2005, 20(3):143-146. DOI: 10.3871/j.1004-7220.2005.3.146.
Abstract:Objective To study the effects of asymmetrical entry velocity profile on the flow separation in carotid artery sinus. Methods A model of "TF-AHCB" is adopted in an experimental simulation of steady flow recirculation, then flow visualization is realized by dyeing method and velocity profiles of the sections in common carotid artery and in carotid artery sinus are acquired by LDV. Results The results demonstrate that asymmetrical entry velocity profile has an apparent influence on the flow separation in the carotid sinus. The size of the separation zone when the peak of velocity profile deviates outward from the axis about 1/3 of the pipe's radius is as large again as that when the peak of velocity profile deviates inward. Conclusion Effects of asymmetrical entry velocity profile on the flow separation in carotid sinus are so significant that the deviation of the peak of entry velocity profile becomes an important factor influencing the distribution of atherosclerotic plaque.
2005, 20(3):147-151. DOI: 10.3871/j.1004-7220.2005.3.151.
Abstract:Objective To reconstruct the complete biological tissue engineered blood vessels(TEBV)in vitro,the biological change of vascular smooth muscle cells(VSMC) planted on the scaffolds of TEBV and the biomechanics characteristic of the TEBV were investigated. Methods The decellularised scaffolds were obtained from swine common carotid arteries by enzyme digestion. VSMC isolated from dog thoracic aorta were seeded onto the inner surface of scaffolds and they were cultured in vitro for 4w. The change of reconstruction TEBV was checked by histological staining and transmission electron microscopy (TEM) observation. The expressions of smooth muscle-alpha-actin (SMA), platelet-derived growth factor- AA(PDGF-AA) and metalloproteinases-2(MMP-2) in TEBV were also detected by immunohistochemistry staining and image analysis. The thoracic aorta of immature dogs and adult dogs were separately chosen as the controls. The biomechanics characteristic of the TEBV, including rupture intensity, the relation ship of stress and strain, and the loose experiment of TEBV were all tested by INSTRON 1122 electron mechanics test system. Results VSMC gradually proliferated a lot and migrated into scaffolds. There were desmosome and gap conjunction of cells in TEBV cultured for 2 or 4w. The expression level of SMA was higher in TEBV cultured for 2 or 4w than that of the immature dog vessels, but significantly higher than that of the adult dog vessels. The expression level of MMP-2 was higher in TEBV cultured for 2 or 4w TEBV was similar to the one of the immature dog. The stress-strain curve of TEBV showed the characteristic viscoelasticity and the value of strain rate,loosen stress, and rupture intensity of TEBV were similar to that of physiological blood vessels. Conclusions With expressing of more PDGF-AA and less SMA and secreting of more MMP-2, VSMC in complete biological TEBV transformed from contractile phenotype to synthetic phenotype and proliferated and migrated rapidly into scaffolds, which resulted in the TEBV wall remodeling and the biomechanics characteristic similar to that of physiological blood vessels.
2005, 20(3):152-155. DOI: 10.3871/j.1004-7220.2005.3.155.
Abstract:Objective To research the viscoelasticity of the cancellous bones of the OS femoris' upper part of the fresh body of our country and provide parameter of biomass for clinical. Methods The experiment on the extending stress relaxation and creep in directions of vertical vertical. Results By using logarithmic and exponential regression analysis method we obtained the reduced stress relaxation and creep curves. Conclusions The extending stress relaxation grade of the cancellous bones of the OS femoris' upper part is 7 200 s, relaxation is 0.422 MPa, the quantities of creep is 0.784%.
2005, 20(3):159-162. DOI: 10.3871/j.1004-7220.2005.3.162.
Abstract:Objectives Three-dimensional finite element method was applied to analyze the influence of various angled abutments on the distribution of the stress and strain in the implant-bone interface. Methods Thin-slice scanning of spiral computed tomography was applied to construct a three-dimensional finite element model of mandible with dental implants. A simulated force of masticatory muscles was loaded in the mathematical models to analyze the stress and strain distribution in the implant-bone interface by using ALGOR software program, when dental implants were conjunct to straight, 10°.20° and 30° abutments, respectively. Results Numerical and graphic results were generated for Von Mises stress and maximum as well as minimum strains. Von Mises stress occurred predominantly in the cortical bone layer-on the neck of implants, and secondly at the bottom of dental implants. With the angle of abutments added, the positions of Von Mises stress.the maximal and minimal principal strain were all transferred from the neck to the bottom of dental implants. Conclusion There was an increase occurred in the magnitude of stress and strain in the implant-bone interface as the abutment angulation increased. It increased obviously when the denture was produced by 30° abutment.
