Abstract:We have little information on the fatigue strength of a compression plate in fixation of a fracture under weight-bearing.Seven models of femoral shaft fractures were prepared with 3 pairs of fresh adult cadaver femora and fixed with the trapezoid compression plates. The strain gauges were placed at the edges of the central screw holes on the surface of the plate.In combination with the simulation electric measurement and the fatigue calculation,it was suggested that losing the stability of a fracture was the internal factor cutting down the fatigue strength of the plate. The fractured fragments should be fixed stably and the functional exercises should be directed reasonably by the safety factor of the plate, which may be helpful to improve the safety of applying the plate.

Abstract:This paper concentrated on the experimental study of mechanical properties of cranial bone.Statistical correlations of properties have been made with apparent density, ash density. This study can provide basic data for the head injury obeserve and research reference only.

Abstract:In order to evaluate the biomechanics effectiveness of Anterior Tibial Tubercle Advancement (ATTA), we measured the contact site, contact area and stress distribution of the patellofemoral joint before and after ATTA procedure in eight fresh human cadaver knee joints with the Fuji Pressure Sensitive Film and the dyeing method. The result shows that the habitual contact site transfer from inferior to superior site after ATTA, which will prevent cartilage lesion site from stress extrusion and concentration, and perhaps reduce or relieve the patellofemoral pains. An assumption of "the patellofemoral pains caused by stress concentration at chondromalacia site" was thus proposed for above finds. after ATTA, the patallofemoral pressure was decreased only in 30°to 60°of knee flexion and became uneven or local high pressure in large degree of knee flexion. The contact area of patellofemoral joint was diminished with the increasing of knee fiexion. The tendofemoral contact appeared advancely at 60°of knee flexion after ATTA, which will affect the biomechanical behavior of patellofemoral joint.

Abstract:This study was designed to monitor localized muscular fatigue with the power spectrum medium frequency of surface myoelectric signal, and test the muscular fatigue of body bices. While sustaining constant force, isometric muscular contraction, the initial past decreasing rate of medium frequency curve, the absolute value of the fitting straight line slope, was increased with the degree of the muscular fatigue. With this rate, it was possible to quantitatively judge the state of the muscular fatigue, reduce the physical consumption and muscular uncomfort of recipients.Monitored parameters were acquized from surface myoelectric signal, reallzing the nonvasive in the monitoring process.

Abstract:This paper has constructed a viscoelastic biomechanical model of the intervertebral disc. In this model, the author takes into account both viscoelasticity of the disc and action of the ligaments,and derives viscoelastic stress and radial bulge formulas when disc is subjected to a constant compression by using linear viscoelastic thoery, and anlyses the distribution of stress and radial bulge in healthy, consolidatory ligaments, degenerated and herniated disc.The computation results coincide with experimental data, and indicate that the maximal initial hoop stress is a major factor that causes dmc injury.

Abstract:This paper reports six young male human cadaver femoral cortical bone 36 specimens in a direction transverse to the long axis of the bone and 36 specimnens in a direction parallel to the long axis of the bone compressive test. The results are that the elastic modulus, yield strength, ultunate strength and yield strain in a direction. parallel to the long axis of the bone is much greater than that in a transverse direction to the long axis of the bone. Their rates are 1.57,1.88,1.35 and 1. 48 respectively(P<0.0001).Statistical analysis, the energy absorption value in a direction parallel to the axis of the bone is significant higher than that in a direction transverse(P<0.05).This supported that human femoral cortical bone is anisotropic heterogeneous material. It supplies a significant data for the clinic.

Abstract:A three-dimensional finite element model has been developed on the anatomic basis of a crown-defected maxillacy central incisor and its casting core. According to the prepared root canal whose diameter is 1/4,1/3 and1/2 wide of the root,three core patterns are devised.Stresses data and distribution are given when the model with vertical or 45 angle incisalgingival loading,The results show that it is ofthe most suitable pattern when the diamter of the core is 1/3 wide of the root.The neck of the core and the root canal wall have more tensile and compressive stresses.The maximal stress of a model with vertical loading is less than with 45 angle incisal-gingival loading.

