Abstract:Muscle action in lower extremities during double support phase of gait was ana-lyzed quantita tively using optimization techniques.Two optimization problems ,one linear and one non-linear,were formulated to solve the indeterminate problem of muscle load sharing.The re-sults show that the predicted muscle action is consistent with the qualitative analysis by other investigators.Two-joint muscles have better mechanical advantage in counter-current move ment between syn ergistic muscles.In a muscle group,greater muscle force is allocated to the muscle with larger physiological cross sectional area or higher percentage of type I muscle fiber.The moment arm of the muscle is not a dominant factor in muscle load sharing.For clinical use,the eccentric control of the two-joint muscles in the knee joint is very important for knee sta-bility during stance phase,and is suggested to be essential in programs of physical therapy for training in double limb support.

Abstract:Objective:To conduct such a study on TSS downstream of mitral stenosis using a finite element model of two dimensions combined with Doppler echocardiography in human beings.Method:Non-invasive Doppler echocar-diography was used to pick up in real-time way two dimensional images of left cardiac cavity and average ve-locities of left atrium and left ven tricle as boundary conditions,we conducted a computational study of TSS downstream of mitral valve in a group of patients with mitral stenosis during their follow-up using the finite el-ement method.Result:There was a significant difference with respect of TSS and Wilkins grade of valvular le-sion between the twice of follow-up(P<0.05),and the two items correlated with each other(r:0.80-0.82).Be-sides,however the extent of valvular lesion and stenosis is,TSS in the centerline locations is lower than that in the boundary locations.The maximul number of the former is less than80N/m 2 .Our results showed coincident with those of previousre searches.Conclusion:There is an obvious relationship between TSS downstream of mi tral stenosis and the aggravation of valvular lesion.The description of TSS and velocity in the local and total flow field of valve with finite element method is quite detailed and intact.So the combination of the two methods makes the quantitative study of TSS in the flow field of cardiac valve to be comprehensive and accurate.

Abstract:The parallel-plate flow chamber(PPFC)with rectangular shape,of which the height is far smaller than its own length and width,is one of the main apparatus for in vitro studies of the mechanical behavior of cultured en-dothelial cells undergoing shear stress.The PPFCs are usually utilized to study the cells'mechanical behavior under steady flow condition.Considering that the Reynolds numbers of the flows in the usually used PPFCs are small,a perturbation solution of laminar pulsatile flows in the PPFCs is presented using Reynolds number as perturbation parameter.The0-order,first-order,second-order approximate calculation formulas of the velocities in the PPFCs and the shear stress at the bottom of the PPFCs are given in this paper.The calculated numeri-cal results and the comparison between the perturbation solution and the Fourier solution demonstrate that,the approximate formulas are highly precise for various commonly used flow parameters and geometrical dimensions of the PPFCs.In particular,the0-order approximate formula,the quasi-steady formula,is much more appropri-ate to the pulsatile flow with higher Reynolds number,which provides a practical method for the calculation of the shear stress in the PPFC under pulsatile flow condition.

Abstract:Objective:To investigate the transmession characteristics of explosive blast in biological tissue.Materials:The transmission characteristics of explosive blast in liver,lung,vessel and tissue under skin were studied through blast pressure detection,and compared with in air.Results:The results showed that,the decline speed of the explosive blast in different media is in order:air>skin>blood;the sensitivity of different tissue on the explosive blast is in order:brain>chest>liver.The transmission to brain mainly is by vibrating through bone,which is dif-ferent from other parts of the body.Conclusion:The results can provide the basis for simulation study in vitro,and can also provide the theoretic basis for diagnosis and treatment of the explosive blast injury.

Abstract:Objective:To evaluate the biomechanical stability of a cervical spine butterfly plate(CSBP)for unstable cervical spine.Method:Fourteen cervical spine specimens(C3～T1)were divided into two group:A and B.All intact,specimens were subjected to nondestructive testing in6loading modalities on a universal testing machine.A cadaveric model of complete C5～C6instability was produced in both groups.Specimens in group A were stabi -lized with CSBPs,and group B with Orion plates.The nondestructive testing was repeated to determine structural stability.Results:The injured spines stabilized with implants in both groups were significantly more stable than the intact specimens in all modes of testing(P<0.05).Stability of injured spines was increased most in flexion-extension,66%in flexion and60%in extension by CSBP while72%in flexion and71%in extension by Orion plate.The two constructs provided similar stability in6loading modalities(P>0.05).Conclusion:This study shows that CSBP provides biomechanical stability for unstable cervical spine.

Abstract:Objective:To study the biomechancial properties of human umbilical cord vein with aging changes and to pro-vide theoretic evidence for clinic in collecting suitable blood graft.Method:33fresh human umbilical cord vein s were collected.The parameters such as pressure,diameter and capacity of blood were also tested,then the com-pliance and elastic mudules were calculated.Result:The P-V curve are highest in37-40weeks while that of elatic mudules are lower,so compliance are best in this period.Conclusion:the author suggest that the umbili-cal vein in37-40weeks should be selected as graft material.

Abstract:The present authors designed and established a new useful artery organ culture system under stress in vitro.After examined the stability of this system,common carotid arteries of pigs were cultured under stable flow and pulsatile flow respectively.The condition of cultured arteries were assayed with morphological,transmission electron microscopy and computer image processing methods.The results showed that arteries kept alive after being cultured for seven days,and the morphormetry and submicroscopic morphology of cultured artery were still normal.The culture system can offer many hemodynamic conditions steadily,and provided a new experimental model for vascular biomechanical and tissue engineering research.

