RESUMO
Objective:To evaluate the validity of adventitial collagen cross-linking by glutaraldehyde(GA) to reduce intimal hyperplasia of vein graft in a rabbit carotid artery bypass graft model.Methods:Harvesting 36 segments of the external jugular vein and 6 segments of the internal carotid artery with 3 cm length from the New Zealand white rabbits. The veins were randomly divided into 6 groups and underwent adventitial collagen cross-linking by 0.3% glutaraldehyde for 0 min, 1 min, 2 min, 3 min, 4 min, and 5 min, respectively. All vessel segments were subjected to biomechanical tests and pathological tests. Carotid artery bypass graft models were established in 24 New Zealand white rabbits including crosslinked group(n=12) and non-crosslinked group(n=12). The vein grafts were obtained for pathological examination 4 weeks after models feeding, and the intimal hyperplasia of vein graft was evaluated.Results:Adventitial cross-linking increased fiber density of adventitia significantly, and increased the stiffness of the veins as the time of cross-linking increased. And in the high strain region(strain ratio 1.4-1.8), the mechanical curve of veins receiving 3min cross-linking was similar to that of the carotid artery. The patent rate of the vein grafts of rabbit models was 100% after 4 weeks. Comparing with non-crosslinked group, the intimal and medial thickness of vein grafts in crosslinked group were reduced remarkably[(78.83±9.02)μm vs.(140.19±19.90)μm, (43.75±5.05)μm vs.(58.35 ± 8.61) μm, P<0.01). Conclusion:Adventitial collagen cross-linking by GA can enhance the mechanical strength of the jugular vein, and reduce the intimal hyperplasia of the jugular vein grafts in rabbit models.
RESUMO
Objective To investigate the pathogenesis of type-B aortic dissection by using morphological analysis and computational fluid dynamics (CFD) method, so as to provide evidence for the effective prediction of type-B aortic dissection. Methods Six primary type-B dissection cases scanned by CT (dissection group) and six normal cases applied to black-blood MRI (control group) were included in this study and patient-specific three-dimensional (3D) models of aorta were established through image segmentation and 3D reconstruction. The pre-type-B dissection aortas were constructed by applying the scaling algorithm to shrink the dissection and then compared with subjects in control group. The differences between morphological parameters and hemodynamic parameters of the two groups were compared. Results Compared with the normal cases, the area of the descending aorta increased dramatically in dissection group ［(892.03±263.78) mm2 vs (523.67±64.10) mm2, P=0.036］. A significant decrease in angle of the left subclavian artery occurred (66.62°±20.11° vs 100.40°±15.35°, P=0.036). The tortuosity of the aorta also had an obvious increase (0.37°±0.07° vs 0.21°±0.51°, P=0.011). The time-averaged wall shear stress (TAWSS) in dissection group was obviously higher than that in control group; the flow in the dissection region was vortex flow at low speed and the oscillating shear index (OSI) was higher. Conclusions The results of this study can be used to provide guidance for the early diagnosis and treatment of type-B aortic dissection.
RESUMO
Objective:To investigate effects of bone-resorptive lesion on stress distribution of femoral head and on progression in patients with osteonecrosis of the femoral head (ONFH).Methods:From April 2014 to September 2018, a total of 155 femoral heads from 94 patients diagnosed with ARCO stage II and III ONFH were retrospectively reviewed, including 77 males and 17 females with aged 39.90±10.45 years old (ranged from 18-64 years). The hips were divided into two groups according to whether there were bone-resorptive lesions. Further, we compared whether there was statistical difference between the two groups in staging. Then, a case of ARCO II hip joint without bone-resorptive lesion was selected from the included patients. Six femoral head with different diameters of spherical bone-resorptive lesion of 5 mm, 7 mm, 10 mm, 14 mm, 18 mm, and 23 mm were simulated. The influence of bone-resorptive lesion on the stress distribution of necrotic area and a spherical shell extending 1 mm radially around the bone-resorptive lesion was investigated by finite element method in slow walking conditions.Results:Of the 155 ONFH hips, 67 hips are complicated by bone-resorptive lesions, of which 17 were ARCO II, 50 were ARCO III. A total of 88 hips did not contain bone-resorptive lesions, of which 58 were ARCO II, ARCO III 30 cases. The proportion of ARCO stage II in the group with bone-resorptive lesions was significantly higher than that in the group without bone-resorptive lesions (χ 2=25.03, P=0.000). The finite element stress distribution cloud diagram showed that there was a stress concentration area around the bone-resorptive lesions. The maximum von Mises stress around bone-resorptive lesions in the models that contained a synthetic bone-resorptive lesions were significantly higher than those reported in the matched, non-synthetic bone-resorptive lesions finite element models ( t=3.139, P=0.026). The values for maximum von Mises stress around bone-resorptive lesions were 6.94±1.78 MPa and 5.01±0.35 MPa for the group with synthetic bone-resorptive lesions and the group non-synthetic bone-resorptive lesions, respectively. There was a positive correlation between the diameter of bone-resorptive lesions and the maximum and mean von Mises stress of necrotic areas as well as the maximum von Mises stress around bone-resorptive lesions. Conclusion:Bone-resorptive lesions can increase the maximum stress and average stress in the necrotic area. The larger the bone-resorptive lesion, the more the stress increases. There is a stress concentration area around the bone-resorptive lesions, which may accelerate the collapse of the femoral head.
