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.

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.

scholarly journals Biomechanical evaluation of type p condylar head osteosynthesis using conventional small-fragment screws reinforced by a patient specific two-component plate

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Tetiana Pavlychuk ◽  
Denis Chernogorskyi ◽  
Yurii Chepurnyi ◽  
Andreas Neff ◽  
Andrii Kopchak
Keyword(s):  
Finite Element ◽  
Screw Fixation ◽  
Cortical Layer ◽  
Fixation Method ◽  
Patient Specific ◽  
Small Fragment ◽  
Element Analysis ◽  
Biomechanical Behavior ◽  
Condylar Head ◽  
Small Patient

Abstract Background The aim of this study was to evaluate via finite element analysis (FEA) the biomechanical behavior of conventional small-fragment screws reinforced by a patient-specific plate in type p condylar head. Methods A finite element model of the mandible was created using Mimics 12.1 software. A type p condylar head fracture was simulated in the right condyle, and the left condyle was used as a control. Two patterns of fixation were investigated: conventional two-screw fixation and the same fixation system reinforced with a small, patient-specific plate. Surface models were imported into the software Ansys 5.7for further volume mesh generation. Results The highest stress gradients were observed in the cortical layer of the lateral fragment, located near the screw. The conventional fixation method resulted in equivalent stresses 2 to 10 times greater than the reinforced method. Rigidity of fixation in the reinforced method increased up to 1.25–3 times compared to the conventional two-screw technique. Conclusion This study’s findings suggest significant benefits in unfavorable biomechanical conditions from reinforcement of the standard two-screw fixation of condylar head fractures with a small, patient-specific plate acting as a washer.

scholarly journals Finite element and biomechanical analysis of risk factors for implant failure during tension band plating

2020 ◽  
Vol 48 (11) ◽  
pp. 030006052097207
Author(s):  
Jing Ding ◽  
Fei Wang ◽  
Fangchun Jin ◽  
Zhen-kai Wu ◽  
Pin-quan Shen
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Biomechanical Model ◽  
Element Model ◽  
Tension Band ◽  
Biomechanical Analysis ◽  
Implant Failure ◽  
Element Analysis

Objective Tension band plating has recently gained widespread acceptance as a method of correcting angular limb deformities in skeletally immature patients. We examined the role of biomechanics in procedural failure and devised a new method of reducing the rate of implant failure. Methods In the biomechanical model, afterload (static or cyclic) was applied to each specimen. The residual stress of the screw combined with different screw sizes and configurations were measured and compared by X-ray diffraction. With regard to static load and similar conditions, the stress distribution was analyzed according to a three-dimensional finite element model. Results The residual stress was close to zero in the static tension group, whereas it was very high in the cyclic load group. The residual stress of screws was significantly lower in the convergent group and parallel group than in the divergent group. The finite element model showed similar results. Conclusions In both the finite element analysis and biomechanical tests, the maximum stress of the screw was concentrated at the position where the screws enter the cortex. Cyclic loading is the primary cause of implant failure.

scholarly journals Design of a Metal 3D Printing Patient-Specific Repairing Thin Implant for Zygomaticomaxillary Complex Bone Fracture Based on Buttress Theory Using Finite Element Analysis

2020 ◽  
Vol 10 (14) ◽  
pp. 4738
Author(s):  
Yu-Tzu Wang ◽  
Chih-Hao Chen ◽  
Po-Fang Wang ◽  
Chien-Tzung Chen ◽  
Chun-Li Lin
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Biomechanical Analysis ◽  
Patient Specific ◽  
Element Analysis ◽  
Posterior Teeth ◽  
Frontal Process ◽  
Metal 3D Printing ◽  
Stress Variations ◽  
Zygomaticomaxillary Complex

