• Volume 25,Issue 2,2010 Table of Contents
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    • Biomechanical compatibility of osteoporotic vertebral augmentation with cancellous bone granules and bone cement: a finite element evaluation

      2010, 25(2):79-88. DOI: 10.3871/j.1004-7220.2010.2.88.

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      Abstract:Objective The goal of this study was to investigate the biomechanical compatibility effects of cancellous bone granule(CBG) augmentation of Optimesh and polymethylmethacrylate (PMMA) augmentation of Kyphoplasty on treated andadjacent non-treated vertebral bodies. Methods Three-dimensional, anatomically detailed finite element (FE) models of the L1–L2functional spinal unit (FSU) were developed on the basis of cadaver computed tomography (CT) scans. The material properties and plug forms of the L2 centrum were adapted to simulate osteoporosis, CBG and PMMA augmentation. The models assumed a three-column loading configuration as the following types: compression, ?exion and extension. Results Compared with the osteoporotic model, changes in stress and strain at adjacent levels both of CBG and PMMA augmentation models were minimal, but stresses/strains within the two reinforcement material plugs were modified distinctly and differently. In addition, osteoporosis, CBG and PMMA augmentation had little effect on either the axial compressive displacement of the three columns or the average disc internal pressure in all models. Conclusion Both morcelized cancellous bone and PMMA augmentation restore the total strength and stiffness level of treated vertebral bodies and benefit the reconstruction of vertebral function. Regarding the biomechanical compatibility and the biocompatibility of the treated vertebral body and reinforcement material, however, the morcelized cancellous bone is better than PMMA augmentation.

    • Biomechanical study on thoracic spine segment fixed by pedicle screws placed with “funnel technique”

      2010, 25(2):89-93. DOI: 10.3871/j.1004-7220.2010.02.93.

      Abstract (3056) HTML (0) PDF 685.97 K (3553) Comment (0) Favorites

      Abstract:Objective To investigate mechanical properties of the thoracic spine fixed with pedicle screws that were placed using a “funnel technique”. MethodFourteen thoracic spinal segments (T6 to T10) were collected from adult cadavers. These specimens were divided into two groups, 7 in each, and fixed with pedicle screw using funnel and Magerl techniques. The displacement stiffness of the spinal segment and the pullout strength of the pedicle screw were tested for intact and fixed spinal specimens. The displacement stiffness was measured from different loading directions, including axial compression, anterior flexion, posterior extension, lateral bending and axial torsion. ResultsCompared to the intact spine segments, the displacement stiffness is significantly increased (P<0.05) at all directions in the segments fixed with either funnel or Magerl technique; however, there is no significant difference between the groups fixed with different technique. The screw pullout strength is significantly decreased (P<0.05) in spine segments fixed with Funnel technique compared to those fixed with Magerl technique. ConclusionsSince funnel technique removed a portion of bone from the posterior side of the vertebral pedicle, it can raise the accuracy and safety for the placement of pedicle screw. Although this technique does not affect the stiffness of fixed spinal segment, it may decrease the anchor strength of pedicle screw. Accordingly, we recommend that the funnel technique can be considered as a complement method for the fixation of vertebral fracture using pedicle screws.

    • Finite element analysis on adjacent segments for its biomechanical changes after artificial cervical disc prosthesis

      2010, 25(2):94-99. DOI: 10.3871/j.1004-7220.2010.2.99.

      Abstract (3132) HTML (0) PDF 714.68 K (3249) Comment (0) Favorites

      Abstract:ObjectiveTo study the range of movement (ROM) in adjacent vertebral segments and the changes in intervertebral disc stress after implanting artificial cervical disc. MethodA 3D finite element model for normal cervical spine was established using CT images scanned from a cadaver cervical spine. Simulation of bone graft and fusion of vertebral bodies as well as implantation of intervertebral disc prosthesis were performed between C5 and C6 . Then the ROM of adjacent functional spinal units (FSU, C4/5、C6/7) and the stress in C4/5 and C6/7 intervertabral disc were analyzed. Results(1)The model including the structures of ligaments, joint capsule and other soft tissue is built with high reality and accuracy;(2)Vertebral fusion increased movement range in adjacent FSU, and the stress in corresponding discs is significantly raised as well. The stress in nucleus pulposus and annulus fibrosus is increased about 70% at upper segment and 40% at lower segment; (3) After implantation of artificial disc, only the extension of cervicle spine is limited(P<0.05); the stress in adjacent intervertebral disks is increased less than 10%. ConclusionsThe implanted artificial cervical disc can appropriately reduce the stress in adjacent vertebral segments, which is beneficial to improve the movement of the cervical spine.

