep into bone but a conservation of polarimetric response. Polarimetric SHG allows for the discrimination of collagen lamellar sheet structures in intact bone. Our work could allow for label-free identification of disease states and monitor the efficacy of therapies for bone disorders.

SIMULATION OF THE MECHANICAL STIMULATION EFFECT ON THE PEN JUNCTION BETWEEN BONE AND PELVIC BASED ON FINITE ELEMENT METHODS

Bone remodeling process influenced by cells osteoblast and osteoclast. The remodeling of cortical and trabecular influenced by mechanical stimuli. In this study, cortical and trabecular bones of 25 years old humans were observed, and the result was the cortical bone has the average Young’s modulo 17.9 MPa with the Poisson’s ratio of 0.4. Trabecular bone has the average Young’s modulo of 13 MPa and the Poisson’s ratio of 0.5. The metal orthopedic bone screw, which has used in this research simulation, was is a Titanium screw. The screw has Young’s modulo of 110 GPa and the Poisson’s ratio of 0.29. The results of the simulation of femoral bone elasticity limit with standing activity at the age of 25 were found in the left femur of 112.9416 MPa and the right femur of 115.5134 MPa. The limit of elasticity of the femur due to walking was found in the left femur of 115.2166 MPa with an accuracy of 94.11% and the right femur of 117.6692 MPa.

Effects of Virgin Olive Oil on Bone Health in Ovariectomized Rats.

Osteoporosis is a pressing concern facing public health, thus making research into the effects of nutrients on bone health particularly important. Evidence from preclinical studies using animal models and a limited number of studies in human suggests that olive oil (OO) is a protective agent for bone. The aim of this work is to study the effects of virgin olive oil (VOO) consumption by ovariectomized rats on bone health. A total of 48 6-month-old female Wistar rats weighing 320 ± 10 g (mean ± SD) were divided into the following groups: SHAM (n = 12), simulated intervention; OVX (n = 12), ovariectomized; OVX + 100 (n = 12), ovariectomized and treated with VOO (100 µL/day by oral gavage); and OVX + 200 (n = 12) ovariectomized and treated with VOO (200 µL/day by oral gavage), all over 3 months. Femoral (F) and lumbar (L) bone mineral density (FBMD and LBMD), microtomographic parameters, fractal dimension D2D and D3D, and biomechanical properties were studied. After 3 months of VOO treatment, although FBMD and LBMD were not affected, bone quality was improved, as the elasticity of bone and fractal dimension (complexity of bone) were more similar to healthy bone. Our results support the findings of previous research suggesting that dietary intake of olive oil may exert beneficial effect on some bone characteristics.

Abstract 29: An Experimental And Computational Analysis Of Mouse Femur Biomechanics Following The Deletion Of Menin In The Osteoblast Lineage

Purpose: Recent studies have established the critical role of menin in the development and maintenance of bone mass by regulating osteoblast, osteoclast and osteocyte function in vivo. In the present study, a combined approach of experimentation and simulation is pursued to provide prediction and comparison of elastic responses to physiological loading of bone in mice harboring a deletion of the Men1 gene in the osteoblast lineage. Methods: The Cre-LoxP recombination system was used; Prx1-Cre; Men1f/f represent mice in which the MEN1gene was inactivated in the mesenchymal stem cells (KO), and Men1f/f represent wild type (WT) controls. Male mice were sacrificed and analyzed at 9 months of age. Results: Major macroscopic geometrical changes were observed in the femora of KO mice, most notably, a significant decrease in length and changes in mid-metaphyseal cross-sectional area. Micro-CT imaging demonstrated marked reductions in trabecular bone volume, altered cortical thickness, and a decrease in trabecular number. Three-point bending tests were conducted to evaluate macroscopic elastic-plastic behavior demonstrating a 30% reduction in bone stiffness in menin-deficient mice. Atomic Force Microscopy was used to examine the elasticity of both cortical and trabecular bone in the longitudinal and transverse directions independently; KO mice demonstrated significant decreases in elasticity of both bone types. Micro-CT 3D solid model reconstructions were assessed via finite element analysis simulation. Bone local mineral density was used to obtain its local elastic modulus. A benchmark problem was then assessed on the reconstructed 3D models, and relevant metrics evaluated and compared. Results indicate that the flexural rigidity of the KO femurs is significantly lower than that of WT following the deletion of the Men1 gene in the osteoblast lineage. Conclusions: The experimental and computational analyses employed in this study may be applied for the phenotypic characterization of murine models in bone physiological studies. Menin plays a critical role in the development and maintenance of bone mass and may thus serve as a potential gain-of-function therapeutic target in bone development and regeneration.