This study developed a zygomaticomaxillary complex (ZMC) patient-specific repairing thin (PSRT) implant based on the buttress theory by integrating topology optimization and finite element (FE) analysis. An intact facial skeletal (IFS) model was constructed to perform topology optimization to obtain a hollow skeleton (HS) model with the structure and volume optimized. The PSRT implant was designed based on the HS contour which represented similar trends as vertical buttress pillars. A biomechanical analysis was performed on a ZMC fracture fixation with the PSRT implant and two traditional mini-plates under uniform axial loads applied on posterior teeth with 250 N. Results indicated that the variation in maximum bone stress and model volume between the IFS and HS models was 15.4% and 75.1%, respectively. Small stress variations between the IFS model and repairing with a PSRT implant (2.75–26.78%) were found for compressive stress at frontal process and tensile stress at the zygomatic process. Comparatively, large stress variations (30.67–96.26%) with different distributions between the IFS model and mini-plate models were found at the corresponding areas. This study concluded that the main structure/contour design of the ZMC repair implant according to the buttress position and orientation can obtain a favorable mechanical behavior.

scholarly journals Comprehensive biomechanical analysis of three clinically used fixation constructs for posterior malleolar fractures using cadaveric and finite element analysis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Adeel Anwar ◽  
Zhenwei Hu ◽  
Atif Adnan ◽  
Yanming Gao ◽  
Bing Li ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Biomechanical Study ◽  
Biomechanical Analysis ◽  
Element Analysis ◽  
High Tendency ◽  
Malleolar Fractures ◽  
Plate Group ◽  
Vertical Displacements ◽  
Group B

Abstract Different fixation modalities are available for fixation of posterior malleolar fractures (PMFs), but the best method is still unclear. The purpose of this study was to carry out a comparative biomechanical analysis of three commonly used fixation constructs for PMFs using experimental and finite element analysis (FEA). 15 human cadaveric ankle specimens were randomly divided into three groups. Specimens in group-A were fixed with two anteroposterior (AP) lag screws, group-B with two posteroanterior (PA) lag screws, and for group-C, a posterior plate was used. Each model was subjected to axial load. Outcomes included loads for 0.5 mm, 1 mm, 1.5 mm, and 2 mm vertical displacements of posterior fragments were noted. 3D FE models were reconstructed from computed tomography (CT) images and subjected to vertical loads. The model’s stress, fracture step-off, and resultant strains in implants were also studied in 3D FE models. Significantly higher amounts of mean compressive loads were observed to cause the same amount of vertical displacements in plate group (265 ± 60.21 N, 796 ± 57.27 N, 901.18 ± 8.88 N, 977.26 ± 13.04 N) than AP (102.7 ± 16.78 N, 169.5 ± 19.91 N, 225.32 ± 15.92 N, 269.32 ± 17.29 N) and PA (199.88 ± 31.43 N, 362.80 ± 28.46 N, 431.3 ± 28.12 N, 541.86 ± 36.05 N) lag screws respectively (P < 0.05). Simulated micro-motion analysis demonstrated that fracture step-off values in plate group (0.03 ± 0.001 mm, 0.06 ± 0.003 mm and 0.13 ± 0.010 mm) were the lowest among the three groups (P < 0.001). The cancellous bone showed the highest amount of stress in AP and PA lag groups respectively, whereas the lowest stress was noted in the plate-group. This biomechanical study concluded that posterior plating is biomechanically the most stable fixation construct for PMFs fixation. AP and PA lag screws with higher bone stress and fracture step-off values have a high tendency of bone cut-through and loss of fixation respectively.

A finite element study on intra-operative corrective forces and evaluation of screw density in scoliosis surgeries

2018 ◽  
Vol 232 (12) ◽  
pp. 1245-1254 ◽  
Author(s):  
Ameneh Musapoor ◽  
Mohammad Nikkhoo ◽  
Mohammad Haghpanahi
Keyword(s):  
Finite Element ◽  
Pedicle Screws ◽  
Element Model ◽  
Applied Force ◽  
Patient Specific ◽  
Scoliosis Surgery ◽  
Element Analysis ◽  
Clinical Images ◽  
Significant Difference ◽  
Screw Density

