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Elastic Modulus and Strength of Emu Cortical Bone
Abstract
The emu (Dromaius novaehollandiae) shows potential as a unique animal model for replicating the femoral head collapse process seen in end-stage human osteonecrosis. Since the collapse phenomenon (and interventions to prevent it) involve mechanical processes, it is important to elucidate the similarities and differences of emus versus humans in terms of hip joint biomechanics. A first step for comparison is the intrinsic mechanical properties of the respective bone tissues, as reflected in cortical bone flexural stiffness and strength. In four-point bending, emu cortical bone was found to have an elastic modulus of 13.1 GPa. Its yield stress was determined to be 113 MPa and the ultimate strength was 146 MPa. Emu cortical bone's elastic modulus was similar to that of other avian species, and falls approximately 25% below that of the human (17.3 GPa).
... Appendicular compact bone is orthotropic, with the highest elastic modulus parallel to the long axis. To the long axis of the element, we applied the elastic modulus E zz of emu (Dromaius novaehollandiae) femoral cortical bone under high strain rates [55] (15.86 GPa). Both emu and ostrich appendicular bone has E zz of 13-14 GPa under lower strain rates [55]. ...
... To the long axis of the element, we applied the elastic modulus E zz of emu (Dromaius novaehollandiae) femoral cortical bone under high strain rates [55] (15.86 GPa). Both emu and ostrich appendicular bone has E zz of 13-14 GPa under lower strain rates [55]. Using the high-strain-rate E zz value for emu is appropriate because bone stiffness is load-rate dependent, and loads from fast running would introduce high strain rates. ...
... We assessed the mechanical integrity of the ostrich tarsometatarsus by comparing simulated stresses and strains to σ ult and ε ult of compact and cancellous bone. σ ult and ε ult are unknown for bone of the ostrich tarsometatarsus, and were assumed to be similar to those of emu, human, and bovine cortical bone [55,36,40], and human and dog appendicular cancellous bone [62,63,64,28]. ...
Background:
The ostrich Struthio camelus reaches the highest speeds of any extant biped, and has been an extraordinary subject for studies of soft-tissue anatomy and dynamics of locomotion. An elongate tarsometatarsus in adult ostriches contributes to their speed. The internal osteology of the tarsometatarsus, and its mechanical response to forces of running, are potentially revealing about ostrich foot function.
Methods/principal findings:
Computed tomography (CT) reveals anatomy and bone densities in tarsometatarsi of an adult and a young juvenile ostrich. A finite element (FE) model for the adult was constructed with properties of compact and cancellous bone where these respective tissues predominate in the original specimen. The model was subjected to a quasi-static analysis under the midstance ground reaction and muscular forces of a fast run. Anatomy-Metatarsals are divided proximally and distally and unify around a single internal cavity in most adult tarsometatarsus shafts, but the juvenile retains an internal three-part division of metatarsals throughout the element. The juvenile has a sparsely ossified hypotarsus for insertion of the m. fibularis longus, as part of a proximally separate third metatarsal. Bone is denser in all regions of the adult tarsometatarsus, with cancellous bone concentrated at proximal and distal articulations, and highly dense compact bone throughout the shaft. Biomechanics-FE simulations show stress and strain are much greater at midshaft than at force applications, suggesting that shaft bending is the most important stressor of the tarsometatarsus. Contraction of digital flexors, inducing a posterior force at the TMT distal condyles, likely reduces buildup of tensile stresses in the bone by inducing compression at these locations, and counteracts bending loads. Safety factors are high for von Mises stress, consistent with faster running speeds known for ostriches.
Conclusions/significance:
High safety factors suggest that bone densities and anatomy of the ostrich tarsometatarsus confer strength for selectively critical activities, such as fleeing and kicking predators. Anatomical results and FE modeling of the ostrich tarsometatarsus are a useful baseline for testing the structure's capabilities and constraints for locomotion, through ontogeny and the full step cycle. With this foundation, future analyses can incorporate behaviorally realistic strain rates and distal joint forces, experimental validation, and proximal elements of the ostrich hind limb.
... Furthermore, sexual dimorphism is apparent in emus, as females are notably heavier, larger and have a higher basal metabolic rate compared to males [18], providing a model system to evaluate differences between male and female bones. Finally, emu tibiae may be a suitable model for long human leg bones as the bipedal nature of emus is analogous to human locomotion [19,20]; the emu model has previously been used as a model for femoral head osteonecrosis [19]. ...
... Leg bones from male and female emus were obtained from slaughterhouses and farms in southern Ontario, Canada. The animals were approximately 3-5 years of age, and therefore skeletally mature [20,21]. The tibiae were carefully separated from the femora and tarsometatarsi with a scalpel. ...
... The mechanical properties of the 0-day and control specimens (14day filled with saline) are similar to results reported in the literature. Reed [20], significant differences were observed between female and male 0-day samples. Female emu tibiae had significantly higher cross-sectional geometry, mass, BMD and BMC values as well as ultimate stress, and failure stress compared to males. ...
... Furthermore , sexual dimorphism is apparent in emus, as females are notably heavier, larger and have a higher basal metabolic rate compared to males [18], providing a model system to evaluate differences between male and female bones. Finally, emu tibiae may be a suitable model for long human leg bones as the bipedal nature of emus is analogous to human locomotion [19,20]; the emu model has previously been used as a model for femoral head osteonecrosis [19]. The objectives of this study were two-fold: to investigate the ability of the MRTA to detect changes in bone mechanical properties induced by changes in the collagen matrix of emu bone, and to evaluate any differences between male and female emu bone. ...
... Leg bones from male and female emus were obtained from slaughterhouses and farms in southern Ontario, Canada. The animals were approximately 3–5 years of age, and therefore skeletally mature [20,21]. The tibiae were carefully separated from the femora and tarsometatarsi with a scalpel. ...
... The mechanical properties of the 0-day and control specimens (14- day filled with saline) are similar to results reported in the literature. Reed and Brown [20] measured the elastic modulus and strength of emu cortical bone (femur, unknown gender) in 4-point bending. They reported that the elastic modulus was 13.1 ± 3.9 GPa, yield stress 113.1 ± 29.2 MPa and the ultimate strength was 146.9 ± 32.2 MPa. ...