    • Assessment for the stability of fracture thoraciclumber spine(T11~L3) fixed with crossbarequipped pedicle screws

      2010, 25(2):100-104. DOI: 10.3871/j.1004-7220.2010.02.104.

      Abstract (3215) HTML (0) PDF 650.61 K (3330) Comment (0) Favorites

      Abstract:Objective To determine the stability of fracture thoraciclumber spine (T11~L3) fixed with crossbarequipped pedicle screws. MethodThe thoraciclumber spine segments (T11~L3) were obtained from calves. A wedge cut was performed on L1 vertebral body to produce a model resembling severe vertebral compressive fracture. Some of the fracture spine segments were fixed with pedicle screws with and without crossbar. Thus, 4 types of spine segments were available: (1) normal segments; (2) unfixed fracture; (3) fracture fixed with crossbarequipped pedicle screws and (4) fracture fixed with pedicle screws without crossbar. The segmental stability was determined by measuring the range of motion (ROM) at directions of flexion/extension, left/right axial rotation and left/right lateral bending using a threedimensional laser scanner. Each ROM was standardized into a stability potential index (SPI) for the comparison among 4 groups. ResultsCompared to unfixed fracture, both fixations significantly increase stability of injuried specimens at each motion direction. The stability of injured segment fix with crossbarequipped pedicle screws is higher than that fixed without crossbar, but the difference does not reach statistically significant. ConclusionsPedicle screw fixation can significantly increase the stability of fracture spine. However, crossbar may not play a further role in raising fixative stability.

    • 3D Simulation of New Sacroliliac Internal Fixation System and Comparing Evaluation

      2010, 25(2):105-111. DOI: 10.3871/j.1004-7220.2010.02.111.

      Abstract (2801) HTML (0) PDF 945.44 K (3184) Comment (0) Favorites

      Abstract:Objective Creating a 3D finite element model of a full pelvis with sacroiliac joint fracture. Comparing the biomechanical properties of the model where the fracture part was fixated by using a new sacroliliac anatomy type Bar-plate internal fixation system to iliosacral screw fixation and front reconstruction plate fixation. Methods A specially designed biomechanical semi-automatic mesh generator was employed to generate the complete pelvis finite element model from CT datas. Then, one side of sacroiliac joint related ligaments was deleted to simulate the case of sacroiliac joint fracture. Using a new sacroliliac bar-plate internal fixation system with anatomic plate (SABP) to fix the fracture part, and the comparing models using iliosacral screw fixation (SS) and front reconstruction plate fixation (SP) were also generated. Finally, all models were simulated under same loading conditions. Results Using SABP fixation, the maximal displayment of the sacroiliac joint decreases about 40% and 42% compared to SS fixation and SP fixation, respectively. The minimal value of maximal stress for main loading transfer regions was reached by SABP fixation and t he maximal stress of SABP decreases about 33%-70% compares to SS in regions of fracture hip cortical bone and cartilages bone, and decreases about 60%-75% to SP in regions of sacral cortical bone and fracture hip cortical bone. Conclusion The new sacroliliac anatomy type Bar-plate internal fixation system has better biomechanical properties than other internal fixations, and deserves to be put into clinical application.

    • Development of a force balance telemetry device for total knee arthroplasty

      2010, 25(2):112-117. DOI: 10.3871/j.1004-7220.2010.02.117.

