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Anterior open bite (AOB) with mild-to-moderate skeletal discrepancies can be camouflaged by an orthodontic tooth movement. Conventional methods can improve occlusal relationships and some profile esthetics, but their mechanics may result in detrimental side effects such as a gummy smile, a high-frequency relapse, and an unfavorable facial profile. The emergence of temporary skeletal anchorage devices (TSADs) has facilitated the treatment of skeletal Class II AOB through intrusion of the posterior teeth and autorotation of the mandible, improving facial esthetics while minimizing the side effects. TSADs can also simplify treatment plans and offer a more predictable treatment result. Finite element studies have identified the location of the center of resistance of the dentition, providing a biomechanical basis for understanding 3-dimensional tooth movement patterns using TSADs. Therefore, biomechanical and clinical considerations are essential for correcting Class II AOB using TSADs. [ABSTRACT FROM AUTHOR]

Background: Resecting the facet joint to relieve nerve pain can lead to spinal instability, deformity, and abnormal pressure on the anterior of the intravertebral disc. To mitigate these issues, surgeons often limit the amount of bone removed during facetectomy or stabilize the spine by fusion to maintain lumbar stability. This study aimed to assess how a M-PEEK rod system influenced the stability of the lumbar spine during graded facetectomy. Methods: Facetectomy was performed on a validated L1-L5 finite element model which was then simulated both with and without the M-PEEK rod system. Results: In extension, models implanted with M-PEEK in the interspinous space of L3/L4 experienced a 35.2% decrease in range of motion (ROM) at L3/L4, while others saw an 8.4–24.8% increase. For axial rotation, the ROM at L3/L4 increased by 2.2–5.4% in models with the M-Rod, and by 4.9–12.9% in models without the implant. In lateral flexion, the ROM at L3/L4 increased by 8.4–14.3% in models without a PEEK M-Rod (facetectomy only), with adjacent segments experiencing a 6.5% decrease in ROM in the implanted models. Overall, the difference in ROM between the intact and implanted models was minimal. Conclusions: Facetectomy involving the removal of 50% or more of the facet joint significantly increases range of motion and maximum intradiscal pressure, potentially accelerating disc degeneration, as shown in our finite element study. Stabilizing the segment with an M-PEEK rod may limit excessive motion, providing stability and maintaining intradiscal pressure closer to that of an intact model. [ABSTRACT FROM AUTHOR]

Abstract Background Resecting the facet joint to relieve nerve pain can lead to spinal instability, deformity, and abnormal pressure on the anterior of the intravertebral disc. To mitigate these issues, surgeons often limit the amount of bone removed during facetectomy or stabilize the spine by fusion to maintain lumbar stability. This study aimed to assess how a M-PEEK rod system influenced the stability of the lumbar spine during graded facetectomy. Methods Facetectomy was performed on a validated L1-L5 finite element model which was then simulated both with and without the M-PEEK rod system. Results In extension, models implanted with M-PEEK in the interspinous space of L3/L4 experienced a 35.2% decrease in range of motion (ROM) at L3/L4, while others saw an 8.4–24.8% increase. For axial rotation, the ROM at L3/L4 increased by 2.2–5.4% in models with the M-Rod, and by 4.9–12.9% in models without the implant. In lateral flexion, the ROM at L3/L4 increased by 8.4–14.3% in models without a PEEK M-Rod (facetectomy only), with adjacent segments experiencing a 6.5% decrease in ROM in the implanted models. Overall, the difference in ROM between the intact and implanted models was minimal. Conclusions Facetectomy involving the removal of 50% or more of the facet joint significantly increases range of motion and maximum intradiscal pressure, potentially accelerating disc degeneration, as shown in our finite element study. Stabilizing the segment with an M-PEEK rod may limit excessive motion, providing stability and maintaining intradiscal pressure closer to that of an intact model.

Premature debonding is identified as the main failure mode in reinforced concrete (RC) beams strengthened with externally bonded Fiber-Reinforced Polymer (FRP) laminates. This issue leads to the underutilization of FRP materials and needs to be addressed. Research has shown that end anchorage systems can effectively delay/mitigate delamination failures and enhance the performance of strengthened beams. FRP U-wraps are an effective means to prevent debonding failure; however, as open-form anchors, U-wraps cannot always guarantee complete resistance to debonding failures. This study proposes an alternative U-wrapping technique where the ends of the U-wraps are flared and inserted into the concrete substrate. The feasibility and effectiveness of this technique were studied by comparing it with conventional U-wraps. The experimental phase involved testing seven RC beams, each measuring 1.96x0.15x0.3 meters, under four-point bending. The results showed that the anchorage technique improved beam performance in terms of load-deflection behavior, failure modes, ductility, and FRP strain. Additionally, finite element simulations were conducted using Abaqus software to assess the effectiveness of the alternative U-wrap scheme. These models incorporated various nonlinear material constitutive laws, including cohesive zone modeling to replicate debonding failures at the CFRP-concrete interface. The numerical predictions were found to be in good agreement with the experimental test data. [ABSTRACT FROM AUTHOR]

Reducing residual deformation of shear links and enhancing structural self-centering performance are two effective strategies to optimize the seismic resilience of Y-eccentrically braced frames. Based on the aforementioned concepts, a novel self-centering Y-eccentrically braced frame structure which composing of self-centering joints and slip connection shear link was introduced in this study. Firstly, a design methodology for the slip connection shear link and anticipated mechanical properties of the novel structure were proposed through theoretical analyses. Subsequently, finite element models were established based on previous experimental data to investigate the lateral load behavior of the novel structure by comparing it with a conventional structure. The results indicate that when possessing sufficient lateral load capacity and energy dissipation capacity, the novel structure exhibits exceptional self-centering performance. Finally, the energy dissipation and self-centering mechanism were obtained by conducting stress analysis on substructures under various seismic conditions. The analysis results indicate that the slip connection mechanism effectively mitigates relative displacement and damage to shear links, restricts frame damage, and enhances structural self-centering performance when combined with self-centering joints. [ABSTRACT FROM AUTHOR]