Current clinical tools for evaluating fracture risk focus only on the mineral phase of bone. However, changes in the collagen matrix may affect bone mechanical properties, increasing fracture risk while remaining undetected by conventional screening methods such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS). The mechanical response tissue analyzer (MRTA) is a non-invasive, radiation-free potential clinical tool for evaluating fracture risk. The objectives of this study were two-fold: to investigate the ability of the MRTA to detect changes in mechanical properties of bone as a result of treatment with 1 M potassium hydroxide (KOH) and to evaluate the differences between male and female bone in an emu model. DXA, QUS, MRTA and three-point bending measurements were performed on ex vivo emu tibiae before and after KOH treatment. Male and female emu tibiae were endocortically treated with 1 M KOH solution for 1-14 days, resulting in negligible collagen loss (0.05%; by hydroxyproline assay) and overall mass loss (0.5%). Three-point bending and MRTA detected significant changes in modulus between days 1 and 14 of KOH treatment (-18%) while all values measured by DXA and QUS varied by less than 2%. This close correlation between MRTA and three-point bending results support the utility of the MRTA as a clinical tool to predict fracture risk. In addition, the significant reduction in modulus contrasted with the negligible amount of collagen removal from the bone after KOH exposure. As such, the significant changes in bone mechanical properties may be due to partial debonding between the mineral and organic matrix or in situ collagen degradation rather than collagen removal. In terms of sex differences, male emu tibiae had significantly decreased failure stress and increased failure strain and toughness compared to female tibiae with increasing KOH treatment time.
... Ostriches and emus are among the fastest-running animals with exceptional stamina, and their dynamics of motion have been the subject of many studies, aimed vast availability is related to the food industry, making these animals ideal to study their physiology and dynamics of motion. Ostriches and emus are among the fastest-running animals with exceptional stamina, and their dynamics of motion have been the subject of many studies, aimed to comprehend their capabilities [1][2][3][4][5][6][7][8][9][10]. Birds are obligate bipedal creatures, like humans, and ostriches have comparable masses to humans, making them an ideal comparison for our species [3,11]. ...
... The tensile tests carried out on the samples oriented alongside the main direction of loadings highlight a clear orthotropic behaviour of the bone. The results obtained from the mechanical tests confirm the literature data, with E ∼ = 17 GPa in tensile tests aligned to the long axis of the bone [7,12,14]. The E x , directed perpendicular to the long axis of the bone, is 100 times smaller than the E y , directed parallel to the long axis of the bone, with values of around 0.1 GPa, highlighting a clear orthotropic behaviour, with the most bearing axis coincident with the main axis of loading of the bone. ...
Ostriches are known to be the fastest bipedal animal alive; to accomplish such an achievement , their anatomy evolved to sustain the stresses imposed by running at such velocities. Ostriches represent an excellent case study due to the fact that their locomotor kinematics have been extensively studied for their running capabilities. The shape and structure of ostrich bones are also known to be optimized to sustain the stresses imposed by the body mass and accelerations to which the bones are subjected during movements. This study focuses on the limb bones, investigating the structure of the bones as well as the material properties, and how both the structure and material evolved to maximise the performance while minimising the stresses applied to the bones themselves. The femoral shaft is hollowed and it presents an imbricate structure of fused bone ridges connected to the walls of the marrow cavity, while the tibial shaft is subdivided into regions having different mechanical characteristics. These adaptations indicate the optimization of both the structure and the material to bear the stresses. The regionalization of the material highlighted by the mechanical tests represents the capability of the bone to adapt to external stimuli during the life of an individual, optimizing not only the structure of the bone but the material itself.
... Young's modulus values ranging from 7 to 21 (Cubo and Casinos, 2000a;Cubo and Casinos, 2000b;Reed and Brown, 2001). Three-point bending tests performed on both fore-and hind limb elements of a wide range of birds indicate that the stiffness is correlated with both chemical composition and the presence or absence of pneumaticity (Cubo and Casinos, 2000a;Cubo and Casinos, 2000b). ...
... Results of this study reveal that considerable variation exists in the mechanical properties both among wing elements within a species and among species that utilize different primary flight modes. Previous studies of mechanical properties of avian bone tend to either pool results from multiple skeletal elements or use results from a single element to get an overall measure of stiffness and/or strength of bone in a given species (e.g., Cubo and Casinos, 2000a;Reed and Brown, 2001). One recent study examined differences in both bending strength and Young's modulus in a variety of birds and found the radius to be significantly stiffer than the humerus, ulna, and hind limb elements (Cubo and Casinos, 2000b). ...
... Assuming perfect plasticity, the calibrated yield point for ovine bone using von Mises yield criterion was found to be 301 MPa. This is far in excess of the yield stress predicted for cortical bone in compression and tension in literature of 84.9-180 MPa (Burstein et al., 1976;Reed and Brown, 2001;. Use of this model predicted pile-up to be 0.28 µm. ...
... The predicted yield strain in tension of 0.88% is within the range reported previously for cortical bone, typically 0.7%-0.88% (Reed and Brown, 2001). In compression the yield strain predicted of 1.54% is also within range of those reported previously in literature for cortical and trabecular bone, typically 0.7%-2.2% ...
In this work, the post-yield behaviour of cortical bone is investigated using finite element modelling, nanoindentation and atomic force microscopy. Based on recent investigations, it is proposed that, since pressure dependent deformation mechanisms may contribute to yielding in bone, constitutive models attempting to capture its post-yield behaviour should also incorporate pressure dependence. Nanoindentation testing is performed using a spheroconical indenter tip, and subsequent atomic force microscopy at the indented site shows that bone does not exhibit surface pile-up. By simulating the nanoindentation test, it is found that a Mises based constitutive law cannot simultaneously capture the deformations and load-displacement curve produced during nanoindentation. However, an extended Drucker-Prager model can capture the post-yield behaviour of bone accurately, since it accounts for pressure dependent yield. This suggests that frictional mechanisms are central to the post-yield behaviour of bone. In this work, the extended Drucker-Prager model is calibrated and validated using further simulations.
... However, Cassie does not have a torso nor arms and head, giving it an advantage with respect to its mass. The quadruped robots Garrison, 1990;Cao et al., 2009;HABA, 2021;Garrison, 1990;Reed and Brown, 2001). The dotted line indicates the linear extrapolation of the normalized average human performance. ...
The incessant progress of robotic technology and rationalization of human manpower induces high expectations in society, but also resentment and even fear. In this paper, we present a quantitative normalized comparison of performance, to shine a light onto the pressing question, “How close is the current state of humanoid robotics to outperforming humans in their typical functions (e.g., locomotion, manipulation), and their underlying structures (e.g., actuators/muscles) in human-centered domains?” This is the most comprehensive comparison of the literature so far. Most state-of-the-art robotic structures required for visual, tactile, or vestibular perception outperform human structures at the cost of slightly higher mass and volume. Electromagnetic and fluidic actuation outperform human muscles w.r.t. speed, endurance, force density, and power density, excluding components for energy storage and conversion. Artificial joints and links can compete with the human skeleton. In contrast, the comparison of locomotion functions shows that robots are trailing behind in energy efficiency, operational time, and transportation costs. Robots are capable of obstacle negotiation, object manipulation, swimming, playing soccer, or vehicle operation. Despite the impressive advances of humanoid robots in the last two decades, current robots are not yet reaching the dexterity and versatility to cope with more complex manipulation and locomotion tasks (e.g., in confined spaces). We conclude that state-of-the-art humanoid robotics is far from matching the dexterity and versatility of human beings. Despite the outperforming technical structures, robot functions are inferior to human ones, even with tethered robots that could place heavy auxiliary components off-board. The persistent advances in robotics let us anticipate the diminishing of the gap.
