Revealing the Proximity of Concrete Specimens to Their Critical Damage Level by Exploring the Cumulative Counts of the Acoustic Emissions in the Natural Time Domain.

This study aims to explore the possibility of detecting indices that could potentially provide warning about the proximity of internal damage to critical levels, beyond which catastrophic fracture is impending. In this direction, advantage was taken of the Cumulative Counts that were recorded during the mechanical loading of specimens made of either plain or fiber-reinforced concrete. The parameter adopted for the analysis was the average rate of change in the Cumulative Counts. Τhe evolution of the specific parameter was considered in the Natural Time Domain, rather than in the conventional time domain. Experimental data from already published three-point bending protocols were used. It was revealed that the specific parameter attains, systematically, a limiting value equal to unity exactly at the instant at which the load reaches its maximum value, which is not identical to the load recorded at the instant of fracture. Similar observations were made for a complementary protocol with uniaxially compressed mortar specimens. The conclusions drawn were supported by the b-values analysis of the respective acoustic data, again in terms of Natural Time. It is, thus, indicated that the evolution of the average rate of change in the Cumulative Counts in the Natural Time Domain provides an index about the proximity of the applied load to a value beyond which the specimen enters into the critical state of impending fracture.

Electrochemical Impedance as an Assessment Tool for the Investigation of the Physical and Mechanical Properties of Graphene-Based Cementitious Nanocomposites.

This investigation explores the potential of electrochemical impedance spectroscopy (EIS) in evaluating graphene-based cementitious nanocomposites, focusing on their physical and structural properties, i.e., electrical resistivity, porosity, and fracture toughness. EIS was employed to study cement mixtures with varying graphene nanoplatelet (xGnP) concentrations (0.05-0.40% per dry cement weight), whereas flexural tests assessed fracture toughness and porosimetry analyses investigated the structural characteristics. The research demonstrated that the electrical resistivity initially decreased with increasing xGnP content, leveling off at higher concentrations. The inclusion of xGnPs correlated with an increase in the total porosity of the cement mixtures, which was indicated by both EIS and porosimetry measurements. Finally, a linear correlation emerged between fracture toughness and electrical resistivity, contributing also to underscore the use of EIS as a potent non-destructive tool for evaluating the physical and mechanical properties of conductive nano-reinforced cementitious nanocomposites.

Spatio-Temporal Distribution of the Sources of Acoustic Events in Notched Fiber-Reinforced Concrete Beams under Three-Point Bending.

The acoustic activity, generated in notched, beam-shaped concrete specimens, loaded under three-point bending, is studied in terms of the position of the sources of acoustic events, and the frequency of their generation. Both plain specimens (without any internal reinforcement) and specimens reinforced with various types of short fibers were tested. The target of the study is to investigate the existence of indices that could be considered as pre-failure indicators of the upcoming fracture. In addition, an attempt is undertaken to classify the damage mechanisms activated to tensile or shear nature. Considering comparatively the spatio-temporal evolution of the position of the acoustic sources and the respective temporal evolution of the frequency of generation of acoustic events, it was concluded that for relatively low load levels the acoustic sources are rather randomly distributed all over the volume of the specimens. As the load increases toward its maximum value, the acoustic sources tend to accumulate in the immediate vicinity of the crown of the notch and the average distance between them approaches a minimum value. When this minimum value is attained, the load is maximized and the generation frequency of the acoustic events increases rapidly. The simultaneous fulfillment of these three conditions is observed a few seconds before the onset of propagation of the catastrophic macrocrack for all classes of specimens tested, providing a kind of warning signal about the upcoming fracture. Moreover, the classification of the damage mechanisms to tensile and shear ones revealed a crucial difference between the plain and the reinforced specimens after the maximization of the load applied. Indeed, while for the plain specimens, the prevailing damage mechanism is tensile microcracking, for the reinforced specimens a balance between tensile and shear damage mechanisms is observed after the load applied has attained its peak and starts decreasing.

Residual strains in ascending thoracic aortic aneurysms: The effect of valve type, layer, and circumferential quadrant.