IntroductionLimited information regarding the biomechanical evaluation of various internal fixation techniques for high-grade L5-S1 spondylolisthesis is available. The stiffness of the operated segment and stress on the hardware can profoundly influence clinical outcomes and patient satisfaction. The objective of this study was to quantitatively investigate biomechanical profiles of various fusion methods used for high-grade spondylolisthesis by using finite element (FE) analysis.MethodsAn FE lumbar spine model of healthy spine was developed based on a patient’s CT scan. High-grade (III-IV) spondylolisthesis (SP model) was created by sliding L5 anteriorly and modifying L5-S1 facet joints. Three treatment scenarios were created by adding various implants to the model. These scenarios included L5-S1 interbody cage in combination with three different fixation methods–the anterior plate system (APS), bilateral pedicle screw system (BPSS), and transdiscal screw system (TSS). Range of motion (ROM), von Mises stress on cage, internal fixation as well as on the adjacent annuli were obtained and compared. The resistance to slippage was investigated by applying shear force on L5 vertebra and measuring its displacement regarding to S1.ResultsUnder different loading conditions all treatment scenarios showed substantial reduction of ROM in comparison with SP model. No notable differences in ROM were observed between treatment models. There was no notable difference in cage stress among models. The von Mises stress on the internal fixation in the TSS model was less than in APS and BPSS. The TSS model demonstrated superior resistance to shear load compared to APS and BPSS. No discernible difference was observed between the SP, APS, BPSS, and TSS models when compared the ROM for adjacent level L4-L5. TSS’s von Mises stress of the adjacent annulus was higher than in APS and BPSS.ConclusionsThe TSS model exhibited biomechanical superiority over the APS and BPSS models.

The incidence of rod fracture after corrective surgery for adult spinal deformity (ASD) is high. Although many reports have investigated the effects of rod bending considering postoperative body motion, and countermeasures, there are no reports investigating the effects during intraoperative correction. The purpose of this study was to investigate the effect of ASD correction on rods by using finite element analysis (FEA) based on the rod shape changes before and after spinal corrective fusion. Five ASD patients (mean age 73 years, all female) who underwent thoracic to pelvic fusion were included in this study. A 3D rod model was created using computer-aided design software from digital images of the intraoperatively bended rod and intraoperative X-ray images after corrective fusion. The 3D model of the bent rod was meshed by dividing each of the screw head intervals into 20 sections and cross-section of the rod into 48 sections. Two surgical fusion methods of stepwise fixation as the cantilever method and parallel fixation as the translational method were simulated to evaluate stress and bending moments on the rods during intraoperative correction. The stresses on the rods were 1500, 970, 930, 744, and 606 MPa in the five cases for stepwise fixation and 990, 660, 490, 508, and 437 MPa for parallel fixation, respectively, with parallel fixation having lower stresses in all cases. In all cases, maximum stress was found around the apex of the lumbar lordosis and near L5/S1. The bending moment was high around L2-4 in most cases. The external forces of intraoperative correction had the greatest effect on the lower lumbar region, especially around the apex of the lumbar lordosis. [ABSTRACT FROM AUTHOR]

Background: There has been no absolute consensus on the optimal implant for fixation of medial clavicle fracture. The purpose of the present study was to test the biomechanical efficacy of inverted lateral clavicle locking compression plate (LCP-LC) in fixation of this specific fracture location by finite element analysis. Methods: Transverse and comminuted medial clavicle fracture simulated models stabilized by three different devices including inverted LCP-LC, superior clavicle LCP (LCP-SC), and dual reconstruction (LCP-RP) with LCP-SC were investigated biomechanical performance under three loading conditions, i.e., axial compression, inferior bending, and axial torsion. Results: EQV stress exhibited on implant and elastic strain at fracture site under inferior bending was greater than other loading cases. LCP-SC construct represented the greatest EQV stress and elastic strain. The inverted LCP-LC construct demonstrated lower EQV stress than the LCP-SC construct and was comparable to dual plating. Under axial compression and axial torsion, elastic strain produced from the inverted LCP-LC construct was comparable to dual plating, but greater than dual plating when subjected to inferior bending. Conclusion: By the results of FE analysis, inverted LCP-LC could be a potential application for fixation of clavicle fracture with short medial fragment. [ABSTRACT FROM AUTHOR]

Background: There has been no scientific mechanical assessment demonstrating the optimal fixation technique in multifragmentary fractures of the distal humeral shaft. The purpose of the present study was to compare the biomechanical performance of 5 fixation constructs as used in minimally invasive plating osteosynthesis (MIPO) for distal humeral shaft fractures. Methods: Three-dimensional (3D) humerus model with 20 mm distal humeral shaft fracture gap simulating multifragmentary fracture was created from computed tomography data and virtually fixed by 5 fixation techniques as MIPO, i.e., anterior narrow dynamic compression plate (DCP), anterior narrow locking compression plate (LCP), anterior reversed proximal humeral internal locking system (R-PHILOS), extra-articular distal humerus locking compression plate (LCP-EADH), and anteromedial LCP. All constructs were biomechanically tested under 6 loading conditions by means of finite element analysis, i.e., 250—N axial compression, 7.5—N m internal rotation, 7.5—N m external rotation, 10—N m posterior bending, 10—N m valgus rotation, and 10—N m varus rotation. In addition, A 3D model of each construct was fabricated as 3D printed models. Fixations were applied to the 3D printing model which were later mechanically tested to validate the FE results. Results: EQV stress exhibited on anterior narrow LCP and anterior R-PHILOS were comparable which were lower than other constructs under axial compression and valgus–varus bending. Anterior R-PHILOS produced lower EQV stress than other constructs under internal–external rotation and posterior bending. On the whole, R-PHILOS demonstrated a comparable fracture displacement to those LCP with anterior or anteromedial approaches, that achieved the lowest displacement values. In addition, the experimental mechanical test values shared a correlation with the FE model results. Conclusion: Overall, the anterior R-PHILOS was considered as a potential candidate for multifragmentary distal humeral shaft fractures. It demonstrated efficacious biomechanical performance in terms of implant stress and distal fragment displacement. [ABSTRACT FROM AUTHOR]