... Stress analysis in the bone tissue under different loading showed that increasing the bone loss levels increases the stress and that buccolingual loading produces more stress than axial loading. The maximum stresses of cortical bone were less than the yield strength, around 113 MPa (Reed and Brown, 2001). For the cancellous bone, the peak stress values under axial loading in all cases were lower than the yield strength (around 3.65 MPa) (Zhang et al., 2013;Nazarian et al., 2009), but in buccolingual loading for both implants, the maximum stress in case (d) with 1.5 bone loss was higher compared to the yield strength. ...
The marginal bone loss remains a controversial issue and one of the major complications in the field of oral and bone health. The goal of this study was to evaluate the biomechanical effect of the implant length, marginal bone loss (MBL) levels, and loads magnitude under axial and buccolingual loading on stress at the bone-implant interface. Four cases models were created (without bone loss, 0.5 mm bone loss, 1 mm bone loss, and 1.5 mm bone loss) and two implants with different lengths (Type A with 12 mm and Type B with 15mm) using Solidworks. In the first part, an axial load of 100 N and a buccolingual load of 50 N were applied separately on the occlusal face of the crown. In the second part, different loadings magnitude (100N, 150N, 200N, 250N) were applied separately with implant A.Simulation results show that the stresses were higher with implant B in cortical bone compared to implant A, and as the bone loss increases, the von Mises stress and displacement in the bone increases in all cases. The stresses were higher in buccolingual loading compared to axial loading, and a higher magnitude of different loading generate higher stresses in the bone tissue. Through this study, it was concluded that progressive marginal bone loss and excessive loading produce higher stresses in the bone tissue and that may affect the bone remodeling process.
... In addition to that, overall weak bone shows higher displacement as compared to the standard bone in both types of implants. [39], in all the cases. The strength and Young's modulus of cortical bone are much higher than the cortical bone, which takes more load and reflects higher stresses as compared to the cancellous bone. ...
This study aims to design titanium (Ti) porous (18–77% porosity) dental implants with conical and cylindrical types for standard and weak bones using 3D finite element (FE) models. The strain intervals of the mechanostat criterion were used to analyze strain intensity. Highly porous implants with the stiffness of 9 GPa and 18 GPa in weak bone produced a very high strain intensity (>3500 µε) which may eventually cause a bone fracture, however, stiffness of 76 GPa and bulk titanium implants in standard bone produced a very low level of strain intensity (<500 µε) which may lead to the bone resorption.
... If the bottom part of the tibia is neglected, the interface between the composite implant and tibia has the maximum Fig. 10 Stress distribution in the implant; total force applied Fig. 9 View cut of the composite implant section; the interior part of the tibia bears most of the stress Silicon stress, while the maximum stress is less than the yield stress of the 58 s bioactive glass/polysulfone composite [21] and cortical bone [65]. Figure 9 shows the view cut of the center of the bone to demonstrate the stress contour better. ...
Bioactive glass/Polysulfone composite has been considered as an appropriate material for biomechanical and medical applications. Time-dependency and nonlinear-elasticity are significant mechanical behaviors of these type of materials. Hence, in this research, the 20% vol. 58 s bioactive glass/polysulfone composite was prepared using the solvent casting method, and tensile tests with 3 different strain rates were performed on the samples. Also, a nonlinear-viscoelastic model based on the Ogden nonlinear-elastic strain energy was generalized to investigate the mechanical behavior of the 20 vol.% 58 s bioactive glass/polysulfone composite. To show the agreement of the model with the experimental results, a rate dependent tensile test was simulated by ABAQUS which validated the results. The tensile test showed a maximum stress of 15 ~ 25 MPa, based on the test speed; also, the simulation demonstrated a 16.2 MPa stress for the 5 mm/min test speed, which were in good agreement. Later, a model of a human tibia bone was constructed using MIMICS, SOLIDWORKS and ABAQUS to study the application of the 58 s bioactive glass/polysulfone composite as an implant. The results revealed that the stress tolerated by the implant was neglectable, and most of the stress was tolerated by the bone itself.
... The average element size was 0.8 mm with aspect ratio less than 10 and 35×10 -2 mm for fine meshing. The properties of modeled materials were obtained from previously published data, [25][26][27][28][29][30][31][32][33] as seen in Table 2. All the components were assumed to exhibit bonded contact except for the interface between the bone and the implants. ...
Statement of problem
The number of implants required for the rehabilitation of completely edentulous mandibles has been controversial. The use of a greater number of implants can produce favorable biomechanical outcomes. However, this will lead to high costs and may require complex surgical procedures. Therefore, the minimum number of implants that can produce desirable outcomes should be used.
Purpose
The purpose of this 3D finite element study was to compare the biomechanics of mandibular 3-implant-supported to 4-implant-supported prostheses. The opposing occlusion was a maxillary complete denture or natural dentition.
Material and methods
Two finite element analysis mandibular anatomic models were created. Implants were virtually placed in the mandibular lateral incisor and second premolar region bilaterally in the 4-implant-supported prosthesis model. For the 3-implant-supported model, they were placed in the midline and bilaterally in the second premolar region. Screw-retained polymethyl methacrylate prostheses were designed. Reverse engineering was used to convert standard tessellation language files into computer-aided design solid models. Vertical and oblique loading was applied twice: simulating an opposing maxillary complete denture and a natural dentition. Von Mises stresses and equivalent strains generated in the peri-implant bone, implants’ von Mises stresses and the maximum vertical displacement of the prosthesis were recorded.
Results
All recorded outcomes reported higher values for the 3-implant-supported prosthesis compared with the 4-implant-supported models for both applied loads. When opposed by a maxillary complete denture, maximum strain values for the 3-implant-supported (2.3×10³ με) and 4-implant-supported (1.6×10³ με) models were less than the different threshold limits for the bone resorption reported (3×10³, 3.6×10³, 6.6×10³ με). When opposed by a maxillary natural dentition, maximum strain values for the 3-implant-supported (4.10×10³ με) and 4-implant-supported (3.88×10³ με) models were less than the highest reported threshold limit for bone resorption (6.6×10³ με) in contrast with other reported threshold limits (3×10³, 3.6×10³ με). In both designs irrespective of the magnitude and direction of loading, the maximum recorded von Mises stresses of the implants (126 MPa) and denture displacement (3.24×10² μm) were less than titanium’s yield strength of (960 to 1180 MPa) and the displacement values (5.2×10³ to 8.8×10³ μm) reported in the literature.
