2000, 15(4):193-198. DOI: 10.3871/j.1004-7220.2000.4.198.
Abstract:Purpose: To establish a simple mathematical model for investigating the mechanism of frequency components in cardiovascular variability. Methods: A close-loop model involved in hemodynamic and autonomic systems was developed. Three peaks of very low frequency(VLF), low frequency(LF) and high frequency(HF) were simulated successfully. The frequency of HF is determined by the ratio of respiratory frequency and heart rate. The results also indicated that nonadditivity of heart rate modulation by sympathetic and parasympathetic efferents may play an important role in mechanism of LF and VLF generation.
2000, 15(4):199-203. DOI: 10.3871/j.1004-7220.2000.4.203.
Abstract:Stem tip callus of chrysanthemum treated with mechanical vibration grow more rapidly than non-treatment callus in vitro. Mechanical vibration treatment enhances the nutriment such as P, K, Ca, Mg element absorption rate of callus in culture. In our experiments we found an optimum frequency, the absorption rate is the highest in this frequency. However, with the frequency increasing, the absorption rate begins to decrease. It is shown that the mechanical vibration has the bidirectional effect. In order to explore the mechanism of the biological eftects caused by mechanical vibration, We studied the distribution of Ca2+ sediments with in cells by electron microscopy and found the Ca2+ distribution was notably different between the control group and treatment groups. In this paper, we also preliminarily approach the mechanism of callus proliferation by mechanical vibration.
2000, 15(4):204-207. DOI: 10.3871/j.1004-7220.2000.4.207.
Abstract:Objective: To the effect of external counterpulsation on arterial shear stress in acute ischemia dpgs. Methods: Blood flows were measured at the arteria carotics, truncus brachiocephalics, thoracic aorta and desending aorta for chest-open dogs on the condition of pre-ischemia, one hour after ischemia, two hour after ischemia, one hour after EECP and two hours after EECP, shear stress were operated. The statistic results show that myocardial ischemia make phasic characteristics of shear stress fallen and EECP phasic characteristics of shear stress increased.
2000, 15(4):208-211. DOI: 10.3871/j.1004-7220.2000.4.211.
Abstract:The purpose of the study is to analyse the biomechanical effects of the maxillary protraction from different directions by the three-dimensional finite element model of a young people's craniofacial skeleton with maxilla retrusion and skeletal class Ⅲdiscrepancy.
2000, 15(4):216-221. DOI: 10.3871/j.1004-7220.2000.4.221.
Abstract:PURPOSE: To investigate the stress distribution patterns at the bone interface around dental implants. MATERIALS AND METHODS: Using three-dimension finite element method and multivariate step regression analysis, authors analyzed influencing factors on the stress distribution patterns at the bone interface based on the stress magnitudes surrounding dental implant neck. RESULTS: Finding the vital influencing factors of stress distribution patterns at the bone interface around dental implants, obtaining the regression equation, revealing the quantity's relation between the varieties' factors and the stress distribution patterns at the bone interface around dental implant neck. CONCLUSIONS: Cantilever, superstructure bar connecting with the implants and loading angles were the vital important factors of influencing the stress magnitudes at the bone interface around dental implants. When implanting a dental fixture the loading angles were the most important one influencing the stress magnitudes at the bone interface.
2000, 15(4):222-226. DOI: 10.3871/j.1004-7220.2000.4.226.
Abstract:Objective: The purpose of this study is to evaluate methods of primary repair of flexor tendon inzone Ⅱd morphologically and biomechanically.Materials and Methods: Twenty-four white Leghorn chickens were divided into 2 groups. The longtoes of each side were assigned for following procedures separately: (1) Group A: On the left side,the FDS and FDP tendons in zone Ⅱd were repaired after tendon transection. On the right side,only the FDP tendon was repaired. (2) Group B: The FDS and FDP tendons were transected with the epitenon and tendon gliding floor damaged. Tendon repair was the same as in group A. Six weeks later, tendon excursion, work of flexion of the toe and extent of.adhesion were evaluated.Results: In group A, there were no significant differences between the two experimental sides. In group B, excursion of the FDP tendon on the left side was less than that on the right side, and work of flexion of the toe and extent of adhesion on the left side were larger than that on the right side significantly (p＜0.05).Conclusions: This experiment demonstrated that the FDS and FDP tendons in zone Ⅱd should berepaired after they were transected, and when severe injuries of the tendons presented, the FDPtendon should be repaired with the FDS tendon partially resected.
2000, 15(4):227-232. DOI: 10.3871/j.1004-7220.2000.4.232.