INDIRECT SINUS LIFT

The indirect sinus lift is a procedure to lift the augment/regenerate alveolar bone in atrophied residual maxillary posterior alveolar crest . The posterior maxilla is always considered as difficult site for the placement of implant than the mandible due to the presence of various anatomical land mark such as maxillary sinus. The anatomical structure of maxillary sinus often makes every dental implant surgeons a challenge task in placement of endosteal implants in the chronic atrophic maxilla and difficulty in osseointegration and further functional and aesthetic implant supported prosthesis. Various techniques in sinus lifting procedure enables the additional anchorage and stability in implants placed support in maxillary segments in with atrophic ridges and pneumatic sinuses. Lack of sufficient bone height along maxillary sinus poses significant difficulty for placement of implants in edentulous maxillary jaw. Minimally invasive sinus augmentation is an effective solution for this problem. In 1960 Boyne introduced sinus lift through lateral access which was initially used as a pre-prosthetic procedure for removable complete dentures purpose. In 1980 Boyne and James used the bone created by sinus lift procedures to place implants. In pursuit of less invasive techniques , in 1994 Summer’s explained a technique which offers access to sinus floor through residual alveolar crest. Using the elasticity of bone, floor dilatation of sinus was performed to increase the length of implants .

Anomalous bone changes in ovariectomized type 2 diabetic rats: inappropriately low bone turnover with bone loss in an estrogen-deficient condition.

Estrogen deprivation accelerates bone resorption, leading to imbalance of bone remodeling and osteoporosis in postmenopausal women. In the elderly, type 2 diabetes mellitus (T2DM) frequently coexists as an independent factor of bone loss. However, little is known about the skeletal changes in a combined condition of estrogen deficiency and T2DM. Herein, we performed ovariectomy (OVX) in nonobese Goto-Kakizaki (GK) T2DM rats to examine changes associated with calcium and phosphate metabolism and bone microstructures and strength. As expected, wild-type (WT) rats subjected to ovariectomy (OVX-WT) had low trabecular bone volume and serum calcium with increased dynamic histomorphometric and serum bone markers, consistent with the high turnover state. T2DM in GK rats also led to low trabecular volume and serum calcium. However, the dynamic histomorphometric markers of bone remodeling were unaffected in these GK rats, indicating the distinct mechanism of T2DM-induced bone loss. Interestingly, OVX-GK rats were found to have anomalous and unique changes in bone turnover-related parameters, i.e., decreased osteoblast and osteoclast surfaces with lower COOH-terminal telopeptide of type I collagen levels compared with OVX-WT rats. Furthermore, the levels of calciotropic hormones, i.e., parathyroid hormone and 1,25(OH)2D3, were significantly decreased in OVX-GK rats. Although the OVX-induced bone loss did not further worsen in GK rats, a three-point bending test indicated that OVX-GK bones exhibited a decrease in bone elasticity. In conclusion, T2DM and estrogen deficiency both led to microstructural bone loss, the appearance of which did not differ from each factor alone. Nevertheless, the combination worsened the integrity and suppressed the turnover, which might eventually result in adynamic bone disease.

Anisotropic elastic properties of human femoral cortical bone and relationships with composition and microstructure in elderly