Conclusions
When opposed by a complete denture, recorded biomechanical outcomes for the 3- and 4-implant-supported designs were within physiologic limits. When opposed by a natural dentition, the von Mises stresses of the implants and denture displacement values for both designs were within a favorable mechanical range, whereas peri-implant stresses and strain exceeded most reported physiologic tolerance levels of bone except for the 6.6×10³ με threshold limit for the bone resorption reported.
... (Vinckier and Semenza, 1998). Es beschreibt das Verhältnis von Spannung und Dehnung im linearen Bereich bei der Verformung des gemessenen Körpers (Reed and Brown, 2001;Vinckier and Semenza, 1998;Wang et al., 2015). Je höher der Betrag, desto steifer ist die gemessene Probe. ...
Der Süßwasserpolyp Hydra gehört zum Stamm der Cnidarier und dient seit über 270 Jahre als Modellorganismus. Die Nesselzellen oder Nematocyten sind charakteristisch für Cnidarier und enthalten spezielle Organelle, die Nematocysten. Diese werden vorwiegend zur Verteidigung und zum Beutefang eingesetzt. Nematocysten bestehen aus einem zylindrischen Körper und einem invertierten Schlauch, der innerhalb von Nano- bis Mikrosekunden wie eine Harpune herausgeschleudert werden kann. Der molekulare Aufbau der elastischen Nesselkapsel, deren Entladung von einem enorm hohen Innendruck (150 bar) angetrieben wird, ist daher von besonderem Interesse für das Gebiet der Biomechanik. Im ersten Teil der Arbeit wurden biochemische und funktionelle Untersuchungen an Proteinen der Nematocystenwand durchgeführt. Das makromolekulare Proteinpolymer der Wandstruktur basiert auf reversiblen Disulfidverknüpfungen. Die Hauptkomponente des Biopolymers sind Minikollagene und das elastische Protein Cnidoin. Diese enthalten an beiden Termini der Proteinkette cysteinreiche Domänen, die für die Polymerisierung essentiell sind. Innerhalb dieser Arbeit wurde erstmalig das Protein CPP-1 in Hydra charakterisiert. Es besitzt eine minikollagenähnliche Architektur mit einer zentralen Polyprolinsequenz und weist Ähnlichkeiten zu den Hydroxyprolin-reichen Glykoproteinen (HRGPs) der Pflanzenzellwand auf. Es konnte gezeigt werden, dass CPP-1 struktureller Bestandteil der Kapselwand ist und wie die HRGPs posttranslational modifiziert wird. Der genetische Knockdown von CPP-1 in Hydra durch siRNAs führte zu einer veränderten Verteilung von Nematocystenproteinen im Verlauf der Morphogenese und deutet auf eine Gerüstfunktion in diesem Prozess. Im zweiten Teil der Arbeit stand die Entwicklung von innovativen Biomaterialien mit Nematocystenproteinen im Fokus. Bei der bioinspirierten Materialsynthese liefert die Natur Strukturen und Funktionalitäten, die als Modell für neuartige Syntheseverfahren verwendet werden. Im Rahmen eines interdisziplinären Kooperationsprojektes wurden mit den cysteinreichen Domänen der Nematocystenproteine Hybridpolymere synthetisiert und funktionelle Oberflächen hergestellt. In einem weiteren Projekt fungierte das Proteinpolymer der Nematocystenwand als Modell für die Herstellung von Nanofasern. Durch Elektrospinning konnten kontinuierliche Fasern aus Cnidoin und CPP-1 synthetisiert werden. Deren Struktur und mechanische Eigenschaften wurden mit dem Atomkraftmikroskop im trockenen und hydratisierten Milieu charakterisiert. Die Biokompatibilität der erhaltenen Fasern wurde durch die Kultur mit humanen mesenchymalen Stammzellen bestätigt. Die etablierten Nanofasern können somit einen Beitrag für die Entwicklung innovativer Zellsubstrate leisten.
... Currey, 2002, and references cited therein; Erickson, Catanese & Keaveny, 2002;Reed & Brown, 2001). The material properties for cartilage and menisci were also conservative estimates, derived from the literature(Currey, 2002, and references cited therein; Kazemi, Dabiri & Li, 2013;Stops, Wilcox & Jin, 2012). ...
This paper is the second of a three-part series that investigates the architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is widely known to be highly sensitive to its mechanical environment, and therefore has the potential to provide insight into locomotor biomechanics in extinct tetrapod vertebrates such as dinosaurs. Here in Part II, a new biomechanical modelling approach is outlined, one which mechanistically links cancellous bone architectural patterns with three-dimensional musculoskeletal and finite element modelling of the hindlimb. In particular, the architecture of cancellous bone is used to derive a single ‘characteristic posture’ for a given species—one in which bone continuum-level principal stresses best align with cancellous bone fabric—and thereby clarify hindlimb locomotor biomechanics. The quasi-static approach was validated for an extant theropod, the chicken, and is shown to provide a good estimate of limb posture at around mid-stance. It also provides reasonable predictions of bone loading mechanics, especially for the proximal hindlimb, and also provides a broadly accurate assessment of muscle recruitment insofar as limb stabilization is concerned. In addition to being useful for better understanding locomotor biomechanics in extant species, the approach hence provides a new avenue by which to analyse, test and refine palaeobiomechanical hypotheses, not just for extinct theropods, but potentially many other extinct tetrapod groups as well.
... The load-displacement data was converted to stress-strain curves using the geometry of the specimens. The apparent elastic modulus was obtained from the slope of the linear elastic portion of the stress-strain curves at the maximum slope of the stress-strain curve by plotting a best-fit straight line over 1% strain, with a varying origin, similar to the method by Keaveny et al., 1997 [31], and Reed and Brown, 2001 [38] (Fig 5). ...
Objectives
Bone material properties are a major determinant of bone health in older age, both in terms of fracture risk and implant fixation, in orthopaedics and dentistry. Bone is an anisotropic and hierarchical material so its measured material properties depend upon the scale of metric used. The scale used should reflect the clinical problem, whether it is fracture risk, a whole bone problem, or implant stability, at the millimetre-scale. Indentation, an engineering technique involving pressing a hard-tipped material into another material with a known force, may be able to assess bone stiffness at the millimetre-scale (the apparent elastic modulus). We aimed to investigate whether spherical-tip indentation could reliably measure the apparent elastic modulus of human cortical bone.
