2002, 17(3):129-133. DOI: 10.3871/j.1004-7220.2002.3.133.
Abstract:Objective In order to solve the problem that only one kind of shear stress values could be observed during each parallel-plate flow chamber (PPFC) experiment, a kind of new PPFC - Two-Dimensional Bifurcation Parallel-Plate Flow Chamber (TDBPPFC) is proposed. Methods The distributions of the velocities inside and the shear stresses at the bottom of the chamber are given by computational simulation with laminar flow in the TDBPPFC. Results The results show that the mechanical behaviors of cultured cells undergoing the shear stresses with various values may be simultaneously observed by using this kind of new flow chamber. Conclusion These results possessed practical importance in optimum design and rational use of the TDBPPFC. And it was also helpful in analyzing the mechanical behavior of the cells and in discussing the effects of the shear stress distribution on the cells in the TDBPPFC.
2002, 17(3):134-136. DOI: 10.3871/j.1004-7220.2002.3.136.
Abstract:Objective To discuss the biomechanical mechanism of clinical representation of gluteal muscle contracture (GMC). Methods Gluteal muscle contracture strips (GMCS) and normal gluteal muscles (NGM) were made into fasciculi. Then the biomechanical character of the specimens were measured on MTS machine.Results The elastic modulus of GMCS is averaged 2.732 N/mm 2, the maximum intension of GMCS is averaged 148.32MPa, and the maximum strain of GMCS is 0.896. In NGM, the elastic modulus is averaged 0.143N/mm 2, the maximum intension is averaged 10.50 MPa, and the maximum strain is 1.434. The difference between elastic modulus and maximum strain of GMCS and those of NGM was great (P<0.05), and the difference between maximum intension of GMCS and that of NGM was significant great (P<0.01). Conclusion The intention and rigidity of GMCS increase greatly than those of NGM. This is the biomechanical foundation for GMC in clinical representation.
2002, 17(3):137-140. DOI: 10.3871/j.1004-7220.2002.3.140.
Abstract:Objective The bond effect of the fluoride-releasing orthodontic adhesive was studied in vitro. Methods To test and compare the shear bond strength and the penetration depth of resin tags of fluoride-releasing orthodontic adhesives with those of the traditional orthodontic adhesive.Results There are no significant statistically differences between fluoride-releasing orthodontic adhesive and the control (nonfluoride) in shear bond strength and penetration depth of resin tags. Conclusion There are no significant statistically differences between fluoride-releasing orthodontic adhesive and the control (nonfluoride) in bond effect.
2002, 17(3):141-146. DOI: 10.3871/j.1004-7220.2002.3.146.
Abstract:Objective To study the stress-strain properties of intestine in vivo. Methods The segments from distal ileum were studied in 16 female Wister rats with 10 rats in in vivo group and 6 rats in in vitro group. Papaverine was injected into the peritoneal cavity to relax the intestine. The pressures were applied from zero to 8 cmH 2O with 1 cmH 2O stepwise. After finishing the distension test, tissue rings and strips were cut from the segments for acquiring the no-load and zero-stress state. The stresses and strains were computed using the definitions by Kirchhoff and Green according to the morphometric data obtained from the photographic images. Results (1) The circumferential and longitudinal stress-strain curves both in vivo and in vitro fitted well to mono-exponential function: τ=(τ *+β)e α(ε-ε *) -β (determination coefficients>0.96). (2) The stress-strain curves in circumferential direction shifted to the right compared to the curves in longitudinal direction. The curves in vivo were steeper than the curves in vitro both in circumferential and in longitudinal directions. (3) Comparing the stress-strain curves with the zero-stress state as reference, the curves referenced to the no-load or zero-pressure state shifted to the left in circumferential direction and to the right in longitudinal direction. The differences between the curves were significant (P<0.05). Conclusion (1) The ileum in vivo showed a high degree of non-linearity and anisotropy. The intestine was stiffer in vivo than in vitro, and stiffer in longitudinal direction than in circumferential direction. (2) It is important to use zero-stress state as the initial reference for the stress-strain analysis.
2002, 17(3):147-150. DOI: 10.3871/j.1004-7220.2002.3.150.
Abstract:Objective To study the fracture mechanism of calcaneus. Methods To analyze the stresses in calcaneus by using bending strength theory, shearing strength theory and main main stress theory in mechanics of materials, to study the shocking loads of calcaneus by using momentum principle, and to determine the destructive load of calcaneus through the static pressing experiment.Results The part in calcaneus around the wedged cave was the weakest part; the destructive load of calcaneus was about 24 times of the body weight; when a person jumped down from the height 1.5 meters to the ground, the shocking loads acted on the calcaneus were 36 times of the per son's weight. Conclusion When a person jumped down from a high place and his heel contacted the ground first, the shocking loads acted on the calcaneus could be very large; in addition, the initial velocity of the person had a great influence on the shocking loads acted on the calcaneus.
2002, 17(3):151-155. DOI: 10.3871/j.1004-7220.2002.3.155.
Abstract:Objective To study the effectiveness of CFEFD, on the treatment of calcaneal fracture to provide the reliable theoretical basis for clinical operations. Methods Seven fresh specimens of adult lower limb heels were collected for experimental stress analysis to establish experimental mechanics modeling. To compare the biomechanical properties between the normal human calcaneus heel bones and those of calcaneal fracture, by using CFEFD. Results The experimental results show that there is no significant difference (P>0.05) in biomechanical properties, bearing capacity, stress of calcaneus heel bones, displacement of instep, and other aspects for posterior bones between the calcaneal fracture with the adjustable external fixation device and the normal human calcaneus heel bones. The rigidity of this device is found to satisfy the design requirements. Conclusion This device is not only able to satisfy the biomechanical requirements for calcaneus heel bones with its endurable strength, strong bearing capacity and favorable reliability in the treatment of calcaneal fracture, but also safe and easy to use, and proves to be one of the best medical apparatuses deserving the popularization in the medical applications.