Abstract Introduction Clear aligner therapy has become increasingly popular in recent years, although it has encountered several difficulties in premolar extraction treatment. These difficulties include anterior dentition, lingual tipping and extrusion. The design of the present clinical scheme usually set a tiny space between the anterior teeth before retraction in order to obtain an ideal outcome. The objective of our research was to analyze the effect of the existing spaces during retraction. Methods Models including maxillary dentition without first premolars, maxilla, periodontal ligaments, gingiva, or aligners were constructed and imported to an ANSYS workbench. Five groups of models were created: without spaces and with 0.25, 0.50, 0.75 and 1.00 mm spaces between the anterior dentition. A 0.20 mm retraction step was applied to all the groups. Results As the spaces between the anterior dentition increased, the bowing effect of the aligner caused by the passive forces decreased gradually. Accordingly, the degree of extrusion of the anterior dentition was alleviated significantly, while sagittal movement was reduced. However, the overall movement tended to be a bodily displacement rather than tipping. Meanwhile, maximum Von Mises stress of the periodontal ligaments (PDLs) was markedly decreased. Conclusion These analyses indicate that spaces between the anterior dentition during anterior retraction are beneficial for decreasing the tendency for extrusion of the anterior dentition and require provision of anchorage. Appropriate spaces can be designed to lest the lingual tipping and extrusion effect of the anterior teeth while simultaneously reducing the maximum stresses on PDLs.

Introduction: Clear aligner therapy has become increasingly popular in recent years, although it has encountered several difficulties in premolar extraction treatment. These difficulties include anterior dentition, lingual tipping and extrusion. The design of the present clinical scheme usually set a tiny space between the anterior teeth before retraction in order to obtain an ideal outcome. The objective of our research was to analyze the effect of the existing spaces during retraction. Methods: Models including maxillary dentition without first premolars, maxilla, periodontal ligaments, gingiva, or aligners were constructed and imported to an ANSYS workbench. Five groups of models were created: without spaces and with 0.25, 0.50, 0.75 and 1.00 mm spaces between the anterior dentition. A 0.20 mm retraction step was applied to all the groups. Results: As the spaces between the anterior dentition increased, the bowing effect of the aligner caused by the passive forces decreased gradually. Accordingly, the degree of extrusion of the anterior dentition was alleviated significantly, while sagittal movement was reduced. However, the overall movement tended to be a bodily displacement rather than tipping. Meanwhile, maximum Von Mises stress of the periodontal ligaments (PDLs) was markedly decreased. Conclusion: These analyses indicate that spaces between the anterior dentition during anterior retraction are beneficial for decreasing the tendency for extrusion of the anterior dentition and require provision of anchorage. Appropriate spaces can be designed to lest the lingual tipping and extrusion effect of the anterior teeth while simultaneously reducing the maximum stresses on PDLs. [ABSTRACT FROM AUTHOR]

Abstract Background This study aimed to compare the biomechanical differences between anterior cervical discectomy and fusion (ACDF) with multiple-level separate plates and conventional long plates by using finite element analysis. Methods The following four finite element models were created to simulate various fixations: (1) C4–6 ACDF with multiple plates, (2) C4–6 ACDF with a single plate, (3) C3–6 ACDF with multiple plates, and (4) C3–6 ACDF with a single plate. The maximum Von-mises stress of the cage and fixation, compressive force of the adjacent intervertebral discs and range of motion (ROM) of different segments in the four models were calculated and analyzed. Results For C4–6 ACDF, the maximum Von-mises stress of the cage and fixation was lower in the multiple plate fixation model in all motion states. Similarly, for the C3–6 ACDF models, the peak stress of the C3–4 and C5–6 cages was lower with multiple plates fixation in all motions but the stress of the C4–5 cage in the multiple plates model was slightly higher in flexion, bending and rotation. Besides, applying multiple plates in C3–6 ACDF models resulted in a decreased maximum stress of the fixation under different motions except for bending. In both the C4–6 ACDF and C3–6 ACDF models, the ROM values of the adjacent motion segments were lower in the multiple plates models in extension, bending and rotation. In the C4–6 ACDF models, the peak stress on the adjacent intervertebral discs in the multiple plates models was slightly smaller. In C3–6 ACDF models, the maximum stress on the adjacent intervertebral discs was larger in the single-plate model under flexion, bending and rotation movements. Conclusion Multiple plates fixation has a positive effect on increasing stiffness and maintaining the ROM of adjacent segments, indicating lower risk of construct failure and adjacent segment degeneration. Further studies are required to confirm its efficacy in clinical practice.

ObjectiveThe aim of this study was to verify the biomechanical properties of a newly designed angulated lateral plate (mini-LP) suited for two-level oblique lumbar interbody fusion (OLIF). The mini-LP is placed through the lateral ante-psoas surgical corridor, which reduces the operative time and complications associated with prolonged anesthesia and placement in the prone position.MethodsA three-dimensional nonlinear finite element (FE) model of an intact L1–L5 lumbar spine was constructed and validated. The intact model was modified to generate a two-level OLIF surgery model augmented with three types of lateral fixation (stand-alone, SA; lateral rod screw, LRS; miniature lateral plate, mini-LP); the operative segments were L2–L3 and L3–L4. By applying a 500 N follower load and 7.5 Nm directional moment (flexion-extension, lateral bending, and axial rotation), all models were used to simulate human spine movement. Then, we extracted the range of motion (ROM), peak contact force of the bony endplate (PCFBE), peak equivalent stress of the cage (PESC), peak equivalent stress of fixation (PESF), and stress contour plots.ResultsWhen compared with the intact model, the SA model achieved the least reduction in ROM to surgical segments in all motions. The ROM of the mini-LP model was slightly smaller than that of the LRS model. There were no significant differences in surgical segments (L1–L2, L4–L5) between all surgical models and the intact model. The PCFBE and PESC of the LRS and the mini-LP fixation models were lower than those of the SA model. However, the differences in PCFBE or PESC between the LRS- and mini-LP-based models were not significant. The fixation stress of the LRS- and mini-LP-based models was significantly lower than the yield strength under all loading conditions. In addition, the variances in the PESF in the LRS- and mini-LP-based models were not obvious.ConclusionOur biomechanical FE analysis indicated that LRS or mini-LP fixation can both provide adequate biomechanical stability for two-level OLIF through a single incision. The newly designed mini-LP model seemed to be superior in installation convenience, and equally good outcomes were achieved with both LRS and mini-LP for two-level OLIF.

