Abstract:Asthma is an old and increasingly life-threatening disease. The mechanism of asthma is, however, not well understood. In asthma, the gas exchange as the primary function of the human lung can be seriously impaired. Since gas exchange is achieved through a series of respiratory acts that are operated via physical forces and stresses acting on each level of the lung structure, biomechanics of lung tissues including airway smooth muscle (ASM) must have an important role in asthma. In this article, we review latest advances in aspects associated with ASM biomechanics. We first discuss the mechanical environment in the lung structure, then introduce the latest findings of ASM structure and function including ASM contractile filament organization, functional length range and adaptation, cellular structure and functional changes in responses to mechanical perturbation, ASM tone as a mediator of strain-induced response, and a novel glassy cytoskeletal dynamics. These provide a multiscale view of the current understanding of ASM biomechanics, which may shed new light, and hopefully lead to a better approach in addressing fundamental issues in asthma phathophysiology.

Abstract:Objective The goal of this study was to develop anatomically detailed, finite element (FE) models of the medial and lateral plantar longitudinal arch (MPLA, LPLA), and to investigate bone and muscle stresses resulting from plantar fasciotomy and major plantar ligament injuries. Method Nonlinear FE models of the second ray of MPLA and the fifth ray of LPLA were constructed on the basis of CT and MRI images of Virtual Chinese Human "female No.1". The models assumed a balanced standing load configuration. Three different degrees of passive intrinsic muscle tension(weak, moderate, or severe)were used in conjunction with simulations of plantar ligamentous structure failures. Result Plantar fasciotomy caused von Mises stress increases in the bones and plantar ligaments while major plantar ligament injuries caused stress increases in the bones, flexor tendons, and plantar fascia. Increasing plantar intrinsic muscle passive tensions decreased stress/strain levels in the both arches, and could adjust abnormal tension/compression stress flows of the arches to close to the normal biomechanical states. Conclusions This study shows that plantar longitudinal arches are concordant combination of bony structures, plantar intrinsic muscles, plantar ligaments and plantar fascia. After plantar ligamentous structure failures, plantar intrinsic muscles have to contribute to stabilize the plantar arches. This mechanism may reduce further musculoskeletal damages such as stress fractures and tendonitis.

Abstract:Objective To quantify the micro-geometric and configuration of micropatterned substrate and analyze its effects on proliferation, differentiation, and migration of bone marrow mesenchymal stem cells (BM MSCs). Method Micropatterned substrates were designed and fabricated to control cells' spreading shape and area. Data of proliferation, differentiation and migration of rat BM MSCs on various patterned substrates were compared. Result Proliferation of BM MSCs was inhibited when their spreading width was narrowed. Osteoblastic differentiation was regulated distinctively in different spreading shape and area. Cell migration was more active when their spreading area was reduced. Dexamethasone was found to play an important role in down-regulating cell proliferation and migration on patterned substrate. Conclusions Cell spreading shape and area is important factors for regulating proliferation, differentiation, and migration of BM MSCs.

Abstract:Objective Delivery of oxygen in tissues is limited in the space where oxygen must diffuse between the vascular and the surrounding tissues. Normal capillaries are relatively straight and well spaced, in contrast, the tumor vascular networks usually display more irregularity and the vessel wall shows higher permeability and less elasticity. The purpose of this study was to investigate the effect of capillary elasticity and tortuosity on the oxygen distribution and make further investigation on the mechanism of the formation of hypoxic regions in tumor. Method One-dimensional capillary model was coupled with the oxygen diffusion model. Oxygen transport was investigated in a Krogh and tortuous tissue model. The capillary geometry was obtained by the one-dimensional model and transferred to the tissue model. Finite element method was employed in the analysis. Result The capillary radii along the flow direction under pressures were obtained for different initial radii and the oxygen distribution in the Krogh cylinder tissue model and the model with a tortuous capillary were computed. Conclusions when the capillary radius is small, the effect of vessel elasticity may have not significant effect on the oxygen distribution. However, with the capillary radius increasing, the effect on the oxygen transport becomes obvious. Moreover, with the tortuosity of the capillary increasing, the oxygen distribution becomes more heterogeneous, which is in agreement with the result in available reference. This work will be helpful to the investigation of oxygen transport within tumor.

Abstract:Objective In order to investigate a method for model construction that could meet particular demands on meshing, a patient-specific model of aortic arch aneurysm was established which can be divided and meshed in finite element software. Method Based on a surface model in STL format, reverse engineering concept was adopted to reconstruct a solid model of aortic arch aneurysm by means of integrating CAD software of Geomagic and Pro/E, and simplified stents model was also created in it. This model was transferred to ANSYS software and divided into several parts. Result Particular meshing was performed especially in boundary layer and around the stents, and hemodynamics simulation was carried out using the finite element model. Conclusions This solid model could be meshed according to particular requirements in several parts respectively, and employed to simulate hemodynamics in aortic arch aneurysm treated with endovascular stent. The method of modeling was applicable and could be used as a reference for similar model construction.