Materials and methods
Cortical bone samples were retrieved from the femoral necks of nineteen patients undergoing total hip replacement surgery (10 females, 9 males, mean age: 69 years). The samples underwent indentation using a 1.5 mm diameter, ruby, spherical indenter tip, with sixty indentations per patient sample, across six locations on the bone surfaces, with ten repeated indentations at each of the six locations. The samples then underwent mechanical compression testing. The repeatability of indentation measurements of elastic modulus was assessed using the co-efficient of repeatability and the correlation between the bone elastic modulus measured by indentation and compression testing was analysed by least-squares regression.
Results
In total, 1140 indentations in total were performed. Indentation was found to be repeatable for indentations performed at the same locations on the bone samples with a mean co-efficient of repeatability of 0.4 GigaPascals (GPa), confidence interval (C.I): 0.33–0.42 GPa. There was variation in the indentation modulus results between different locations on the bone samples (mean co-efficient of repeatability: 3.1 GPa, C.I: 2.2–3.90 GPa). No clear correlation was observed between indentation and compression values of bone elastic modulus (r = 0.33, p = 0.17). The mean apparent elastic modulus obtained by spherical indentation was 9.9 GPa, the standard deviation for each indent cycle was 0.11 GPa, and the standard deviation between locations on the same sample was 1.01 GPa. The mean compression apparent elastic modulus was 4.42 GPa, standard deviation 1.02 GPa.
Discussion
Spherical-tip indentation was found to be a repeatable test for measuring the elastic modulus of human cortical bone, demonstrated by a low co-efficient of repeatability in this study. It could not, however, reliably predict cortical bone elastic modulus determined by platens compression testing in this study. This may be due to indentation only probing mechanical properties at the micro-scale while platens compression testing assesses millimetre length-scale properties. Improvements to the testing technique, including the use of a larger diameter spherical indenter tip, may improve the measurement of bone stiffness at the millimetre scale and should be investigated further.
... Tensile tests revealed a mean (±1 s.d.) elastic modulus (E) of 24.01 ± 1.57 GPa and an ultimate stress (σ ult ) of 153.9 ± 42.3 MPa. This finding compares well with measures from an ostrich (Struthio camelus; E: 13.90 GPa [55]) and emu (Dromaius novaehollandiae; E: 13.05 ± 3.94 GPa, range: 5.62 to 19.83 GPa; σ ult : 146 MPa [59]), with the caveat that these authors examined the compact bone of fresh (undried) femora. In our tests, the stress-strain behaviour of dry, tibiotarsal compact bone was relatively linear-elastic, showing a brittle response and failure before 1% strain (see electronic supplementary material, figure S4). ...
Bone daggers were once widespread in New Guinea. Their purpose was both symbolic and utilitarian; they functioned as objects of artistic expression with the primary function of stabbing and killing people at close quarters. Most daggers were shaped from the tibiotarsus of cassowaries, but daggers shaped from the femora of respected men carried greater social prestige. The greater cross-sectional curvature of human bone daggers indicates superior strength, but the material properties of cassowary bone are unknown. It is, therefore, uncertain whether the macrostructure of human bone daggers exists to compensate for inferior material properties of human femora or to preserve the symbolic value of a prestigious object. To explore this question, we used computed tomography to examine the structural mechanics of 11 bone daggers, 10 of which are museum-accessioned objects of art. We found that human and cassowary bones have similar material properties and that the geometry of human bone daggers results in higher moments of inertia and a greater resistance to bending. Data from finite-element models corroborated the superior mechanical performance of human bone daggers, revealing greater resistance to larger loads with fewer failed elements. Taken together, our findings suggest that human bone daggers were engineered to preserve symbolic capital, an outcome that agrees well with the predictions of signalling theory.
... The samples were tested to 100 N at the rate of 33.33 m/s. The elastic modulus (E) was obtained using the equation (Reed and Brown 2001) ...
We propose an ultrasound-guided remote measurement technique, utilizing an acoustic radiation force beam as our excitation source and a receiving hydrophone, to assess non-invasively a bone's mechanical properties. Features, such as velocity, were extracted from the acoustic pressure received from the bone surface. The typical velocity of an intact bone (3540 m/s) was higher in comparison to that of a demineralized bone (2231 m/s). According to the receiver operating characteristic curve, the optimal velocity cutoff value of ≥3096 m/s yields 80% sensitivity and 82.61% specificity between intact and demineralized bone. Utilizing a support vector machine, the hours of bone demineralization were successfully classified with maximum accuracy >80% using 18% training data. The results indicate the potential application of our proposed technique and support vector machine for monitoring bone mechanical properties.
... The four-noded, tetrahedral, solid elements models were imported into ANSYS APDL version 13.0 (Canonsburg, PA), where we manually selected elements to represent the nasal-frontal hinge. Cortical bone was assigned a Young's modulus (E) of 13.5 GPa based on data from ostrich and chicken (Reed and Brown 2001). Because data on trabecular bone of birds were not available, we used data of mammals (Ding et al. 2005) and assumed that the ratio between the Young's modulus of cortical and trabecular bone (cortical bone eight times stiffer) was the same in the two taxa, resulting in a Young's modulus of E = 13.5/8 ...
Ostrich-like birds (Palaeognathae) show very little taxonomic diversity while their sister taxon (Neognathae) contains roughly 10000 species. The main anatomical differences between the two taxa are in the crania. Palaeognaths lack an element in the bill called the lateral bar that is present in both ancestral theropods and modern neognaths, have thin zones in the bones of the bill, and robust bony elements on the ventral surface of their crania. Here we use a combination of modelling and developmental experiments to investigate the processes that might have led to these differences. Engineering-based finite element analyses indicate that removing the lateral bars from a neognath increases mechanical stress in the upper bill and the ventral elements of the skull, regions that are either more robust or more flexible in palaeognaths. Surgically removing the lateral bar from neognath hatchlings led to similar changes. These results indicate that the lateral bar is load-bearing and suggest that this function was transferred to other bony elements when it was lost in palaeognaths. It is possible that the loss of the load-bearing lateral bar might have constrained diversification of skull morphology in palaeognaths and thus limited taxonomic diversity within the group. This article is protected by copyright. All rights reserved.
... To estimate the sound created by the collision, elastic properties of avian bone (with a density, ρ s , of 1800 ± 200 kg m -3 (Dumont, 2010) and Elastic modulus, E, of 12 ± 1 GPa (Reed & Brown, 2001)) and geometric properties of the M. vitellinus radius (Table 2) were used to calculate the fundamental frequencies associated with the impact, as follows. Prior to the collision, the outer wing's inertia and aerodynamic resistance help set the velocity of the wings Journal of Experimental Biology @BULLET Advance article just prior to contact, as recorded in the kinematic data, and is on the order of 10 m/s at the wrist. ...