The stress distribution in ascending thoracic aortic aneurysms is determined by the mechanical properties, geometry, loading conditions, and zero-stress state of the aneurysmal aorta. Our objective was to fully characterize the zero-stress state of the aneurysmal aorta in twelve tricuspid aortic valve patients and eight (age/aortic diameter-matched) bicuspid aortic valve patients, for which little data are available. Opening angles and residual stretches were measured for the intact wall and individual layers according to quadrant and were similar in the two patient groups. The intact-wall and medial opening angles were comparable; their circumferential but not their axial ones peaked in the left lateral quadrant, with non-significant regional differences in the other layers. The intima's circumferential opening angles were the highest of all layers (∼300 deg) and the adventitia's the lowest (∼165 deg), with lesser layer differences in the axial opening angles. Upon radially cutting aortic rings, the released circumferential residual stretches were tensile (of large magnitude) externally and compressive (of small magnitude) internally, unlike the axial residual stretches released when cutting intact-wall strips, whose magnitude was small externally and large internally. Nevertheless, large circumferential compressive residual stretches were released in the adventitia upon layer dissection, counteracting the large circumferential tensile stretches of the intact wall externally. Moreover, the large axial tensile residual stretches of the intima counteracted the large axial compressive stretches of the intact wall internally. These layer-specific residual stretches may moderate the in-vivo stress gradients across wall thickness, serving as a protective mechanism against aortic dissection or rupture.

The Effect of Ceratonia siliqua Supplement on Bone Mineral Density in Ovariectomy-induced Osteoporosis in Rats.

AIM: This study aimed to investigate the effect of Ceratonia siliqua on bone mineral density (BMD) as a non-pharmaceutical alternative treatment for postmenopausal osteoporosis. MATERIALS AND METHODS: Thirty mature female Wistar rats were randomly separated into three groups of 10: Control, ovariectomized (OVX), and ovariectomized-plus-C. siliqua (OVX+CS). Total and proximal BMD were measured by dual-energy X-ray absorptiometry (DEXA) in all groups before ovariectomy, and at 3 and 6 months postoperatively. At the end of the study, the femurs were subjected to a three-point bending test. RESULTS: DEXA revealed no statistically significant difference in absolute values or percentage changes for total tibial BMD between OVX+CS and OVX groups throughout the study. In the proximal tibia, both absolute values and BMD percentage changes from baseline were higher in the OVX+CS group compared to the OVX group after 3 and 6 months of C. siliqua administration. Three-point bending test revealed a significantly higher thickness index in the OVX+CS group compared to the OVX group and a higher cross-sectional area index compared to the control group. CONCLUSION: Long-term administration of C. siliqua may be considered a non-pharmaceutical alternative treatment for postmenopausal osteoporosis. Further research is required to properly investigate the effects, and suitable treatment dose and schedule.

Effects of Incretin Pathway Elements on Bone Properties.

Introduction The effects of incretin-based drugs, such as receptor agonists of glucagon-like peptide-1 and inhibitors of dipeptidyl peptidase-4, on bone metabolism are not completely clear yet. The aim of this study is to compare the effects of glucagon-like peptide-1 and inhibitors of dipeptidyl peptidase-4 on the bone to see how different elements of the incretin pathway affect bone quality in terms of biomechanical properties, bone turnover, and mineral properties. Materials and methods Forty 10-week-old Wistar rats were divided into four groups: a control group, a control diabetic group, a diabetic group treated with sitagliptin, and a diabetic group treated with exenatide. Type 2 diabetes was simulated by dietary manipulation in addition to low-dose streptozotocin, and then two different incretin-based drugs were administered. The rats were sacrificed after five weeks of therapeutic treatment. Their serum was analyzed with the enzyme-linked immunosorbent assay (ELISA) method for basic bone turnover markers, and their right femur was subjected to a three-point bending test. Finally, Hematoxylin & Eosin staining, in addition to Raman spectroscopy, were employed to access the collagen and mineral properties of the bone. Results Both incretin-based drugs reduced osteoclast function; however, they were not able to restore osteoblastic function to normal. The net effect on bone strength was surprising: bone elasticity was restored by the antidiabetic treatment, but bone strength deteriorated. Exenatide had a slightly more pronounced effect, which, although not significant, points to the direction that dipeptidyl peptidase-4 (DPP4) may be a linking factor between reduced osteoclastic function and reduced bone formation, as suggested by the literature. Conclusion DPP4 receptors seem to be one of the links between reduced osteoclast function and reduced bone remodeling, so DPP4 inhibition can be more detrimental to the bone than glucagon-like peptide-1 (GLP-1) receptor agonists.