Abstract:Objective A biodynamic modeling method of human musculoskeletal system based on the general Hamilton and Lie group theory was proposed. Method First, the general coordinate and the Lie configuration manifold of human musculoskeletal system were defined. Second, the biodynamic model of human musculoskeletal system was constructed under the general Hamilton theory. In the end, the computer program of this new algorithm was developed. Result The biodynamic equations of human musculoskeletal system based on the general Hamilton and Lie group theory were developed. A weight lifting behavior's model based on this method was given as an example which proved this method valid. Conclusions The biodynamic equations in this paper could model the human musculoskeletal kinematic and kinetic behavior efficaciously and genuinely which provides a new method for human musculoskeletal biodynamic analysis.

Abstract:Objective To evaluate the biomechanical properties of a modified Herbert screw as a suture anchor in repairing patellar ligament. Method 1) twenty-two fresh goat knee joints were divided into two groups: screw and suture group. All patellar ligaments were cut at the site 6mm proximal to tibia tuberosity. In the screw group, modified Herbert screw acted as a suture anchor in repairing the patellar ligament. In the suture group, patellar ligament was simply sutured according the Kessler method. Tensile force at failure and maximum tensile force were measured. 2)twenty-two hind legs of 11 hybrid canines were divided into two groups: screw and suture group. The patellar ligaments were treated respectively as mentioned before. 4 weeks after operation, the patellar ligaments were inspected and measured. Result 1) For goat knee joints, the average tensile force at failure was (71.13±14.23) N in the screw group and (46.09±8.41) N in the suture group, respectively (P<0.05). The average maximum tensile force was (80.46±11.73) N in screw group, (54.60± 9.79)N in suture group, (P<0.05).2) There were 5 cases in the screw group of canine showed complete healing of the patellar ligament while there were 2 cases shown in the suture group. The average tensile force at failure was (202.99±12.17) N in the screw group and (162.41±15.80) N in the suture group (P<0.05). The average maximum tensile force was (219.69±15.73) N in the screw group and(177.92±15.31)N in the suture group(P<0.05). Conclusions The modified Herbert screw as a suture anchor was a good choice for repairing the torn ligament near its insertion.

Abstract:Objective Compare the biomechanical properties of four groups with different posterior monosegmental fixation and make the evaluation. Method Twenty four fresh frozen of one-week-old calf spines (T11-L3) were divided into four groups following the introduction of incomplete compression fracture at the vertebral body of L1 by the method of excision. Four types of monosegmental fixation were applied to the four groups respectively to restore spinal stability. A cyclic loading were applied to the specimens at rate of 1.0 Hz up to 3000 cycles in flexion/extension, left/right lateral bending and left/right rotation respectively. Segmental stability (T13-L1) tests were then performed on the specimens in the condition of intact, injured, fixation respectively. Range of motion(ROM)in flexion/extension, left/right axial rotation, left/right lateral bending were determined by three dimensional laser scanner. Then the ROM was standardized into stability potential index(SPI)to compare the stability in six loading directions of four types of fixation in four conditions. Result All of the four groups with monosegmental fixation could significantly increase the stability in six motion directions when compared to their injury condition(P<0.01), and significant superior than that of intact condition(P<0.01), but there was no significant difference among the four groups(P>0.05).The stability in six motion directions after cyclic loading was inferior when compared to that of before cyclic loading respectively, but there was no significant difference in between(P>0.05), or among the four groups(P>0.05). Conclusions As long as it could ensure to implant the pedicle screw into pedicle and vertabra, and avoid the fractured areas in the affected segment, the angle of pedicle screw directed to superior or inferior endplate will not affect both the instant and post-fatigue stability.

Abstract:Objective The identification of lower limb axes plays an important role in the kinematics research and clinical operation of total knee replacement surgery. This paper presents a method to extract the femoral axes based on CT images automatically. Method Using a series of image pre-processing algorithms such as segmentation, smoothing and rotations of the images, to get the 3-D fine mesh of lower limb bones. Then, by analyzing the morphological feature of 3-D femoral surface and based on the definitions of femoral mechanic axis and femoral anatomical axis, three feature points located on femoral head, femoral distal intercondylar notch and femoral shaft centre are selected to define the mechanical and anatomical axes of femur. In the light of the morphological feature of femur head, the center of femoral head was decided according to the changes of the gradient between each cross section of the femoral head. Meanwhile, we got the center of femoral intercondylar notch by calculating the closed-loop zone of cross sections of the bone. Those two points could finally define the mechanical axis of the femur. Result Based on a series of image processing procedures, three dimensional (3-D) surface model of lower limb bone were generated. By analyzing the morphological features of femoral head and knee joint center, a simple and convenient way was proposed to extract the coordinate of three feature points and further the femoral axes automatically. Conclusions Experimental results show that this processing procedure can extract the femoral mechanic axis and femoral anatomical axis precisely with 3-D CT images.