Male Golden-collared manakins (Manacus vitellinus), small suboscine passeriform birds of Panamanian forests, communicate acoustically using a variety of nonvocal sonations. The most prominent sonations are single or multiple intense 'wingsnaps' with a dominant acoustic frequency around 5 kHz. Several hypotheses have been proposed addressing the source of the sound, ranging from purely aerodynamic origins (due to a rapid jet of air formed by the wings or by a 'whiplike' motion) to purely structural origins (such as physical contact of the wings), but without definitive assessment. Using anatomical analysis as well as high-speed video and synchronized audio recordings, we show that compared to related species, Manacus radii are morphologically unique and confirm that they collide over the back of the bird at the moment (± 1 ms) the wingsnap is produced. Using aeroacoustic theory, we quantitatively estimate the acoustic signatures from three previously proposed sonation mechanisms. We conclude that only the physical contact hypothesis, wherein the wing collisions create the sound, is consistent with the measured sonation.
... Load and displacement data were collected every 5 N. The elastic modulus (E) of the bone was obtained using the following equation [13] ...
In this work, a novel ultrasound-guided remote measurement technique is proposed for bone quality assessment. The technique utilizes an acoustic radiation force (ARF) excitation source to generate vibrational waves from the bone, and the ensuing radiating acoustic pressure is captured for analysis. Of particular interest, are extracting acoustic features related to the bone mechanical properties. Ex-vivo experiments of demineralized and intact (non-demineralized) bones are conducted, in order to determine the best acoustic features delineating the effects of demineralization. Mechanical tests demonstrate a reduction in the bone elastic modulus with demineralization. The acoustic waves from the intact bones travel faster than the demineralized bones. The spectra of the acoustic response of the demineralized bones exhibit higher attenuation for frequencies below 200 kHz in comparison to the intact bones. A time-frequency analysis exhibits a frequency shift with demineralization. Acoustic features related to these observations are extracted from the acoustic response of the bare bone experiments. Thereafter, attempts are made to recover these features from bone phantom experiments with overlaying tissue-like material. The results are summarized and discussed.
... In addition, ostriches might not be the most appropriate study Fig. 9 The angiographic findings of bilateral ostrich femoral heads at postoperative week 6. a The operation side. b The control side subjects because of the high costs of feeding and rearing, their large body size, and the nature of the species, which differs from that of mammals [18,21]. ...
This study aimed to develop a simple method of creating an animal model of non-trauma femoral head osteonecrosis and collapse using African ostriches with weights similar to those of humans.
Eighteen African ostriches were subjected to liquid nitrogen cryo-insult in the unilateral femoral head through surgical procedures using homemade cryogenic equipment combined with tract drilling inside the femoral head. Three animals were sacrificed at postoperative weeks 6 and 12, respectively, and the remaining animals were sacrificed at postoperative week 24. Bilateral femoral heads were harvested and subjected to gross observation, histological examination using hematoxylin and eosin staining, and radiographic examination. Micro-computed tomography was performed on a portion of the specimens at postoperative week 24, and angiographic examination of the femoral head was performed before sacrificing the animals.
Eight ostriches developed a limp at postoperative week 8, with a mean duration of 16.5 weeks. The postoperative femoral head specimens showed changes in contour and articular cartilage degeneration. Sagittal sectioning of the collapsed femoral head specimens revealed distinct boundaries among the osteonecrotic areas, osteosclerotic areas, and normal trabeculae. Histological examinations revealed active bone resorption in the osteonecrotic area of the subchondral bone, an increased number of fat cells, and active trabecular bone regeneration in the osteosclerotic areas. The postoperative radiographic examinations revealed that the height of the femoral head gradually decreased and progressed to collapse. Micro-computed tomography scans showed the interrupted trabecular bone with an irregular shape in the collapsed femoral head. Compared with the normal samples, angiographic findings revealed interrupted blood supply of the cryo-injured samples in some areas of the femoral heads, blood vessel narrowing, and decreased number of blood vessels in the cryo-injured areas.
This study indicates that an animal model of osteonecrotic femoral head progressing to collapse can be established via a simplified method of cryosurgery. This model possesses histological features that are similar to those of humans; thus, it can be used as an ideal animal model for the study of femoral head necrosis.
... Bone material properties were isotropic and linear-elastic. Young's modulus was chosen as 13.05 GPa by assuming that the elastic properties of trabecular and cortical tissues were similar [31,32]. Poisson's ratio was set to 0.3 [33,34]. ...
... The results are listed in Tables 2 and 3. Results of bending tests reveal an improvement in bending strength and elastic modulus (see Table 2) with respect to pure magnesium. Among Mg-Ca alloys, Mg-0.6Ca shows the highest bending strength (143.4 ± 4.4 MPa) which is comparable to that of the strongest human bone, i.e., cortical bone (180 MPa as listed in Table 2 [16,17]). Clearly, Mg-0.6Ca has the highest fracture deflection among the four Mg-Ca alloys. ...
Magnesium alloys are currently used in many structural applications. It is believed that magnesium and its alloys may also find applications in biomedical fields. In this study, a new biomedical magnesium-based alloy, i.e., magnesium–calcium (Mg–Ca) has been designed from biological and metallurgical viewpoints. The microstructure, mechanical and corrosion behaviors of Mg–Ca alloys with varying calcium content were investigated. The results show that a magnesium alloy with 0.6 wt.% calcium content (denoted as Mg–0.6Ca) shows good corrosion and mechanical properties. Our preliminary results demonstrate a good potential of this Mg–0.6Ca alloy as a new biomedical material.
The bone quality of patients undergoing hip replacement surgery is poorly predicted by radiographs alone. With better bone quality information available to a surgeon, the operation can be performed more safely. The aim of this study was to investigate whether ultrasound signals of cortical bone at peripheral sites such as the tibia and radius can be used to predict the compressive mechanical properties of cortical bone at the femoral neck.
We recruited 19 patients undergoing elective hip arthroplasty and assessed the radius and tibia of these patients with the Azalee guided wave ultrasound to estimate the porosity and thickness of the cortex. Excess bone tissues were collected from the femoral neck and the compressive mechanical properties of the cortex were characterised under a mechanical loading rig to determine stiffness, ultimate strength, and density. The correlations between the ultrasound measurements and mechanical properties were analysed using linear regression, Pearson correlation statistics, and multiple regression analysis.
Cortical mechanical properties were weakly to moderately correlated with the ultrasound measurements at various sites (R² = 0.00–0.36). The significant correlations found were not consistent across all 4 peripheral measurement sites. Additionally, weak to moderate ability of the ultrasound to predict mechanical properties at the neck of femur with multiple regression analysis was found (R² = 0.00–0.48). Again, this was inconsistent across the different anatomical sites. Overall, the results demonstrate the need for ultrasound scans to be collected directly from clinically relevant sites such as the femoral neck due to the inconsistency of mechanical properties across various sites.
