ABSTRACT
Treating an abdominal aortic aneurysm (AAA) with a stent graft (SG) and a multilayer stent (MS) is a key technology in isolating flow fields. Clinically, dual stents (an SG in the proximal and an MS in the distal of AAA) are used for treatment of AAA, but only a few studies have examined the relationship between SG coverage and treatment effects. Through numerical simulation of the hemodynamics after SG and MS implantation, the SG coverage and position were simulated at 0% (0 mm), 25% (13.75 mm), 50% (27.5 mm), and 75% (41.25 mm). With increasing SG coverage, the pressure on the aneurysm sac wall and the flow of branch vessels gradually decreased, and the lower wall shear stress (WSS) gradually increased. The changes in pressure, lower WSS, and the mass flow rate of the branch vessels did not change significantly. The coverage of the SG has a nonsignificant effect on hemodynamics in the treatment of AAA; the implantation position need not be very precise. This research can provide theoretic support for clinicians' decision-making.
Subject(s)
Aortic Aneurysm, Abdominal/therapy , Stents , Aortic Aneurysm, Abdominal/physiopathology , Hydrodynamics , Models, Theoretical , Pressure , Shear Strength , Software , Stress, Mechanical , Treatment OutcomeABSTRACT
Muscle atrophy of the residual limb after lower-limb amputation is a disadvantage of amputees' rehabilitation. To investigate the biomechanics mechanism of muscle atrophy of the residual limb, we built a finite element model of a residual limb including muscle, skeletons and main vessels based on magnetic resonance images of a trans-femoral amputee, and studied the biomechanics effects of the socket of the lower-limb prosthesis on the soft tissue and vessels in the residual limb. It was found that the descending branch of the lateral femoral circumflex artery suffered the most serious constriction due to the extrusion, while that of the deep femoral artery was comparatively light. Besides, the degree of the constriction of the descending branch of the lateral femoral circumflex vein, femoral vein and deep femoral vein decreased in turn, and that of the great saphenous vein was serious. The stress-strain in the anterior femoral muscle group were highest, while the stress concentration of the inferior muscle group was observed at the end of the thighbone, and other biomechanical indicators at the inferior region were also high. This study validated that the extrusion of the socket on the vessels could cause muscle atrophy to some degree, and provided theoretical references for learning the mechanism of muscle atrophy in residual limb and its effective preventive measures.
ABSTRACT
The phenomenon of sex differences exists in patients who have abdominal aortic aneurysms (AAA). The occurrence rate of AAA is higher in male, while the rates of rupture and postoperative mortality are higher for female. This phenomenon of sex differences would affect the diagnosis, treatment and postoperative rehabilitation for AAA patients. This article reviewed the recent research status of sex differences on AAA, and explored the phenomenon of sex differences from the aspects of threshold determination, biomechanics and mechanobiology. This review points out that the sex differences on AAA could ascribe to the differences of biomechanical environment and biological properties induced by the vascular size, anatomy structure and structure components of abdominal aortic artery. The comprehensive investigations of the sex differences on AAA could help to optimize the diagnosis, treatment and device design, patient care and rehabilitation strategy of AAA based on sex differences phenomenon.
