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Abstract:Individualized treatment is an important direction in the development of orthopaedics. Either the application of the custom-made implants or using patient-specific surgical instrument to assist the implantation of conventional prosthesis, theoretically, could improve the matching between the implants and adjacent bony structures, so as to improve the overall function of the patients. However, the superiority of individualized treatment in theory cannot compensate its complexity and time-lag caused by individualized therapy in preoperative planning, design, manufacturing, etc. Therefore, individualized treatment is just a concept in most of the time. With the development of image technology and the maturity of 3D printing technique, the efficiency of individualized design and manufacturing is expected to be improving significantly, which shows the potential to translate this elegant concept into a practical principle.

Abstract:Objective To investigate the plantar force characteristics during human walking and running under different gravity environment. Methods Seven healthy male volunteers walked and ran in vertical position on a weight-loss suspension treadmill under simulated Mars gravity (1/3 G) and lunar gravity (1/6 G), and traditional earth gravity (1 G) respectively at three different velocities (3, 7 and 10 km/h). During the exercise, parameters such as stance phase, plantar force, and gait balance in gait cycle were analyzed by using the F-scan insole pressure distribution measurement system. Results At the same velocity during a gait cycle, the contact phase was significantly shorter with the decrease of gravity, but the swing phase was significantly longer (P<0.01). With the increase of velocity, the contact phase was obviously reduced (P<0.01), while the swing phase was unaffected (P>0.05). The peak and average plantar force, force integrity were significantly reduced with the decrease of gravity. Under normal gravity, the increase of velocity could lead to an obvious increase in peak and average plantar force and an obvious decrease in force integrity. While under simulated lunar and Mars gravity, no significant changes were found in plantar force (P>0.05). Under the three gravities, the ratio of vertical impact was quite different in between (P<0.05), but no significant difference was found in the phase symmetry index. Conclusions As compared to normal gravity environment, parameters benefiting for skeleton and muscle function such as plantar force and contact phase were found to be much smaller under low gravity environment, indicating the necessity of considering these factors when designing countermeasures or exercise prescriptions for space flight so as to sustain the astronaut’s normal function of skeleton and muscle.

Abstract:Objective To construct and validate a 3D finite element model of pelvis-femur-soft tissue complex including artery, and investigate the mechanical response of pelvis artery under side impact loads. Methods The 3D finite element model of the pelvis-femur-soft tissue complex was constructed from CT images of one female volunteer, including bone tissues, arteries, enveloping soft tissues, cartilage and ligaments of the pelvic joints (sacroiliac joint, hip joint and pubic symphysis). The whole model utilized linear elastic solid elements to simulate bone tissues. Nonlinear elastic connector elements were employed to represent ligaments. Soft tissues, including the cartilage, enveloping soft tissues and arteries, were modeled as solid elements with hyper-elastic material. Side impact was conducted on the complex with impact mass of 22.1 kg at the impact velocity of 3.13 and 5 m/s, respectively, and the output of the complex model was then recorded. Results Simulation results matched the results of pelvic side impact experiments reported in literature. When the complex model was impacted at the velocity of 3.31 and 5 m/s, respectively, the maximum equivalent stress of arteries was 98 and 216 kPa, and the maximum principle strain was 14.9% and 20%, respectively. The risk of artery injury was relatively low. Conclusions This established pelvis-femur-artery complex model was validated and thus reliable to be used for investigating the dynamical response and injury analysis on pelvis artery under impact loads, and provides some biomechanical foundation for predicting artery injuries.

