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Abstract:Objective To compare biomechanical properties between the anatomical clavicle plate and the reconstructed clavicle plate, and investigate the influence of pre-bending or repeated bending process on biomechanical properties of the reconstructed clavicle plate, so as to provide biomechanical evidence for treating midshaft clavicle fracture in clinic. Methods The reconstructed clavicle plate was bent by 1, 2, 3, 5 times respectively based on shape of the anatomical clavicle plate. The biomechanical differences in anatomical plate group, reconstructed plate group and pre-bending plate group were compared by static compression test. Results The fixation stiffness and strength of the anatomical plate were better than those of the reconstructed plate. There was no significant difference in stiffness and strength between the anatomical plate group and one-time bending group. Pre-bending had a great effect on mechanical properties of the clavicle plate, and stiffness and strength of the clavicle plate were obviously improved after one-time bending. The mechanical properties of the clavicle plate were obviously reduced by bending of the clavicle plate after one-time bending. Conclusions The stiffness and strength of the anatomical plate and one-time bending plate are higher than those of the normal reconstructed plate. It is recommended that surgeons should perform bending appropriately according to the patient’s clavicle anatomy when using the reconstructed clavicle plate for fracture fixation, and minimize the number of repeated bending to maintain stiffness and strength of the clavicle plate.

Abstract:Objective To explore the biomechanical effect from different volumes of bone cement on osteoporotic spine T11-L3 at different levels of osteoporosis in vertebroplasty by the finite element method, so as to offer theoretical foundation for the selection of cement volume before vertebroplasty. Methods Based on CT scan images, the finite element models of spine T11-L3 were built and validated. Twelve models of osteoporotic spine T11-L3 without bone cement were developed as the control models. The spine L1 was injected with 1.8 mL and 3.6 mL bone cement, respectively, to strengthen the spine and build 24 models of spine T11-L3 at different levels of osteoporosis. The vertical load (500 N) and the torque (7 N·m) were applied on superior face of the spine T11 to calculate and analyze vertebral stress and displacement under the working conditions of standing, backward extension, anteflexion, lateral bending and rotation, respectively. Results After injection of bone cement, the changes in vertebral stress and displacement under torsional loads were the maximum. For the models with injection of 1.8 mL bone cement, as the levels of osteoporosis increased, the stress of spine L1 increased from 55.0% to 87.7%, and the displacement decreased from 6.5% to 32.0% under torsional loads. The torsional stress of spine T12 and L1 at the highest level of osteoporosis increased by 3.6% and 5.7%, respectively. For the models with injection of 1.8 mL bone cement, as the level of osteoporosis increased, the stress of spine L1 increased from 288.5% to 313.8%, and the displacement decreased from 8.9% to 44.7% under torsional loads. The torsional stress of spine T12 and L1 at the highest level of osteoporosis increased by 7.3% and 7.6%, respectively. Conclusions The deterioration in osteoporosis and the increase in cement volume will lead to the increase in vertebral stress. The vertebral stress and displacement will increase most under torsional loads. Therefore, for patients with vertebral fracture at high level of osteoporosis, low-dosage bone cement should be considered in order to avoid a large increase in stress, and torsional movement of the patients should be restricted.

Abstract:Objective To quantitatively study the pressure of residual lateral displacement in distal radius AO C3.1 fracture after manual reduction corrected by dynamic airbag pad using finite element analysis and to verify its effectiveness for correcting the residual displacement of fractures. Methods Imageware 13.0, Mimics 15.0 and ANSYS Workbench were used to simulate 1 cm residual lateral displacement after manual reduction of distal radius fracture corrected by dynamic airbag pad. Then the correlation between the distance of residual lateral displacement and the adjustment of dynamic airbag pad pressure were quantitatively analyzed. Results In the case of constant load restrained by airbag ribbon, during the process of pressure adjustment by splint pad, the stress was mainly distributed in the fracture end where the airbag pad was located. About 2.4 kPa pressure was needed to correct 1 mm displacement on radial side, while about 1.3 kPa pressure was needed to correct 1 mm displacement on dorsal side. The dynamic airbag pad was depressurized after the restoration of residual shift. At this time, displacement could be effectively prevented due to the constant load of airbag ribbon and the frictional load at the fracture end. Conclusions In the case of constant load constrained by airbag ribbon, intelligent airbag splint can effectively correct the residual lateral displacement after the manual reduction of the distal radius AO C3.1 fracture and prevent it from being displaced by adjusting pressure of the dynamic airbag pad.