In the last decades, steel beams with web opening were used extensively as useful structural and architectural elements due to their many advantages. In this research, steel beams with web opening subjected to static loading were modelled using the multi-purpose finite element software ANSYS and the finite element results were compared with previous research. Then, steel beams with a single web opening subjected to fatigue loading were investigated numerically. The effect of changing the location of web opening on the fatigue assessment of H section steel beams with web opening was studied taking normal stress into account. It was clear that, normal stress fatigue life of the steel beams was affected significantly by changing web opening location along the beam span when compared to a beam with solid web while the beam span, opening size and steel section were kept constant. The most convenient location of web opening along the beam span was found to be at mid span.

Lumbar disc herniation (LDH) is a common condition which can lead to back pain. Although surgical treatments for LDH are well established, complications such as spinal instability and narrowing of adjacent facet joints are still frequently reported. The purpose of this study was to use finite element models to evaluate the stability of the L3–L4 segment after conservative or aggressive percutaneous transforaminal endoscopic discectomy (PTED) with and without an artificial material filler to correct LDH. Compared to the intact model, aggressive PTED reduced the stability of the segment (increased ROM) and narrowed the space between facet joints in the medial/lateral (ML) direction during flexion (maximum 6.7 degrees change in ROM and 90.5% spacing between facet joints), extension (maximum 2.1 degrees and 38.6%), and axial rotation (maximum 4.2 degrees and 90.1%). Aggressive PTED had a similar effect in the anterior/posterior (AP) direction during lateral bending (maximum 2.0 degrees and 44.2%). Augmenting the nucleus pulposus with a polyurethane filler after aggressive PTED improved spinal stability in both the ML and AP directions in all simulated motions, with results similar to the intact model. However, using a hydrogel filler did little to stabilize the spine, likely because the material is too soft to support the heavy, sustained loading. In conclusion, this study found that if an aggressive discectomy is required, augmenting the nucleus pulposus with a PU filler provides sufficient support to stabilize the spine, while hydrogel fillers offer little support. [ABSTRACT FROM AUTHOR]

This study analyzed the effects of implant design factors (diameter, length, and connection type) and bone quality on the long-term success of implantation via finite element (FE) analysis, considering the bone remodeling process. A total of 36 cases of the threedimensional FE model, with an implant complex located in the mandibular bone section of the molar region, were considered. An FE analysis considering dental bone remodeling was implemented in the Abaqus UMAT subroutine. A preload of 32 Ncm and an average biting force of 50 N were applied during the bone remodeling process as the loading conditions. After the bone remodeling process, amaximum biting force of 200 N was applied in the oblique direction. The stability of the peri-implant bone was analyzed by measuring the apparent bone density over time and the principal strain in the cancellous bone. The stability of the peri-implant bone differs depending on the host bone conditions and implant design features. The initial bone condition greatly influenced the final density andmaximumprincipal strain distribution in the cancellous bone surrounding the implant. The need for a stability evaluation considering the bone remodeling process has increased under the conditions of placing short-length and narrow-diameter implants in poor-quality bones. [ABSTRACT FROM AUTHOR]

Objective: To analyse the biomechanics of molar protraction through clear aligner therapy (CAT) with and without a buccal cantilever., Methods: Models were composed of mandible, lower dentition, periodontal ligaments, attachments, a buccal cantilever, and clear aligner. Four groups were designed: (1) control (aligner only), (2) aligner+buccal cantilever with buccal class II traction, (3) aligner+buccal cantilever with buccal class II and lingual class II tractions, (4) aligner+buccal cantilever with buccal horizontal traction named buccal class I, buccal class II, and lingual class II tractions., Results: CAT alone caused mesial tipping, lingual tipping, and intrusion of mandibular second molar. Adding the buccal cantilever on the mandibular second molar with 100-g buccal class II traction was effective in preventing the mesial tipping of mandibular second molar, but resulted in a greater lingual tipping tendency. Further addition of lingual class II traction prevented aforementioned lingual tipping and bodily protraction was achieved in sagittal dimension, while buccal tipping was present. Bodily protraction without buccolingual tipping was achieved through clear aligner, buccal class II, lingual class II, and buccal class I tractions, and the stress concentrated on the alveolar bone was reduced., Conclusion: CAT produced mesial tipping, lingual tipping, and intrusion of mandibular molar during protraction. The incorporation of the buccal cantilever into the clear aligner improves the biomechanical effect of molar protraction. Bodily molar protraction can be achieved with a judicious combination of buccal class II, lingual class II and buccal class I tractions with clear aligner and buccal cantilever., (Copyright © 2024 CEO. Published by Elsevier Masson SAS. All rights reserved.)

An eccentrically braced composite frame with a low-yield-point (LYP) steel shear link is an efficient energy dissipation system that exhibits good mechanical properties. However, existing experimental studies have not fully demonstrated the superiority and applicability of the structural system. We present a structural mechanics and finite element model analysis of an eccentrically braced composite frame with a vertical shear link. The effect of the design parameters on the seismic performance of the structure is analyzed. First, a theoretical model of the mechanics of the structural system is established to provide a comprehensive description of the key parameters. Then, a finite element model is developed using the computer program ABAQUS to analyze the mechanical and energy dissipation mechanisms. Finally, the beam-to-column stiffness ratio, shear link web thickness, shear link web width and length, and diagonal brace stiffness are analyzed to determine their effects on the mechanical properties of the structural system. Furthermore, some design parameter values are suggested. [ABSTRACT FROM AUTHOR]

In order to study the compressive torsional behavior of concrete-filled CFRP steel tubes (CF-CFRP-STs), the static test of eight circular section CF-CFRP-ST compression torsional specimens was carried out. The characteristics of the torque–angle (T–θ) curve and shear stress shear–strain (τ–γ) curve, failure mode, cooperative work between steel tubes and CFRP, and cross-section assumption were studied. The T–θ curve, τ–γ curve, and failure mode of the specimen are simulated by ABAQUS. Based on the above research, the stress distribution of each component material is analyzed. The effects of transverse CFRP layers, material strength, steel ratio, and axial compression ratio on the static performance of members are discussed. Based on the performance analysis, the bearing capacity equation of CF-CFRP-ST compression-torsional members is proposed.

