The Effect of Increasing Fracture Site Stiffness on Bone–Pin Interface Stress and Foot Contact Pressure within the Equine Distal Limb Transfixation Cast: A Finite Element Analysis

2020 ◽  
Vol 33 (05) ◽  
pp. 348-355
Author(s):  
Timothy B. Lescun ◽  
Stephen B. Adams ◽  
Eric A. Nauman ◽  
Gert J. Breur
Keyword(s):  
Finite Element ◽  
Fracture Healing ◽  
Contact Pressure ◽  
Ex Vivo ◽  
Fracture Site ◽  
Interface Stress ◽  
Distal Limb ◽  
Element Analysis ◽  
Composite Tissue ◽  
Tissue Block

Abstract Objective The aim of this study was to determine how increasing stiffness of fracture site tissues distal to the pins in an equine distal limb transfixation cast influences stress at the bone–pin interface, within the bones distal to the transcortical pins, and contact pressure between the foot and the cast. Study Design A transfixation cast finite element model was used to compare the bone–pin interface stress, pin stress, bone stress distal to the pins and contact pressure between the foot and the cast, using six stiffness values for a composite tissue block representing progressive stages of fracture healing. Results Increasing stiffness of the composite tissue block resulted in a decrease in the maximum stresses at the bone–pin interface, an increase in stresses distal to the transcortical pins and a decrease in the maximum pin stresses. As the composite tissue block stiffness was increased, contact pressure between the bottom of the composite tissue block and the cast increased and the stress patterns surrounding the pin holes became less focal. Conclusion The findings of this study illustrate that with good foot to cast contact within a transfixation cast, increases in tissue stiffness due to progressive fracture healing are expected to reduce bone-pin interface stresses, and increase fracture site loading and stress. Increasing the contact pressure between the foot and the cast could reduce transfixation casting complications such as pin loosening, pin hole fracture and poor fracture healing, if these results transfer to ex vivo and in vivo settings.

Effect of Intramedullary Nailing Patterns On Interfragmentary Strain in a Mouse Femur Fracture: a Parametric Finite Element Analysis

2021 ◽  
Author(s):  
Gregory Lowen ◽  
Katherine Garrett ◽  
Moore-Lotridge Stephanie ◽  
Sasidhar Uppuganti ◽  
Scott A. Guelcher ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Healing ◽  
Bone Repair ◽  
Bone Fractures ◽  
Fracture Site ◽  
Fracture Repair ◽  
Long Bone ◽  
Design Parameters ◽  
Element Analysis

Abstract Delayed long bone fracture healing and nonunion continue to be a significant socioeconomic burden. While mechanical stimulation is known to be an important determinant of the bone repair process, understanding how the magnitude, mode, and commencement of interfragmentary strain (IFS) affect fracture healing can guide new therapeutic strategies to prevent delayed healing or non-union. Mouse models provide a means to investigate the molecular and cellular aspects of fracture repair, yet there is only one commercially available, clinically-relevant, locking intramedullary nail (IMN) currently available for studying long bone fractures in rodents. Having access to alternative IMNs would allow a variety of mechanical environments at the fracture site to be evaluated, and the purpose of this proof-of-concept finite element analysis study is to identify which IMN design parameters have the largest impact on IFS in a murine transverse femoral osteotomy model. Using the dimensions of the clinically relevant IMN as a guide, the nail material, distance between interlocking screws, and clearance between the nail and endosteal surface were varied between simulations. Of these parameters, changing the nail material from stainless steel (SS) to polyetheretherketone (PEEK) had the largest impact on IFS. Reducing the distance between the proximal and distal interlocking screws substantially affected IFS only when nail modulus was low. Therefore, IMNs with low modulus (e.g., PEEK) can be used alongside commercially available SS nails to investigate the effect of initial IFS or stability on fracture healing with respect to different biological conditions of repair in rodents.

Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads

1992 ◽  
Vol 20 (2) ◽  
pp. 83-105 ◽  
Author(s):  
J. P. Jeusette ◽  
M. Theves
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Contact Pressure ◽  
Element Model ◽  
Shear Stresses ◽  
Detailed Knowledge ◽  
Stress Distributions ◽  
Element Analysis ◽  
Plane Shear ◽  
Normal Contact

Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.

scholarly journals Real-time finite element analysis allows homogenization of tissue scale strains and reduces variance in a mouse defect healing model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Graeme R. Paul ◽  
Esther Wehrle ◽  
Duncan C. Tourolle ◽  
Gisela A. Kuhn ◽  
Ralph Müller
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fracture Healing ◽  
Real Time ◽  
Mechanical Stimulus ◽  
Stimulus Level ◽  
Micro Computed Tomography ◽  
Reference Distribution ◽  
Element Analysis ◽  
Computed Tomography Images

AbstractMechanical loading allows both investigation into the mechano-regulation of fracture healing as well as interventions to improve fracture-healing outcomes such as delayed healing or non-unions. However, loading is seldom individualised or even targeted to an effective mechanical stimulus level within the bone tissue. In this study, we use micro-finite element analysis to demonstrate the result of using a constant loading assumption for all mouse femurs in a given group. We then contrast this with the application of an adaptive loading approach, denoted real time Finite Element adaptation, in which micro-computed tomography images provide the basis for micro-FE based simulations and the resulting strains are manipulated and targeted to a reference distribution. Using this approach, we demonstrate that individualised femoral loading leads to a better-specified strain distribution and lower variance in tissue mechanical stimulus across all mice, both longitudinally and cross-sectionally, while making sure that no overloading is occurring leading to refracture of the femur bones.

scholarly journals Effect of coronal plane acetabular correction on joint contact pressure in Periacetabular osteotomy: a finite-element analysis

2022 ◽  
Vol 23 (1) ◽  
Author(s):  
Kenji Kitamura ◽  
Masanori Fujii ◽  
Miho Iwamoto ◽  
Satoshi Ikemura ◽  
Satoshi Hamai ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Contact Pressure ◽  
Periacetabular Osteotomy ◽  
Anterior Wall ◽  
Coronal Plane ◽  
Patient Specific ◽  
Element Analysis ◽  
Joint Contact ◽  
Joint Contact Pressure

Abstract Background The ideal acetabular position for optimizing hip joint biomechanics in periacetabular osteotomy (PAO) remains unclear. We aimed to determine the relationship between acetabular correction in the coronal plane and joint contact pressure (CP) and identify morphological factors associated with residual abnormal CP after correction. Methods Using CT images from 44 patients with hip dysplasia, we performed three patterns of virtual PAOs on patient-specific 3D hip models; the acetabulum was rotated laterally to the lateral center-edge angles (LCEA) of 30°, 35°, and 40°. Finite-element analysis was used to calculate the CP of the acetabular cartilage during a single-leg stance. Results Coronal correction to the LCEA of 30° decreased the median maximum CP 0.5-fold compared to preoperatively (p <  0.001). Additional correction to the LCEA of 40° further decreased CP in 15 hips (34%) but conversely increased CP in 29 hips (66%). The increase in CP was associated with greater preoperative extrusion index (p = 0.030) and roundness index (p = 0.038). Overall, virtual PAO failed to normalize CP in 11 hips (25%), and a small anterior wall index (p = 0.049) and a large roundness index (p = 0.003) were associated with residual abnormal CP. Conclusions The degree of acetabular correction in the coronal plane where CP is minimized varied among patients. Coronal plane correction alone failed to normalize CP in 25% of patients in this study. In patients with an anterior acetabular deficiency (anterior wall index < 0.21) and an aspherical femoral head (roundness index > 53.2%), coronal plane correction alone may not normalize CP. Further studies are needed to clarify the effectiveness of multiplanar correction, including in the sagittal and axial planes, in optimizing the hip joint’s contact mechanics.

scholarly journals Finite element analysis to assess the biomechanical behavior of a finger model gripping handles with different diameters

2019 ◽  
Vol 11 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Benedict Jain A.R. Tony ◽  
Masilamany S. Alphin
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Subcutaneous Tissue ◽  
Fe Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Biomechanical Behavior ◽  
Biomechanical Response ◽  
Human Finger ◽  
Finger Model