The strong dependence between cortical bone elasticity at the millimetre-scale (mesoscale) and cortical porosity has been evidenced by previous studies. However, bone is an anisotropic composite material made by mineral, proteins and water assembled in a hierarchical structure. Whether the variations of structural and compositional properties of bone affect the different elastic coefficients at the mesoscale is not clear. Aiming to understand the relationships between bone elastic properties and compositions and microstructure, we applied state-of-the-art experimental modalities to assess these aspects of bone characteristics. All elastic coefficients (stiffness tensor of the transverse isotropic bone material), structure of the vascular pore network, collagen and mineral properties were measured in 52 specimens from the femoral diaphysis of 26 elderly donors. Statistical analyses and micromechanical modeling showed that vascular pore volume fraction and the degree of mineralization of bone are the most important determinants of cortical bone anisotropic mesoscopic elasticity. Though significant correlations were observed between collagen properties and elasticity, their effects in bone mesoscopic elasticity were minor in our data. This work also provides a unique set of data exhibiting a range of variations of compositional and microstructural cortical bone properties in the elderly and gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone. Statement of SignificanceThis study reports the relationships between microstructure, composition and the mesoscale anisotropic elastic properties of human femoral cortical bone in elderly. For the first time, we provide data covering the complete anisotropic elastic tensor, the microstructure of cortical vascular porosity, mineral and collagen characteristics obtained from the same or adjacent samples in each donor. The results revealed that cortical vascular porosity and degree of mineralization of bone are the most important determinants of bone anisotropic stiffness at the mesoscale. The presented data gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone.

Homogenization of cortical bone reveals that the organization and shape of pores marginally affect elasticity.

With ageing and various diseases, the vascular pore volume fraction (porosity) in cortical bone increases, and the morphology of the pore network is altered. Cortical bone elasticity is known to decrease with increasing porosity, but the effect of the microstructure is largely unknown, while it has been thoroughly studied for trabecular bone. Also, popular micromechanical models have disregarded several micro-architectural features, idealizing pores as cylinders aligned with the axis of the diaphysis. The aim of this paper is to quantify the relative effects on cortical bone anisotropic elasticity of porosity and other descriptors of the pore network micro-architecture associated with pore number, size and shape. The five stiffness constants of bone assumed to be a transversely isotropic material were measured with resonant ultrasound spectroscopy in 55 specimens from the femoral diaphysis of 29 donors. The pore network, imaged with synchrotron radiation X-ray micro-computed tomography, was used to derive the pore descriptors and to build a homogenization model using the fast Fourier transform (FFT) method. The model was calibrated using experimental elasticity. A detailed analysis of the computed effective elasticity revealed in particular that porosity explains most of the variations of the five stiffness constants and that the effects of other micro-architectural features are small compared to usual experimental errors. We also have evidence that modelling the pore network as an ensemble of cylinders yields biased elasticity values compared to predictions based on the real micro-architecture. The FFT homogenization method is shown to be particularly efficient to model cortical bone.

Material anisotropy and elasticity of cortical and trabecular bone in the adult mouse femur via AFM indentation

This paper investigates the elastic properties of bone tissue in the adult mouse femur through Atomic Force Microscopy (AFM) indentation with the goal of understanding its microstructure and underlying mechanics at the nano length scale. Both trabecular and cortical bone types are studied. In particular, we examined the elasticity of cortical bone and individual trabeculae in the longitudinal and transverse directions of the samples. For cortical bone, the elastic modulus in the longitudinal direction was found to be 10–15% higher than that in the transverse direction; for trabecular bone, this difference was 42%. For the trabeculae, this value was found to be in a lower range (0.92 ± 0.22 GPa). As per the transverse elastic modulus, an average of 1.58 ± 0.36 GPa was measured for cortical bone, and 0.55 ± 0.21 GPa for trabecular bone. The anisotropy ratio was within the range of 1.2–1.5 for cortical bone and 1.7–2 for trabecular bone. While the elastic modulus of cortical bone varied along the length of the femur with up to 30% variation, no significant differences were observed within each transverse section. The effect of indentation frequency (1–500 Hz) on the longitudinal elastic moduli was also investigated for cortical and trabecular bone, with results showing a correlation between indentation frequency and elastic modulus.Statement of significance: This study examines the adult mouse femur with a twofold aim: to investigate the anisotropy and inhomogeneity of cortical and trabecular bone tissues and to elucidate their elastic behavior at the nanometer length scale. The elastic moduli of cortical bone and individual trabecula are measured in the longitudinal and transverse cross-sections via AFM indentation at selected locations and in specific directions of the adult mouse femur. The results provide insights into the relationship between mechanical properties and structural morphology of cortical and trabecular bone tissue.