Adjacent segmental degeneration (ASD) is the long-term complication of transforaminal lumbar interbody fusion (TLIF) combined with pedicle screw fixation. Both osteoporosis and whole-body vibration (WBV) can alter the biomechanics of adjacent segments. However, the effect of pedicle screw fixation on ASD in an osteoporotic spine after TLIF under WBV was unknown. According to a previously validated model of L1-S1, 2 osteoporotic TLIF models with and without pedicle screw fixation were developed. In each model, a 400 N preload was applied and a 5-Hz, 40 N sinusoidal vertical load with a 40-kg mass point was imposed on the superior surface of L1. The parameters of intradiskal pressure, shear stress of annulus fibrosus, disk bulge, superior and inferior end plate stress, and facet joint contact pressure at L3-L4 and L5-S1 levels were evaluated. At L3-L4, the dynamic responses in intradiskal pressure, shear stress, facet joint contact pressure, superior end plate stress, and inferior end plate stress generated an increase after pedicle screw fixation, and their maximum values increased by 15.1%, 9.5%, 18.6%, 10.6%, and 9.3%, respectively. However, the parameter of disk bulge demonstrated an opposite trend. At L5-S1, the differences in maximum values of the parameters were slight and the corresponding dynamic response curves were close, overlapping, or intersecting. In an osteoporotic spine after TLIF, removal of pedicle screw fixation can mitigate ASD in the upper adjacent segment but has no apparent influence on the lower adjacent segment under WBV. [ABSTRACT FROM AUTHOR]

Aims: To draw a comparison of the pullout strengths of buttress thread, barb thread, and reverse buttress thread bone screws. Methods: Buttress thread, barb thread, and reverse buttress thread bone screws were inserted into synthetic cancellous bone blocks. Five screw-block constructs per group were tested to failure in an axial pullout test. The pullout strengths were calculated and compared. A finite element analysis (FEA) was performed to explore the underlying failure mechanisms. FEA models of the three different screw-bone constructs were developed. A pullout force of 250 N was applied to the screw head with a fixed bone model. The compressive and tensile strain contours of the midsagittal plane of the three bone models were plotted and compared. Results: The barb thread demonstrated the lowest pullout strength (mean 176.16 N (SD 3.10)) among the three thread types. It formed a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains within the surrounding bone structure. The reverse buttress thread demonstrated the highest pullout strength (mean 254.69 N (SD 4.15)) among the three types of thread. It formed a considerably larger region with high compressive strains and a slightly smaller region with high tensile strains within the surrounding bone structure. Conclusion: Bone screws with a reverse buttress thread design will significantly increase the pullout strength.

Abstract Background The procedure of percutaneous Achilles tenotomy (PAT) is an important component of the Ponseti method. However, few studies reported the influence of Achilles tendon on kinematic coupling relationship between tarsal bones. The purpose of present study was to demonstrate the effect of Achilles tendon on the kinematic coupling relationship between tarsal bones, and to illustrate how kinematic coupling relationship between tarsal bones works in term of finite element analysis. Methods A three-dimensional finite element model of foot and ankle was constructed based on the Chinese digital human girl No.1 (CDH-G1) image database using the software of mimics, Geomagic studio, HyperMesh, and Abaqus. The last manipulation of the Ponseti method before the procedure of PAT was simulated. The talus head and the proximal tibia and fibula bone were fixed in all six degrees of freedom, and the outward pressure was added on the first metatarsal head to investigate the kinematic coupling relationship between tarsal bones. Results The least relationship of kinematic coupling between tarsal bones was found in calcaneus. Stress concentration was mainly observed at the navicular, talus and the medial malleolus. The difference in displacement of the navicular was only found with the Achilles tendon stiffness of 0 N/mm and others. No difference in the navicular displacement was found in the stiffness of Achilles tendon between 40, 80, 200, 400, and 1000 N/mm. The maximum displacement of navicular was observed at the ankle position of PF-20° (plantar flexion-20°). The difference in displacement of the navicular was greater at the ankle position of PF-20° with the Achilles tendon stiffness of 0 N/mm than that at the ankle position of PF-40° with the Achilles tendon stiffness of 40 N/mm. Conclusions Based on the findings from this study, it was demonstrated that the Achilles tendon existence or not and ankle position had great influence, while increased stiffness of Achilles tendon had no influence on kinematic coupling relationship between tarsal bones. For the cases with severe equinus, earlier implementation of PAT procedure (with the purpose of release the Achilles tendon and reduce the degree of ankle plantar flexion) may be beneficial to the deformity correction.

Abstract Purpose To compare the effect of conventional pedicle screw (CPS) and cement-augmented pedicle screw instrumentation (CAPSI) on adjacent segment degeneration (ASD). Methods A normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected, an intact L3-S1 three-dimensional finite element model was created by software including Mimics, Geomagic, and SolidWorks, and the fixation methods were performed accordingly. A common pedicle screw model and a cement-augmented pedicle screw model of L4–L5 with fusion and internal fixation were constructed. With ANSYS Workbench 17.0, a 500 N load was applied to the upper surface of L3 to simulate the weight of a human body, and a 7.5 N m moment was applied at the neutral point to simulate flexion, extension, left/right bending, left/right rotation of the spine. The peak von Mises stress of intervertebral disc and the range of motion (ROM) on the adjacent segments (L3–4 and L5–S1) were compared. Results The validity of the intact model shows that the ROM of the model is similar to that of a cadaveric study. Compared with the intact model, CPS model and CAPSI model in all motion patterns increased the ROM of adjacent segments. The intervertebral disc stress and the ROM of adjacent segments were found to be higher in the CAPSI model than in the CPS model, especially in L3–4. Conclusion In general, the biomechanical analysis of an osteoporotic lumbar spine showed that both CPS and CAPSI can increase the ROM and disc stresses of osteoporotic lumbar models, and compared with CPS, CAPSI is more likely to increase the potential risk of adjacent segment degeneration.