Piezoresistive Properties of Natural Hydraulic Lime Binary Pastes with Incorporated Carbon-Based Nanomaterials under Cyclic Compressive Loadings.

Natural Hydraulic Limes (NHL) are extensively used for the restoration of Monuments of Cultural Heritage, often combined with pozzolanic materials, such as natural pozzolans and metakaolin etc. In the present study, five (5) different cases of binary lime-based pastes composed of a specific type of NHL (NHL5) and metakaolin as pozzolanic addition were examined, that were reinforced with carbon nanostructures, namely graphene and carbon nanotubes. For the first time in restoration mortars, the incorporation of carbon nanostructures was investigated, aiming to produce materials with adequate piezoresistive response, so that they have the potential to be exploited for in situ structural health monitoring. The compressive strength, flexural strength, electrical resistance and piezoresistive response of the composite pastes was examined. The results showed that all modified carbon nanostructures lead to a significant reduction in electrical resistance. The pastes reinforced with 2D nanostructures (graphene family) displayed up to 30% increase in compressive strength and the pastes reinforced with 1D nanostructures (carbon nanotubes) displayed enhanced flexural strength (up to 100% increase). Piezoresistivity was attained for almost all investigated pastes, nevertheless the graphene oxide (GO) was considered as optimal reinforcement as the sensing ability of such pastes was found to be almost proportional to the applied compressive load level.

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants.

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars' electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively.

Chios Mastic Gum Consumption Has a Protective Effect on Ovariectomy-Induced Bone Loss in Rats.

The purpose of this study was to examine the potential effect of Chios Mastic Gum (CMG) consumption on bone mineral density (BMD) and strength of ovariectomized rats. CMG is a known resin used from ancient times for its beneficial biological properties. Thirty mature female Wistar rats were randomized into three equal groups: sham-operated (control), ovariectomized (OVX), and ovariectomized and administered CMG per os (OVX+CMG). BMD of the total tibia, proximal tibia, and the 6th lumbar vertebra were measured at baseline and at 3 and 6 months post ovariectomy. Bone strength was assessed with three-point-bending (3pb) of the right femur. At 3 and 6 months, BMD values of the OVX+CMG group were significantly higher for the anatomical cites evaluated than those of the OVX group. Femoral thickness assessed via 3pb had intermediate values in the treated group compared to the other groups. Cytology of vaginal smears and uterine weight of the OVX+CMG group were consistent with estrogen depletion. Gastrocnemius muscle and intraperitoneal fat ratios to body weight (BW) of the OVX+CMG group did not significantly differ from the control group. Daily consumption CMG had a protective effect on BMD of the total and proximal tibia and the 6th lumbar vertebra of the rats, without causing undesirable effects on the vaginal epithelium and uterus. The 3pb results also demonstrated a favorable effect on the thickness of rat femurs. In addition, CMG was beneficial for both the muscular system and the intraperitoneal fat/BW ratio of the rats.

Layer-Specific Residual Deformations and Their Variation Along the Human Aorta.

This study described the regional distribution of layer-specific residual deformations in fifteen human aortas collected during autopsy. Circumferentially and axially cut strips of standardized dimensions from the anterior quadrant of nine consecutive aortic levels were photographed to obtain the zero-stress state for the intact wall. The strips were then dissected into layers that were also photographed to obtain their zero-stress state. Changes in layer-specific opening angle, residual stretches, and thickness at each aortic level and direction were determined via image analysis. The circumferential and axial opening angles of the intima were ∼240 deg and ∼30 deg, respectively, throughout the aorta; those of the adventitia were ∼150 deg and -20 deg to 70 deg. The opening angles of the intact wall and media were similar in either direction. The circumferential residual stretches of the intima and the axial residual stretches of the media showed high values in the aortic arch, decreasing in the descending thoracic aorta and increasing toward the iliac artery bifurcation, while the axial residual stretches of the adventitia increased distally. The remaining residual stretches did not vary significantly with aortic level, suggesting an intimal role in determining circumferential, as well as medial and adventitial roles in determining axial residual stretches. We conclude that the tensile residual stretches released in the intima and media upon separation, and the compressive residual stretches released in the adventitia may moderate the inverse transmural stress gradients under physiologic loads, resulting from the >180 deg circumferential opening angle of the intact wall.

