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An epiretinal membrane (ERM) is a fibrocellular proliferation on the inner surface of the retina causing blurred and distorted central vision. Surgery is the only effective method for ERM removal. This paper investigated the mechanical properties of ERM peeling using the finite element (FE) method. A FE model of ERM formation on the retina surface was constructed. The failure criterion was applied to the attachment pegs to represent the adhesive force between the ERM and retina. The simulation results were consistent with the experimental data in published research. The maximum peeling force was 4.1 mN at a peeling velocity of 2 mm/s and an angle of 30°. The peeling force was minimum at the peeling angle of 45° and increased with the increase in peeling velocity and Young's modulus of the membrane. The outcome of this paper can improve the safety and efficiency of ERM removal. [ABSTRACT FROM AUTHOR]

The bone lacunar-canalicular system (LCS) is a unique complex 3D microscopic tubular network structure within the osteon that contains interstitial fluid flow to ensure the efficient transport of signaling molecules, nutrients, and wastes to guarantee the normal physiological activities of bone tissue. The mass transfer laws in the LCS under microgravity and hypergravity are still unclear. In this paper, a multi-scale 3D osteon model was established to mimic the cortical osteon, and a finite element method was used to numerically analyze the mass transfer in the LCS under hypergravity, normal gravity and microgravity and combined with high-intensity exercise conditions. It was shown that hypergravity promoted mass transfer in the LCS to the deep lacunae, and the number of particles in lacunae increased more significantly from normal gravity to hypergravity the further away from the Haversian canal. The microgravity environment inhibited particles transport in the LCS to deep lacunae. Under normal gravity and microgravity, the number of particles in lacunae increased greatly when doing high-intensity exercise compared to stationary standing. This paper presents the first simulation of mass transfer within the LCS with different gravity fields combined with high-intensity exercise using the finite element method. The research suggested that hypergravity can greatly promote mass transfer in the LCS to deep lacunae, and microgravity strongly inhibited this mass transfer; high-intensity exercise increased the mass transfer rate in the LCS. This study provided a new strategy to combat and treat microgravity-induced osteoporosis. [ABSTRACT FROM AUTHOR]

This paper aimed to investigate the biomechanical changes during the talus impact with the calcaneus at varying velocities. Various three-dimensional reconstruction software was utilized to construct a finite element model that consisted of the talus, calcaneus, and ligaments. The explicit dynamics method was used to explore the process of the talus impacting on the calcaneus. The velocity of impact was altered from 5 m/s to 10 m/s with a 1 m/s interval. Stress readings were collected from the posterior, intermediate, and anterior subtalar articular (PSA, ISA, ASA), calcaneocubic articular (CA), Gissane Angle (GA), calcaneal base (BC), medial wall (MW), and lateral wall (LW) of the calcaneus. The changes in the amount and distribution of stress in the different regions of the calcaneus that varied with velocity were analysed. The model was validated through comparison with findings from the existing literature. During the process of impact between the talus and calcaneus, the stress in the PSA reached its peak first. Notably, stress was concentrated mainly in the PSA, ASA, MW, and LW of the calcaneus. At varying impact velocities of the talus, the mean maximum stress of the PSA, LW, CA, BA, and MW exhibited statistically significant differences (P values were 0.024, 0.004, <0.001, <0.001, and 0.001, respectively). However, the mean maximum stress of the ISA, ASA, and GA was not statistically significant (P values were 0.289, 0.213, and 0.087, respectively). In comparison with the velocity at 5 m/s, the mean maximum stress increases in each region of the calcaneus at a velocity of 10 m/s were as follows: PSA 73.81%, ISA 7.11%, ASA 63.57%, GA 89.10%, LW 140.16%, CA 140.58%, BC 137.67%, MW 135.99%. The regions of stress concentration were altered, and the magnitude and sequence of peak stress in the calcaneus also varied according to the velocity of the talus during impact. In conclusion, the velocity of the talus during impact had a significant influence on the magnitude and distribution of stress within the calcaneus, which was a crucial factor in the development of calcaneal fractures. It was possible that the magnitude and sequence of stress peaks played a vital role in determining the emergence of fracture patterns. [ABSTRACT FROM AUTHOR]

