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Recent research has shown that lumbar disease has become common in China. Since the structure of the lumbar spine is extremely complex, a finite element analysis method was used to perform biomechanical simulation and analysis of stress and strain on the L3–L4 lumbar segment to provide both a scientific and theoretical basis for clinical diagnosis and medical research. The MC volume-rendering 3D reconstruction method was the first step to accurately constructing the finite element model of the L3–L4 lumbar sacral segment, which was simulated prior to the addition of the ligaments, fibrous ring, and other major spinal tissue. The finite element model network was classified and the material properties of the corresponding parts were described. According to the normal model, careful simulation and deformation were performed, in addition to intervertebral disc degeneration in various cases. We have provided a detailed and professional analysis of the biomechanical properties, providing a powerful biomechanical basis for the diagnosis of intervertebral disc bulge and degeneration.

Purpose: The goal of the study was to investigate the influence of independently varied parameters on the tear-out force of small intestinal anastomoses of abattoir pigs using methods which provide a high grade of standardization and reproducibility.

Methods: The tear-out force of sutured small intestine tissue was recorded, while independently varying the thread type (I), the number of stitches (II), the stitch-to-stitch distance (III), and the stitch to sample-edge distance (IV).

Results: The tear-out force was shown to be significantly higher when using Vicryl 3-0 in comparison to PDS II 3-0, the significance being highest for small numbers of stitches. Given a fixed number of stitches, small stitch-to-stitch (stitch-to-edge) distances <~5.0 mm yield a significantly lower tear-out force than larger stitch-to-stitch distances.

Conclusion: Standardization of methods used in the investigation of anastomoses of the small intestine is desirable and shown to be possible. Significant dependence of the tear-out force on some of the investigated parameters can be observed.

Many biomechanical models of whole body vibrations have been developed, as part of the design, optimization, and vibrations control of vehicle seat systems, with the aim of achieving greater comfort. Most of these models are complex and result in large errors. In this paper, we introduce two new models, with and without backrest support, within a specific frequency domain. One is an optimized seven-degrees-of-freedom (7-DoF) lumped-parameter model with a unique structure to display vertical vibrations in one direction. The other is a new type of model called the coupled model, where the stiffness and damping matrices are employed instead of the spring and damper scalar parameters to present vertical vibrations in two directions — vertical and horizontal. The use of matrices not only simplifies and reduces DoF, but also gives more accurate results in comparison with the conventional multi-body models. With the help of a genetic algorithm (GA) through the global criterion method, we obtained numerical parameters of both models including mass, stiffness, and damping, which minimized the errors. The mean error for the 7-DoF model was 2.2%, while the best lumped-parameter models previously developed produced 12.6%. For the coupled model, we measured a mean error of 7%, a significant improvement over a well-known multi-body model with a mean error of 22.4%. Finally, we compared the transmissibility of vibrations in the human body applying the two models in the frequency range below 6 Hz, in both cases of with and without a backrest. These confirmed the importance of the backrest.

Mechanical response of the human head under a side car crash impact is crucial for modeling traumatic brain injuries (TBI) or concussions. The current advances in computational methods and the finite element models of the human head provide a significant opportunity for biomechanical study of brain injuries; however, limited experimental data is available for delineating the injury relationship between the head injury criteria (HIC) and the tensile pressure or von Mises stress. In this research, we assess human head injuries in a side impact car crash using finite element (FE) simulations that quantify the tensile pressures and maximum strain profiles. In doing so, five FE analyses for the human head have been carried out to investigate the correlations between the HIC measured in the dummy model at different moving deformable barrier (MDB) velocities increasing from 10 mph to 30 mph in 5 mph increments and the pressure and von Mises stress of the skull, the skin, the cerebral spinal fluid (CSF) and the brain. The computational simulation results for the tensile pressures and von Mises stresses correlated well with the HIC15 and peak accelerations. Also a second-order polynomial seemed to fit the stress levels to the impact speeds and as such the presented method for using FE human head analysis could be used for reconstruction of head impacts in different side car crash conditions; furthermore, the head model would provide a tool for investigation of the cause and mechanisms of head injuries once the type and locations of injuries are quantified.

Locking unicortical screw fixation of diaphyseal fractures may be clinically necessary due to internal constructs or prosthetic implants. The biomechanical effects of substituting one or more bicortical nonlocking screws to create a "hybrid" construct are unknown. Use of an initial nonlocking screw may be clinically desirable for creating initial plate-to-bone fixation prior to locking. A validated transverse fracture model was used with eighteen synthetic humerus models. Plate and screw fixation was performed in three treatment groups (n = 6): Unicortical locking screws only, fixation with two unicortical locking screws and one bicortical nonlocking screw on either side of the fracture and fixation with one unicortical locking screw and two bicortical locking screws on either side of the fracture. Displacement and gap strain measurements were made with a cyclic 4-point bending test. No significant differences were noted for construct stiffness or gap micromotion among the three groups on cyclic testing. Measurements at 1000, 5000, and 10,000 cycles showed stable fixation of all construct types with no significant changes in stiffness or micromotion. Substitution of one or more bicortical nonlocking screws in a unicortical locked construct does not affect construct stiffness or fracture gap strain. Data proven through controlled laboratory study.