The effect of table olive wastewater extract administration on the adult ovariectomised rat model of osteoporosis.

Recent efforts for alternative non-pharmaceutical treatments for postmenopausal osteoporosis are focused on nutritional measures. The aim of this study was to investigate the effect of table olive wastewater extract (OE) administration on bone mineral density (BMD) and biomechanical strength in ovariectomised rats. Thirty mature 9-month-old female Wistar rats were separated into three groups of ten: Control, Ovariectomised (OVX) and OVX + OE. BMD was measured before ovariectomy, 3 and 6 months afterwards. At the end of the study, blood, both femurs and tibias, internal organs and abdominal fat were collected. After 3 months, the percentage changes from baseline of the total and proximal tibial BMD of the OVX + OE group were both higher compared with the OVX group (P < 0·005). Similar results were found after 6 months, when the percentage changes from baseline of the total and proximal tibial BMD of the OVX + OE group were both higher compared with the OVX group (P < 0·005). Biomechanical testing of the femurs did not reveal any statistically significant difference between the groups. Body weights throughout the study, organs' and abdominal fat ratios to final body weight and blood results (alanine aminotransferase (ALT), gamma-glutamyltransferase (γ-GT), total cholesterol, HDL-cholesterol, LDL-cholesterol, Ca and P) were within normal limits and did not show any significant difference between the treated and untreated groups. As a conclusion, the administration of OE for 6 months protected tibial BMD loss in comparison with the untreated OVX group without causing adverse effects.

Variation of Axial Residual Strains Along the Course and Circumference of Human Aorta Considering Age and Gender.

Our understanding of aortic biomechanics is customarily limited by lack of information on the axial residual stretches of the vessel in both humans and experimental animals that would facilitate the identification of its actual zero-stress state. The aim of this study was thus to acquire hitherto unreported quantitative knowledge of axial opening angle and residual stretches in different segments and quadrants of the human aorta according to age and gender. Twenty-three aortas were harvested during autopsy from the aortic root to the iliac bifurcation and were divided into ≥12 segments and 4 quadrants. Morphometric measurements were taken in the excised/curled configuration of rectangular strips considered to be under zero-stress using image-analysis software to study the axial/circumferential variation of axial opening angle, internal/external residual stretch, and thickness of the aortic wall. The measured data demonstrated: (1) an axial opening angle peak at the arch branches, decreasing toward the ascending and to a near-constant value in the descending thoracic aorta, and increasing in the abdominal aorta; (2) the variation of residual stretches resembled that of opening angle, but axial differences in external residual stretch were more prominent; (3) wall thickness showed a progressive diminution along the vessel; (4) the highest opening angle/residual stretches were found in the inner quadrant and the lowest in the outer quadrant; (5) the anterior was the thinnest quadrant throughout the aorta; (6) age caused thickening but greatly reduced axial opening angle/residual stretches, without differences between males and females.

Design of Improved Intertrochanteric Fracture Treatment (DRIFT) Study: Protocol for Biomechanical Testing and Finite Element Analysis of Stable and Unstable Intertrochanteric Fractures Treated With Intramedullary Nailing or Dynamic Compression Screw.