Abstract:Objective:To evaluate biomechanically and clinically the posterior STB thoracolumbar transpedicular screw-plate system.Methods:The STB screw-plate system was made by titanium alloy(TC4,Ti6Al4V).The three-dimensional motions of T12～L1segment of six adult fresh spine specimens in normal,injured,Steffee fixation or STB fixa-tion states were measured and analyzed.Axial stiffness of STB system was also measured.Clinical results of STB system in the treatment fifty-three cases with thoracolumbar fracture and lumbar spondylolisthesis were ob-served.Results:Both Steffee and STB devices can restore the stability of injured thoracolumbar verte brae in flexion,extension,lateral bending and axial rotation,especially in right/left lateral bending.No statistical differ-ence of spinal stability capacity was found between Steffee and STB devices.The axial stiffness of STB device was106.8N/mm±24.8N/mm.Clinical results showed that STB has excellent reduction and fixation capacity on injured thoracolumbar vertebrae.Conclusion:STB has excellent bromechanical properties and can be used in the thoracolumbar fracture and lumbar spondylolisthesis.

Abstract:Objective:To compare the biomechanical effectiveness of three diferent techniques to prove the advantage of the cannulated screws plus the tension band through stress analyses.Methods:eight pairs of fresh cadaver knees were used for test.Fractures were created in sixteen knees and fixed with cerclage wiring,parallel kirschner wires plus the tension band and the cannulated screws plus the tension band,respectively.The biomechanical properties of three methods were analysed.Results:The cannulated screws plus the tension band have better biomechanical properties in the treatment of patella fracture than the cerclage wiring and parallel kirshner plus the tension band(P<0.05).Conclusion:The cannulated screws plus the tension band are the best way to treat the patella fracture.

Abstract:To investigate and compare the effect of self-design three dimension L steel plate(TDLP)and other internal fixation devices on unstable intertrochanteric fracture of femur.Method The two-part,three-part and four -part trochanteric fractures of feumr have been made by using12fresh cadaver femur samples.Six strain patches have been sticked along the medical and lateral cortices of femur.Measure strain of proximal femur and com-pression,bending and twisting under different condition.Then the femur fractures have been fixed by using TDLP,Gamma nail,Richards nail and SHS nail,respectively,And their experimental results and biomechanical functions have been compared systematically.Results Using TDLP interfixation to cure intertrochanteric fracture of femur has the similar strength rigidity as compared with Gamma nai.and the standard values(P>0.05).The TDLP offered more distinct biomechanical advantage than the Richards nail and SHS nail,there exist obvious differences(P<0.05).72cases of unstable intertrochanteric fracture of femur have been treated by self-design TDLP since1994,with the average patient age63.5and average followed-up period32months.X-ray photos showed fracture headings were excellent good and satisfactory funciton of the limbs were recovered.No slow u-nion of fracture,coxa vara deformity and rotary displacement have happened.Conclusion TDLP is more ideal in-ternal fixation object in the treatment for intertrochanteric fracture of femur.

Abstract:Objective:To investigate hemorheological characteristics of patients with cervical symdrom.Methods:Indexes of hemorheology of patients were measured and then its abnormality of hemorheological indexes characteristics were analyzed.Results:In male patients,the indexes of k values,ESR,HCT,η b ,η p ,η r and EPT were higher than those of normal controls(p<0.01).In female patients,the indexes of ESR,K values,FIB,η p get the same results as male patients.(p<0.01).Conclusion:the abnormality of hemorheological characteristics is one of the primary causes that arouse or aggravate cervical symdrom.

Abstract:Objective:To know the biomechanical properties of five techniques of internal fixation of absorbable suture cer-clage with an anterior tension band in the treatment patella fracture.Methods:20flesh cadaveric knee joint specimens were divided into5groups randomly and transversal osteotomies of the patella were performed.The simulated fractures were fixed with the absorbable suture cerclage with and anterior tension band,cerclage wire,Magnuson's wire,AO tension band and Weber's modified tension band,respectively.The biomechanical prop-ertres of the techniques were evaluated by the KJ-20biomechanical testing machine.Results:All techniques functioned well and satisfied1KN tensile force of the quadriceps.The biomechanical properties of the ab-sorbable suture cerclage with an anterior tension band technique performed well and there are no significant dif-ferences(P>0.05)as comparing with other techniques.Conclusion:The absorbable suture cerclage with an anteri-or tension band technique has good biomechanical properties and stability between the fracture fragments with no need for a second operation to remove the implants after bone union.It enlarges the indications of the internal fixation of patella fractures and can avoid the unwanted patellectomy.

Abstract:Objective:The biomechanical properties of new type interlocking compression nail(NLN)and auto-branching in-terlocking compression nail(ALN)were compared to give us scientific evidences for clinical application.Methods:8pairs of fresh adult femora were used and fixed with these2instruments and plum-shaped intramedullary nail and C-K nail and biomechanical properties were compared.Results:The auto-branching interlocking compression nail is the best in the biomechanical properties compared with other devices(p<0.05).Conclusions:The Auto-branching Iterlocking compression Nail is better than other instruments because of better biomechanical properties and less no stress-shielding.It's a good device of the internal fixation of the unstable fracture of femoral shaft.