Conservative management of root-fractured primary incisor – case report

Most frequent trauma to primary dentitions are injures to the supporting tissue i.e. luxations, but root fractures are relatively uncommon. The difference in the trauma pattern favoring luxation rather than fracture has been found to be typical for the primary dentition, since the elasticity of the alveolar bone surrounding the primary teeth is high and primary tooth held in alveolar socket is less strong. Incidence of foot fractures increases at the age of 3-4 years where physiologic root resorption has begun, thereweakening the root. Traumatic injuries to the primary dentition present special problems and the management is often different as compared with the permanent dentition. Because of potential sequelae of trauma to primary teeth, a treatment method that minimizes any additional risks of further damage to the permanent successors should be selected. The report presents a case of 3.5 year-old boy after traumatic injury – extrusion of tooth 51, which required surgical treatment, and apical third horizontal root fracture of tooth 61 treated conservatively. Written consent from subject’s parents/subject’s legal guardians was obtained. Root-fractured primary tooth has been followed clinically and radiographically for 3.5 year, till advanced root resorption. Presented case and cases described in cited literature demonstrate that conservative treatment of root-fractured primary teeth is a favorable method of the treatment that allows the teeth to function naturally until the term of physiological resorption and exfoliation.

Strain rate dependency of bovine trabecular bone under impact loading at sideways fall velocity

There is currently a knowledge gap in scientific literature concerning the strain rate dependent properties of trabecular bone at intermediate strain rates. Meanwhile, strain rates between 10 and 200/s have been observed in previous dynamic finite element models of the proximal femur loaded at realistic sideways fall speeds. This study aimed to quantify the effect of strain rate (ε̇) on modulus of elasticity (E), ultimate stress (σu), failure energy (Uf), and minimum stress (σm) of trabecular bone in order to improve the biofidelity of material properties used in dynamic simulations of sideways fall loading on the hip. Cylindrical cores of trabecular bone (D = 8 mm, Lgauge = 16 mm, n = 34) from bovine proximal tibiae and distal femurs were scanned in µCT (10 µm), quantifying apparent density (ρapp) and degree of anisotropy (DA), and subsequently impacted within a miniature drop tower. Force of impact was measured using a piezoelectric load cell (400 kHz), while displacement during compression was measured from high speed video (50,000 frames/s). Four groups, with similar density distributions, were loaded at different impact velocities (0.84, 1.33, 1.75, and 2.16 m/s) with constant kinetic energy (0.4 J) by adjusting the impact mass. The mean strain rates of each group were significantly different (p < 0.05) except for the two fastest impact speeds (p = 0.09). Non-linear regression models correlated strain rate, DA, and ρapp with ultimate stress (R2 = 0.76), elastic modulus (R2 = 0.63), failure energy (R2 = 0.38), and minimum stress (R2 = 0.57). These results indicate that previous estimates of σu could be under predicting the mechanical properties at strain rates above 10/s.

Estimation of the effective bone-elasticity tensor based on μ CT imaging by a stochastic model. A multi-method validation

Abstract In previous work, we proposed a stochastic model to describe the elasticity of bone matrix (so-called ultrastructure, US) based on basic statistical information on the tissue mineral density ( TMD ). This information was obtained by analyzing high-resolution images of a human femoral neck realized by means of synchrotron radiation micro-computed tomography ( SR − μ CT ). In this paper, we extend this study by focusing at the upper scale where cortical bone is described as a two-phase mixture made up of water-filled Haversian pores (HP) embedded in the surrounding solid US. The goal of this paper is to develop a stochastic model of cortical bone elasticity accounting for the effect of uncertainty affecting both phases, the US via the TMD and the HP. Experimental information was assumed to be given in terms of mean values and dispersions of the average TMD (denoted TMD ¯ ) and HP at the millimeter scale. To this aim, SR − μ CT images were used to extract several representative volume elements (RVEs) spanning the whole cortical tissue which, in turn, were analyzed to obtain the required statistical information on TMD ¯ and HP. This information has been used for constructing a stochastic multiscale model of cortical bone based on the Maximum Entropy (denoted MaxEnt) principle. This stochastic multiscale model is used in the estimation of the effective elastic properties of cortical bone (CB-S μ M) based on continuum micromechanics ( μM). In parallel, a deterministic nominal multiscale model of cortical bone (CB-NμM) was developed by using as input data the mean values of TMD ¯ and HP. The elastic moduli estimated with CB-NμM has been compared with the average value of the same counterpart obtained with the CB-SμM model. The two estimates differ for less than 1 % , proving the robustness of the CB-NμM model to uncertainties. Moreover, the accuracy of the SμM stochastic model has been tested. Estimations of the cortical bone elasticity of each RVE with the μ M (cylindrical HP and homogeneous US), has been compared with other estimation obtained through others homogenization techniques: finite elements (FEM) and fast Fourier transform (FFT), both able to account for the real morphology of Havesian porosity and the heterogeneity of the ultrastructure. Results show that (1) the transverse isotropic (TI) elastic μM model correctly approximates the FEM and FFT estimates (∼98% TI); (2) the μM model accurately estimates the axial modulus ( Y 3 ) in longitudinal direction and the lateral contraction ratio ν 31 .