Scoliosis is an abnormal sideways curvature of the spine and rib cage, which may need surgical treatments. Most of the corrective maneuvers in scoliosis surgeries are based on surgeon’s experience; hence, there is great interest of understanding how the correction ratio can be influenced by the magnitude of forces and moments. Therefore, the objective of this study was to develop and validate a detailed finite element model of the thoracolumbar which can be used to simulate the scoliosis surgeries based on patient-specific clinical images. The validated models of five patients were carefully developed, and the surgery procedures were simulated and the corrective forces were estimated using inverse finite element analysis during the surgery. Furthermore, parametric studies including the influences of the corrective force magnitude and screw density were evaluated. The results showed that the maximum estimated correction force and moment were 173 (±55.43) N and 10.67 (±2.02) N m, respectively, which were aligned with measured clinical observations. The sensitivity analysis on the magnitude of applied force to the screws showed that correction ratio was slightly increased in level 1 (i.e. FB = 1.3 ×  F) but decreased in level 2 (i.e. FB = 1.6 ×  F). In addition, the parametric study on increasing the number of pedicle screws showed that there was no significant difference between lower and higher screw density. However, the stress distribution was significantly greater using higher screw density during correction maneuvers. In conclusion, this study shows a direct relationship between the applied force/moment and screw density and the correction ratio up to a border line which should be defined accurately. This detailed computational modeling can be used in clinic in hope of achieving the optimum outcome of scoliosis surgery using individual patient-specific characterization.

Patient Specific Finite Element Modeling of a Human Skull

2006 ◽  
Vol 49 ◽  
pp. 227-234 ◽  
Author(s):  
Norio Inou ◽  
Michihiko Koseki ◽  
Koutarou Maki
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Modeling ◽  
Image Data ◽  
Element Model ◽  
Biomechanical Study ◽  
Modeling Method ◽  
Patient Specific ◽  
Human Skull ◽  
Element Modeling

This paper presents automated finite element modeling method and application to a biomechanical study. The modeling method produces a finite element model based on the multi-sliced image data adaptively controlling the element size according to complexity of local bony shape. The method realizes a compact and precise finite element model with a desired total number of nodal points. This paper challenges to apply this method to a human skull because of its intricate structure. To accomplish the application of the human skull, we analyze characteristics of bony shape for a mandible and a skull. Using the analytical results, we demonstrate that the proposed modeling method successfully generates a precise finite element model of the skull with fine structures.

scholarly journals Biomechanical evaluation and finite element analysis of axial-loading simulated experiment of wrist fracture

2020 ◽  
Author(s):  
Yuan-Wei Zhang ◽  
Liang-Yu Xiong ◽  
Zu-Tai Huang ◽  
Xin Xiao ◽  
Su-Li Zhang ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Element Model ◽  
Wrist Fracture ◽  
Biomechanical Analysis ◽  
Control Group ◽  
Element Analysis ◽  
Obvious Effect ◽  
Physiological Load ◽  
Experimental Group

Abstract Objectives This study combined mechanical experiments and finite element analysis (FEA), and verified each other, to assess the biomechanical analysis and effect of wrist fracture, providing theoretical basis for the simulation experiments of wrist fracture and optimal design of wrist protector. Methods and Materials Six cadaveric wrists were included to create experimental specimens. After grouping, the wrist models were axially loaded under physiological load of 600 N, the stress magnitude and distribution of experimental group and control group were obtained. Moreover, a three-dimensional (3D) wrist finite element model (FEM) of a healthy volunteer was developed to verify the rationality and effectiveness of wrist models. Results Within the range of physiological load, the stress of radioulnar palmar unit was high and in shape of pressure, while the stress of radioulnar dorsal unit was relatively lower and in shape of tension. The stresses of radial distal palmar, ulnar distal palmar, radial distal dorsal, ulnar distal dorsal, radial proximal palmar and ulnar proximal palmar units in experimental group were less than those in control group. However, the stresses of radial proximal dorsal and ulnar proximal dorsal units were higher than those in control group. Conclusions Under physiological load, wearing wrist protector can apparently reduce the stress on radioulnar distal palmar, radioulnar proximal palmar and radioulnar distal dorsal units, while has no obvious effect on radioulnar proximal dorsal units. During the process of designing and improving the wrist protector, it is reasonable to place the stress center on radioulnar distal palmar and dorsal units.