Lumbar disc herniation (LDH) is a common condition which can lead to back pain. Although surgical treatments for LDH are well established, complications such as spinal instability and narrowing of adjacent facet joints are still frequently reported. The purpose of this study was to use finite element models to evaluate the stability of the L3–L4 segment after conservative or aggressive percutaneous transforaminal endoscopic discectomy (PTED) with and without an artificial material filler to correct LDH. Compared to the intact model, aggressive PTED reduced the stability of the segment (increased ROM) and narrowed the space between facet joints in the medial/lateral (ML) direction during flexion (maximum 6.7 degrees change in ROM and 90.5% spacing between facet joints), extension (maximum 2.1 degrees and 38.6%), and axial rotation (maximum 4.2 degrees and 90.1%). Aggressive PTED had a similar effect in the anterior/posterior (AP) direction during lateral bending (maximum 2.0 degrees and 44.2%). Augmenting the nucleus pulposus with a polyurethane filler after aggressive PTED improved spinal stability in both the ML and AP directions in all simulated motions, with results similar to the intact model. However, using a hydrogel filler did little to stabilize the spine, likely because the material is too soft to support the heavy, sustained loading. In conclusion, this study found that if an aggressive discectomy is required, augmenting the nucleus pulposus with a PU filler provides sufficient support to stabilize the spine, while hydrogel fillers offer little support.

Adjacent segmental degeneration (ASD) is one of the common complications after posterior lumbar interbody fusion (PLIF). Both whole body vibration (WBV) and osteoporosis are important factors associated with the biomechanics of the lumbar spine. However, to the best of our knowledge, no studies have investigated the effects of osteoporosis on ASD after PLIF under WBV. In the present study, using one normal model, one PLIF model and one PLIF with osteoporosis model of the L1–S1 segment were developed. A 5-Hz, 40-N sinusoidal vertical load was imposed on the superior surface of L1 of each model to simulate WBV, and the dynamic responses and maximal values of intradiscal pressure, shear stress on annulus fibrosus, total deformation, and disc bulge were evaluated in the L1-L2, L2-L3, L3-L4, and L5-S1 segments. At the L1-L2, L2-L3, and L3-L4 levels, the differences in the dynamic responses and maximal values in intradiscal pressure, shear stress, total deformation, and disc bulge between the PLIF and PLIF with osteoporosis models were slight. However, at the L5-S1 level, the dynamic response curves and maximal intradiscal pressure, shear stress, and disc bulge values in the PLIF with osteoporosis model were significantly lower than those in the PLIF model. Osteoporosis can mitigate the development of ASD in the lower adjacent segment but has no obvious influence on the upper adjacent segments during WBV. [ABSTRACT FROM AUTHOR]

Dual-phase (DP) steel has an excellent blend of various mechanical properties; hence it is used immensely in the automotive industries. It is challenging to form high strength DP steel into desirable complex shapes because of their limited formability at room temperature conditions. One of the proven alternatives is warm/hot forming. In-detail investigation of forming limits over DP590 steel has been carried out in present work. Firstly, various constitutive models and yield criteria have been formulated for DP steel at different temperatures and strain rates. The modified Arrhenius (m-A) constitutive model and Barlat 1989 yielding function displayed the best prediction of flow stress and anisotropic yielding behavior, respectively. The experimental forming limits (FLD) were evaluated at 300, 473 and 673 K temperatures using Nakazima tests. The forming limits of the material are improved by approximately 24% on increasing the temperature from 300 to 673 K. The textural analysis of the deformed surface has been done using electron back scattered diffraction (EBSD) studies, and γ fibers are found to be responsible for improvement in the formability of the material. Additionally, Marciniak and Kuczynski (MK) model was used to predict the theoretical FLD using all the possible combinations of constitutive models and yield criteria. Finally, the m-A constitutive model, along with Barlat 1989 yielding function has shown the best prediction for forming limits at all the temperatures. The finite element study has also been performed using mentioned material models for accurate prediction of dome height, surface strain and thickness distribution across the specimens. [ABSTRACT FROM AUTHOR]

An eccentrically braced composite frame with a low-yield-point (LYP) steel shear link is an efficient energy dissipation system that exhibits good mechanical properties. However, existing experimental studies have not fully demonstrated the superiority and applicability of the structural system. We present a structural mechanics and finite element model analysis of an eccentrically braced composite frame with a vertical shear link. The effect of the design parameters on the seismic performance of the structure is analyzed. First, a theoretical model of the mechanics of the structural system is established to provide a comprehensive description of the key parameters. Then, a finite element model is developed using the computer program ABAQUS to analyze the mechanical and energy dissipation mechanisms. Finally, the beam-to-column stiffness ratio, shear link web thickness, shear link web width and length, and diagonal brace stiffness are analyzed to determine their effects on the mechanical properties of the structural system. Furthermore, some design parameter values are suggested.

Background/Aim: Plate screw fixation is an important method in femoral shaft fractures. Although there are many studies on plate screw fixation, the ideal plate screw configuration has not yet been determined. In our study, we investigated the optimal plate-screw configuration in femoral shaft fractures using the 3D finite element analysis method. Methods: A fracture model was created by removing the segment from the femur model obtained from 3D computed tomography scanning. Five different fixation models were designed using a 4.5 mm diameter steel locked femoral shaft plate and different screw configurations. Screws with double cortex locks of 4.5 mm in width were used in different configurations. To evaluate the effect of screw diameter, a 5.5 mm diameter screw with a double cortex lock was used in one model. Static linear analyses of these prepared Finite Element models were performed using Ansys Workbench 2020 R2 Finite Elements software. Results: The maximum stresses on the plate at the fracture sites were 156 MPa at 200 N, and 546 MPa at 700 N in model 1, 274 MPa at 200 N, and 784 MPa at 700 N in Model 2, 274 MPa at 200 N, and 959 MPa at 700 N in Model 3, 389 MPa at 200 N, and 1118 MPa at 700 N in Model 4, and 200 N is 274 MPa, and 961 MPa at 700 N in Model 5. Conclusion: The stress on the plate in the fracture area increases in parallel with the increase in screw diameter, plate length and plate working distance. Filling all screw holes does not alter the stress on the plate at the fracture line level. [ABSTRACT FROM AUTHOR]