Abstract:Objective To investigate the variation of stress distributions on proximal femur after hip resurfacing arthroplasty (HRA) by using three-dimensional (3D) finite element method. Methods The 3D finite element model of proximal femur was reconstructed based on 64-slice spiral CT scan image data. Both the stress distributions on proximal femur after metal-on-metal HRA and normal proximal femur were studied, so as to analyze the biomechanical environment changes after HRA. Results After HRA, the superior, anterior, rear and inferior area of the proximal femoral head showed significant stress shielding, with peak stress of 0.60, 0.57, 0.66, 0.79 MPa, respectively, and stress shielding rate of 99.80%, 99.16%, 98.92%, 96.66%, respectively. Increased stress occurred in most regions of the distal femoral head, while stress shielding appeared only in rear area of the distal femoral head, with stress shielding rate of 4.92%. Increased stress occurred in anterior region of the proximal femoral neck, while stress shielding appeared in the superior, inferior and rear area of the proximal femoral neck, with shielding rate of 16.48%, 22.75% and 7.83%, respectively. Increased stress also occurred in inferior area of the distal femoral neck, while the remaining area showed stress shielding. The stress in greater trochanter increased by 9.22%, and the stress shielding rate for lesser trochanter area and basal area of femoral neck were 2.49% and 14.44%, respectively. Conclusions Stress distributions on most regions of proximal femur after HRA were similar to that on normal femur, and the stress transfer was close to physiological status, which could effectively avoid obvious stress shielding in proximal femur and preserve bone mass, which could contribute to normal physiological activity of patients.

Abstract:Objective To investigate ISO 7206 standard used as a guidance for clinical selection of total hip prosthesis. Methods Kinematics and dynamics process of normal walking gait was simulated by establishing a numerical musculoskeletal model; the corresponding finite element model of total hip prosthesis was constructed, and gait loads were applied to calculate stress distribution on prosthesis, which were compared with that on ISO finite element model. Results Peaks of hip joint reaction forces were achieved at 20% gait and 54% gait during normal walking gait, which were used as gait loads for finite element simulation, and the results showed that the maximum Von Mises stress of prosthesis was reached at 20% gait. The maximum Von Mises stress of prosthesis in loosening model was higher than that in non-loosening model, and some differences existed in the distribution pattern. The maximum stresses of prosthesis both under ISO loads and gait loads by different body weights were analyzed and compared, and the maximum stress of prosthesis under ISO loads was equivalent to that under gait loads by body weight between 108 kg and 142 kg. ConclusionsThe prosthesis that passed ISO test can meet the strength requirement for normal gait loads of 100 kg body weight.

Abstract:Objective To investigate the influence of competitive flow at different lelves on wall shear stress (WSS) of left internal mammary artery graft after coronary artery bypass grafting. Methods The left internal mammary artery (LIMA)left anterior descending (LAD) anastomotic model was extracted and reconstructed from CT images based on thresholding method by using SimVascular software. The competitive flow was divided into three groups according to different stenosis of LAD, including no competitive flow group (100% stenosis of LAD), mild competitive flow group (50% and 75% stenosis of LAD) and severe competitive flow group (0% and 30% stenosis of LAD). The hemodynamic performace of the anastomotic model under different conditions of competitive flow was observed by computational fluid dynamics (CFD) method. Results With the increment of competitive flow, the value of WSS was decreased gradually while the oscillation of WSS was increased remarkably in LIMA graft. The time average WSS (TAWSS) of LIMA graft in severe competitive flow group (0% stenosis: 2.73 Pa, 30% stenosis: 2.85 Pa) was lower than that in the mild competitive flow group (50% stenosis: 4.77 Pa, 75% stenosis: 6.01 Pa) and no competitive flow group (100% stenosis: 8.64 Pa), while its oscillatory shear index (OSI) (0% stenosis: 0.206; 30% stenosis: 0.085) was much higher than that in other two groups (50% stenosis: 0.014; 75% stenosis: 0.013; 100% stenosis: 0.006). Conclusions When the stonosis of LAD was smaller than 50%, the WSS in LIMA graft was obviously lower and oscillatory due to severe competitive flow. Such unfavorable feature of WSS may influence the long term-patency of LIMA graft and long term-survival of operations.

Abstract:Objective To establish the contact deformation model of biological tissues contacting with endoscopic instruments, and to make mechanical analysis on contact stress and strain. Methods Based on Kelvin-Voigt model and Hertz contact theory, the contact deformation model of instruments (with both wedge-shaped teeth and cylinder-shaped teeth) contacting with biological tissues was established, and the variation of contact stress and strain changing with time in different endoscopic instruments were obtained through finite element analysis method and bio-impedance measurement. Results Endoscopic instruments with different structures of the teeth could cause different strain and stress on tissues during laparoscopic grasping. The stress of the instrument with wedge-shaped teeth on tissues was largest, while that with cylinder-shaped teeth was smallest, and that of instrument with hybrid structure of wedge-shaped and cylinder-shaped teeth was in between. Conclusions The hybrid structure of wedge-shaped and cylinder-shaped teeth can effectively reduce the peak pressure during laparoscopic grasping, thus prevent less tissue damage caused by wedge-shaped teeth, and enhance the grasping ability with cylinder-shaped teeth. This study provides an important reference for the safety use and better design of laparoscopic instruments in clinic.