The dynamic study of frog’s swimming style contributes to the modeling of the nature-inspired robots. To study the torque matrix produced in the joints during continuous modeling, the dynamic model of the Xenopus laevis swimming is reproduced in the coronal plane. The necessary kinematic data for the modeling is extracted from the frog movement graphs and diagrams during swimming. In the dynamic model, legs are considered as a group of rigid links. In order to verify this method, the generated forward force in half a cycle is studied. Unlike the previous studies, the role of geometry, dimensions and mechanical properties of the legs’ fundamental links in generating thrust force is modeled in this study, leading to finding the most proper form for this mechanism design.

Taking the lower maxillary incisors as an example and the orthodontic forces along the near–far middle direction, the orthodontic forces along the crown–root direction and the orthodontic moment around the tongue–cheek direction as loading condition, the biomechanical simulation of the tooth is carried out by the method of finite element simulation in this paper. The CT images of the skull are segmented and denoised by Mimics. The solid models of teeth, periodontal ligament (PDL), alveolar bone and brackets are established by Gomagic and Solidworks. The material characteristics of the PDL are defined by the two-order Ogden hyperelastic model. Taking the PDL capillary pressure as a criterion for orthodontic safety, combined with the stress response of PDL, the safe orthodontic force range of mandibular central incisors is obtained by ANSYS finite element software.

In this paper, we investigate the behavior of biological tissues (skin) coupled to a substrate (sensor) based on a numerical model taking into account the relationship between strain/stress components at the interface. Based on this study, we understand and quantify the most appropriate biomechanical factors in order to optimize sensor/biological tissue interface conditions. A micromechanical description based on a mathematical formulation has been developed to evaluate the biomechanical behavior provided by a 2D viscoelastic model of Kelvin–Voigt. The results show a spatio-temporal law of tissue motion highlighting the need for an optimized interface for reliable data transmission in the case of connected device in a dynamic movement or in the manufacturing of intelligent and reactive prosthesis device.

A customized knee implant numerical modeling using finite element analysis (FEA) during flexion extension has been investigated in this paper with varying loads with an objective of studying its kinematics. Computed tomography (CT) images of 15 osteoarthritis subjects’ images were used in this work. Various morphological characteristics were extracted from clinical images using a commercial CAE software and biomechanical properties were studied on applying standard loads on customized implant and off-the-shelf (OTS) implants. Patient-specific knee implants have been designed according to the morphological characteristics and bone dimension of patient with compressive loads (1500, 1700 and 3000N) during normal gait and were compared with the normal knee. Results showed that the stresses are distributed equally to the spacer and the tibial plate, unlike the standard femoral component where the stresses get concentrated on the cut edges. In compressive load, active stress and strain ($\sim 5$–20MPa) are lesser ($\sim 5\%$) and in flexion extension also lesser with a scaling factor of 0.785 and 1.0. The designed implant was found to produce similar biomechanical properties when compared to normal knee joint and thus it can be considered as a valuable implant and could replace the standard OTS knee implants.

Background: Flexor tendon injuries are extremely common and they are usually the result of incised traumatic glass or knife injury. The process of tendon healing is a complicated and exceptionally-regimented mechanism that is originated and monitored by a vast number of diverse molecules. One of the most pivotal groups of mediators that are crucial to the healing process are growth factors (GF). Intense pulse light (IPL) can lead to evidence of new collagen formation with associated clinical improvement in tissue healing. The biological benefit of Intense pulse light (IPL) relies on judicious photothermolysis, where heat driven radiation is dissipated and focused at the cellular level. The aims of this study is to set out the effect of growth factor and IPL on healing following a tendon repair.

Methods: Bovine common digital extensor tendons (CDET) were used as an ex vivo model. 44 tendon repairs were performed by the lead author using 2.5 × magnification loupes and standard instruments. Clamped tendons were assigned into the following groups; control, IPL, GF, IPL and GF. After culturing, biomechanical testing was carried out using monotonic tensile testing with displacement-controlled uniaxial tension to failure.

Results: The mean values for ultimate tensile stress (UTS) for the control group was 53.51 N, for IPL it was 51.15 N, for growth factor was 70.10 N and for combined growth factor and IPL it was 75.16 N.

Conclusions: This study showed significant improvement in UTS when repaired tendons were cultured with growth factor compared to control and IPL. This would suggest a biomechanical advantage for tendon healing.