The tilting of the cab seat when the tractor is in deep ploughing operation changes the sitting position of the driver, which may accelerate lumbar spine injury. This paper adopts the musculoskeletal model and the finite element model of the lumbar L4–L5 segment to predict the maximum Von-Mises stress and maximum strain of the driver's lumbar L4–L5 segment intervertebral disc. In this study, we used 3D motion capture to obtain the driver's spine position spatial data when the tractor tilted at different angles. A tractor-driver musculoskeletal model and a finite element model of the lumbar spine L4–L5 segments were created in AnyBody™ and Abaqus, respectively. The tractor-driver musculoskeletal model was used to calculate the load of the driver's lumbar spine L4–L5 segment at different angles of tractor tilt, which was used as the load condition of the finite element model of the lumbar spine L4–L5 segment, and then the influence of tractor tilt angle and vibration on the driver's lumbar spine L4–L5 disc was studied. The results show that the maximum Von-Mises stress and maximum strain of the driver's lumbar L4–L5 intervertebral disc will increase due to the tilt. The maximum Von-Mises stress occurs in the annulus II, and the maximum strain occurs in the upper end plate of the intervertebral disc. With the occurrence of tilt, the position of the maximum Von-Mises stress changes, which can lead to disc injury to the driver, and vibration may exacerbate this injury. [ABSTRACT FROM AUTHOR]

In order to understand the distribution of streaming potentials in cartilage pores, this paper established finite element model to analyze. The results showed that the streaming potential in cartilage micro-pores increased along the axis. The electric potential in 5 μm straight micro-pore was about 50 μV, and the electric potential of curved bifurcation model was about 30 μV. The pressure and Zeta potential had a linear growth relationship with the streaming potential. The streaming potential decreased with the increase of ion concentration until ion concentration was saturated. These results could provide a theoretical basis for cartilage research. [ABSTRACT FROM AUTHOR]

In the intervention with stent implantation for iliac vein compression syndrome (IVCS), it remains unclear about the influencing mechanism of the structure and implantation position of the stent for the hemodynamics of the affected site. In this paper, an iliac vein model was established. Besides, the computational fluid dynamics (CFD) was utilized to analyze the time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) in a sine period after stent implantation based on the three different implantation positions of two iliac vein stents (the left branch outlet, contralateral disturbed flow and main iliac vein). The influence of the structure and implantation position of the stent on blood flow was revealed. These findings were verified by the particle image velocimetry (PIV) experiment. The results indicated that the maximum blood flow velocity of the iliac vein decreased after the stent implantation. Among the three positions, the influence of stent implantation on the iliac vein blood flow was the least when the stent implantation was performed at the left branch outlet; the influence of stent implantation on the iliac vein blood flow was the greatest when the stent implantation was performed at the contralateral disturbed flow. Moreover, there was little influence of Venastent implantation on the blood flow. These results could provide a scientific foundation for implantation treatment and stent design related to IVCS. [ABSTRACT FROM AUTHOR]

Finite element simulation is used to analysis stent designs, extension as well as interaction between a stent and a vessel. In this paper, two different stents with different geometries have been simulated. One is Zilver stent and the other one is Navalis stent. The aim of this study is to determine the effect of stents deployment with various designs that are made of shape memory alloy (SMA) on the distribution of vessel wall stresses by using computational modeling approach. The constitutive model which described the behavior of SMA is based on Microplane model. In addition, SMA stents have been simulated under torsion loading to compare the flexibility of various designs under different conditions. The superelastic behavior and shape memory effect of SMA stents are investigated in this paper. The numerical simulation results show the different geometries of stents have significant effect on the arterial wall. The results show the Navalis stent causes less stress on the arterial wall and it is more flexible than the Zilver stent under the same torsion loading. [ABSTRACT FROM AUTHOR]

This paper discussed the size of 3 D-printed personalized titanium plates that can gain maximum stability of mandibular fracture and minimize stress shielding through finite element analysis. A 3 D virtual model of mandible with mandibular angle fracture was created from the CT data of patient. 3 D-printed personalized titanium plates varying in length and thickness were designed, and finite element analysis was performed under different loading conditions and fracture healing periods. After that, the stress distribution and deformation of the mandible with gonial fracture could be observed, and the stress shielding rate could be obtained. Finally, SPSS21.0 was used for statistical analysis. The results of finite element analysis indicated that as the thickness of titanium plates and the healing time decreased, the maximum displacement increased, under a certain condition in which the pore size, the width, the hole distance and the bridge spacing were 2.0 mm, 4.0 mm, 6.0 mm, 12.0 mm, respectively. What's more, in this condition, the thicker the titanium plate and the shorter the healing time were, the higher the stress shielding was at central occlusion. When the thickness of the personalized 3 D-printed titanium plate was 1.0 mm, the maximum displacement tended to be stable and the stress shielding was minimized. It can not only improve the bone stability after tension band fixation, but also minimize the stress shielding, which is expected to expand the indications of tension band fixation. [ABSTRACT FROM AUTHOR]

