Effects of Aneurysmal Neck Angle on Stent Displacement after Endovascular Repair of Abdominal Aortic Aneurysm / 医用生物力学

Objective To study the effects of aneurysmal neck angle on stent displacement after endovascular repair of abdominal aortic aneurysm (AAA). Methods The CT images of 28 patients were selected to establish preoperative AAA model, postoperative AAA model and covered stent model respectively, and the models were divided into non-severe angulation group ( n = 14) and severe angulation group ( n = 14) according to the preoperative angle of tumor neck. The geometric shape of each model was measured, and the changes of AAA geometric parameters and postoperative stent displacements before and after surgery were analyzed. The displacement force of the model during the first follow-up was calculated by hemodynamic simulation. Results Significant differences were found in tumor length, maximum diameter, displacement force, tumor neck length and tumor volume between two groups of patients (P 0. 05). For the incidence of internal leakage, there were 2 cases in non-severe angulation group and 4 cases in severe angulation group (P>0. 05).Conclusions Severe neck angulation can lead to a significant increase in support displacement force and decrease in proximal anchorage zone, and thus increase the possibility of support displacement. It is suggested that doctors should strengthen postoperative follow-up for patients with severe neck angulation and be vigilant of the occurrence of long-term internal leakage in clinic.

Research on solid shell element based on penalty method.

Since the angle degrees of freedom do not have the vector property, it is critical to handle this for nonlinear geometrical behavior. To simulate the nonlinear geometrical behavior of shell structure efficiently, we developed a solid-shell element type without drilling degrees of freedom. In this paper, the element satisfies the assumption of the straight normal of the shell and we established penalty functions in the thickness direction of the shell. The formulations of equivalent node force and tangent stiffness obtained by 3D isoparametric element theory can be expressed by matrix forms clearly. The constitutive relationship in the global system is derived from the local constitutive matrix according to the tensor coordinate transform. Finally, taking a series of classic flat plate problems and curved shell problems as examples, the solid shell element using the penalty method is compared with the solid shell element using the artificial stiffness method and other shell elements. The results show that the solid element proposed in this paper can effectively eliminate shear self-locking after using the reduced integral scheme and obtain satisfactory accuracy for thin shells and medium-thickness•A type of solid shell element without rotational degrees of freedom is introduced using the penalty method.•A suitable penalty factor of this element is determined through numerical experiments.•This element is more efficient than the traditional shell elements and can be programmed with less time.

Biomechanical evaluation and optimal design of two parameters of dental implant with arbitrarily adjusted angles / 中国组织工程研究

BACKGROUND:Oversize stress of a dental implant and its surrounding tissue is the main factor to affect the long-term use of dental implants. So, the reasonable and precise design of implant shape is one of the important methods of prolonging the life span of dental implants. OBJECTIVE:To make the optimal analysis and design of the diameters of connector screw and central screw of the adjustable-angle dental implant invented in the earlier stage. METHODS: The finite element analysis model of the edentulous mandible with adjustable-angle dental implant was established by software Pro/E 5.0, Mimics 10.0 and ANSYS Workbench 14.5. The maximum equivalent stress of dental implant-edentulous mandibular model was analyzed. RESULTS AND CONCLUSION:The maximum equivalent stress of dental implant-edentulous mandibular model