      Abstract (3385) HTML (0) PDF 803.20 K (3282) Comment (0) Favorites

      Abstract:Objective A new type of tibialfemoral forcebalancing telemetry device was developed for measuring force balance on the tibialfemoral contact surface in knee joint. MethodThe forcebalance telemetry device was designed imitating the configuration of tibial part of total knee prosthesis, in which force sensors and telemetry circuit were embedded. During total knee arthroplasty(TKA), this device was implanted as a tibial prosthesis to measure tibialfemoral force while the knee joint was being placed at different angles. The tension balance was adjusted by releasing soft tissue around knee joint. ResultsThe results indicat that this device has advantage of high accuracy for force measurement (r>0.98,RMS= 65 g), which is sufficient to meet clinical demand. ConclusionsThe measurement of force balance on the tibialfemoral contact surface with telemetry device can provide new insight into the estimation of optimal knee prosthesis position and selection of appropriate polyethylene insert.

    • Research on dynamic plantar pressures distribution of 7 to 11 years obese children

      2010, 25(2):118-123. DOI: 10.3871/j.1004-7220.2010.2.123.

      Abstract (2990) HTML (0) PDF 679.72 K (3497) Comment (0) Favorites

      Abstract:Objective To compare the parameters of plantar pressures between the obese children and normal children during walking on the flat ground at normal speed, and to discuss the effect of obesity on dynamic plantar pressures for 7-11 years obese children. MethodThere were 40 volunteer subjects, twenty obese children and twenty normal children between 7 and 11 years of age in this study. Subjects were asked to walk at their own paces on a 10 m walkway with a 0.5 m footscan plate (footscan from RSscan International, Olen, Belgium) Sampling at 300 Hz. Data were processed statistically by SPSS11.5 and EXCEL. ResultsCompared to the normal children: 1.the obese children have the longer foot support duration and shorter pushoff duration; 2.the peak plantar pressures are larger and appearing time is longer of Metatarsal 4 (M4) and Metatarsal 5 (M5), the peak plantar pressures of Toe 2 (T2) to Toe 5 (T5) on obese children group are higher. 3. AI (arch index) and impulse percentage of midfoot and heel of obese children group are much larger. 4. Supination extent of the left foot in heel strike phase, supination extent of the right foot in footsupport phase and in pushoff phase on obese children group are also larger. In addition, significant difference in pronation extent appeared between left and right foot in obese children group. 5. The footaxis angle of obese children group is obviously larger. ConclusionsCompared to the normal children: 1. the walking stability of obese children group in this study is weaker. 2. Obese children are vulnerable to injure their foot foresole, ankle joint and knee joint. 3. Obese children endure flat foot more easily. 4. Obese children walk more frequently with outward splayfoot.

    • Investigation on gait initiation in young men

      2010, 25(2):124-128. DOI: 10.3871/j.1004-7220.2010.2.128.

      Abstract (3011) HTML (0) PDF 624.44 K (3525) Comment (0) Favorites

      Abstract:Objective To obtain kinematic and kinetic parameters of gait initiation from young men when they are walking with constant speed. MethodDLUT4060 piezoelectric multicomponent force platform and DVM8820 threedimensional infrared image capture system were used to test gait initiation in 9 young men (average age was (21.3±0.5) years). ResultsThe lower limb kinematic and dynamic characteristics during gait initiation differ significantly from its subsequent steadystate. The characteristic feature of gait initiation is the moving leg swinging a larger range and the stance leg performing a more powerful thrust. The center of pressure (COP) in the foot bottom shows a moving track which moved to the lateral of the moving leg firstly and then to the extension of the stance leg. ConclusionsNormal gait initiation has its unique characteristics, and the kinematics and dynamics parameters obtained in such status will be helpful for gait analysis and biorobot design.

    • Three dimensional numerical simulation of microcirculation and drug delivery in solid tumors

      2010, 25(2):129-135. DOI: 10.3871/j.1004-7220.2010.02.135.

      Abstract (2917) HTML (0) PDF 687.59 K (3432) Comment (0) Favorites

      Abstract:Objective To study the characteristics of microenvironmental flow and the process of macromolecular drug delivery in solid tumor. Method3D models simulating tumor hemodynamics and drug delivery were developed. Microcirculation and concentration distribution of two macromolecular drugs in tumor were simulated. ResultsThe model successfully reflected abnormal tumor hemodynamics, which results in impeded drug delivery and uneven concentration distribution of the drug. The results also shows that the drug with lower molecular weight is more easy to spread in tumor and excrete with interstitial fluid flow. In contrast, the drug with higher molecular weight tends to accumulate and maintain an effective concentration in tumor for a longer period. ConclusionsThe results derive from this model can reflect physiological conditions, providing a reliable numerical model for the investigation of tumor microenvironment, drug delivery and strategy of therapy.

