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Study on the three-dimensional chitosan-decellularised-derma scaffolds for bone tissue engineering

Yan ZHANG ; Ruixin LI ; Xizheng ZHANG ; Yong GUO

Journal of Medical Biomechanics.2010;25(1):11-15.

Objective To observe the adhesion of MC3T3-EI osteoblastic progenitor cells to the three-dimensional chitosan-decellularised-derma scaffolds,and evaluate the cytocompatibility of the scaffolds.Method The threedimensional chitosan-decellularised-derma scaffolds were prepared by the freeze-dtying method,the porosity,density and water absorption of which were measured.The microscopic morphology of the composite scaffolds was analyzed by the scanning electron microscopy(SEM).The MC3T3-E1 cells cultivated in vitro were seeded onto the composite scaffolds,and then co-cultured for 2,3,4 and 5 hours.At each time point,three specimens from each matrix were taken to determine the cell-adhesion rate and the best time of the cell-adhesion.The cells were seeded onto the composite scaffolds,and then co-cultured for 1,3,5,7,9,11 and 13 days.The MC3T3-E1 cells inside were evaluated with MTS test.The cell morphology was observed by the histological staining.The compression tests were performed using a Universal Testing Machine,at room temperature,as compared with no-cell-scaffolds.Results The three-dimensional chitosan-decellularised-derma scaffolds have high interval poroslty with the porosity(92.8%),the density(0.09796 g/ml)and the water absorption(2169±100)%.The cytocompatibility test shows that the seeded MC3T3-E1 cells can adhere to the scaffolds and proliferate.Conclusions The three-dimensional chitosan-decellularised-derma scaffolds have high interval porosity with the welldistributed diameter.The MC3T3-E1 cells are easy to adhere the scaffolds and proliferate which shows that the scaffolds have a good cytocompatibility.

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Research on brain tissue mechanical Style in brain model deceleration Impact

Shengxiong LIU ; Zhiyong YIN ; Hui ZHAO ; Guangyu YANG

Journal of Medical Biomechanics.2009;24(6):458-461.

Objective to research the mechanical style(compressive or tensile force)of the key site of brain tissue in brain deceleration impact.Method a transparent physical brain model with air bubbles was built and loaded on an upright brain decaler ation impacting expedmentel platform.Then,the moveable platform was made a free fall from a height of 400mm and impacted on the fixed platform,and the whole deceleration impacting process was recorded by a high-speed video camera.Using the serial pictures analyzing Software,the length change of the long ads(vertical to the impacting direction)and the short axis(in the impacting di-rection)of the air bubbles were analyzed and calculated.Result the length change of the long axis of air bub-ble with in site coup was smallerthan the absolute value of that of the short axis;while with the air bubble in the contrecoup site,the length change of the long axis was bigger than the absolute value of the short axis.Conclusions the results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compres-sive force in the impacting direction.Since the propeny of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.

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Biomechanics of lumbar spondylolysis: Finite element modeling and validation

Xiaomin GU ; Lianshun JIA ; Xiongsheng CHEN ; Chenglin LU ; Yang LIU ; Dongsheng ZHANG

Journal of Medical Biomechanics.2010;25(1):45-50.

Objective To construct three-dimensional finite element model of lumbar spondylolysis,then to verify its validity by comparison of biomechanics in vitro.Method According to the radiological data of a patient with lumbar spondylolysis,the bone and intervertebral disc of L4-S1 were reconstructed by Simpleware software.The lumbar attaching ligaments and articular capsule were added into simulating model by Ansys software.The three-dimensional finite element model of lumbar spondylolysis was finally simulated successfully,and validated by lumbar spondylolysis biomechanical experiment in vitro.Results The reconstruction of digital model contained the bones of lumbar spine which include vertebral cortical bone,cancellous bone,facet joint,pedicle,lamina,transverse process and spinous process,as well as the annulus fibrosus,nucleus pulposus,superior and inferior end-plates.Besides,anterior and posterior longitudinal ligaments,flavum ligament,supraspinal and interspinal ligaments and articular capsule of facet joint are also attached.The model consisted of 281,261 nodes and 661,150 elements.Imitation of spondylolysis is well done in this model.The validity of the model was verified by comparison of the results of biomechanics in vitro which involved in the trends under loading of stress/strain of L4 inferior facet process,L5 superior and inferior facet process,S1 superior facet process and the trends of stress/strain of lateral and medial L4 inferior facet process.Conclusions Three-dimensional model of lumbar spondylolysis is reconstructed using finite element analysis,and can be further used in the research in biomechanics of lumbar spondylolysis.