Abstract:Objective To analyze influences of the braiding angle and material on performance of ventricular septal defect (VSD) occluders, so as to provide theoretical basis and guidance for their design. Methods The finite element models of occluders with different braiding angles (30°, 45° and 60°) were developed respectively. The radial supporting and axial bending performances of nickel titanium (NiTi) occlude and poly-p-dioxanone (PPDO) occlude were then compared. Results Under 5 kPa radial loading, radial stiffness of the 30°, 45° and 60° NiTi occluder waists were 8.60, 1.51 and 0.99 mN/mm3,respectively, while that of 45° PPDO occluder waist was 7.35 mN/mm3. Under axial bending of 0.5 rad, the maximum radial deformation of the 30°, 45°, 60° NiTi occluder waists were 1.17, 1.24 and 0.22 mm, while that of the 45° PPDO was 0.54 mm. Conclusions Under the condition of using the same material, occluders with braiding angle of 60° show the lowest radial stiffness, indicating they have the best radial supporting ability. Furthermore, they also show the smallest maximum radial deformation, indicating they have the best axial bending ability and the compliance. On the other hand, under the condition of using the same braiding angle, NiTi occluders show lower radial stiffness, indicating they have better radial supporting ability. However, PPDO occluders show lower maximum radial deformation, indicating they have better axial bending ability and compliance.

Abstract:Objective To investigate the structure and mechanical properties of pods after dehydration and the biomechanical mechanism of spreading pod seed injection due to torsion crack. Methods The layered pods, the cell size and direction at different cellular layers were analyzed by histology, microstructure observation, mechanical property test and high-speed photography. The process of pod ejection was observed, and the principle of pod ejection was summarized. Results The ejection of pods started from the crack of the bottom, and cracked gradually from the bottom to the top. The cell arrangement of two parts of the same pod was opposite. Each pod was divided into 4 layers wherein the first exterior layer and the middle layer were orthogonal to each other. There was a layer of cells between the first exterior layer and the middle layer, of which the cell wall was broken. In the process of dehydration, fibers in the outer layer shrank and fibers in the middle layer stretched. Conclusions Pod fiber will be contracted in the orthogonal direction after dehydration to accumulate elastic performance and generate pre-stress, and finally the pod is cracked to release the pre-stress.

Abstract:Objective To study the effect from personalized insoles with different structural heel pads on plantar stress concentration of patients with heel pain. Methods Base on statistics and finite element analysis method, the finite element model of foot and personalized insoles for patient with heel pain were established. The effects from different insoles on stress of soft tissues and plantar fascia were simulated. Results The internal stress of plantar soft tissues was higher than that of plantar epidermis, and the stress of the third plantar fascia was the highest. During barefoot standing, the internal peak stress of plantar soft tissues was 1.34 times of plantar epidermis, and the stress of the third plantar fascia was 1.50 MPa. The result of orthogonal experiment showed that the optimized insole model could reduce the internal peak stress of plantar soft tissues by 51%, meanwhile relieve the stress of the third plantar fascia by 11.3%. Conclusions The optimum scheme of personalized buffer insole is the design of vertical ellipse and honeycomb groove. Such structure can assist the absorption or buffering of concussion from calcaneal fat pad, and relieve the plantar stress concentration and tension of the plantar fascia. This study is helpful to understand plantar stress distributions of patients with heel pain, which is of great significance to the study of pathology and prevention of heel pain.

Abstract:Objective To investigate the biomechanical properties of human calcaneus by finite element method. Methods Through CT scanning, Mimics, Geomagic and other software, the finite element model of calcaneus was established. The stress distribution and displacement tendency of calcaneus under normal standing and external force were analyzed. Results Under normal standing, the calcaneal stress was uniformly distributed and small. Under external force, the entire calcaneus stress increased significantly, and the stress on calcaneocuboid articular surface also obviously increased. Conclusions The analysis of the stress and strain distribution on calcaneus in neutral position under different loading, and the investigation on biomechanical properties of calcaneus and mechanism of calcaneal fracture will provide theoretical basis for clinical treatment of calcaneal fractures.