Numerical investigation of the effect of bone cement porosity on osteoporotic femoral augmentation.

Femoroplasty is the injection of bone cement into the proximal femur, enhances the bone load capacity, and is typically applied to osteoporotic femora. To minimize the required injected volume of bone cement and maximize the load capacity enhancement, an optimization problem must be solved, where the modulus of elasticity of the augmented bone is a key element. This paper, through the numerical investigation of a fall on the greater trochanter of an osteoporotic femur, compares different ways to calculate this modulus and introduces an approach, based on the concept of bone cement porosity, which provides results statistically similar to those obtained with other considerations. Based on this approach, the present paper quantifies the correlation between degree of osteoporosis and optimum volume of bone cement. It concludes with an exhaustive search that reveals the effect of the bone cement porosity on the optimum volume of PMMA, for various combinations of the frontal and transverse angles of the fall on the greater trochanter.

Effects of static magnetic fields on bone microstructure and mechanical properties in mice

ABSTRACTAll the living organisms originate, evolve and live under geomagnetic field (GMF, 20–70 µT). With rapid development in science and technology, exposure to various static magnetic fields (SMFs) from natural and man-made sources remains a public environmental topic in consideration of its probable health risk for humans. Many animal studies related to health effect have demonstrated that SMF could improve bone formation and enhance bone healing. Moreover, most of the studies focused on local SMF generated by rod-type magnet. It was difficult to come to a conclusion that how SMF affected bone metabolism in mice. The present study employed hypomagnetic field (HyMF, 500 nT), and moderate SMF (MMF, 0.2 T) to systematically investigate the effects of SMF with continuous exposure on microstructure and mechanical properties of bone. Our results clearly indicated that 4-week MMF exposure did not affect bone biomechanical properties or bone microarchitecture, while HyMF significantly inhibited the growth of mice and elasticity of bone. Furthermore, mineral elements might mediate the biological effect of SMF.

Bone Strength in Growing Rats Treated with Fluoride: a Multi-dose Histomorphometric, Biomechanical and Densitometric Study.

Bone deformation and fragility are common signs of skeletal fluorosis. Disorganisation of bone tissue and presence of inflammatory foci were observed after fluoride (F-) administration. Most information about F- effects on bone has been obtained in adult individuals. However, in fluorosis areas, children are a population very exposed to F- and prone to develop not only dental but also skeletal fluoroses. The aim of this work was to evaluate the bone parameters responsible for the effect of different doses of F- on fracture load of the trabecular and cortical bones using multivariate analysis in growing rats. Twenty-four 21-day-old Sprague-Dawley rats were divided into four groups: F0, F20, F40 and F80, which received orally 0, 20, 40 or 80μmol F-/100g bw/day, respectively, for 30days. After treatment, tibiae were used for measuring bone histomorphometric and connectivity parameters, bone mineral density (BMD) and bone cortical parameters. The femurs were used for biomechanical tests and bone F- content. Trabecular bone volume was significantly decreased by F-. Consistently, we observed a significant decrease in fracture load and Young's modulus (YM) of the trabecular bone in F--treated groups. However, cortical bone parameters were not significantly affected by F-. Moreover, there were no significant differences in cortical nor trabecular BMD. Multivariate analysis revealed a significant correlation between the trabecular fracture load and YM but not with bone volume or BMD. It is concluded that when F- is administered as a single daily dose, it produces significant decrease in trabecular bone strength by changing the elasticity of the trabecular bone.