scholarly journals Biomechanical investigation of extragraft bone formation influences on the operated motion segment after anterior cervical spinal discectomy and fusion

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Won Man Park ◽  
Yong Jun Jin
Keyword(s):  
Energy Density ◽  
Bone Formation ◽  
Trabecular Bone ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Rotation Angle ◽  
Von Mises Stress ◽  
Stress And Strain ◽  
Mechanical Stimuli ◽  
Motion Segment

AbstractAlthough the clinical importance of extragraft bone formation (ExGBF) and bridging (ExGBB) has been reported, few studies have investigated the biomechanical influences of ExGBF on the motion segment. In this study, ExGBF was simulated at the C5-C6 motion segment after anterior cervical discectomy and fusion using a developed finite element model and a sequential bone-remodelling algorithm in flexion and extension. The computer simulation results showed that extragraft bone was primarily formed in the extension motion and grew to form ExGBB. A stepwise decrease in the intersegmental rotation angle, maximum von Mises stress and strain energy density on the trabecular bone with ExGBF were predicted in extension. When ExGBB was formed in the trabecular bone region, the intersegmental rotation angle slightly decreased with additional bone formation. However, the stress and strain energy density on the trabecular bone region decreased until ExGBB reached the peripheral cortical margin. The results offer a rationale supporting the hypothesis that mechanical stimuli influence ExGBF. ExGBF was helpful in increasing the stability of the motion segment and decreasing the fracture risk of trabecular bones, even in cases in which ExGBB was not formed. ExGBB can be classified as either soft or hard bridging based on a biomechanical point of view.

Mechanical states encoded by stretch-sensitive neurons in feline joint capsule

1996 ◽  
Vol 76 (1) ◽  
pp. 175-187 ◽  
Author(s):  
P. S. Khalsa ◽  
A. H. Hoffman ◽  
P. Grigg
Keyword(s):  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Neuronal Response ◽  
Neural Response ◽  
Joint Capsule ◽  
Stress And Strain ◽  
Mechanical State ◽  
Simple Correlation ◽  
Strain Components

1. The sensitivity of group II joint afferents innervating cat knee joint capsule to in-plane stretch was studied in vitro. Single afferents were recorded from teased filaments of the posterior articular nerve. The capsule was stretched by applying forces through tabs along the edges of the capsule (3 tabs/edge) with the use of an apparatus that allowed for independent control of each load. The relationships between the neural responses of these afferents and the local continuum mechanical state of the joint capsule have been investigated. By appropriately loading the tissue margins, it was possible to establish states of uniaxial and biaxial tension, including shear. 2. Plane stress was calculated from the loads along the tissue margins. Stress at the location of the mechanoreceptor ending was estimated by interpolation. Strain was calculated from deformations of the capsule measured by tracking markers on its surface. Full characterization of tissue stress and strain made it possible to determine strain energy density and the magnitudes of other coordinate invariant mechanical quantities. 3. Individual afferents (n = 15) exhibited pronounced selectivity to the direction of applied stress and strain. There was no overall preferred orientation across neurons, and simple correlation of individual stress or strain components with the neuronal response revealed no consistent relationship between neuronal response and any single tensor component. However, linear multiple regression of the combined stress and strain components with the neuronal response revealed high correlation (mean R = 0.91), indicating that the measured mechanical states strongly determine the neuronal response. There was a much stronger relationship between neuronal response and stress variables than with strain variables. Simple correlation of the first invariant of the stress tensor with neuronal response had the highest mean correlation of the tensor quantities (R = 0.51). On average, strain energy density was only modestly correlated with the neural response (R = 0.28). 4. These findings indicate that capsule mechanoreceptors are encoding the local continuum mechanical state in the joint capsule. The neural response of these mechanoreceptors is more strongly correlated to local stress than to local strain.

New aspects of the trabecular bone remodeling regulatory model resulting from the shape optimization studies

2019 ◽  
Vol 234 (3) ◽  
pp. 282-288
Author(s):  
Michał Nowak ◽  
Jan Sokołowski ◽  
Antoni Żochowski
Keyword(s):  
Energy Density ◽  
Shape Optimization ◽  
Trabecular Bone ◽  
Bone Remodeling ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Natural Phenomenon ◽  
Bone Surface ◽  
Clinical Observations ◽  
Trabecular Bone Remodeling

The trabecular bone can adapt its form to mechanical loads and form structures that are both lightweight and very stiff. In this sense, it is a problem similar to structural optimization, especially topology optimization. The natural phenomenon leading to mechanical optimization of the bone structures is called trabecular bone remodeling. The main assumption and the benchmark for the numerical models of the phenomenon is the observation that the strain energy density on the structural surface is constant. This constant value corresponds to the homeostatic strain energy density, the state of bone tissue with a perfect balance of the loss, and gain of the bone mass. We assumed that the trabecular bone can form an optimal structure. The idea behind the investigation is to carry out studies on the ground of mechanics and to interpret clinical observations in the context of the results obtained from the optimization studies. In this way, clinical observations have been confirmed by strict arguments based on mechanics, leading to the unequivocal conclusion that equalization of the strain energy density on the trabecular bone surface allows minimizing the strain energy in the whole structure of the bone. This proves the veracity of the assumption that the remodeling process leads to the formation of the structure with the highest stiffness. In addition, this article elaborates on two new aspects of the remodeling phenomenon resulting directly from the considerations in the field of shape optimization important for numerical simulation. The first one concerns the influence of surface curvature on the remodeling process. The second one concerns the role of the bone surface where different loads are analyzed. Both aspects show the need of actual trabecular bone geometry model for the simulation of the trabecular bone remodeling phenomenon.

