This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the spa...This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the space spiral curve, a three-dimensional parametrical geometrical model is constructed. The finite element model is built by using the beam-beam contact elements and 3D beam elements. The constituent nitinol wires are assumed to be linear elastic material. The finite element analysis figures out that the radial stiffness of the stent and the stress distribution of the wires are influenced by all the structural parameters. The helix pitch of the wires is the most important factor. Under the condition of the same load and other structural parameters remaining unchanged, when the number of wires is 24, the stress of the wire crosssection is at the minimum. A comparison between the vitro experimental results and the analytical results is conducted, and the data is consistent, which proves that the current finite element model can be used to appropriately predict the mechanical performance of the braided esophageal stents.展开更多
AIM： To introduce and evaluate a new method to re- pair bile duct defect with a degradable stent and au- tologous tissues. METHODS： Eight Ba-Ma mini-pigs were used in this study, Experimental models with common bile...AIM： To introduce and evaluate a new method to re- pair bile duct defect with a degradable stent and au- tologous tissues. METHODS： Eight Ba-Ma mini-pigs were used in this study, Experimental models with common bile duct （CBD） defect （0,5-1,0 cm segment of CBD resected） were established and then CBD was reconstructed by duct to duct anastomosis with a novel degradable stent made of poly [sebacic acid-co-（1,3-propanediol）-co- （1,2-propanediol）]. In addition, a vascularized greater omentum was placed around the stent and both ends of CBD. Cholangiography via gall bladder was per- formed for each pig at postoperative months 1 and 3 to rule out stent translocation and bile duct stricture. Complete blood count was examined pre- and post- operatively to estimate the inflammatory reaction. Liver enzymes and serum bilirubin were examined pre- and post-operatively to evaluate the liver function. Five pigs were sacrificed at month 3 to evaluate the healing of anastomosis. The other three pigs were raised for one year for long-term observation. RESULTS： All the animals underwent surgery success- fully. There was no intraoperative mortality and no bile leakage during the observation period, The white blood cell counts were only slightly increased on day 14 and month 3 postoperatively compared with that before operation, the difference was not statistically significant （P = 0.652）. The plasma level of alanine aminotrans- ferase on day 14 and month 3 postoperatively was also not significantly elevated compared with that before operation （P = 0.810）. Nevertheless, the plasma level of y-glutamyl transferase was increased after opera- tion in both groups （P = 0.004）, especially 2 wk after operation. The level of serum total bilirubin after opera- tion was not significantly elevated compared with that before operation （P = 0.227）, so did the serum direct bilirubin （P = 0.759）. By cholangiography yia gall blad- der, we found that the stent maintained its integrity of shape and was stillin situ at month 1, and it disap- peared completely at month 3. No severe CBD dilation and stricture were observed at both months 1 and 3. No pig died during the 3-too postoperative observation period. No sign of necrosis, bile duct stricture, bile leak- age or abdominal abscess was found at reoperation at month 3 postoperatively. Pigs had neither fragments of stent nor stones formed in the CBD. Collagen deposit was observed in the anastomosis by hematoxylin and eosin （HE） and Masson＇s trichrome stains. No severe cholestasis was observed in liver parenchyma by HE staining. Intestinal obstruction was found in a pig 4 mo after operation, and no bile leakage, bile duct stricture or biliary obstruction were observed in laparotomy. No sign of bile duct stricture or bile leakage was observed in the other two pigs. CONCLUSION： The novel method for repairing bile duct defect yielded a good short-term effect without postoperative bile duct stricture. However, the long- term effect should be further studied.展开更多
This study aimed to evaluate the feasibility and safety of a novel stent manufactured by metal injection molding(MIM)in clinical practice through animal experiments.Vessel stents were prepared using powder injection m...This study aimed to evaluate the feasibility and safety of a novel stent manufactured by metal injection molding(MIM)in clinical practice through animal experiments.Vessel stents were prepared using powder injection molding technology to considerably improve material utilization.The influence of MIM carbon impurity variation on the mechanical properties and corrosion resistance of 316L stainless steel was studied.In vitro cytotoxicity and animal transplantation tests were also carried out to evaluate the safety of MIM stents.The results showed that the performance of 316L stainless steel was very sensitive to the carbon content.Carbon fluctuations should be precisely controlled during MIM.All MIM stents were successfully implanted into the aortas of the dogs,and the MIM 316L stents had no significant cytotoxicity.The novel intravascular stent manufactured using MIM can maintain a stable form and structure with fast endothelialization of the luminal surface of the stent and ensure long-term patency in an animal model.The novel intravascular stent manufactured using MIM demonstrates favorable structural,physical,and chemical stability,as well as biocompatibility,offering promising application in clinical practice.展开更多