Abstract:Objectives: In order to provide the scientific base for clinical application of multi - function femoral plate(MFFP), we studied the MFFP system on supracodylar fracture and intercondylar fracture of femur and we compared the advantages and disadvantages of the different kinds of internal fixations to the MFFP system. Methods: Twelve femoral condyles of fresh cadaver were measured and analysed the biomechanical performances of the MFFP system and the other internal fixations. Results: The results show that the MFFP system is prior to dynamic condylar screw, L-steel plate and the other internal fixations, because the stress and the strength of the MFFP system is more different than the others. The experimental and theoretical results show that the stress of intercondylar process become bigger, the stress of femoral shaft become greater and the separate displacement of intercondyle become smaller. Conclusions: The MFFP system has following advantages. It has proper design, fitting humans biomechanical performances effctive ability on the anti-rotation and being easy to insert. The MFFP system was used on twelve supracodylar fracture and intercondylar fracture of femur. The result was shoued that the ratio escellent and good results was 96.8% and that all cases were cured and no complication. The result was showed that MFFP system oh supracodylar fracture and intercondylar fracture of femur was an excellent internal fixation. Therefore, it is worth popularizing.
2000, 15(4):233-236. DOI: 10.3871/j.1004-7220.2000.4.236.
Abstract:Object: To study the effect of Resection of the facets and discs on the lumbar Stability in lumbar disc protrusion. Method: Lumbar specimens from eight fresh cadavers were biomechaniclly analysed and compared in flexion, extension and left and right lateral bendings. There was a variety of stability after L4-5 bilateral graded facetectomy. Result: The decompressed recess with resection of a half of the processes in lumbar disc protrusion was significantly different from the normal subjects in the stress, the displacement and ROM(P<0.05). Conclusion: (1)The ertent of resection to the decompression of the recess is completely enough in the treatment of lumbar disc protrusion. (2)If facetectomy of a half of the processes is needed, there an internal fixation should be added.
2000, 15(4):237-241. DOI: 10.3871/j.1004-7220.2000.4.241.
Abstract:Purpose: To investigate the axis tension-strain relation of femoral arteries and veins in rabbit and to evaluate the particular reference to the option of vascular repair. Methods: A mechanical analysis of stretch experiment was undertaken to evaluate the axis tension-strain relation of femoral arteries and veins in rabbit. Results: In 35.0 mm, the curve regression equation of femoral artery between the tension and the stretch ratio was shown: Fa=0.22(e5.75(λa-1)-1); and the curve regression equation of femoral vein between the tension and the stretch ratio was shown: Fv=6.15 ×10-3(e7.89(λv-1)-1). Conclusion: It suggested to repair the injuried vessel according to the actual defect length and the actual isolated length(AcIL). The length of vein graft (LVG) was shown: (LVG/λv) × λv + (RIL/λa ) ×λa=AcIL,RIL(Residual isolated length)=AcIL-LVG.
2000, 15(4):250-254. DOI: 10.3871/j.1004-7220.2000.4.254.
Abstract:Objective: In order to provide the scientific bias for clinical application, We analysed the biomechanic of self-designed 3 hollow compression screws+planting a piece of ilium (HSI) on femoral neck fracture (under the head). Method: Through experimental stress analysis on fresh cadaver femoral samples. Cure femoral neck fracture (under the head) with 3 hollow compression screws+planting a piece of ilium(HSI), compare this method with that by using 3 hollow compression screws only (HS) and observe the differences in biomechanical performance between these two internal fixation methods. Results Experimental results showed that there is no obvious difference in biomechanical performance between HSI method and HS method. 13 clinical practices have proved that to cure femoral neck fracture by using HSI method will not result femoral head necrosis(at least it has not happened yet). Conclusion To cure femoral neck fracture(under the head) by using HSI method is a very effective new method.
2000, 15(4):255-257. DOI: 10.3871/j.1004-7220.2000.4.257.
Abstract:The aim of this study is to evaluate the effect of immobilization at different angles on the mechanical properties of rabbit Achilles tendon. The left hindlegs were immobilized with knee in extension, ankle either in extension or plantar flexion 90°. After 4 weeks, the exponential functions, stress-strain curves of Achilles tendon were compared between different groups. The results showed that compared with normal group, the stress-strain curves and material constants of Achilles,tendon were different significantly in either immobilized-I group or immobilized-Ⅱ group, but there were no significant difference between these two immobilized groups. From these findings, we concluded that static stress could not prevent the changes of mechanical properties of Achilles tendon induced by immobilization.