2002, 17(3):156-158. DOI: 10.3871/j.1004-7220.2002.3.158.
Abstract:Objective An analysis on the relation between the arterial branching angles and branch radii has been performed in detail. Methods Basic biomechanical principles are used in the analysis. Results The branching angle θ depends on the ratio of r/r 0:r is the radius of daughter blood vessel and r 0 is the radius of parent blood vessel. Their relation is cosθ=r/r 0. The average velocity of blood flow in any segment is proportional to r, and υ=υ 0 cos θ, where υ is the average velocity of blood flow in the daughter vessel and υ 0 is that in the parent. The smaller the daughter vessel radius, the lower the hematocrit in it, thus explaining the plasma skimming effect.Conclusion The cardiovascular system is not only a blood transport organ, but also a distribution system of blood flow and red blood cells
2002, 17(3):159-164. DOI: 10.3871/j.1004-7220.2002.3.164.
Abstract:Objective Two-dimensional symmetrical models are used to simulate the steady flow in the AAA models.Methods A commercial CFD software FLUENT v4.3.2 is used for the flow simulation of AAA models.Results The velocity vectors,streamlines,wall shear stresses and pressure drops in AAAs are examined.Reynolds number and diameter ratio which affected the flow pattern and wall shear stress in the aneurysm are dealt with.Conclusion The results show that the shape of AAA and the D/d ratio have little effect on the flow patterns but the increases of Reynolds number would strengthen the vortex within the AAA.
2002, 17(3):165-168. DOI: 10.3871/j.1004-7220.2002.3.168.
Abstract:Objective The purpose of this study was to investigate the effects of periostitis of tibia on bone remodeling .Methods The rabbits were put in an electric cage with pulsed high voltage, which made the rabbits jumping and running for 60 min. per day for 1～6 weeks. The histologic, radiologic and computed image analysis methods were used to detect the sectional charactesistics of the tibia. Results and conclusion The analysis results show that the periostitis can help to remodel the tibia to adapt the intensive exercise.
2002, 17(3):169-173. DOI: 10.3871/j.1004-7220.2002.3.173.
Abstract:Objective To establish a new model of cardiac rhythm. Methods Two Hodgkin-Huxley equations are used to simulate the potential of SA node and AV node, and to describe the regular pattern of cardiac rhythm. Results It has been found out that the results of the model analysis are similar as the actual situation on the influence of external stimulus and ions to the cardiac rhythem.Conclusion This mathematics model can describe the change of cardiac rhythm. The structure of the model is clear enough and the data have some physiological meaning.
2002, 17(3):174-177. DOI: 10.3871/j.1004-7220.2002.3.177.
Abstract:Objective To design a type of intervertebral manual joint with grooving spring and analyse its mechnical analysis. Methods The joint consists of two parts: cage and internal nucleus. The cage with flat olive bore looks similar to the contour of the Ray-TFC, and has grooving spring on lateral sides. The internal nucleus also looks like flat olive in appearance but little smaller than the bore. After the insertion of the internal nucleus into the bore, the analogous motion of flexion, extension and lateral bending could be achieved through the stretching of the spring and the minute sliding of the nucleus. The intensity and fatigue tests then were carried out on MTS 858 machine. Results The results of intensity test proved that when the pressure reached to 130N, the cage still remained intact, and the spring was reduced 0.70mm . The fatigue test shew that there was no damage caused to the joint after 1×10 5 stress circulations in four days. Conclusion This type of manual joint may replace cervical disc well.
2002, 17(3):178-182. DOI: 10.3871/j.1004-7220.2002.3.182.
Abstract:Objective To study the anti-twisting biomechanical properties of two new type interlocking intramedullary pin so as to provide some scientific theory for clinical application. Methods To collect four fixed damp femurs of adult cadaver , and engaged in experimental stress analysis. The anti-twisting biomechanical properties of two new type interlocking intramedullary pins fixed into the fractured shaft of femur were determined and compared them with those of Plum Blossom Nail. Results The tests of biomechanics indicated that the anti-twisting intensity and rigidity of Expansive Screw Type self-locked intramedullary pin are 2 times and 1.6 times of those of the Plum Blossom Nail, while those of Partiality Bolt Locked interlocking intramedullary pin are 1.6 times and 1.5 times compared with the Plum Blossom Nail. but only the 30% of those of integrity bone.Conclusion Both two new type interlocking intramedullary pins can gratify the demand of biomechanics. So they can serve stable or unstable fracture in the isthmus or excluding isthmus of shaft of femur.
2002, 17(3):183-188. DOI: 10.3871/j.1004-7220.2002.3.188.
Abstract:Objective To evaluate the efficacy of the shelf operation using a ilium segment atteched tensor fascia latae and the intertrochanteric osteotomy to cure the congenital dislocation of hip or hip dysplasia patients more than eight years;To establish normal value ranges of biomechanical indexes of normal adults and normal children. Methods Using Legel's mathematical model ,the standard pelvic X-rays of normal adults?normal children? hip displasia patients and postoperation was measured and calculated. Results 15 years′ fellow-up and the results of the mathematical analysis proved that the operation can improve the biomechanics of the patients' hip joints. The operation also accords with biomechanical principles. Conclusion Operateional method should be selected flexible according to the biomechanical principles and the patients conditions.