SummaryStudy aim: Interactions between the fingers and a handle can be analyzed using a finite element finger model. Hence, the biomechanical response of a hybrid human finger model during contact with varying diameter cylindrical handles was investigated numerically in the present study using ABAQUS/CAE.Materials and methods: The finite element index finger model consists of three segments: the proximal, middle, and distal phalanges. The finger model comprises skin, bone, subcutaneous tissue and nail. The skin and subcutaneous tissues were assumed to be non-linearly elastic and linearly visco-elastic. The FE model was applied to predict the contact interaction between the fingers and a handle with 10 N, 20 N, 40 N and 50 N grip forces for four different diameter handles (30 mm, 40 mm, 44mm and 50 mm). The model predictions projected the biomechanical response of the finger during the static gripping analysis with 200 incremental steps.Results: The simulation results showed that the increase in contact area reduced the maximal compressive stress/strain and also the contact pressure on finger skin. It was hypothesized in this study that the diameter of the handle influences the stress/strain and contact pressure within the soft tissue during the contact interactions.Conclusions: The present study may be useful to study the behavior of the finger model under the static gripping of hand-held power tools.

scholarly journals Is Perpendicular Double Two-Hole Plates Fixation Superior to Single Four-Hole Plate Fixation to Treat Mandibular Symphysis Fracture?—A Finite Element Study

2021 ◽  
Vol 11 (18) ◽  
pp. 8629
Author(s):  
Li-Ren Chang ◽  
Ya-Pei Hou ◽  
Ting-Sheng Lin
Keyword(s):  
Finite Element ◽  
Plate Fixation ◽  
Mandibular Condyle ◽  
Fracture Site ◽  
Von Mises Stress ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Mandibular Symphysis ◽  
Lower Border ◽  
Von Mises

The effectiveness of a single four-hole plate (S4HP), perpendicularly oriented four-hole and two-hole plate (Per4H2HP), and perpendicularly oriented double two-hole plate (PerD2HP) for the fixation of a mandibular fracture was studied. A finite element analysis of the mandibular symphysis fractures treated with S4HP, Per4H2HP, and PerD2HP was performed. All surface nodes were fixed in the mandibular condyle region and occlusal muscle forces were applied. The maximal von Mises stress (MaxVMS) values of the plates, screws and screw holes were investigated. The displacement of the fracture site on the lower border of the mandibular symphysis was recorded. The displacement on the lower border of the fracture sites in the S4HP group was greater than that in the Per4H2HP group and the PerD2HP group. There was no eversion at the fracture site among all groups. Both the S4HP and Per4H2HP groups showed stress concentrations on the screws close to the fracture site. The MaxVMS increased when the number of screw holes on the mandibular anterior lower border decreased. The displacement of the fracture site and eversion with Per4H2HP and PerD2HP were far lower than those with S4HP. PerD2HP is a stable and green fixation technique for mandibular symphysis fractures.

scholarly journals Finite Element- and Design of Experiment-Derived Optimization of Screw Configurations and a Locking Plate for Internal Fixation System

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Wei Sheng ◽  
Aimin Ji ◽  
Runxin Fang ◽  
Gang He ◽  
Changsheng Chen
Keyword(s):  
Finite Element ◽  
Internal Fixation ◽  
Locking Plate ◽  
Orthogonal Design ◽  
Structural Parameters ◽  
Uniform Design ◽  
Fracture Site ◽  
Element Analysis ◽  
Internal Fixation System ◽  
Fixation System

Objectives. The optimization for the screw configurations and bone plate parameters was studied to improve the biomechanical performances such as reliable internal fixation and beneficial callus growth for the clinical treatment of femoral shaft fracture. Methods. The finite element analysis (FEA) of internal fixation system under different screw configurations based on the orthogonal design was performed and so was for the different structural parameters of the locking plate based on the combination of uniform and orthogonal design. Moreover, orthogonal experiment weight matrixes for four evaluation indexes with FEA were analyzed. Results. The analytical results showed the optimal scheme of screw configuration was that screws are omitted in the thread holes near the fracture site, and single cortical screws are used in the following holes to the distal end, while the double cortical screws are fixed in thread holes that are distal to the fracture; in the other words, the length of the screws showed an increasing trend from the fracture site to the distal end in the optimized configuration. The plate structure was optimized when thread holes gap reached 13 mm, with a width of 11 mm and 4.6 mm and 5 mm for thickness and diameter of the screw, respectively. The biomechanical performance of the internal fixation construct was further improved by about 10% based on the optimal strain range and lower stress in the internal fixation system. Conclusions. The proposed orthogonal design and uniform design can be used in a more efficient way for the optimization of internal fixation system, which can reduce the simulation runs to about 10% compared with comprehensive test, and the methodology can be also used for other types of fractures to achieve better internal fixation stability and optimal healing efficiency, which may provide a method for an orthopedist in choosing the screw configurations and parameters for internal fixation system in a more efficient way.

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