An Innovative Yield Criterion Considering Strain Rates Based on Von Mises Stress

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Jingwei Yu ◽  
Qingguo Fei ◽  
Peiwei Zhang ◽  
Yanbin Li ◽  
Dahai Zhang ◽  
...  
Keyword(s):  
Energy Density ◽  
Yield Strength ◽  
Constitutive Model ◽  
Strain Rate ◽  
Dynamic Load ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Yield Criterion ◽  
Von Mises Stress ◽  
Von Mises

Abstract An innovative yield criterion based on von Mises stress is proposed to represent the strain rate-dependent behavior under dynamic load. Considering the strain rate in the constitutive model, the distortional strain energy density is derived and the yield criterion is established. A plot of yield strength for a range of strain rate reveals that despite the differences in material properties and test methods, the yield strength rise can be represented by a unified criterion. The overall yield behavior of the material under dynamic load can be explained by introducing the strain rate into the constitutive model and threshold distortional strain energy density. This criterion is in a simple form that may be widely applied.

Experimentally determined microcracking around a circular hole in a flat plate of bone: comparison with predicted stresses

1995 ◽  
Vol 347 (1322) ◽  
pp. 383-396 ◽  
Keyword(s):  
Energy Density ◽  
Circular Hole ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Bone Remodelling ◽  
Von Mises Stress ◽  
Analysis Model ◽  
Material Interfaces ◽  
Empirical Examination ◽  
Von Mises

We examined the microcracking (damage) in the vicinity of a circular hole in bovine femoral bone specimens. The stresses near the hole were derived by a finite element analysis model using the bone’s elastic constants and yield stresses, which were determined from a series of mechanical tests specifically for the type of bone under examination. The spatial occurrence and distribution of microcracking was compared to the patterns of the predicted maximum principal stress, the von Mises stress, and the strain energy density function (all implicated by various workers as stimuli for bone remodelling) and to the predictions derived by the use of two engineering criteria for anisotropic yield under mixed mode of stress. The predictions for stresses and the strain energy density were all very similar, making it impossible to claim that any of them is superior to the others. However, empirical examination of the results of the Hencky-von Mises and Tsai-Wu anisotropic yield criteria showed that the Tsai-Wu criterion approximated reasonably the pattern of microcracking around the hole. We suggest that, in the light of the considerable damage observed in the vicinity of stress concentrators, similar damage in irregular material interfaces (i.e. near orthopaedic implants) would require the re-examination of the theories concerning bone remodelling so as to account for the possibility of occurrence of damage and the quantification of its magnitude and likely effect. The presence of considerable microdamage in bone long before it fails suggests that damage-based criteria are more likely to be successful predictors of bone remodelling behaviour than would stress or strain-based criteria.

Microstructure Evolution and Analysis of a Single Crystal Nickel-Based Superalloy during Tensile Creep

2011 ◽  
Vol 689 ◽  
pp. 154-158 ◽  
Author(s):  
Shu Zhang ◽  
Su Gui Tian ◽  
Yong Su ◽  
Ben Jiang Qian
Keyword(s):  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Lattice Misfit ◽  
Tensile Creep ◽  
Von Mises Stress ◽  
Stress Axis ◽  
Directional Growth ◽  
Misfit Stress ◽  
Von Mises

By means of the finite element method (FEM) for calculating the von Mises stress and strain energy density in the cubic γ/γ′ phases, the regularity of γ′ phase directional growth is investigated. Results show that the change of the strain energy density in the different planes of the cubical γ′ phase occurs during tensile creep of alloy, the cubical γ′ phase is directionally grown, along the crystal plane with bigger strain energy, to transform into the mesh-like rafted structure along the direction perpendicular to the applied stress axis. The change of the atomic potential energy, interfacial energy and lattice misfit stress is thought to be the driving force for promoting the elements diffusion and directional growth of γ′ phase.

scholarly journals The role of PDL-cementum enthesis in protecting PDL under masticatory loading: A finite element investigation

2021 ◽  
Author(s):  
Hossein Jokar ◽  
Gholamreza Rouhi ◽  
Nabiollah Abolfathi
Keyword(s):  
Computed Tomography ◽  
Finite Element ◽  
Periodontal Ligament ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Alveolar Bone ◽  
Von Mises Stress ◽  
Mechanical Stimuli ◽  
Von Mises

Abstract PURPOSE. Function of periodontal ligament-cementum enthesis (PCE) in transferring mechanical stimuli within tooth-periodontium (PDT)-bone complex was not made clear yet. This study aimed to evaluate the effects of PCE on the mechanical stimuli distribution within the PDL and alveolar bone in the tooth-PDT-bone complex under occlusal forces using finite element method (FEM). METHODS. A computed tomography (CT) based model of alveolar bone and 2nd premolar of mandible was constructed, in which the PDT was considered at the interface of alveolar bone and tooth. Under a 3MPa distributed occluso-apical masticatory load, applied over the uppermost surface of crown, the von Mises strain (vMST) and strain energy density (SED) within PDL, and von Mises stress (vMSR) and SED within alveolar bone were calculated in two situations: 1. When the PCE was absent; and 2. When the PCE was present between the PDL and cementum. RESULTS. PCE levels-off the SED and vMST within PDL by maximum values of 92 kPa and 0.04 mm/mm, respectively, compared to the model without PCE. Moreover, it increased the alveolar bone SEDs and vMSR by maximum values of 0.36 kPa and 0.63 MPa, respectively, compared to the without PCE model.CONCLUSION. By including PCE in the tooth-PDT-bone model, the mechanical stimuli shift from PDL to its surrounding alveolar bone. Thus, it can be speculated that the tooth-PDT-bone complex has the capability of, through shifting excess mechanical stimuli from PDL toward the alveolar bone, reducing the risk of PDL damage.

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