2005, 20(3):163-168. DOI: 10.3871/j.1004-7220.2005.3.168.
Abstract:Objective To evaluate the stability and compressive mechanical functions of the cervical spine after implanting a new minimally embedded invasive fusion cage made of Nititanium shape memory alloy (NiTi-TFC/C). Method Anterior cervical discectomies were performed on 24 mature sheep spines which were divided randomly into four groups of six sheep cervical spines each: the discectomy group, the autogenic iliac bone graft group, the NiTi-TFC/C group, and the Inter Fix (Sofamor Danek) group. The stability of each group was tested by experimental stress analysis. Result There was no significant difference between the groups of NiTi-TFC/C and Inter Fix in the biomechanical characters (P>0.05). There was significant difference between the groups of NiTi-TFC/C and autogenic iliac bone graft (P<0.05). Conclusion NiTi-TFC/C shows effective characters with high strength and stiffness, less depression displacement. It provides a new kind of device for cervical fusion.
2005, 20(3):169-172. DOI: 10.3871/j.1004-7220.2005.3.172.
Abstract:Objective To reconstruct three-dimensional finite element model with occlusion and bilateral condyles to analyze the regularities of TMJ stress distribution resulting from dental occlusion alteration. Methods A skull was scanned with CT in the direction parallel to the Frankfort Horizontal plane. Occlusion surface of it's plaster casts were scanned with a 3D scanner. The parameters of the cast and CT image were converted into the same coordinate system. A simulated disc was added over each of the condyles. Constraints were applied to the upper surface of the disc and the angle of mandible. Load 1: Onto the different positions of the teeth in half of the dentition, FEM were applied with upright loads. Load 2: Onto three different occlusal areas of the lower second molar, ICO load.distal load.buccal load were applied. The stresses on condyle under each of the conditions above was analyzed. Results 1. The FEM containing bilateral condyles.simulated discs, and dental occlusion was formed to analyze the association of occlusion and TMJ.2. As occlusal load was applied to different teeth on dentition from anterior to posterior, the stress distribution of bilateral condyles were found different and asymmetrical. The lateral, middle, anterior and top area of condyle were found loading with high compression. 3. The morphological features of loading area had effect on the stress characteristics and distribution of bilateral condyles. Loading from distal direction would cause stress concentrating over the medial pole of ipsi-lateral condyle while loading from buccal direction would cause stress concentrating over the medial pole of contra-lateral condyle. Conclusion The distribution of stress over condyles was found changed in response to the alternation of occlusal contact position and direction.
2005, 20(3):173-176. DOI: 10.3871/j.1004-7220.2005.3.176.
Abstract:Objective To study the techniques of cranial flap fixation (suture.stainless steel wire and rivet-like titanium clamp). Methods 24 cadaver craniotomy flaps were divided into three groups, then every eight flaps were reattached with sutures.stainless steel wires and rivet-like titanium clamps respectively. Bone flap fixation was timed and measured for offset with craniotomied skull for every fixation technique, load-bearing tests were performed by applying an external force until failure of the fixation system. The results were compared. Results Rivet-like titanium clamp required signifi cantly less time (94±13)s to fix than either suture (172±14)s or stainless steel wire (399±45)s. Rivet-like titanium clamp also showed significantly smaller offset (0.20±0.12)mm than either suture (2.20±0.24)mm or stainless steel wire (1.32±0.34)mm. Rivet-like titanium clamp was stronger than suture and stainless steel wire. Conclusion Rivet-like titanium clamp is ease to use, require less time consumption, and show accuracy and strength.
2005, 20(3):177-181. DOI: 10.3871/j.1004-7220.2005.3.181.
