Objective To investigate the stability and the stress distributions of L3-5 fused with three different approaches (interbody, posterolateral and circumferential fusions) and to investigate degeneration of thesegment adjacent to the fused functional spinal unit. Methods A detailed L3-5 three-dimensional nonlinear finite element model of a normal man aged 32 was established and validated. Based on the model, the destabilized model, the interbody, posterolateral and circumferential fusions models of L4-5 were established. After the loadings were placed on all the models, we recorded the angular motions of the fused segment and the Von Mises stress of the adjacent intervertebral disc. Results The circumferential fusion was most stable than the others, and the interbody fusion was more stable than the posterolateral fusion. The maximal Von Mises stress of the adjacent L3,4 intervertebral disc in all the models was ranked descendingly as flexion,lateral bending,torsion and extension. For the three kinds of fusions, the stress increment of the L3,4 intervertebral disc was ranked ascendingly as interbody fusion,posterolateral fusion and circumferential fusion. Conclusion After destabilization of the L4,5 segment, the stability of the circumferential fusionis better than that of the others, particularly under the flexional or extensional loading. The stability of the interbody fusion is better than that of the posterolateral fusion, except for under the flexional loading. The feasibility of adjacent segment degeneration can be ranked descendingly as: circumferential fusion,posterolateral fusion and interbody fusion.
Ginger moxibustion has the effect of regulating zang-fu organs and activating qi and blood circulation. When used, ginger paste is required to be close to human skin. Currently, the ginger box used clinically in the hospital can't meet the requirement of large area fitting human skin, and the efficacy of ginger moxibustion is significantly reduced. In this study, a flexible ginger paste box was proposed, which was composed of flexible components polydimethylsiloxane (PDMS), spring and wire netting. The large flexibility of the structure made it fit well with human skin. Finite element method was used to study the fitting degree between ginger paste box and waist soft tissue. Finite element models of flexible ginger paste box and waist soft tissue were established based on Hypermesh and Abaqus software. The equivalent contact area between the flexible ginger paste box and waist was obtained by numerical simulation under different PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness. The four parameters were taken as the influencing factors, and the equivalent contact area was taken as the optimization objective. The typical value analysis and variance analysis of S/N were performed by Taguchi method, and the results showed that among the four influencing factors, the wire netting diameter had the largest influence on equivalent contact area and its contribution rate reached 41.98%. The contribution rates of PDMS unilateral thickness, spring wire diameter and ginger paste layer thickness reached 36.48%, 13.97% and 6.50%, respectively. The optimized PDMS unilateral thickness, spring wire diameter, wire netting diameter and ginger paste layer thickness were 1.5, 0.4, 0.15, 35 mm, respectively, and the equivalent contact area was 95.60 cm2. The optimized flexible ginger paste box with great fitting performance can improve the effect of ginger moxibustion.
A certain degree of varus alignment is physiological in the native knee, and alignment strategies such as kinematic and functional alignment permit residual postoperative varus. However, identical total varus angles may result from varying combinations of femoral and tibial varus, whose biomechanical implications for implant loading and ligament stress remain unclear. This study aims to investigate the biomechanical effects of different femoral–tibial varus configurations in total knee arthroplasty (TKA). Using combined geometric modeling and finite element analysis, TKA models with different varus combinations were constructed to evaluate changes in limb moment arms, polyethylene insert stress, and ligament forces during static knee flexion (0°–90°). Results demonstrated that a higher proportion of femoral varus, under equivalent total varus and flexion angles, led to reduced maximum polyethylene stress and decreased tension in the medial collateral ligament (MCL) and anterolateral ligament complex (ALL). Knee flexion angle had a more significant impact on polyethylene stress than varus: stress increased by approximately 2.48 times at 90° flexion compared to 0°, whereas 12° varus increased stress by only approximately 14%. The ALL experienced the greatest tensile load during flexion, indicating a key stabilizing role. In conclusion, optimizing the combination of femoral and tibial varus may help redistribute loads and improve implant longevity. This study reveals, from a biomechanical perspective, how different varus configurations affect stress distribution in the prosthesis and surrounding soft tissues, suggesting that intraoperative osteotomy strategies should comprehensively consider the combined alignment of the femur and tibia.
Objective To discuss the method of constructingbiomechanical model of rabbit femur.Methods The sample of rabbit femur was prepared as follows:firstly，femur section images were obtained，then the image wasput into the computer and processed to get the boundary contour line; secondly, through programming the contour line coordinate for modeling was obtained, then the data were put into the model software to find the threedimensional entity model. Results Whole three-dimensional model of rabbit femur was constructed. It simulated actually dissection form of femur. Conclusion The establishment of the model lays a foundation for ascertaining optimal parameter of vibration improving bone minerydensity by finite element analysis.
The pulse amplitude of fingertip volume could be improved by selecting the vascular dense area and applying appropriate pressure above it. In view of this phenomenon, this paper used Comsol Multiphysics 5.6 (Comsol, Sweden), the finite element analysis software of multi-physical field coupling simulation, to establish the vascular tissue model of a single small artery in fingertips for simulation. Three dimensional Navier-Stokes equations were solved by finite element method, the velocity field and pressure distribution of blood were calculated, and the deformation of blood vessels and surrounding tissues was analyzed. Based on Lambert Beer's Law, the influence of the longitudinal compression displacement of the lateral light surface region and the tissue model on the light intensity signal is investigated. The results show that the light intensity signal amplitude could be increased and its peak value could be reduced by selecting the area with dense blood vessels. Applying deep pressure to the tissue increased the amplitude and peak of the signal. It is expected that the simulation results combined with the previous experimental experience could provide a feasible scheme for improving the quality of finger volume pulse signal.