The objective of this paper is to elucidate the response to contact stresses of Polymer Infiltrated Ceramic Network (PICN) using the microscopic viscoplastic finite elements, validated by clinically relevant in vitro tests. A feldspathic ceramic material, namely Vita Mark II, is an interconnected structure infiltrated with the polymer (PMMA). Axisymmetric finite element microstructure models are reconstructed from two-dimensional images of a PICN microstructure. Viscoplastic finite element analysis (FEA) with various degrees of microscopic damages occurring over contact is performed. The force-displacement responses obtained from FEA are validated with Hertzian contact tests. Finite element results for force-displacement, stresses and strains in each phase are discussed. We hypothesize that the resistance to fracture of PICN can be further improved by microstructural tailoring. The experimental evidence suggests that a composite material is both more resistant to displacement under load and more resistant to crack initiation and propagation, as hypothesized. Further parametric study on the effects of various volume fractions of two phases in PICN is done to provide some insight on increased contact damage resistance of PICN as well as potential optimization of microstructures. [ABSTRACT FROM AUTHOR]

In this paper, two mathematical models have been formulated by extending the basic reaction–diffusion model, along with suitable initial and boundary conditions to study the drug delivery and its diffusion in biological tissues from multi-layered capsules/tablets and other drug delivery devices (DDDs), respectively. These devices are either taken orally or through other drug-administration routes. The formulated models are solved using the variational finite element method followed by the fundamental matrix method, to study the drug delivery and its diffusion more efficiently. The main aim of this work is to provide an effective model, using optimal mathematical techniques to help researchers and biologists in medicine in decreasing the endeavours and expenses in designing DDDs. The outcomes obtained are compared with the experimental data to demonstrate the validity and the feasibility of the proposed work. [ABSTRACT FROM AUTHOR]

In endoscopic surgery, the surgical navigation system needs to calculate the deformation of soft tissue by biomechanical model which requires elastic properties and boundary conditions. However, patient-specific elastic parameters and boundary conditions of soft tissue are hard to measure accurately from the preoperative images, especially the boundary conditions will change during the operation due to the ligament cutting. In addition, simple boundary conditions such as fixed constraints and free-force constraints are not physically adequate to simulate the elastic effect of ligaments attached to the liver. In this paper, we present a novel method to identify the Young's modulus and equivalent spring constraint boundary conditions of a locally observed soft tissue. Based on the spring constraint boundary condition, a two-step inverse algorithm is developed based on the finite element method (FEM) with integration of energy regularized Gauss-Newton (GN) method and l 1 -regularized method, which takes external forces and displacements of observable nodes as inputs. A series of numerical simulations and physical hydrogel phantom experiments were conducted. The results of simulation and physical experiments show that the Young's modulus and equivalent spring constraint boundary conditions identified by the proposed method agree well with their setup true values. [ABSTRACT FROM AUTHOR]

Tear force of the capsulotomy edge is a paramount parameter to affect the surgical safety in cataract surgery. This paper aimed to investigate the stretch force of the capsulotomy edge using finite element (FE) method. A FE model of capsule bag was developed to simulate dynamic response of the lens capsule to the stretch of retractors. The failure criterion based on the distortion energy theory was applied to predict the rupture of the anterior capsule. The simulation results showed a good agreement with the experimental data reported in the literature. Sensitivity studies were then conducted to evaluate the effect of the various parameters on tear force, including the stretching velocity, capsulorhexis dimension, age, retractor width and shape, and rim morphology. The rupture force was proportional to the stretching velocity, capsulorhexis dimension and retractor width, while the age showed the opposite trend. In addition, the retractor shape has a greatly effect on the tear force and the rim of continuous curvilinear capsulorhexis (CCC) has the higher tear resistance. This work can contribute to the understanding of the regularity for capsule rupture. [ABSTRACT FROM AUTHOR]