    • Numerical simulation and postprocessing of tumor microvasculature

      2010, 25(2):136-142. DOI: 10.3871/j.1004-7220.2010.2.142.

      Abstract (3462) HTML (0) PDF 901.75 K (3096) Comment (0) Favorites

      Abstract:Objective In order to provide a more realistic microvasculature model for the study on tumor hemodynamics and drug delivery, a simulated tumor microvascular network was developed by the technique of numerical simulation and postprocessing. Method We constructed a tumor microvascular model with host arteriolevenule system, in which the variation in vascular branching and dimensions was taken into account. A sensitivity analysis was made for the parameters of the model to evaluate the adjustability of simulated results. The connectivity of the vascular network was tested to ensure the integrity of the network. The vascular network was smoothed afterwards to reduce flow resistance resulting from numerical networks. Results The simulated results are consistent with the characteristics of real tumor microvasculature, which show intact circulation, local adjustability, high network connectivity and smooth degree. Conclusions This study provid a numerical microvasculature model for the research on tumor hemodynamics, drug delivery and vasculartargeted therapy.

    • Effect of inhibiting cytoskeleton on the mechanical properties of normal rat kidney cells

      2010, 25(2):143-147. DOI: 10.3871/j.1004-7220.2010.2.147.

      Abstract (3171) HTML (0) PDF 527.24 K (3747) Comment (0) Favorites

      Abstract:Objective To determine whether the alteration of cytoskeleton interfere with the mechanical properties of normal rat kidney cells (NRKCs).Method NRKCs were treated with cytochalasin D, colchicine and blebbistatin using micropipette aspiration technique, and the changes in Young’s modulus and viscoelasticity of NRKCs were assessed. Results The Young's modulus of is significantly decreased after treated with all cytoskeleton inhibitors. Compared to the control, the viscoelasticity is significantly decreased in NRKCs treated with cytochalasin D and blebbistatin, but in not in colchicinestreated cells. Conclusions The effect of blebbistatin on NRKCs mechanical properties is independent of cytoskeleton. Inhibition of assembling of actin meshwork or the activity of myosin II ATPase will reduce cell's Young's modulus and viscoelasticity. In addition, microtubule assembling is correlated with Young's modulus rather than viscoelasticity.

    • Conception of parameters for acetabulur orientation

      2010, 25(2):148-151. DOI: 10.3871/j.1004-7220.2010.02.151.

      Abstract (2998) HTML (0) PDF 460.88 K (3136) Comment (0) Favorites

      Abstract:The parameters with respect to acetabular orientation, including anteversion and inclination, are important for preoperative planning, intraoperative guide and postoperative evaluation for total hip arthroplasty (THA). Malposition of the acetabular component in THA is a major risk factor to reduce the service life of the prosthesis. At present, several definitions are available for the acetabular anteversion and inclination, whereas there are different expressions for one definition. It will make the clinicians confused if these definitions are not elucidated clearly.

    • Mechanical effect of Myosin Ⅱ on cell mitosis

      2010, 25(2):152-156. DOI: 10.3871/j.1004-7220.2010.2.156.

      Abstract (2552) HTML (0) PDF 646.61 K (3310) Comment (0) Favorites

      Abstract:Cytoskeleton can cause active deformations and resist passive deformations which related to some active deformations of cells known as mitosis. Mitosis occurs through a series of stereotypical shape changes resulted in the mechanical separation of a mother cell into two daugther cells, accompanied by mechanical phenomena throughout the whole course. As a molecular motor of cytoskeleton, myosin II is a kind of multifunctional protein that can participate in mitosis. To make deep study on the roles of myosin II in mitosis could get important theoretical and application value. This paper will sum up the recent research achievements on roles of myosin II in mitosis.

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