In this work, an ultrasound-guided remote measurement technique is proposed for bone demineralization assessment. Utilizing an acoustic radiation force (ARF) beam as our excitation source and a receiving hydrophone, the mechanical properties of a bone can be noninvasively assessed. Focusing the ARF beam on the bone surface acts as point force generating vibrational waves. Coupling the bone surface and hydrophone, the ensuing radiating acoustic pressure from these vibrational waves are captured for analysis. Of particular interest, are the features best related to the bone’s mechanical properties. Conducting ex-vivo experiments demonstrated that the velocity feature best delineates intact and demineralized bones. The typical velocity of an intact bone (3000 m/s) is higher in comparison to a 72 h demineralized bone (1600 m/s). According to the receiver operating characteristic (ROC) curve, the optimal velocity cut-off value of 3096 m/s yields 80% sensitivity and 82.61% specificity between the intact and demineralized bones. Other features, such as the spectra of the demineralized bones’ acoustic response, exhibited higher attenuation for frequencies below 200 kHz in comparison to the intact bones. A time-frequency analysis demonstrated a frequency shift with demineralization. These results demonstrate the potential application of our proposed technique for monitoring bone demineralization.
Ligaments are regularly subjected to repetitive loading in vivo. Typically, mechanical studies focus on repetitive loading protocols of short duration, while those characterizing damage accumulation over a longer duration (i.e., fatigue studies) are lacking. The aims of this study were as follows: (a) to demonstrate that damage does accumulate in ligament tissue subjected to repetitive loading and (b) to evaluate existing and new methods for characterizing fatigue damage accumulation. It was hypothesized that ligaments would accumulate damage with repetitive loading as evidenced by failure at stresses well below ultimate tensile strength, creep curve discontinuities, and by reductions in stiffness during loading. Eight normal medial collateral ligaments from female New Zealand white rabbits were cycled in tension, between 0 MPa and 28 MPa, to failure or until 259,200 cycles, whichever came first. Medial collateral ligaments that did not fail were subsequently loaded to failure. Displacement rates (dl(max)/dt) as well as primary, secondary, and tertiary creeps were monitored as indices of damage accumulation and impending mechanical failure. Additionally, the relative utilities of tangent, secant, and chord stiffness parameters were critically evaluated. Finally, new uses for the second derivative of force-displacement data were explored. Three out of eight ligaments failed during testing, demonstrating that ligaments can fail in fatigue under moderate tensile stress in vitro. The evaluation of displacement rates (dl(max)/dt), as well as primary through tertiary creep patterns, were not well suited to predicting failure in normal ligaments until rupture was all but imminent. Tangent stiffness, which was calculated from a mathematically defined start of the "linear region," was surprisingly constant throughout testing. Secant stiffness dropped in a predictable fashion, providing a global indicator of tissue stiffness, but did not provide any insight into fiber mechanics. Chord stiffness, on the other hand, appeared to be sensitive to fiber recruitment patterns. The second derivative of force-displacement data proved to be a useful means of (a) objectively defining the start of the linear region and (b) inferring changes in fiber recruitment patterns within ligament tissue. Tangent, secant, and chord stiffnesses highlight different attributes of ligament responses to loading; hence these parameters cannot be used interchangeably. Additionally, the second derivative of the force-displacement curve was introduced as a useful descriptive and analytical tool.
While titanium has been clinically successful as an orthopedic or dental implant material, performance problems still persist related to implant-bone interfacial strength and mechanical modulus mismatch between titanium and tissue. We describe here the preparation of a titanium foam as a better mechanical match to tissue with surfaces attractive to bone cells through deposition of an organically-modified apatite layer (organoapatite). In a rotating bioreactor, these organoapatite-coated foams are successfully colonized by preosteoblastic cells. Finite element analyses suggest that ingrown tissue in these systems may improve both implant performance and tissue formation through load-sharing and stress distribution. The novel metal-ceramic-polymer hybrid materials described here hold great promise for bone tissue engineering.
Porous titanium with elongated and aligned pores, mimicking the anisotropic structure of bone, was created by solid-state expansion of argon trapped in elongated pores between titanium wires. Both elastic moduli and yield strengths are larger in the longitudinal direction (E = 51 GPa, sigma y = 338 MPa) than in the transverse direction (E = 41 GPa, sigma y = 267 MPa). Finite-element analysis of simplified anisotropic structures provides insight into the local micromechanical behavior of these porous materials, evaluating elastic modulus, resistance to plastic deformation, and localized stress concentrations which may be experienced under biological loading. Preliminary in vitro cell culture studies further demonstrate the influence of the elongated porous microstructure on osteoblast colonization behavior. These studies suggest that as an optimized material, titanium with aligned, elongated pores is promising for applications in orthopedic tissue engineering, as it combines high strength, toughness, and biocompatibility of titanium with the reduced stiffness and open porosity suitable for mechanical integration with bone tissue produced by aligned pores.
Spin-echo MR imaging has been shown to be highly sensitive in the detection of avascular necrosis. Very early avascular necrosis can, however, appear normal on MR images. We compared dynamic contrast-enhanced MR imaging with conventional spin-echo and short Tl inversion-recovery (STIR) sequences for detecting acute osteonecrosis in an animal model.
Avascular necrosis was induced unilaterally in the femoral heads of five dogs that were imaged with a 1.5-T system within 3 hr of devascularization. After standard T1-weighted, T2-weighted, and STIR images, gradient-recalled echo images, 28/5 (TR/TE) with a 45 degrees flip angle, were obtained at 6-sec intervals for 90 sec synchronous with the IV administration of 0.2 mmol of gadoteridol per kilogram of body weight at a rate of 2 ml/sec via an automated injector. Two animals were reimaged after 7 days.
Spin-echo and STIR images did not show any acute changes in the ischemic femoral heads. In contrast, significant differences were present in the enhancement profiles of the marrow spaces in the normal and ischemic femoral heads (p = .005). Normal marrow was characterized by rapid enhancement, with an average signal intensity increase of 83% peaking at 36 sec; no measurable enhancement was seen in the marrow of the ischemic femoral head. Spin-echo images, obtained 7 days after devascularization (n = 2), showed changes characteristic of avascular necrosis. Dynamic contrast-enhanced MR images showed persistent lack of enhancement in the avascular marrow of the ischemic femoral head. A junctional zone, characterized by rapid contrast enhancement in excess of 120% without early washout, was identified at the interface between normal and avascular marrow.
In this experimental model, dynamic contrast-enhanced MR imaging proved significantly more sensitive than conventional spin-echo and STIR imaging in the detection of acute avascular necrosis.