Abstract:The purpose of this experiment was to find out the three dimensional motion of lumbar spinal various conditions after multiple-segmental segimple total laminectomies and to answer some questions which have not been clear yet about lumbar spinal instability on biomechanics.We also want to get the reliable scientific data for selecting operations,improving surgical techniques,increasing the good outcome,reducing operative complications.Then we collected these data to esta blish the mathematical-biomechanical model of the lumbar spine.

Abstract:Beware of three-dimensional motion change on Occipito-atlanto-axial joint complex following the fractures of the dens is very important for selecting treatment methods.The purnose of this in vitro study was to quantitatively determine e three-dimensional motions of the Occiputo-C:and C1-C2 oints.Eleven Occipito-atlanto-axial complex of fresh cadaveric specunen were studied,using the three-dimensional spinal montion measure and analysis system to document their physiological three-dimensional six degree of freedom rotation movements.An osteotomy at the base of the dens was performed.Pure movements of a maximum of 1.53N.m were applied,each movement was applied individually and in three load/unload cycles. Parameters of neutral zone,elastic zone and range of motion were computed.We found that their ranges of three-dimensional rotation and their neutral zones increased at different degrees after the dens fractured,and so did their coupling motion;but only were ranges of the main motion for left/right axial rotation and fiexion significantly increased,and coupling rotation motion when accompanied with main motion of flexion/extension and left/right lateral bending.

Abstract:Plating of fractures results in osteoporosis beneath the plate because of the stress-shielding effect,so we designed a new plate system with a washer inserted between screw hole and screw. This study was performed to analysis the reaction of bone-plate system to cyclic vertical compressive loading.The in vitro experiment demonstrated that the new plate fixed to a osteotimized stimulant bone loosened due to fatigue damage of washer materials and thus decreased its stress-shielding rate with cyclically loaded l0 times. While the new plate-undrplate construct didn’t fail early with cyclically loaded 10 times before early fracture union culd occur. The investigation showed that the new plate system provided strong initial fixation and gradually loosened with cyclic loading in vitro and therefore should decrease the stress-shielding effect when applied in vivo.

Abstract:The stress change was tested of Luschka joints under axial load after partial cervical discectomy in fresh male cadavers with 12 functional spinal units. We putted the pressure sensitive film of excessive low-pressure into Luschka joints to test the change under the axial load of 39.2N,49N and 58.8N orderly. The data wae calculated by EPD 301 concentration meter and EPD-302.pressure-scale lneter.The results showed that cervical discs beared the load of axial pressure physically,but Luschka joints did it little;Compressive stress in Luschka joints increased statistically because of narrow intervertabra causing new stress distributuion after panial discectomy(P<0.01).The result suggest physical function of the discs be important, It is an important subject how to reconstruct discs function, matain cervical intervertebra height and cervical spinal stability.

Abstract:Three-point bending test was carried out to determine the femoral load-deformntion curve when the SD rats'bilateral ovariectomies were performed six months ago. Compared to stham-operated control rats,the breaking stress indicating the biomechanical propery of femoral material was significantly decreased,the maximum lood reflecting was slightly diminished.The results show:(1)the biomechanical property of ovariectomized rats femora material was significanthy impaired.(2)attributed to the superior change of geometric configuration,the biomechanical quality of femoral diaphysis has no apparently change.

Abstract:This paper gives a concise investigation of offline signal sampler(inventing Patent number 89105489.3)and a example of its application. We mainly introduce how to sample various curve,signals which were depicted on the tracing paper into computer precisely,Afterwards,applying our developed softwares to process these discrete signals,and to extract various characteristic information for some application;We have carried out the samling analysis of cardiac function signals as a example of its application.