Abstract:Objective To explore the plantar pressure and surface electromyography (sEMG) parameters during human stair walking, so as to provide theoretical support for foot structure design of dynamic walker, selection of power element and distribution of installation location. Methods Ten healthy young males were recruited to perform stair walking trials, respectively. The motion capture system, plantar pressure system and surface myoelectricity acquisition system were used to collect plantar peak pressure, trajectory of COP(center of pressure) and sEMG parameters of lower limb muscles at the same time. Results Compared with level walking, the percentage of stance time in the whole gait cycle increased during stair walking. The peak pressure of forefoot area increased during stair ascent, while the peak pressure of toe area decreased during stair descent. During stair walking, rectus femoris, biceps femoris, medialis and lateralis gastrocnemius played a main role in maintaining the stability of human body. Conclusions The plantar pressure distribution should be fully considered for foot structure design of dynamic walker and the function of main muscles should be considered for selection of power element and distribution of installation location.

Abstract:Objective To simulate the orthodontic tooth movement (OTM) after corticotomy in rat and analyze its effects on mechanical distribution in dentoalveolar structures.Methods 3D finite element model of corticotomy-facilitated OTM in rat was established and the circumscribing corticotomy approach was simulated. The periodontal ligament (PDL) and alveolar bone around the mesial root were partitioned according to direction of the orthodontic load and corresponding part of the root. The initial displacement of the first molar and segmented alveolar bone as well as the stress and strain in PDL and alveolar bone were calculated. Results The first molar presented a tipping movement and the distal cusp showed the maximum displacement. Corticotomy could increase the relative displacement of bone segment. The maximum principal strain in PDL concentrated on the mesial and distal cervical region, while the minimum principal strain concentrated on the distal apical region. Corticotomy could change the distribution and magnitude of the maximum and minimum principal strain in PDL and Von Mises stress in alveolar bone. Conclusions Corticotomy can affect the mechanical distribution of orthodontic force in tooth and periodontal tissues around, and hence facilitate regional bone remodeling to realize rapid OTM. The research findings contribute to understanding the mechanism of corticotomy to facilitate OTM from the aspect of biomechanics.

Abstract:Objective To establish the 3D hydrogel cell model and apply compressive stress with different intensities, frequencies and durations on osteoclasts, so as to observe the effect of compressive stress on osteoclast differentiation and investigate the appropriate compressive stress solution for inhibiting osteoclast differentiation. Methods M-CSF and RANKL were used to induce bone marrow mononuclear cells into osteoclasts. After the 3D cell-agarose mixture was seeded in compression culture plate, compressive stress was applied on osteoclasts with different intensities, frequencies and durations the next day. The cells in control group were not interfered. The cells were divided as following: G0 (control group), G1 (1%, 0.5 Hz, 4 h), G2 (2%, 0.5 Hz, 4 h), G3 (3%, 0.5 Hz, 4 h), G4 (1%, 1.0 Hz, 4 h), G5 (2%, 1.0 Hz, 4 h), G6 (3%, 1.0 Hz, 4 h). After the loading plan with the most effective intensity and frequency was calculated by statistical analysis, compressive stresses were applied on cells with different durations as following: D1(4 h), D2(8 h), D3(12 h), D4(16 h), and each group had two samples. Once compressive loading was finished, the total RNA extraction from cell-gel constructs were performed and Ctsk mRNA, NFATc1 mRNA, TRACP mRNA, M-CSF mRNA and RANK mRNA were measured by quantitative testing. Results RANK and TRACP mRNA expression significantly depended on intensities and frequencies of the compressive stress (P<0.01), and Ctsk mRNA significantly depended on intensities(P<0.01) while it differed notably with different frequencies (P<0.01). M-CSF mRNA expression with 8 h was much lower than that with 12 h (P<0.01) and 16 h (P<0.05). RANK mRNA expression with 8 h was lower than that with 12 h (P<0.05) and 16 h (P<0.01). In addition, Ctsk and NFATc1 mRNA expression with 16 h was higher than that with 4 h and 8 h (P<0.05). Conclusions In the 3D hydrogel model, 1% intensity, frequency of 0.5 Hz, cyclic compression intervention with 8 h can suppress the differentiation of osteoclasts. The research findings provide the theoretical basis for preventing osteoporosis and improving the peak bone mass by appropriate exercise.