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Internal boundary parameters identification of human middle ear with neural network

Yingxi LIU ; Sheng LI ; Xiuzhen SUN

Journal of Medical Biomechanics.2009;24(6):414-417.

Objective To study the method of internal boundary parameters identification of middle ear.Method The numerical model is created using CT technology.Based on Matlab tools,the neural network for identifying internal boundary is proposed.Result The uniform pressure of 105 dB is applied at the outside of the tympanic membrane,and the harmonic analysis is calculated on the model to take the training samples.The internal condition parameters are identified using the good neural network.Conclusions The investiga-tion shows that the inverse method reveals a fast convergence and a high degree of accuracy.

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Reevaluation on the mechanical properties of dentine microstructure

Xiaosong LUO ; Yixia ZHANG ; Yuhong CUI ; Jun PAN

Journal of Medical Biomechanics.2011;26(2):181-188.

Objective:It is demostrated that the porous protein-mineral mechanics model could provide more accurate prediction for biomaterial properties of dentine compared with the other established models.This paper would use the model to reevaluate the mechanical properties and its interacting mechanism of human dentine.Method:By using a porous proteinmineral mechanics model,the effect from the interactions between tubules,pedtubular and intertubular matrix on dentine microstructure was discussed.Results:The dentinal micromechanical properties were dependent on the tubular direction,and the absolute values of the stresses derived from the hydraulic and gas tubular pressures increased parabolically with theincreasing diameter of the tubules.It was also found that the effective elastic constants of the dentine microstructure would vary with the aging and the distribution of mineral and collagen within peritubular and intertubular matrix of detine.Conclusions:The theoretical analyses provided in this paper demonstrated that the microstructural characteristics of tubules,peritubular and intertubular dentinal matdx could have different influences on the micromechanical properties of human dentine,which showed the validity of porous protein-mineral mechanics model,and the limitation of some models that neglected the interacting mechanism.

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Experimental study on biomechanical property of the Skin in pig's back

Xinfeng WU ; Guozheng KANG ; Linmao QIAN

Journal of Medical Biomechanics.2009;24(6):452-457.

Objective To investigate and evaluate the biomechanical property of the skin in pig's back in order to provide the essential theoretical basis for clinical and skin products.Method Taking the skin in pig's back as experimental material,the monotonic tensile and cyclic tension-tension tests with difierent loading rates was researohed respectivaly.Meanwhile,with different loading directions and stress levels the creep and cy-clic tension-tension tests were also been studied experimentally.Result The capacity of resisting tensile,creep and cyclic deformation of pig's skin in the direction along the Langer's line is stronger than that perpen-dicuiar to the Langer's line.The creep curve of pig's skin is load-dependent and consisted of three phases a-bout deceleration phase,stabilization phase and destruction stage.Pig's skin exhibits apparent ratcheting un-der asymmetry stress cycle.Ratcheting deformation displays significant mean stress,stress amplitude and loading speed dependence.Condusion Based on the experiment,the biomechanics property of skin's vis-coelasticity and anisotropic feature have been sysmarie stadied,it's provide necessaw theoretical fundation for clinical and leather products.

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Effects of adhesive thickness on internal stress distribution in fullceramic crowns

Bin LIU ; Chenglin LU ; Xiuyin ZHANG ; Dongsheng ZHANG

Journal of Medical Biomechanics.2010;25(1):56-62.