BACKGROUND: Intertrochanteric hip fractures rank in the top 10 of all impairments worldwide in terms of loss in disability-adjusted years for people aged older than 60 years. The type of surgery is usually carried out with dynamic hip screw (DHS) devices or cephalomedullary nails (CMN). Cut-out of the hip screw is considered the most frequent mechanical failure for all implants with an estimated incidence ranging from 2% to 16.5%; this entails both enhancing our understanding of the prognostic factors of cut-out and improving all aspects of intertrochanteric fracture treatment. OBJECTIVE: The Design of Improved Intertrochanteric Fracture Treatment (DRIFT) study's main objective is to provide intertrochanteric fracture treatment expertise, requirements and specifications, clinical relevance, and validation to improve treatment outcomes by developing a universal algorithm for designing patient- and fracture-oriented treatment. The hypothesis to be tested is that a more valgus reduction angle and implants of higher angles will lead to a more favorable biomechanical environment for fracture healing-that is, higher compressive loads at the fracture site with lower shear loads at the hip screw femoral head interface. A new implant with enhanced biomechanical and technical characteristics will be designed and fabricated; in addition, an integrated design and optimization platform based on computer-aided design tools and topology optimization modules will be developed. METHODS: To test this hypothesis, a biomechanical study comprising experimental loading of synthetic femora (Sawbones Inc) and finite element analysis (FEA) will be conducted. Detailed FEA of existing implants (DHS and CMN) implemented in different clinical cases under walking conditions will be performed to derive the stress and strain fields developed at the implant-bone system and identify critical scenarios that could lead to failure of therapy. These models would be validated against instrumented mechanical tests using strain gages and a digital image correlation process. RESULTS: After testing, geometric drawbacks of existing implants will be fully recognized, and geometric characteristics will be correlated with critical failure scenarios. The last step would be the numeric design, computer-aided design (using FEA codes and design packages), and optimization of the new proposed implant with regard to improved biomechanical surgical technique and enhanced mechanical performance that will reduce the possibility for critical failure scenarios. CONCLUSIONS: The optimization of the biomechanical behavior of the fracture-osteosynthesis model by the application of the ideal reduction angle and implant is expected to have a positive effect to the rate of mechanical failure and, subsequently, the healing rates, morbidity, and mortality in this fragile patient group. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/12845.

Protective effect of Glycyrrhiza glabra roots extract on bone mineral density of ovariectomized rats.

OBJECTIVE: The aim of this study was to evaluate the potential effect of the methanolic extract of plant Glycyrrhiza glabra roots on bone mineral density and femoral bone strength of ovariectomized rats. METHODS: Thirty 10-month-old Wistar rats were randomly separated into three groups of ten, Control, Ovariectomy and Ovariectomy-plus-Glycyrrhiza in their drinking water. Total and proximal tibial bone mineral density was measured in all groups before ovariectomy (baseline) and after 3 and 6 months post ovariectomy. Three-point-bending of the femurs and uterine weight and histology were examined at the end of the study. RESULTS: No significant difference was noted in bone density percentage change of total tibia from baseline to 3 months between Control and Ovariectomy-plus-Glycyrrhiza groups (+5.31% ± 4.75 and +3.30% ± 6.31 respectively, P = non significant), and of proximal tibia accordingly (+5.58% ± 6.92 and +2.61% ± 13.62, P = non significant) demonstrating a strong osteoprotective effect. There was notable difference in percentage change of total tibia from baseline to 6 months between groups Ovariectomy and Ovariectomy-plus-Glycyrrhiza (-13.03% ± 5.11 and -0.84% ± 7.63 respectively, P < 0.005), and of proximal tibia accordingly (-27.9% ± 3.69 and -0.81% ± 14.85 respectively, P < 0.001), confirming the protective effect of Glycyrrhiza glabra extract in preserving bone density of the Ovariectomy-plus-Glycyrrhiza group. Three-point-bending did not reveal any statistically significant difference between Ovariectomy and Ovariectomy-plus-Glycyrrhiza groups. Uterine weights of the Ovariectomy-plus-Glycyrrhiza group ranged between the other two groups with no statistically significant difference to each. CONCLUSIONS: Glycyrrhiza glabra root extract notably protected tibial bone mineral density loss in Ovariectomy-plus-Glycyrrhiza rats in comparison with ovariectomized rats, but did not improve biomechanical strength.

Chios mastic gum decreases renin levels and ameliorates vascular remodeling in renovascular hypertensive rats.

