Spine stability after implantation of an interspinous device: an in vitro and finite element biomechanical study

2010 ◽  
Vol 13 (5) ◽  
pp. 568-575 ◽  
Author(s):  
Federica Anasetti ◽  
Fabio Galbusera ◽  
Hadi N. Aziz ◽  
Chiara M. Bellini ◽  
Alessandro Addis ◽  
...  
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Radicular Pain ◽  
Biomechanical Study ◽  
Neutral Position ◽  
Spinal Stabilization ◽  
Interspinous Devices ◽  
Segmental Lordosis ◽  
Device Size

Object Interspinous devices are widely used for the treatment of lumbar stenosis. The DIAM spinal stabilization system (Medtronic, Ltd.) is an interspinous implant made of silicone and secured in place with 2 laces. The device can be implanted via posterior access with the sacrifice of the supraspinous ligament (SSL) or via lateral access with preservation of the ligament. The aim of the present work was to evaluate the role of the laces, the SSL, and the device size and positioning to determine the device's ability in reducing segmental lordosis and in stabilizing motion. Methods Biomechanical tests were performed in flexion and extension on 8 porcine spines implanted with the DIAM either with or without the laces and the SSL. A finite element model of the human L4–5 spine segments was also created and used to test 2 sizes of the device implanted in 2 different positions in the anteroposterior direction. Results Implantation of the DIAM induced a shift toward kyphosis in the neutral position. Laces, the SSL, and device size and placement had a significant influence on the neutral position, the stiffness of the implanted spine, and the positions of the instantaneous centers of rotation. Conclusions The shift of the neutral position toward kyphosis may be beneficial in reducing symptoms of spinal stenosis such as radicular pain, sensation disturbance, and loss of strength in the legs. The authors recommend preservation of the SSL and the use of the fixation laces, given their relevant mechanical role. Choosing the proper device size and placement should be achieved by using a correct surgical technique.

Biomechanical Study of Lumbar Spine (L2-L4) Using Hybrid Stabilization Device - A Finite Element Analysis

2020 ◽  
Vol 10 (1) ◽  
pp. 20-32 ◽  
Author(s):  
Pushpdant Jain ◽  
Mohammed Rajik Khan
Keyword(s):  
Finite Element ◽  
Compressive Force ◽  
Element Model ◽  
Biomechanical Study ◽  
Bottom Surface ◽  
Element Analysis ◽  
Axial Compressive Force ◽  
Hybrid Stabilization ◽  
Flexion Extension ◽  
Lumbar Segment

Spinal instrumentations have been designed to alleviate lower back pain and stabilize the spinal segments. The present work aims to evaluate the biomechanical effect of the proposed Hybrid Stabilization Device (HSD). Non-linear finite element model of lumbar segment L2-L4 were developed to compare the intact spine (IS) with rigid implant (RI) and hybrid stabilization device. To restrict all directional motion vertebra L4 bottom surface were kept fixed and axial compressive force of 500N with a moment of 10Nm were applied to the top surface of L2 vertebrae. The results of range of motion (ROM), intervertebral disc (IVD) pressure and strains for IVD-23 and IVD-34 were determined for flexion, extension, lateral bending and axial twist. Results demonstrated that ROM of HSD model is higher than RI and lower as compared to IS model. The predicted biomechanical parameters of the present work may be considered before clinical implementations of any implants.

Physiological Elongation of Ligamentous Complex Surrounding the Hindfoot Joints: In Vitro Biomechanical Study

1997 ◽  
Vol 18 (5) ◽  
pp. 277-283 ◽  
Author(s):  
Zong-Ping Luo ◽  
Harold B. Kitaoka ◽  
Horng-Chaung Hsu ◽  
Hideji Kura ◽  
Kai-Nan An
Keyword(s):  
In Vitro Study ◽  
Biomechanical Study ◽  
Vitro Study ◽  
Ligament Length ◽  
Neutral Position

Ligaments surrounding the hindfoot joints play an important role in hindfoot stability. This in vitro study investigated anatomical and biomechanical characteristics of nine major ligamentous structures, including length and orientation at neutral position and physiological elongation with the foot in five different positions relative to the neutral position. The results showed that ligament elongation depended on the ligament length, orientation in neutral position, and movement of bones to which they were attached.