scholarly journals Biomechanical Effects of a Cross Connector in Sacral Fractures – A Finite Element Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Meike Gierig ◽  
Fangrui Liu ◽  
Lukas Weiser ◽  
Wolfgang Lehmann ◽  
Peter Wriggers ◽  
...  
Keyword(s):  
Finite Element ◽  
Operative Procedure ◽  
Element Model ◽  
Biomechanical Properties ◽  
Patient Specific ◽  
Fe Model ◽  
Principal Stresses ◽  
Element Analysis ◽  
Fracture Area ◽  
Maximum Stresses

Background: Spinopelvic fractures and approaches of operative stabilization have been a source of controversial discussion. Biomechanical data support the benefit of a spinopelvic stabilization and minimally invasive procedures help to reduce the dissatisfying complication rate. The role of a cross connector within spinopelvic devices remains inconclusive. We aimed to analyze the effect of a cross connector in a finite element model (FE model).Study Design: A FE model of the L1-L5 spine segment with pelvis and a spinopelvic stabilization was reconstructed from patient-specific CT images. The biomechanical relevance of a cross connector in a Denis zone I (AO: 61-B2) sacrum fracture was assessed in the FE model by applying bending and twisting forces with and without a cross connector. Biomechanical outcomes from the numerical model were investigated also considering uncertainties in material properties and levels of osseointegration.Results: The designed FE model showed comparable values in range-of-motion (ROM) and stresses with reference to the literature. The superiority of the spinopelvic stabilization (L5/Os ilium) ± cross connector compared to a non-operative procedure was confirmed in all analyzed loading conditions by reduced ROM and principal stresses in the disk L5/S1, vertebral body L5 and the fracture area. By considering the combination of all loading cases, the presence of a cross connector reduced the maximum stresses in the fracture area of around 10%. This difference has been statistically validated (p &lt; 0.0001).Conclusion: The implementation of a spinopelvic stabilization (L5/Os ilium) in sacrum fractures sustained the fracture and led to enhanced biomechanical properties compared to a non-reductive procedure. While the additional cross connector did not alter the resulting ROM in L4/L5 or L5/sacrum, the reduction of the maximum stresses in the fracture area was significant.

scholarly journals Biomechanical evaluation of type p condylar head osteosynthesis using conventional small-fragment screws reinforced by a patient specific two-component plate

2020 ◽  
Author(s):  
Tetiana Pavlychuk ◽  
Denis Chernogorskyi ◽  
Yurii Chepurnyi ◽  
Andreas Neff ◽  
Andrii Kopchak
Keyword(s):  
Finite Element ◽  
Screw Fixation ◽  
Cortical Layer ◽  
Fixation Method ◽  
Patient Specific ◽  
Small Fragment ◽  
Element Analysis ◽  
Biomechanical Behavior ◽  
Condylar Head ◽  
Small Patient

Abstract Background. The aim of this study was to evaluate via finite element analysis (FEA) the biomechanical behavior of conventional small-fragment screws reinforced by a patient-specific plate in type p condylar head. Methods. A finite element model of the mandible was created using Mimics 12.1 software. A type p condylar head fracture was simulated in the right condyle, and the left condyle was used as a control. Two patterns of fixation were investigated: conventional two-screw fixation and the same fixation system reinforced with a small, patient-specific plate. Surface models were imported into the software Ansys 5.7 for further volume mesh generation. Results. The highest stress gradients were observed in the cortical layer of the lateral fragment, located near the screw. The conventional fixation method resulted in equivalent stresses 2 to 10 times greater than the reinforced method. Rigidity of fixation in the reinforced method increased up to 1.25–3 times compared to the conventional two-screw technique. Conclusion. This study’s findings suggest significant benefits in unfavourable biomechanical conditions from reinforcement of the standard two-screw fixation of condylar head fractures with a small, patient-specific plate acting as a washer.

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