Objective To investigate the effects of the thickness of the adhesives(3 M ESPE RelyX ARC)on the internal stress distribution of the IPS Empress Ⅱ full-ceramic crowns by using Finite Element Analysis(FEA).Method A dummy Empress Ⅱ ceramic crown restoration of the mandible right first molar was prepared according to standard dental process.Followed by micro-CT scanning,four 3D numerical models with cement thickness 60,90,120 and 150 μm were established respectively.The models were subjected to four loading conditions and stresses in veneer and core layers were presented.Result Numerical results indicate that when adhesive thickness increases from 60 μm to 90 μm,the maximum principal stress either in veneer or core decreases.However,when thickness increases to 150 μm,stress variation trends differ from adhesives.Conclusions The normal stresses in adhesives remain a low level when the thickness varies from 90 μm to 120 μm,while the shear stress is less sensitive to the thickness when it exceeds 90 μm.There is an optimal thickness which can reduce the tensile stress in the core and veneer.Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.

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Three-dimensional finite element numerical analysis of the Ni Ti shape memory alloy clutching internal fixator

Guoping CHEN ; Yubo FAN ; Daiquan ZHANG

Journal of Medical Biomechanics.2010;25(1):36-39.

Objective Clutching internal fixtor(CIF)loose and the fixed part weakly heal up are often found in orthopedic clinic.In the present paper,biomechanics methods were used to try to explain and analyze these issues,providing a helpful suggestion for the application of CIF in clinic.Method Commerical finite element models(FEM)Program ANSYS was applied to set up the finite element models of orthopedic CIF and bone tissue to analyze and evaluate the biomechanical performances of the NiTi shape memory alloy CIF.Results There is an interaction force between embracing force of CIF and resistant force of bone tissue during the orthopedic clinical treatment.The embracing force along two semi-circular arms of CIF is increasing from the open position and reached the maximum value at the open symmetry position where the deformation of the bone occurred.Conclusion It is the key to choose the force loading position during the practical treatment,as the concentration force is the main force when there is an interactive force between the bone and the CIF.

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Diagnosis value of urodynamics in patients with benign prostate hypertrophy

Zhihua ZHOU ; Yawei WANG ; Liang YING ; Ming LUO ; Fang QIU

Journal of Medical Biomechanics.2010;25(1):74-76.

Objective To evaluate the diagnosis value of urodynamics in patients with benign prostate hypertrophy(BPH).Method With urodynamic device,the full set of urodynamic exam was administrated in 427 patients with BPH,and the externalsphincter urethral myogram was monitored simultaneously in pressure-flow studies(PFS).The umdynamic finding such as Q_(max),P_(det)-Q_(max),DS(descending slope)and post-voiding residual(PVR)were recorded,as well as the situation of bladder detrusor constraction and bladder compliance and urethral sphincter coodination.The bladder outflow obstruction was diagnosed by A-G nomogram,P-Q plot and DS.The IPSS score and prostate volume were also acquired.Results The diagnostic rate of BOO is 81.5%,among them concomitantly detrusor muscle impair in 117 cases (27.4%),decreased bladder compliance in 162 case(37.9%),urethral sphincter dyssynergia in 148 cases(34.7%),and unstable bladder in 164 cases(38.4%).The increase degree of BOO show an increasing tendency with urodynamic finding such as Q_(max),P_(det)-Q_(max),P_(open),DS,IPSS score and prostatic volume respectively,but a decreasing tendency with Q_(max) and bladder compliance.Conclusions The urodynamic exam plays an important role in diagnosis of BOO.There is a positive relation among degree of BOO with urodynamic findings such as P_(det)-Q_(max),P_(open),DS and IPSS score and prostatic volume,however,a negative relation with Qmax and bladder compliance respectively.

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Contribution of co-contraction to arm impedance in the free planar movement

Chunjiang FU ; Rubin WANG

Journal of Medical Biomechanics.2009;24(6):427-433.

Objective Impedance control plays an important role in stability.This paper intends to explore such mechanism through modeling human reaching movement.Method Implemented with revised model,we ap-ply optimal control theory to neuro-muscle-skeleton model to calculate the stiffness ellipses.Result Com-pared with the original model and experimental figures,the model we proposed could overcome the shortage of monotonous changing of the original one and fit the data better.Conclusions So that this paper concludes that co-contraction contributes to impedance control even during free upper limb planar movement.

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