Objective: To investigate the biomechanical effects of osteoporosis on adjacent segments after posterior lumbar interbody fusion (PLIF). Methods: This study was designed and conducted in the Traumatology and Orthopedics Laboratory, School of Chinese Medicine, Jinan University, Guangzhou, China, between December 2019 and February 2020. A healthy finite element model of L3-S1 was developed along with one PLIF model and one PLIF with osteoporosis model. Based on a hybrid test method, the inferior surface of S1 was entirely fixed, and a preload of 400N combined with an adjusted moment was imposed on the superior surface of L3 in each model to simulate flexion, extension, lateral bending and axial rotation. The intradiscal pressure (IDP), shear stress on annulus fibrosus, and the range of motion (ROM) of L3-L4 and L5-S1 were calculated and compared. Results: In each direction, the highest value of IDP and shear stress on annulus fibrosus at L3-L4 and L5-S1 was found in the PLIF model, and the lowest value in the healthy model. The largest ROM at L4-L5 appeared in the healthy model, and the smallest value in the PLIF model in each direction. At L3-L4 and L5-S1, the highest ROM in most directions was found in the PLIF model, followed by the PLIF with osteoporosis model, and the lowest value in the healthy model. Conclusions: Osteoporosis can decrease IDP, shear stress on annulus fibrosus, and ROM at adjacent levels, and slow down the development of ASD after PLIF. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to determine the ideal placement of the lag screw taking into account the fracture morphology in the sagittal plane.Materials and Methods: Three different morphology of fractures were created on the sagittal plane in femur models obtained in 3D CT scanning: posteriorly angled (Type A), transverse (Type B) and anteriorly angled (Type C). The lag screw was applied in each of the three fracture morphology as neutral, anteverted and retroverted in the sagittal plane. The nine models created were transferred to the Ansys Workbench program and analyzes were performed.Results: In Type A fracture, the stress value at the lag screw apex increase as the lag screw placement changes from the anteverted position to the retroverted position. It decreases in the Type B and Type C fractures. As the lag screw placement is changed towards the anteverted position, the stress at the lag screw-nail junction decreases in the Type A fracture and increases in the Type C fracture . There is no significant change in the Type B fracture. As the lag screw placement is changed towards the anteverted position, the stress in the calcar region increases in Type A fractures and decreases in Type C fractures. There is no significant change in type B fractures.Conclusion: While the ideal lag screw placement in a type A fracture in the sagittal plane is the retroverted placement, the anteverted placement is ideal placement in type C fractures. Fracture morphology in the sagittal plane should be taken into account in the lag screw placement. [ABSTRACT FROM AUTHOR]

Adjacent segment degeneration is a common complication following anterior lumbar interbody fusion (ALIF). Osteoporosis is becoming increasingly prevalent in the elderly population and thus patients undergoing ALIF may experience osteoporosis with age. However, the influence of osteoporosis on adjacent segment degeneration after ALIF remains unclear. Three finite element models of the L3-S1 segment, including a healthy model, an ALIF model, and an ALIF with osteoporosis model, were used for analysis. ALIF was simulated at the L4-L5 segment. Based on a hybrid test method, the models were imposed with a preload of 400 N and an adjusted moment in flexion, extension, lateral bending, and axial torsion. Intradiscal pressure, shear stress on anulus fibrosus, and range of motion at L3-L4 and L5-S1 were calculated and compared. In each direction, the maximal values of intradiscal pressure and shear stress on anulus fibrosus at L3-L4 and L5-S1 were found in the ALIF model, and the minimal values were found in the healthy model. At L3-L4 and L5-S1, the maximal values of range of motion in most directions were found in the ALIF model followed by the ALIF with osteoporosis model, and the minimal values were found in the healthy model. However, the maximal value of range of motion at L5-S1 in axial torsion was found in the ALIF with osteoporosis model. Osteoporosis may mitigate the adverse influence of ALIF on adjacent segments. [ABSTRACT FROM AUTHOR]

Abstract Background Numerous reports have shown that rigid spinal fixation contributes to a series of unwanted complications in lumbar fusion procedure. This innovative micro-dynamic pedicle screw study was designed to investigate the biomechanical performance of lumbar implants using numerical simulation technique and biomechanical experiment. Methods Instrumented finite element models of three configurations (dynamic fixation, rigid fixation and hybrid fixation) using a functional L3-L4 lumbar unit were developed, to compare the range of motion of the lumbar spine and stress values on the endplate and implants. An in vitro experiment was simultaneously conducted using 18 intact porcine lumbar spines and segmental motion analyses were performed as well. Results Simulation results indicated that the dynamic fixation and the hybrid fixation models respectively increased the range of motion of the lumbar spine by 95 and 60% in flexion and by 83 and 55% in extension, compared with the rigid fixation model. The use of micro-dynamic pedicle screw led to higher stress on endplates and lower stress on pedicle screws. The outcome of the in vitro experiment demonstrated that the micro-dynamic pedicle screw could provide better range of motion at the instrumented segments than a rigid fixation. Conclusion The micro-dynamic pedicle screw has the advantage of providing better range of motion than conventional pedicle screw in flexion-extension, without compromising stabilization, and has the potential of bringing the load transfer behavior of fusional segment closer to normal and also lowers the stress values of pedicle screws.