Abstract:Objective To investigate whether extracorporeal shockwave could induce differentiation of human mesenchymal stem cells (hMSCs) into osteoprogenitor cells by ATP release and the activation of P2X7 receptors. Methods Cultured bone marrow-derived hMSCs were subjected to shockwave treatment and ATP release was assessed. Osteogenic differentiation and mineralization of hMSCs were evaluated by examining alkaline phosphatase (ALP) activity, osteocalcin (OC) production, and calcium nodule formation. The mRNA expression of P2X7 receptors was determined with real-time RT-PCR. P2X7-siRNA, apyrase, and P2 receptor antagonists were used to evaluate the roles of ATP release and P2X7 receptors in shockwave-induced osteogenic hMSCs differentiation. Results Shockwave treatment released significant amounts of ATP from hMSCs. Shockwaves and exogenous ATP induced hMSC differentiation. Removal of ATP with apyrase, targeting of P2X7 receptors with P2X7-siRNA or selective antagonists prevented osteogenic differentiation of hMSCs. Conclusions Shockwaves can contribute to osteogenic differentiation of hMSCs by realeasing cellular ATP that activate signaling. These research findings provide the theoretical basis for shockwave therapy in treating fracture healing and bone nonunion.

Abstract:Objective To explore the role of tendon synovial sheaths in tendon regeneration in vivo. Methods Thirty-six Roman chicken were randomly divided into Group A and B, with 18 chicken in each group. In Group A, the synovial sheaths of the deep flexor tendons in the left middle toes were separated from the up, right and down side without cutting off the tendons themselves. The allograft decellularized tendons were coated with synovial sheaths which were detached partly and fixed on the left side of the normal deep flexor tendons in the middle toes of the left foot. In Group B, the allograft decellularized tendons were directly implanted on the left side of the deep flexor tendons without coating of synovial sheaths. The normal deep flexor tendons from the right foot were used as the control group. The maximum loads and elastic modulus of the tendons at 4th, 8th and 12th week were obtained by mechanical testing, and HE staining was conducted to observe histological changes of the tendons. Results The maximum load at 8th and 12th week and elastic modulus at 4th, 8th and 12th week in Groups A were greater than those in Group B, with significant differences (P<0.05). Group A showed more densely deposited matrices and longitudinally aligned collagen fibers than Group B, and inflammatory cells and fibrous tissues could hardly be found in Group A. In Group B, the collagen fibers were decreased gradually, with disordered alignment. Furthermore, more inflammatory cells infiltration and hyperplasia of fibrous tissues were found in Group B. Conclusions The synovial sheaths can contribute to tendon regeneration, indicating that a proper environment in vivo plays an important role in the engineered tendons. This study has a positive effect on finding proper tendon replacements for patients with tendon deficiency.

Abstract:Objective To study the feasibility of using digital volume correlation (DVC) method to track displacement and deformation of lung tumor and chest during the period of respiration. Methods A DVC algorithm suitable for tracking 3D movement of tissues in chest was proposed. The 4D CT imaging technique was adopted to acquire images of a patient with lung cancer during one complete respiration stage. The inhalation was set as the initial stage for reference, to determine the locations of lung cancer and chest. Four specified regions of both the tumor and chest at the initiation of inhalation stage were selected. The corresponding 3D displacement of lung in the following 5 inhalation phase stages, i.e. 20%, 40% 60%, 80% and 100% as well as 3D displacement of chest in 100% inhalation phase stage were analyzed by DVC software. Results The displacement and deformation error of tumor was within 1 mm, while that of chest was within 0.5 mm. The maximum displacement of tumor presented itself along the vertical direction of human body during respiration, while that of chest at the end of inhalation stage appeared along the front and back direction of human body. Conclusions DVC methods can be potentially used to detect displacement and deformation of body tissues such as lung tumor and chest during the respiratory cycle. This study provides references for noninvasive, non X-ray, real-time image-guided radiation therapy for lung cancer based on DVC method.