Abstract:Objective To evaluate the effects of locked plates with different screw layouts on stability of the internal fixation system for femoral shaft fracture, so as to provide guidance for clinical study on screw layout of the internal fixation system for femoral shaft fracture. Methods Orthogonal test design method was used with 4 groups of screws at 3 parametric levels. Biomechanical properties of the internal fixation system for femoral shaft fracture under 9 screw layouts were analyzed respectively by the finite element method, and 4 inspection indices, namely, the maximum equivalent stress of the plate, the screw and the femur, and the maximum axial displacement of the internal fixation system were obtained from each group of the experiment, and the orthogonal test weight matrix analysis method was conducted for data analysis. Results The influences of different screw parameters on stability of the internal fixation system varied, and the maximum weights of the 4 sets of screw parameters in stability of the internal fixation system were 13.86%, 7.57%, 7.53% and 5.91%, respectively. Conclusions The best scheme for screw layout in orthogonal test is the screw with none-fixed threaded holes in the first group, the single cortical screws with fixed threaded holes in the second group and the double cortical screws with fixed threaded holes in the third and fourth group.

Abstract:Objective To study the mechanical characteristics of lumbar vertebral manipulation by lifting-rotating and oblique-pulling using multi-film pressure measurement system. Methods Twenty-one male operators were divided into groups of experts, skilled operators and beginners. Everyone completed 7 actions of Lin’s lumbar manipulation continuously, and repeated 3 times. The graphs and data were collected and processed. Results The time-force curve by the experts had regularity. The average pre-load force was (147.25±26.04) N, duration was (0.98±0.20) s, the average minimum force was (79.22±9.50) N, the maximum impact force was (706.26±56.21) N, the flip time was (0.44±0.09) s, and flip speed was (1 666.33±411.91) N/s, the impulse was (310.95±56.67) N·s. The curve graphs and the index by the skilled operators were similar to those by the experts, but the average maximum impact force was (464.51±53.49) N, which was relatively smaller. The curve graphs by the beginners could be broadly divided into three categories. Class Ⅰ was chaotic and unregulated; Class Ⅱ only had impact force and did not have pre-load force, and the maximum impact force varied in size; Class Ⅲ had both impact force and pre-load force, but the forces were relatively small and stable. Conclusions The multi-film pressure measurement system can preferably display the mechanical characteristics of manipulation by lifting-rotating and oblique-pulling, which is an ideal testing tool for quantitative research on mechanical parameters of Lin’s lumbar vertebral manipulation. The experimental results provide a scientific basis for visualization, quantification and standardization of the manipulation.

Abstract:Long distance running is a popular sport with a high risk of getting musculoskeletal injuries, which is closely related to running shoes and foot-strike patterns. Biomechanical researches on relationship of running shoes and foot-strike patterns with running injuries were searched on the chain cloud library and Google academic database, and a total of 42 papers published from 1981 to 2016 were reviewed. There is not enough evidence to prove that running shoes have an effective cushioning and motor controlling function as what they claim, while barefoot running as a kind of more natural running pattern should be encouraged. Generally speaking, the forefoot strike has a lower injury risk on the knee, but increases the load on ankle and metatarsal bones. On the contrary, the rear foot strike always has a higher injury risk on the knee while a lower load on ankle and metatarsal bones. Therefore, runners should choose a suitable running method depending on their own conditions. The influence of running method transformation on biomechanical characteristics of lower limbs is not clear, and researches in such area may give more effective suggestions for runners to change their running methods.

Abstract:The research progress of finite element method (FEM) applied in biomechanics of lumbar fusion and artificial lumbar disc replacement was reviewed and its prospect was forecasted. The main research directions of FEM are optimal selection of operation plans before the surgery, performance evaluation of implanted devices and prediction of postoperative outcomes. Based on the recent research progress, the application prospects of FEM in simulation of personalized surgery, evaluation of elastic implants and postoperative prediction of novel operation method were discussed. By reviewing and prospecting the application of FEM in biomechanical research of lumbar fusion and artificial lumbar disc replacement, the purpose of this paper is to provide theoretical references and practical guidance for the treatment of lumbar diseases in clinic.

Abstract:Notch signaling pathway has a wide range of effects in the field of embryonic development, nervous system, vascular system, endocrine system and tumor. In recent years, studies have shown that Notch plays an important role in the regulation of bone metabolism, especially in bone remodeling. The disorder of bone remodeling is closely related to the progress of diseases such as osteoporosis and osteoarthritis. Notch signaling pathway can affect the process of bone remodeling by regulating the function of different cells in bone tissues, but its specific participation in different cells is still unknown. This review summarizes recent advances about the role of Notch signaling in bone remodeling.