Chios mastic gum (CMG) exerts robust anti-inflammatory and antioxidant properties and it affects pathways that are implicated in the pathophysiology of endothelial and vascular inflammation. Aim of this study was to test the hypothesis that CMG administration lowers blood pressure (BP) and improves hypertension-induced target organ damage. 2-kidney, 1-clip (2K1C) hypertensive rats were treated with CMG (40 mg/kg body weight/day) for 2-weeks after the establishment of hypertension. Acute CMG administration lowered systolic, diastolic and mean arterial BP, while these hemodynamic effects were sustained throughout the 2-week administration period. CMG group also exhibited alleviated target organ damage as proposed by amelioration of biomechanical properties of the aorta -including cross-sectional area (CSA), aortic wall stiffness and thickness-, reversal of myocardial small vessel hypertrophy and maintenance of serum albumin levels. The anti-hypertensive effects of CMG are likely to be mediated by the decrease in renin serum levels. Regression analysis indicated that the effect of CMG on organ damage was BP-lowering dependent and was not associated with direct effects of renin or with its anti-inflammatory properties. We suggest a BP lowering effect of CMG via down-regulation of renin excretion associated with attenuation of target organ damage and inflammatory status. These observations provide profound evidence for the beneficial role of CMG in hypertension, which could possibly translate to further clinical research.

Regional and age-dependent residual strains, curvature, and dimensions of the human ureter.

The ureters are retroperitoneal structures controlling urine transport from the kidneys to the bladder. Because of the relative scarcity of data on the biomechanical properties of human ureter and the established importance of knowing these properties for understanding its physiology, we initiated biomechanical studies in cadaveric tissue. Herein, we report definite zero-stress/no-load geometrical characterization at 15 regions along the ureter of human cadavers aged 23-82 years, estimating the opening angle, circumferential residual strains, axial curvature, and dimensional parameters. Opening angle decreased along the proximal 25% of ureter, increased and reached a maximum near the mid-ureter, and then gradually decreased toward the vesicoureteral junction (young: p < 0.05; middle-aged: p < 0.05; old: p > 0.05; males: p < 0.05; females: p < 0.05). Similar were the regional distributions of residual strain at the interface between epithelium-lamina propria and muscle and of internal but not external residual strain. Wall thickness increased steadily with aging ( p < 0.05 at few regions), while ureteral circumference did not ( p > 0.05 at most regions) and opening angle decreased ( p < 0.05 at several regions). Consistent with Fung's stress-growth law, the muscle layer thickened with age unlike the epithelium-lamina propria that thinned ( p < 0.05 at most regions for both thicknesses). Moderate-to-strong direct correlations of residual strain difference (= external - internal) with opening angle, wall thickness, and curvature were found in most ureters. The presented data will provide insight into the biomechanical response of ureter under zero/low-stress conditions and the relationship between ureteral remodeling and aging. Importantly, they may also be used to inform finite element models and computational studies simulating the ureter.

Assessment of bone metabolism and biomechanical properties of the femur, following treatment with anastrozole and letrozole in an experimental model of menopause.

The aim of the present study was to investigate the impact of anastrozole and letrozole supplementation following surgically induced menopause on bone metabolism and biomechanical properties. A total of 45 Wistar rats underwent ovariectomy and were then randomly allocated to receive no treatment, anastrozole or letrozole. At 2 and 4 months following the initiation of the present study, the serum levels of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) were determined, and the animals were sacrificed at the end of the 4-month period to assess the biomechanical properties of the femoral bones. The applied force and the deflection of the central section were recorded during the test. Taking advantage of these quantities, the fracture force, the stiffness of the bone and the energy absorbed until fracture were determined. At 2 months following the initiation of the experimental protocol, the mean OPG levels were significantly increased in the control group compared with the anastrozole-treated group (P<0.01). Similarly, RANKL levels were significantly increased in the control rats compared with the anastrozole-treated animals (P<0.001) and animals that received letrozole (P<0.05). Notably, these trends were not observed at the end of the experiment (4 months). A biomechanical study of the femoral bones revealed significantly decreased stiffness among animals that received anastrozole (P<0.05) and letrozole (P<0.01) compared with their control counterparts. The results of the present study indicate that treatment with anastrozole and letrozole significantly increases the levels of OPG and RANKL in bone, an effect that appears to be directly associated with the biomechanical properties of bones.

Supplementary medial locking plate fixation of Ludloff osteotomy versus sole lag screw fixation: A biomechanical evaluation.