Uniaxial fatigue tests were conducted of devitalized cortical bone specimens machined from human femora. Specimens were tested at strain ranges from 0.005 to 0.010 under physiologic loading rates. The influence of compressive, zero, and tensile mean strains on fatigue life and on the stress/strain histories during fatigue were examined. Results showed that bone fatigue is a gradual damage process accompanied by a progressive increase in hysteresis and a loss of bone stiffness. The total number of cycles to fatigue failure was influenced only by the total strain range and was not affected by mean strain. Bone was shown to have extremely poor fatigue resistance. Fully reversed cyclic loading to one half of the yield strain caused fatigue fracture in 1000 cycles. Biological implications. The bone regions which experience the highest strain ranges in vivo generally have a compressive mean strain. The results of this study indicate that mechanical fatigue damage accumulates more rapidly in these "compressive" areas than in "tensile" areas of bone.
Finite element stress and strain distributions were studied parametrically for a curved long bone using several common material simplifications. A new technique is presented whereby local material axes conforming to local surface topology were automatically computed. Linearly elastic stress/strain solutions were evaluated as a function of the manner in which principal material directions are defined. The simplifications inherent in assumptions of local isotropy or globally registered transverse isotropy led to appreciably different solutions, particularly for some of the lesser-magnitude components of the strain tensor.
Nonhuman animal research is advantageous only if the ethical dilemma surrounding the use of live animals for this purpose is resolved in one's laboratory and institution. Investigators have struggled in creating an animal model of the disease that realistically mimics the natural course of the disease in humans. It has been exceptionally difficult to develop a model that proves capable of progressing to the end-stage condition of frank mechanical collapse that occurs in humans. This paper attempts to describe the significant findings of various animal models, their advantages and disadvantages, and their key methodologies that could assist in the development of that elusive ideal model.
We investigated the effects of hyperbaric oxygenation (HBO) on ischemic osteonecrosis and on ossification disturbance of the femoral heads in growing, spontaneously hypertensive rats (SHR). 10 male SHRs aged 5 weeks (Group A) and another 10 male SHRs aged 8 weeks (Group B) were treated with HBO at 2.8 atmosphere absolute (ATA) for 6 weeks in a total of 30 hours. The control animals, 10 male SHRs (Group C) and 10 male wistar Kyoto rats (WKY, Group D), were kept under normal laboratory conditions. All the rats were killed at the age of 17 weeks for microscopic examination. In Group A, there was no evidence of osteonecrosis, and only 2 femoral heads with ossification disturbance were observed. In Group B, there were 2 femoral heads with osteonecrosis and 1 with ossification disturbance. In contrast, there were 6 femoral heads with osteonecrosis and 4 with ossification disturbance in Group C. It was concluded that HBO prevented osteonecrosis and ossification disturbance of the femoral heads in SHR.
The magnetic resonance (MR) signal behavior of freshly excised pig femoral heads undergoing ischemic necrosis in vitro was evaluated. Ten femoral heads removed from skeletally immature pigs were stored at 37 degrees in a sealed, sterile container during the observation period. Imaging was initially performed 40 minutes after excision (base-line) and repeated at six, 12, 24, 48, and 72 hours. Changes in MR signal intensity were measured, and the T1 and T2 relaxation times were calculated for selected epiphyseal and metaphyseal areas. Signal intensities decreased during the first 24 hours and returned to baseline by 72 hours. T1 relaxation time increased most significantly between baseline and 24 hours and then decreased to near baseline level between 48 and 72 hours. T2 changes over time were not statistically significant. The type of localized, distinctive decreases in MR signal intensity occurring in clinical cases of early nontraumatic femoral head osteonecrosis was not observed in pigs. Such changes appear to require the presence of an intact and vigorous repair response within adjacent viable bone. However, the transient decrease in signal intensity and prolongation of T1 relaxation time at 12, 24, and 48 hours after traumatic vascular insult may be indicators of early femoral head ischemia.
The ultimate compressive strength and modulus of elasticity of femoral cortical bone from adult geese (Anser anser), were determined by sex and by quadrant by compressing small right circular cylinders which were 2.4 mm in height and 0.8 mm in diameter. The average ultimate compressive strength was 183 +/- 29 MPa. The average modulus of elasticity was 13.2 +/- 3.4 GPa. The bending strength and bending modulus of elasticity were determined by a three point bend test on rectangular prisms which had the approximate dimensions 0.75 mm X 0.75 mm X 25 mm. The average bending strength was 263 +/- 44 MPa while the average bending modulus was 19.6 +/- 3.1 GPa. The calcium content was determined by atomic absorption spectrophotometry and no correlation was found with the mechanical properties. The histology of the cortical bone was examined both quantitatively and qualitatively. A unique type of Haversian bone is described. Goose bone was found to be morphologically similar to adolescent human bone and to have mechanical properties similar to those of adult human bone.
We investigated early osteonecrosis using in vivo magnetic resonance imaging in a nontraumatic rabbit model of serum-sickness osteonecrosis in which osteonecrosis was induced after two intravenous injections of horse serum with a 3-week interval. One week (group A, 17 rabbits) and 3 weeks (group B, 13 rabbits) after the second serum injection, coronal magnetic resonance images of the femur were obtained and it was removed for histological study. Some of the necrotic lesions in the diaphysis were detected on T1-weighted, T2-weighted, or fat-suppression T1-weighted images (six of 24 necrotic lesions in group A and 16 of 18 in group B), and all of the necrotic lesions in the epiphysis, metaphysis, and diaphysis were detected on T1-weighted or fat-suppression T1-weighted images enhanced with gadolinium-diethylene triamine pentaacetic acid. All focal homogeneous enhanced areas on T1-weighted or fat suppression T1-weighted images corresponded to necrotic lesions (22 of 24 necrotic lesions in group A and 18 of 18 in group B); the contours of the enhanced areas were displayed more clearly on the fat-suppression T1-weighted than on the T1-weighted images. The fat-suppression T1-weighted image enhanced with gadolinium-diethylene triamine pentaacetic acid was thus the most sensitive and specific of five kinds of magnetic resonance images for the detection of early necrotic lesions. The results suggest that this image may be useful for early diagnosis of clinical osteonecrosis and for obtaining information about the pathomechanism of osteonecrosis.
Collapse Attainment in a New Animal Model of Osteonecrosis
- Conzemius
Conzemius, et al.: "Collapse Attainment in a New
Animal Model of Osteonecrosis" Proceedings of the
46 th Annual meeting of the Orthopaedic Research Society (2000) p. 206.
Magnetic Resonance Imaging of the Ischemic Femoral Head in Pigs
- B A Lang
- H E Jergesen
- H K Genant
- M E Moseley
- J Schulte-Monting
Lang, B.A., Jergesen, H.E., Genant, H.K.,
Moseley, M.E., Schulte-Monting, J.: "Magnetic
Resonance Imaging of the Ischemic Femoral Head
in Pigs" Clin Orthop (1989) 244, 272-280.