To investigate the biomechanical effects of direct ventricular assistance and explore the optimal loading mode, this study established a left ventricular model of heart failure patients based on the finite element method. It proposed a loading mode that maintains peak pressure compression, and compared it with the traditional sinusoidal loading mode from both hemodynamic and biomechanical perspectives. The results showed that both modes significantly improved hemodynamic parameters, with ejection fraction increased from a baseline of 29.33% to 37.32% and 37.77%, respectively, while peak pressure, stroke volume, and stroke work parameters also increased. Additionally, both modes showed improvements in stress concentration and excessive fiber strain. Moreover, considering the phase error of the assist device's working cycle, the proposed assist mode in this study was less affected. Therefore, this research may provide theoretical support for the design and optimization of direct ventricular assist devices.
Objective To establ ish sophisticated three-dimensional finite element model of the lower cervical spine and reconstruct lower cervical model by different fixation systems after three-column injury, and to research the stress distribution of the internal fixation reconstructed by different techniques. Methods The CT scan deta were obtained from a 27-year-old normal male volunteer. Mimics 10.01, Geomagic Studio10.0, HyperMesh10.0, and Abaqus 6.9.1 softwares were usedto obtain the intact model (C3-7), the model after three-column injury, and the models of reconstructing the lower cervical spine after three-column injury through different fixation systems, namely lateral mass screw fixation (LSF) and transarticular screw fixation (TSF). The skull load of 75 N and torsion preload of 1.0 N•m were simulated on the surface of C3. Under conditions of flexion, extension, lateral bending, and rotation, the Von Mises stress distribution regularity of internal fixation system was evaluated. Results The intact model of C3-7 was successfully establ ished, which consisted of 177 944 elements and 35 668 nodes. The results of the biomechanic study agreed well with the available cadaveric experimental data, suggesting that they were accord with normal human body parameters and could be used in the experimental research. The finite element models of the lower cervical spine reconstruction after three-column injury were establ ished. The stress concentrated on the connection between rod and screw in LSF and on the middle part of screw in TSF. The peak values of Von Mises stress in TSF were higher than those in LSF under all conditions. Conclusion For the reconstruction of lower cervical spine, TSF has higher risk of screw breakage than LSF.
For the transportation process of rescuing wounded personnel on naval vessels, a new type of shoulder type exoskeleton stretcher for individual soldier was designed in this paper. The three-dimensional model of the shoulder type exoskeleton stretcher for individual soldier was constructed using three dimensional modeling software. Finite element analysis technique was employed to conduct statics simulation, modal analysis, and transient dynamics analysis on the designed exoskeleton stretcher. The results show that the maximum stress of the exoskeleton stretcher for walking on flat ground is 265.55 MPa, which is lower than the allowable strength of the fabrication material. Furthermore, the overall deformation of the structure is small. Modal analysis reveals that the natural frequency range of the exoskeleton stretcher under different gait conditions is 1.96 Hz to 28.70 Hz, which differs significantly from the swing frequency of 1 Hz during walking. This indicates that the designed structure can effectively avoid resonance. The transient dynamics analysis results show that the maximum deformation and stress of exoskeleton stretcher remain within the safety range, which meets the expected performance requirements. In summary, the shoulder type exoskeleton stretcher for individual soldier designed in this study can solve the problem of requiring more than 2 people to carry for the existing stretcher, especially suitable for narrow spaces of naval vessels. The research results of this paper can provide a new solution for the rescue of wounded personnel on naval vessels.
Objective To establ ish sophisticated three-dimensional finite element model of reconstructing the whole pelvis and defects in pelvis caused by the resection of periacetabular tumor, and to research the stress distribution regularity ofthe pelvis reconstructed by the fibular transplantation through three different internal fixation techniques. Methods The CTdatasets including L3 to middle-femur, unilateral fibular and internal fixation system from 1 healthy 35-year-old male volunteer were collected to establ ish finite element models of reconstructing the pelvis after the resection of periacetabular tumors through 3 different internal fixation means, namely fibular with plates, pedicle-rods and sacral-il iac rods. Bilateral leg standing position was simulated, then vertical load of 500 N was imposed on the surface of L3, the stress distribution regularity of reconstructed pelvis, transplanted fibular and internal fixation system were evaluated. Results The finite element models of the pelvis reconstruction after resection of periacetabular tumors were establ ished. The stress concentration of transplanted fibular was extremely high in the vicinity of the host junction sites. For the three internal fixation systems, the connection between steel plate and screw or between titanium bar and screw inclined to have stress concentration; and when the titanium bar was adopted to reconstruct, the transplanted fibular and the healthy side of femoral neck had less stress concentration, while sacral-il iac rods had the most obvious stress concentration. Conclusion For the reconstruction pelvis, the three fibula transplantation and steel plate internal fixation are consistent with intact state of pelvis in terms of the stress distribution, which is a relatively good method for the treatment of bone defect after periacetabular tumor. The finite element model can be used as a tool for the pelvis biomechanics research.
Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.