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Background: The procedure of percutaneous Achilles tenotomy (PAT) is an important component of the Ponseti method. However, few studies reported the influence of Achilles tendon on kinematic coupling relationship between tarsal bones. The purpose of present study was to demonstrate the effect of Achilles tendon on the kinematic coupling relationship between tarsal bones, and to illustrate how kinematic coupling relationship between tarsal bones works in term of finite element analysis. Methods: A three-dimensional finite element model of foot and ankle was constructed based on the Chinese digital human girl No.1 (CDH-G1) image database using the software of mimics, Geomagic studio, HyperMesh, and Abaqus. The last manipulation of the Ponseti method before the procedure of PAT was simulated. The talus head and the proximal tibia and fibula bone were fixed in all six degrees of freedom, and the outward pressure was added on the first metatarsal head to investigate the kinematic coupling relationship between tarsal bones. Results: The least relationship of kinematic coupling between tarsal bones was found in calcaneus. Stress concentration was mainly observed at the navicular, talus and the medial malleolus. The difference in displacement of the navicular was only found with the Achilles tendon stiffness of 0 N/mm and others. No difference in the navicular displacement was found in the stiffness of Achilles tendon between 40, 80, 200, 400, and 1000 N/mm. The maximum displacement of navicular was observed at the ankle position of PF-20° (plantar flexion-20°). The difference in displacement of the navicular was greater at the ankle position of PF-20° with the Achilles tendon stiffness of 0 N/mm than that at the ankle position of PF-40° with the Achilles tendon stiffness of 40 N/mm. Conclusions: Based on the findings from this study, it was demonstrated that the Achilles tendon existence or not and ankle position had great influence, while increased stiffness of Achilles tendon had no influence on kinematic coupling relationship between tarsal bones. For the cases with severe equinus, earlier implementation of PAT procedure (with the purpose of release the Achilles tendon and reduce the degree of ankle plantar flexion) may be beneficial to the deformity correction. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effect of conventional pedicle screw (CPS) and cement-augmented pedicle screw instrumentation (CAPSI) on adjacent segment degeneration (ASD). Methods: A normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected, an intact L3-S1 three-dimensional finite element model was created by software including Mimics, Geomagic, and SolidWorks, and the fixation methods were performed accordingly. A common pedicle screw model and a cement-augmented pedicle screw model of L4–L5 with fusion and internal fixation were constructed. With ANSYS Workbench 17.0, a 500 N load was applied to the upper surface of L3 to simulate the weight of a human body, and a 7.5 N m moment was applied at the neutral point to simulate flexion, extension, left/right bending, left/right rotation of the spine. The peak von Mises stress of intervertebral disc and the range of motion (ROM) on the adjacent segments (L3–4 and L5–S1) were compared. Results: The validity of the intact model shows that the ROM of the model is similar to that of a cadaveric study. Compared with the intact model, CPS model and CAPSI model in all motion patterns increased the ROM of adjacent segments. The intervertebral disc stress and the ROM of adjacent segments were found to be higher in the CAPSI model than in the CPS model, especially in L3–4. Conclusion: In general, the biomechanical analysis of an osteoporotic lumbar spine showed that both CPS and CAPSI can increase the ROM and disc stresses of osteoporotic lumbar models, and compared with CPS, CAPSI is more likely to increase the potential risk of adjacent segment degeneration. [ABSTRACT FROM AUTHOR]

This study presents a rapid sizing technique for interior permanent magnet (IPM) machine in traction application considering saturation effects. It is demonstrated that with limited computing resources, sizing, parameters considering saturation effects, and efficiency maps (loss maps) of an IPM machine can be generated within seconds with acceptable accuracy in comparison with finite element study and measurements. Thus, the proposed rapid sizing method is highly essential at the preliminary design stage of electric vehicle powertrains.

Objectives: To clarify the mechanics of tooth movement in mesialization of the whole mandibular dentition when changing the force angulation.Setting: A finite element method was used to simulate long-term movements of the whole mandibular dentition.Material and Methods: Tooth movement was simulated by accumulating the initial displacement, which was produced by elastic deformation of the periodontal ligament. Mesial forces of 3 N were applied to the second molar bracket at -30°, -15°, 0°, 15° and 30° to the occlusal plane.Results: The whole dentition and occlusal plane were rotated depending on the direction of the force with respect to the centre of resistance (CR). At a force angulation of -30°, the line of action of the force passed near the CR, and the whole dentition translated without rotation of the occlusal plane. The second molar tipped buccally due to a clearance gap between the archwire and bracket slot. When increasing a force angulation from -30°, the line of action of the force passed above the CR, and thereby, the occlusal plane rotated clockwise. This rotation of the whole dentition induced tipping of the individual teeth. Buccal tipping of the molar due to an elastic deformation of the archwire was prevented by using a lingually pre-bent archwire.Conclusions: Careful selection of force angulation and biomechanics is essential to obtain proper tooth movement in total mesialization of the mandibular dentition. [ABSTRACT FROM AUTHOR]

This study presents a rapid sizing technique for interior permanent magnet (IPM) machine in traction application considering saturation effects. It is demonstrated that with limited computing resources, sizing, parameters considering saturation effects, and efficiency maps (loss maps) of an IPM machine can be generated within seconds with acceptable accuracy in comparison with finite element study and measurements. Thus, the proposed rapid sizing method is highly essential at the preliminary design stage of electric vehicle powertrains. [ABSTRACT FROM AUTHOR]

Percutaneous full-endoscopic anterior cervical discectomy (PEACD) and posterior cervical foraminotomy (PCF) have been reported as effective treatments for the cervical spondylosis radiculopathy (CSR), but the biomechanical effects on the discs and facet joints of PEACD and PCF remain largely unclear. The purpose of this paper is to investigate and compare the biomechanical changes on cervical spine after PECAD and PCF procedures, thus providing evidences for surgeons to select a more appropriate approach. An intact cervical C5-C6 digital model was constructed and then modified to obtain the PCF and PEACD models using finite element method. All the models were subjected to a 73.6N preload accompanied by a 1.8 Nm moment during flexion, extension, axial rotation, lateral bending. The range of motion (ROM), intervertebral disc pressure (IDP), facet joint contact area, and contact pressure were calculated under different loading conditions. The ROM of the PCF model changed slightly (0.28%), whereas that of the PEACD model increased significantly (20.49%) compared with intact model. The trend of IDP changes in these 2 surgical models were similar to ROM in the corresponding motion state. The contact pressure on the facet joint of the PEACD model increased by 20.53%, 33.38%, and 17.46% during extension, lateral bending, and axial bending, respectively, compared with the intact model, and the PCF increased by 33.53% and 16.16% during extension and lateral bending, respectively, whereas it decreased 0.97% in axial rotation. The facet joint contact area of the PCF model increased by 85.71%, 1.54%, and 2.17% during extension, lateral bending, and axial rotation, respectively, and the area of the PEACD model increased by 157.14% and 36.96% during extension and axial rotation, whereas it decreased by 13.85% during lateral bending. This is the first biomechanical finite element study comparing PEACD with PCF for the treatment of CSR. Our results showed that PEACD led to hypermobility with high IDP within the cervical segment undergone surgery, whereas the ROM and IDP changed slightly after PCF. The variations of the contact stress indicated that both procedures changed the transmission path of the force on the facet joint and may accelerate the degeneration of the facet joint. PCF may be a better choice for the treatment of CSR compared with PEACD. [ABSTRACT FROM AUTHOR]