BACKGROUND: The Ludloff oblique osteotomy is inherently unstable, which might lead to delayed union and loss of correction. Supplementary fixation to two lag screw fixation has been proposed. The hypothesis is that the osteotomy fixation constructs supplemented by a mini locking plate provide greater resistance to osteotomy gaping and loss of angular correction in response to cyclic loading. METHODS: Twenty fourth generation composite 1st metatarsals were used and underwent a Ludloff osteotomy. They were divided in two fixation groups: two lag screws (Group A), and with a supplementary mini locking plate (Group B). Specimens were subjected to either monotonic loading up to failure or to fatigue (cyclic) tests and tracked using an optical system for 3D Digital Image Correlation. FINDINGS: The osteotomy gap increased in size under maximum loading and was significantly greater in Group A throughout the test. This increase was observed very early in the loading process (within the first 1000cycles). The most important finding though, was that with the specimens completely unloaded the residual gap increase was significantly greater in Group A after only 5000cycles of loading up to the completion of the test. The lateral angle change under maximum loading was also significantly greater in Group A throughout the test, with that increase observed early in the loading process (5000cycles). With the specimens completely unloaded the residual lateral angle change was also significantly greater in Group A at the completion of the test. INTERPRETATION: Supplementary fixation with a mini locking plate of the Ludloff osteotomy provided greater resistance to osteotomy gaping and loss of angular correction compared to sole lag screws, in response to cyclic loading.

Regional distribution of circumferential residual strains in the human aorta according to age and gender.

The biomechanical response of the human aorta varies with axial location, but little is known about the respective variation of residual strains. Such data are available for common lab animals, but in the traditional opening angle measurement the aorta is considered as an ideal cylinder and average residual strains are measured, so that the spatial variations of local residual strains are not determined. The present study provides opening angle and residual strain data throughout the course and around the circumference of the aorta harvested during autopsy. Opening angle showed notable topographical variation; the highest value was at the top of aortic arch, declining abruptly toward the ascending aorta and to a near-constant value in the descending aorta, and rising in the abdominal aorta. The variation of curvature and of external but not internal residual stretch resembled that of opening angle. Extensive residual stress and wall thickness differences were evidenced among quadrants, with the more pre-stressed being also the thicker quadrants. Gender had overall minor effects, but aging led to increased parameters, occurring earlier in the distal aorta but at later stages becoming predominant proximally. Differences in caliber were pronounced in older subjects, unlike those in opening angle, residual stretches, and thickness that were striking in middle-aged subjects. By contrast, curvature decreased with aging in relation to the smaller percentwise opening angle differences. Detailed knowledge of the zero-stress/no-load geometry of the human aortic wall is critical for an in-depth understanding of aortic physiology, while providing the basis for comparison with disease.

Age- and region-related changes in the biomechanical properties and composition of the human ureter.

The ureter has been largely overlooked heretofore in the study of the biomechanics of soft biological tissues, although there has been significant motivation to use its biomechanical properties as inputs to mathematical models of ureteral function. Herein, we used histological analysis for quantification of collagen contents and thickness/area of ureteral layers, with concomitant geometrical analysis of zero-stress and no-load states, and inflation/extension testing to biomechanically characterize with the Fung-type model the ureters from cadavers. The effects of age and gender on the regional distribution of those properties were examined. Tissue properties did not differ (p>0.05) between the left and right ureter. Regional heterogeneity was established that was profoundly age-related but seldom gender-related, based on the following evidence: 1) In younger subjects, the axial stress-circumferential strain curves of upper ureter were shifted to smaller stresses and model parameter a2 representing axial stiffness was smallest (p<0.05), i.e. upper ureter was the least stiff region axially; 2) upper ureter underwent axial stiffening with advanced age, evidenced by the increasing (p<0.05) parameter a2, and the stress-strain curves were uniformly exhibited along the ureter, evidenced by the non-varying (p>0.05) parameters C,a1,a2,anda4; 3) aging raised (p<0.05) the collagen content of upper ureter to favor a near-uniform regional distribution; 4) wall thickness increased with age, unlike the opening angle and residual strains, reflecting the thickening of outer (muscular) vs. inner (mucosal) layers in aged subjects, with significant differences (p<0.05) in some regions; and 5) gender affected little (p>0.05) the opening angle and morphometry of no-load and zero-stress states.