BIOMECHANICAL BEHAVIOUR OF BOVINE SKIN: AN EXPERIMENT-THEORY INTEGRATION AND FINITE ELEMENT SIMULATION

2015 ◽  
Vol 76 (10) ◽  
Author(s):  
Nor Fazli Adull Manan ◽  
Jamaluddin Mahmud ◽  
Aidah Jumahat
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Deformation Behaviour ◽  
Element Model ◽  
Tensile Tests ◽  
Theory Integration ◽  
Element Simulation ◽  
Knowledge Enhancement ◽  
First Time

This paper for the first time attempts to establish the biomechanical characteristics of bovine skin via experiment-theory integration and finite element simulation. 30 specimens prepared from fresh slaughtered bovine were uniaxially stretched in-vitro using tensile tests machine. The experimental raw data are then input into a Matlab programme, which quantified the hyperelastic parameters based on Ogden constitutive equation. It is found that the Ogden coefficient and exponent for bovine skin are μ = 0.017 MPa and α = 11.049 respectively. For comparison of results, the quantified Ogden parameters are then input into a simple but robust finite element model, which is developed to replicate the experimental setup and simulate the deformation of the bovine skin. Results from experiment-theory integration and finite element simulation are compared. It is found that the stress-stretch curves are close to one another. The results and finding prove that the current study is significant and has contributed to knowledge enhancement about the deformation behaviour of bovine skin.

Strain Measurement in Coronary Arteries Using Intravascular Ultrasound and Deformable Images

2002 ◽  
Vol 124 (6) ◽  
pp. 734-741 ◽  
Author(s):  
Alexander I. Veress ◽  
Jeffrey A. Weiss ◽  
Grant T. Gullberg ◽  
D. Geoffrey Vince ◽  
Richard D. Rabbitt
Keyword(s):  
Finite Element ◽  
Intravascular Ultrasound ◽  
Coronary Arteries ◽  
Strain Distribution ◽  
Plaque Rupture ◽  
Element Model ◽  
Cross Sectional ◽  
Image Pairs

Atherosclerotic plaque rupture is responsible for the majority of myocardial infarctions and acute coronary syndromes. Rupture is initiated by mechanical failure of the plaque cap, and thus study of the deformation of the plaque in the artery can elucidate the events that lead to myocardial infarction. Intravascular ultrasound (IVUS) provides high resolution in vitro and in vivo cross-sectional images of blood vessels. To extract the deformation field from sequences of IVUS images, a registration process must be performed to correlate material points between image pairs. The objective of this study was to determine the efficacy of an image registration technique termed Warping to determine strains in plaques and coronary arteries from paired IVUS images representing two different states of deformation. The Warping technique uses pointwise differences in pixel intensities between image pairs to generate a distributed body force that acts to deform a finite element model. The strain distribution estimated by image-based Warping showed excellent agreement with a known forward finite element solution, representing the gold standard, from which the displaced image was created. The Warping technique had a low sensitivity to changes in material parameters or material model and had a low dependency on the noise present in the images. The Warping analysis was also able to produce accurate strain distributions when the constitutive model used for the Warping analysis and the forward analysis was different. The results of this study demonstrate that Warping in conjunction with in vivo IVUS imaging will determine the change in the strain distribution resulting from physiological loading and may be useful as a diagnostic tool for predicting the likelihood of plaque rupture through the determination of the relative stiffness of the plaque constituents.

scholarly journals Applicability assessment of a stent-retriever thrombectomy finite-element model

2020 ◽  
Vol 11 (1) ◽  
pp. 20190123 ◽  
Author(s):  
Giulia Luraghi ◽  
Jose Felix Rodriguez Matas ◽  
Gabriele Dubini ◽  
Francesca Berti ◽  
Sara Bridio ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Blood Circulation ◽  
Blood Clot ◽  
Invasive Procedure ◽  
Element Model ◽  
Stent Deployment ◽  
Numerical Finite Element

An acute ischaemic stroke appears when a blood clot blocks the blood flow in a cerebral artery. Intra-arterial thrombectomy, a mini-invasive procedure based on stent technology, is a mechanical available treatment to extract the clot and restore the blood circulation. After stent deployment, the clot, trapped in the stent struts, is pulled along with the stent towards a receiving catheter. Recent clinical trials have confirmed the effectiveness and safety of mechanical thrombectomy. However, the procedure requires further investigation. The aim of this study is the development of a numerical finite-element-based model of the thrombectomy procedure. In vitro thrombectomy tests are performed in different vessel geometries and one simulation for each test is carried out to verify the accuracy and reliability of the proposed numerical model. The results of the simulations confirm the efficacy of the model to replicate all the experimental setups. Clot stress and strain fields from the numerical analysis, which vary depending on the geometric features of the vessel, could be used to evaluate the possible fragmentation of the clot during the procedure. The proposed in vitro / in silico comparison aims at assessing the applicability of the numerical model and at providing validation evidence for the specific in vivo thrombectomy outcomes prediction.