Abstract:Objective By measuring the microstructure parameters of cancellous bone in vertebral bodies with different bone mineral density (BMD) levels, to study the correlation between such parameters and the corresponding maximum pullout strength (MPS) when fixed by pedicle screws, so as to understand if the microstructure parameters are related with screw stability and further to reveal the cause of screw loosening. Methods Based on the BMD detection results, fresh human cadaver spines were stratified into four levels: normal, osteopenia, osteoporosis and severe osteoporosis, according to diagnosis criteria in clinic. The corresponding vertebral specimens were then instrumented with pedicle screws, and screw pullout tests were conducted to measure the MPS of such screws. All the vertebral specimens were collected subsequently, and the cancellous bone cylinders were drilled from the center of each vertebra for microCT scanning. Microstructure parameters of the vertebral trabecular bone at different BMD levels were obtained to investigate the interrelationships in between, and the relationships between the microstruture parameters and corresponding MPS of pedicle screws with osteoporosis severity were then compared. Results With the decline of BMD from normal to severe osteoporosis level, the corresponding MPS of pedicle screws was significantly declined. With the severity of osteoporosis increasing, the progressive bone volume loss, mechanical incompetence and microstructure deterioration also appeared evidently. Significant differences were found in microstructure parameters at different BMD levels. Strong correlations were extensively observed among BMD, microstructure parameters and MPS of screws. The MPS of pedicle screws was highly correlated with bone volume over total volume (BV/TV), trabecular thickness (Tb.Th) and trabecular separation (Tb.Sp) from micro-CT scanning. Conclusions Significant deterioration would occur in bone tissues with the decline of BMD level, and the MPS of pedicle screws was highly correlated with some microstructure parameters.

Abstract:Objective To study and compare biomechanical properties of a newly developed magnesium AZ31B alloy intramedullary nail (AZ31B) with that of imported Poly-L-lactic acid intramedullary nail (PLLA) and pure titanium rib plate (TPRP), so as to provide scientific evidences for better internal fixation in clinical operation. Methods Forty fresh adult ribs were used and divided into 4 groups randomly. Three groups were made lateral rib fracture in midaxillary line and fixed by AZ31B, PLLA and TPRP, respectively, while the group with normal ribs was used as control. Biomechanical properties of specimens in each group were measured and tested using experimental stress analysis. Results (1) Three-point bending strength of internal fixation with AZ31B was close to that of control group (P>0.05), but significantly different to that of TPRP group and PTRP group (P<0.05); (2) No significant differences in torsional strength were found between AZ31B group, PTRP group and control group (P>0.05), and the torsional strength of both AZ31B and PTRP was superior to that of PLLA (P<0.05). Conclusions The internal fixation with AZ31B is an ideal mode for treating rib fracture since AZ31B has larger flexural strength than PLLA and TPRP, and its torsional strength was close to PTRP and normal ribs. This study provides some support for future research on biomechanical properties of AZ31B.

Abstract:Objective To study the age-related changes in biomechanical properties of rabbit cornea by using the data from uniaxial extension testing on rabbit cornea strips. Methods To obtain the experiment data, the uniaxial extension test on rabbit cornea strips of both 3-month old and 7 to 8 month-old were performed. The exponential function model and power function model were used to fit the strain-stress curves, and two kinds of viscoelastic mechanical models were used to analyze the stress relaxation curves. Results The mechanical behavior of the rabbit cornea strip presented a nonlinear and viscoelastic property. Within the range of error permitting, the age was not an important factor to affect the stress-strain, as no significant difference was found in nonlinear stress-strain curve of rabbit cornea strips between different ages. The cornea strips of 7 to 8 month-old rabbit had a slightly bigger elastic modulus and a faster stress relaxation than those of 3 month-old one. Different stretching rates had no obvious influence on the nonlinear stress-strain of 3-month old rabbit cornea strips, but the cornea strips at high stretching rate could have a faster stress relaxation. Conclusions The tangent modulus of rabbit cornea increases slightly with age, but its relaxation properties would change greatly with age.