Abstract:Objective The three-dimensional finite element model of mandible with dental implants for immediate loading was established to analyze stress distribution of bone around the dental implants with different implant length. Method Five three-dimensional finite element models of thread dental implants with immediate loading were constructed using CT scanning and USIS(Universal Surgical Integration System)software developed by ourselves. Each of them included different length implants which was 6 mm、8 mm、10 mm、12 mm、14 mm respectively. The values of Von Mises stress and strain at implant-bone interface were calculated with the software of ANSYS, when the dental implants were loaded with vertical、buccolingual force of 150 N. Result The values of Von Mises stress and strain on the bone around implants all decreased with the length of dental implants increased. With the length increased from 6 mm to 8 mm, the value of Von Mises stress at implant-bone interface reduced remarkably, especially when the dental implants were loaded with buccolingual force. However, when the length increased from 8 mm to 10 mm, from 10 mm to 12 mm and from 12 mm to 14 mm, the values of Von Mises stress decreased unapparent. The value of Von Mises stress at implant-bone interface also reduced obviously with the length increased from 6 mm to 8 mm. Conclusions With the length of dental implants increased, the value of stress at implant-bone interface decreased, which showed a negative correlation in between. But the increase only appears apparently when the length of dental implants added from 6 mm to 8 mm. It suggests that we should choose sufficient longer implants in clinical treatment and avoid use the implant of 6mm length if possible.

Abstract:Objective To observe the stress distribution of maxillary first molar alveolar bone under different orthodontic forces using finite element model. Method The finite element model was built by using advanced 3-dimensional laser scanning, comprising a maxillary first molar, periodontal ligament, alveolar bone, and a buccal tube. Different loads were applied at a point of the buccal tube and its stress of alveolar bone was analyzed. Result With a simple horizontal or vertical force, the stress pattern in the alveolar bone showed high concentration at the cervical level or furcation level. When the maxillary first molar was moving bodily, the stress of alveolar bone was uniform and comparatively small. Conclusions When the tooth obtained bodily movement, the stress of alveolar bone was uniform and low, which displays that the bodily movement profits the healthy of the alveolar bone. Since the biggest stress of the maxillary first molar alveolar bone was in cervial region or furcation level, the changes of these regions should be observed carefully

Abstract:Objective In order to maximumly remain the residual function of the lower residual limbs of amputation patient, and sufficiently bring in to full play of prosthesis, a rehabilitative training system of lower residual limbs was developed. Method The system comprises two parts: hip-joint training system and knee-joint training system, which could make the joint active angle improved, increase muscle volume of the residual limb and boost the concrescence of residual limb. Result Based on multidisciplinary research, the rehabilitative training system has finally developed. Conclusions With this system, it could be realized to improve the function of the amputation patients, promote the residual limbs setting and improve the conditions needed in assembling prosthesis fundamentally.

Abstract:Objective To observe the effects of quadriceps exercises with electrical stimulation on the patients who developed extensor lag after knee operation. Method 30 cases after knee operation were randomly divided into 2 groups: quadriceps exercises group A(12cases), exercises with Electrical Stimulation group B(18cases), and both groups were also given routine rehabilitation treatment. Evaluation was given to the lag degree of knee before and after 2 weeks treatment. Result The lag degree of group A was 14.5°±7.33° before treatment and 8.4°±6.75° after treatment, while that of group B was 13.9°±9.15° before and 3.9°±3.56° after treatment. To compare the lag degree before and after treatment, the significant improvement could be found in both groups, (P<0.05) and the improvement in group B is much better than that in group A, P<0.05. Conclusions The effect of exercises with Electrical Stimulation is better than that with pure quadriceps exercises to treat the extensor lag.

Abstract:Exact quantitative characteristic description of human spine 3-dimension motion can help to understand the pathology of spine disease and provide proper therapy and functional substitution synchronously with evaluating the effect of spine damage and surgical on spine motion correctly. The author summarized the former researching findings and expatiated on research of spine motion measuring in vitro in three aspect of spine motion measurement index, loading parameter and mode. It also gave out major outgrowth and deficiency of spine 3-dimention motion measurement and brought forward the research direction that provided reference and help on research of spine motion measurement in future.