The Patient-Specific Brace Design and Biomechanical Analysis of Adolescent Idiopathic Scoliosis

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Wen-Zhong Nie ◽  
Ming Ye ◽  
Zu-De Liu ◽  
Cheng-Tao Wang
Keyword(s):  
Finite Element ◽  
Measurement System ◽  
Element Model ◽  
Biomechanical Study ◽  
Biomechanical Analysis ◽  
Patient Specific ◽  
Sacral Slope ◽  
Element Analysis ◽  
Biomechanical Behavior ◽  
Idiopathic Adolescent Scoliosis

Brace application has been reported to be an effective approach in treating mild to moderate idiopathic adolescent scoliosis. However, little attention is focused on the biomechanical study of patient-specific brace treatment. The purpose of this study was to propose a design method of personalized brace and to analyze its biomechanical behavior and to compare the brace forces with the I-Scan measurement system. Based on a three-dimensional patient-specific finite element model of the spine, rib cage, pelvis, and abdomen, a parametric patient-specific model of a thoracolumbosacral orthosis was built. The interaction between the torso and the brace was modeled by surface-to-surface contact interface. Three standard strap tensions (20 N, 40 N, and 60 N) were loaded on the back of the brace to simulate the strap tension. The I-Scan distribution pressure measurement system was used to measure the different region pressures, and the equivalent forces in these regions were calculated. The spinal curve changes and the forces acted on the brace generated by the strap tension were evaluated and compared with the measurement. The reduction in the coronal curvature was about 60% for a strap tension of 60 N. The sacral slope and the lordosis were partially reduced in this case, but the kyphosis had no obvious change. The brace slightly modified the axial rotation at the apex of the scoliotic curve. The forces generated in finite element analysis were approximately in good agreement with the measurement. The design and biomechanical analysis methods of patient-specific brace should be useful in the design of more effective braces.

IMAGE-BASED SKELETAL MUSCLE COORDINATION: CASE STUDY ON A SUBJECT SPECIFIC FACIAL MIMIC SIMULATION

2018 ◽  
Vol 18 (02) ◽  
pp. 1850020 ◽  
Author(s):  
TIEN TUAN DAO ◽  
ANG-XIAO FAN ◽  
STÉPHANIE DAKPÉ ◽  
PHILIPPE POULETAUT ◽  
MOHAMED RACHIK ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Coordination Mechanism ◽  
Neutral Position ◽  
Muscle Coordination ◽  
Facial Muscle ◽  
Facial Muscles ◽  
Subject Specific

Facial muscle coordination is a fundamental mechanism for facial mimics and expressions. The understanding of this complex mechanism leads to better diagnosis and treatment of facial disorders like facial palsy or disfigurement. The objective of this work was to use magnetic resonance imaging (MRI) technique to characterize the activation behavior of facial muscles and then simulate their coordination mechanism using a subject specific finite element model. MRI data of lower head of a healthy subject were acquired in neutral and in the pronunciation of the sound [o] positions. Then, a finite element model was derived directly from acquired MRI images in neutral position. Transversely-isotropic, hyperelastic, quasi-incompressible behavior law was implemented for modeling facial muscles. The simulation to produce the pronunciation of the sound [o] was performed by the cumulative coordination between three pairs of facial mimic muscles (Zygomaticus Major (ZM), Levator Labii Superioris (LLS), Levator Anguli Oris (LAO)). Mean displacement amplitude showed a good agreement with a relative deviation of 15% between numerical outcome and MRI-based measurement when all three muscles are involved. This study elucidates, for the first time, the facial muscle coordination using in vivo data leading to improve the model understanding and simulation outcomes.

scholarly journals Simulating the Growth of Articular Cartilage Explants in a Permeation Bioreactor to Aid in Experimental Protocol Design

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Timothy P. Ficklin ◽  
Andrew Davol ◽  
Stephen M. Klisch
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Articular Cartilage ◽  
Element Model ◽  
Cartilage Explants ◽  
Solid Matrix ◽  
Cartilage Growth ◽  
Growth Laws ◽  
Competing Hypotheses

Recently a cartilage growth finite element model (CGFEM) was developed to solve nonhomogeneous and time-dependent growth boundary-value problems (Davol et al., 2008, “A Nonlinear Finite Element Model of Cartilage Growth,” Biomech. Model. Mechanobiol., 7, pp. 295–307). The CGFEM allows distinct stress constitutive equations and growth laws for the major components of the solid matrix, collagens and proteoglycans. The objective of the current work was to simulate in vitro growth of articular cartilage explants in a steady-state permeation bioreactor in order to obtain results that aid experimental design. The steady-state permeation protocol induces different types of mechanical stimuli. When the specimen is initially homogeneous, it directly induces homogeneous permeation velocities and indirectly induces nonhomogeneous solid matrix shear stresses; consequently, the steady-state permeation protocol is a good candidate for exploring two competing hypotheses for the growth laws. The analysis protocols were implemented through the alternating interaction of the two CGFEM components: poroelastic finite element analysis (FEA) using ABAQUS and a finite element growth routine using MATLAB. The CGFEM simulated 12 days of growth for immature bovine articular cartilage explants subjected to two competing hypotheses for the growth laws: one that is triggered by permeation velocity and the other by maximum shear stress. The results provide predictions for geometric, biomechanical, and biochemical parameters of grown tissue specimens that may be experimentally measured and, consequently, suggest key biomechanical measures to analyze as pilot experiments are performed. The combined approach of CGFEM analysis and pilot experiments may lead to the refinement of actual experimental protocols and a better understanding of in vitro growth of articular cartilage.

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