Abstract:Objective To elucidate the biomechanical foundation of Acetabular Tridimensional Memoryalloy - Fixation System (ATMS) for treatment of acetabular fractures. Methods The experiment consists of two parts, one is to study the stability of the fixed acetabulum posterior wall with ATMS, the other is to research the fitness of the femoral head and the fixed acetabulum as well as the stress distribution. Six fresh pelvis and femur specimens were divided into two groups, the experimental group consists of the left sides, and the control group consists of the right sides. After the fractures of the posterior wall were made, the acetabular fragments were replaced and were fixed by ATMS in the experimental group, whereas fixated by the plates and screws in the control group. A adjustable jig which can be adjusted in multiple directions was made. The specimens were loaded from 100N to 500N in three status: flexion, extension, and erection. The fixation in latitude and longitude of the two groups was compared, and the stability of fixation of posterior wall of the acetabulum was analyzed. The two groups were then loaded to 1000N in erection status. And the pressure-sensitive slices were used to calculate the contact area, the mean pressure and maximum pressure of anterior wall, superior aspect and posterior wall of the acetabulum, and to analyzed the fitness of femoral head and the acetabulum as well as the stress distribution. Results There was no significant difference between the two groups in the different status with different loads. It also showed that when loaded with 1000N, there was no significant difference between two groups in the contact area, mean pressure and maximum pressure of every part of acetabulum. Conclusion Fixation of posterior wall of the acetabulum with ATMS had good stability and good fitness and stress distribution of the femoral head and the repaired acetabulum.
2005, 20(3):182-184. DOI: 10.3871/j.1004-7220.2005.3.184.
Abstract:Objective To explore the diagnostic value of Video electroencephalogram (Video-EEG) monitoring in children epilepsy. Methods Video-EEG monitoring under the state of awaking and sleeping were performed 4-8 hr in 102 epilepsy children. We analysed the relation between clinical seizures and abnormal discharge, observed the phase when abnaomal discharge appeared. Results abnormal discharge were captured in 76 patients (76/102,74.51%), and among the 76 patients, 23 patients had clinical seizures accompanied synchronous abnormal discharge, 53 patients just had interictal epileptiform discharge only, all of them were diagnosed epilepsy according to Video-EEG and case history.Among of them, 52 were focal (52/76,68.42%), and 55 were found in sleeping (55/76,72.37%). 10 patients (10/102,9.80%)were just clinical seizures unaccompanied synchronous abnormal discharge, and these cases were defined nonepileptic seizures. Conclusions Video-EEG can improve epilepsy diagnostic rate, is favourable to localization of epilepsy. Partly sleep deprivation is an effective method to increase detection of epileptiform discharge.
2005, 20(3):185-188. DOI: 10.3871/j.1004-7220.2005.3.188.
Abstract:The utilization of computer-aided technologies in tissue engineering has evolved in the development of a new field of Computer-Aided Tissue Engineering. This article reviews recent development and application of enabling computer technology, imaging technology, computer-aided design and manufacturing, and rapid prototyping technology in tissue engineering, particularly, in computer-aided tissue anatomical modeling, 3D anatomy visualization and 3D reconstruction, CAD-based anatomical modeling, computer-aided tissue classification, computer-aided tissue implantation and prototype modeling assisted surgical planning and reconstruction.
2005, 20(3):189-192. DOI: 10.3871/j.1004-7220.2005.3.192.
Abstract:Objective Osteocytes are the most numerous cells in mature bone .However,study and subsequent understanding of osteocyte biology has been thwarted by the remote location of the cell in the mineralized matrix. This review is intended to synthesize current understanding of osteocyte network that will promote understanding of this obscure cell.
2005, 20(3):193-198. DOI: 10.3871/j.1004-7220.2005.3.198.
Abstract:Cytoskelelon biomechanics has emerged as a new field of cell mechanics. The cytoskeleton modeling is critical for investigating the transduclion and distribution of mechanical forces in cell, which is fundamental to cell function and biochemical events. Cytoskeleton is also the transduction medium of forces and biochemical signals. The applied mechanical forces control the chemical reaction and signal transduction through the interconnected aetin cyloskeletal network. In this paper, we review three major models, approachs and key accomplishments in cytoskeleton mechanics from a mechanical point.