A vein model was established to simulate the periodic characteristics of blood flow and valve deformation in blood-induced valve cycles.Using an immersed finite element method which was modified by a ghost fluid techn...A vein model was established to simulate the periodic characteristics of blood flow and valve deformation in blood-induced valve cycles.Using an immersed finite element method which was modified by a ghost fluid technique,the interaction between the vein and blood was simulated.With an independent solid solver,the contact force between vein tissues was calculated using an adhesive contact method.A benchmark simulation of the normal valve cycle validated the proposed model for a healthy vein.Both the opening orifice and blood flow rate agreed with those in the physiology.Low blood shear stress and maximum leaflet stress were also seen in the base region of the valve.On the basis of the healthy model,a diseased vein model was subsequently built to explore the sinus lesions,namely,fibrosis and atrophy which are assumed stiffening and softening of the sinus.Our results showed the opening orifice of the diseased vein was inversely proportional to the corresponding modulus of the sinus.A drop in the transvalvular pressure gradient resulted from the sinus lesion.Compared to the fibrosis,the atrophy of the sinus apparently improved the vein deformability but simultaneously accelerated the deterioration of venous disease and increased the risk of potential fracture.These results provide understandings of the normal/abnormal valve cycle in vein,and can be also helpful for the prosthesis design.展开更多
Objective： To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint （AAOJ） arthroplasty by comparing with a conventional method. Methods： Afte...Objective： To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint （AAOJ） arthroplasty by comparing with a conventional method. Methods： After anterior decompression, 24 human ca- daveric spinal specimens of C0-C3 were randomly divided into two groups： Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw （ATAS） fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation. Results： Compared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a sig- nificant decrease in the range of motion （ROM） and neu-tral zone （NZ） during flexion, extension and lateral bending （P〈0.05）; however, with regard to axial rotation, there was no significant difference in ROM and NZ （P〉0.05）. Com- pared with anterior decompression with ATAS fixation, an- terior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant differ- ence was found in ROM and NZ （P〉0.05）; however, as for axial rotation, there was a significant increase in ROM and NZ （P〈0.05）. Conclusion： The self-designed AAOJ has an excellent biomechanical performance, which can restore excellent in- stant stability and preserve the movement of the atlanto- axial joint.展开更多
基金by Key Aviation Scientific and Technological Laboratory of High-speed Hydrodynamic under grant MJ-2015-F-028.
文摘A vein model was established to simulate the periodic characteristics of blood flow and valve deformation in blood-induced valve cycles.Using an immersed finite element method which was modified by a ghost fluid technique,the interaction between the vein and blood was simulated.With an independent solid solver,the contact force between vein tissues was calculated using an adhesive contact method.A benchmark simulation of the normal valve cycle validated the proposed model for a healthy vein.Both the opening orifice and blood flow rate agreed with those in the physiology.Low blood shear stress and maximum leaflet stress were also seen in the base region of the valve.On the basis of the healthy model,a diseased vein model was subsequently built to explore the sinus lesions,namely,fibrosis and atrophy which are assumed stiffening and softening of the sinus.Our results showed the opening orifice of the diseased vein was inversely proportional to the corresponding modulus of the sinus.A drop in the transvalvular pressure gradient resulted from the sinus lesion.Compared to the fibrosis,the atrophy of the sinus apparently improved the vein deformability but simultaneously accelerated the deterioration of venous disease and increased the risk of potential fracture.These results provide understandings of the normal/abnormal valve cycle in vein,and can be also helpful for the prosthesis design.
基金The program was supported by Medical Research Found of Zhejiang Provincial Health Department，Ningbo Natural Science Foundation
文摘Objective： To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint （AAOJ） arthroplasty by comparing with a conventional method. Methods： After anterior decompression, 24 human ca- daveric spinal specimens of C0-C3 were randomly divided into two groups： Group A receiving artificial AAOJ arthroplasty; Group B experiencing anterior transarticular screw （ATAS） fixation. Two groups underwent flexibility test in intact and instrumented states. Rotational angle of the C0-C3 segments was measured to study the immediate stability and function of anterior decompression with AAOJ arthroplasty compared with the intact state and ATAS fixation. Results： Compared with the intact state, anterior decompression with AAOJ arthroplasty resulted in a sig- nificant decrease in the range of motion （ROM） and neu-tral zone （NZ） during flexion, extension and lateral bending （P〈0.05）; however, with regard to axial rotation, there was no significant difference in ROM and NZ （P〉0.05）. Com- pared with anterior decompression with ATAS fixation, an- terior decompression with AAOJ arthroplasty during flexion, extension and lateral bending, significant differ- ence was found in ROM and NZ （P〉0.05）; however, as for axial rotation, there was a significant increase in ROM and NZ （P〈0.05）. Conclusion： The self-designed AAOJ has an excellent biomechanical performance, which can restore excellent in- stant stability and preserve the movement of the atlanto- axial joint.