Abstract:Objective To investigate the effects of inflammatory factors TNF-α, IL-1β, IL-6 on expression of mechano growth factor (MGF). Methods In the experimental group, TNF-α and IL-6 at concentration of 25, 50, 100 ng/mL, or IL-1β at concentration of 2.5, 5.0, 10 ng/mL were applied to fibroblast-like synoviocytes (FLSs) for 12 hours. The inhibitor groups were pretreated with PKA pathway inhibitor KT5720 at concentration of 1.0 mmol for 1 hour. The control group remained under the same culture condition as the experimental group, but without any growth factor. Real-time PCR was used to measure the gene expression of MGF. Results Treated with TNF-α at concentration of 25 ng/mL and IL-1β at concentration of 10 ng/mL, the MGF expression in FLSs was significantly increased (P＜0.05). IL-6 had no effect on MGF expression. A specific inhibitor of cAMP-dependent protein kinase, at concentration of 1.0 mmol significantly decreased the activation of MGF synthesis by TNF-α and IL-1β in FLSs (P＜0.05). Conclusions TNF-α at concentration of 25 ng/mL and IL-1β at concentration of 10 ng/mL significantly induce the MGF expression in FLSs, which activate MGF synthesis via the PKA pathway. This study is of significance in improving the application of MGF used in tissue repair area to make up the insufficient stress stimulation.

Abstract:Objective In order to meet the needs of more precise surgical navigation during interventional procedures and minimally invasive surgery, Aurora electromagnetic tracking technology-assisted surgical navigation with free combination of various surgical instruments was tested, trying to further solve problems encountered in surgery. Methods Aurora electromagnetic tracking system was used to match the medical surgical environment with metal-containing material. The built-in control software in this electromagnetic tracking system, which was equipped with the software development kit, was used to write a set of VC programming language suitable for real-time display of clinical surgical navigation system, and relative performance tests and comparative experiments were conducted for different medical surgical navigation application in the hospital to measure the precision degree of the tracking system, as well as the statistics of various surgical instruments corresponding to the application in different surgeries. Results 160 patients in interventional surgery with coronary angiography were randomly selected, 80 patients treated by digital subtraction angiography(DSA) with electromagnetic tracking systems as the experimental group, and 80 patients by DSA only as the control group. It was found out that with obviously less operating time, the amount of contrast agent was significantly reduced in the experimental group, and the degree of controllability for interventional surgical procedure was increased from 95% success rate to 99%. Conclusions The comparative experiments proved that Aurora electromagnetic tracking technology could significantly improve the accuracy in surgery, with the mean value of navigation less than 2 mm. In terms of interventional procedures and minimally invasive surgery, this electromagnetic tracking technology can greatly relieve patients' suffering and reduce medical risks to make medical care safer, and enhance the surgical technology level in hospital.

Abstract:With the development of space life science, researches on ground-based microgravity simulation become more and more important for spaceflight to complement their limited missions. It is well known that bone marrow mesenchymal stem cells (BMSCs) are pluripotent, self-renewing cells with multi-lineage differentiation capacity on the ground, but their responses under microgravity and the underlying regulatory mechanisms are poorly understood. Ground-based microgravity simulation might affect cell proliferation, apoptosis and expression of surface molecules, and induce cytoskeletal reorganization, as well as alter the differentiation potential of BMSCs. In this review, how groundbased microgravity simulation mediates BMSCs’ responses and its involved mechanisms are summarized to further understand the mechano-biological coupling in such process and provide theoretical references for space flight-induced pathophysiological alterations.

Abstract:Focal adhesion plaques (FAPs) are multi-protein aggregates，which act as physical connections between extracellular matrix and cytoskeleton (CSK). FAPs and CSK play important roles in the conversion of mechanical signals into intracellular chemical signals followed by physiological and pathological responses. With focus on FAPs-CSK system, this review summarized the process of fluid shear stress-induced mechanotransduction and the roles of FAPs and CSK in this process in detail, introduced important proteins in FAPs, discussed the relationship between FAPs and other mechanotransduction pathways. The review established the theoretical foundation for understanding of the relationship between fluid shear stress and shear stress-related diseases, as well as development of clinical drug and treatment of these diseases.