基金The National Natural Science Foundation of China(No.51005124)the Opening Foundation of Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments(No.JS-NB-2009-1-1)
文摘This paper aims to find the relationship between the structural parameters and the radial stiffness of the braided stent and to understand the stress distribution law of the wires. According to the equation of the space spiral curve, a three-dimensional parametrical geometrical model is constructed. The finite element model is built by using the beam-beam contact elements and 3D beam elements. The constituent nitinol wires are assumed to be linear elastic material. The finite element analysis figures out that the radial stiffness of the stent and the stress distribution of the wires are influenced by all the structural parameters. The helix pitch of the wires is the most important factor. Under the condition of the same load and other structural parameters remaining unchanged, when the number of wires is 24, the stress of the wire crosssection is at the minimum. A comparison between the vitro experimental results and the analytical results is conducted, and the data is consistent, which proves that the current finite element model can be used to appropriately predict the mechanical performance of the braided esophageal stents.
基金Supported by Grants from Science and Technology Department of Zhejiang Province, No. 2009C33027 and No. 2009R50040
文摘AIM： To introduce and evaluate a new method to re- pair bile duct defect with a degradable stent and au- tologous tissues. METHODS： Eight Ba-Ma mini-pigs were used in this study, Experimental models with common bile duct （CBD） defect （0,5-1,0 cm segment of CBD resected） were established and then CBD was reconstructed by duct to duct anastomosis with a novel degradable stent made of poly [sebacic acid-co-（1,3-propanediol）-co- （1,2-propanediol）]. In addition, a vascularized greater omentum was placed around the stent and both ends of CBD. Cholangiography via gall bladder was per- formed for each pig at postoperative months 1 and 3 to rule out stent translocation and bile duct stricture. Complete blood count was examined pre- and post- operatively to estimate the inflammatory reaction. Liver enzymes and serum bilirubin were examined pre- and post-operatively to evaluate the liver function. Five pigs were sacrificed at month 3 to evaluate the healing of anastomosis. The other three pigs were raised for one year for long-term observation. RESULTS： All the animals underwent surgery success- fully. There was no intraoperative mortality and no bile leakage during the observation period, The white blood cell counts were only slightly increased on day 14 and month 3 postoperatively compared with that before operation, the difference was not statistically significant （P = 0.652）. The plasma level of alanine aminotrans- ferase on day 14 and month 3 postoperatively was also not significantly elevated compared with that before operation （P = 0.810）. Nevertheless, the plasma level of y-glutamyl transferase was increased after opera- tion in both groups （P = 0.004）, especially 2 wk after operation. The level of serum total bilirubin after opera- tion was not significantly elevated compared with that before operation （P = 0.227）, so did the serum direct bilirubin （P = 0.759）. By cholangiography yia gall blad- der, we found that the stent maintained its integrity of shape and was stillin situ at month 1, and it disap- peared completely at month 3. No severe CBD dilation and stricture were observed at both months 1 and 3. No pig died during the 3-too postoperative observation period. No sign of necrosis, bile duct stricture, bile leak- age or abdominal abscess was found at reoperation at month 3 postoperatively. Pigs had neither fragments of stent nor stones formed in the CBD. Collagen deposit was observed in the anastomosis by hematoxylin and eosin （HE） and Masson＇s trichrome stains. No severe cholestasis was observed in liver parenchyma by HE staining. Intestinal obstruction was found in a pig 4 mo after operation, and no bile leakage, bile duct stricture or biliary obstruction were observed in laparotomy. No sign of bile duct stricture or bile leakage was observed in the other two pigs. CONCLUSION： The novel method for repairing bile duct defect yielded a good short-term effect without postoperative bile duct stricture. However, the long- term effect should be further studied.
基金the Major Project of the Ministry of Science and Technology of Changsha,China(No.kh2003014)the Hunan Provincial Natural Science Foundation,China(Nos.2018JJ2584,2018JJ3507)+1 种基金the Beijing Municipal Science and Technology Comission,China(No.D171100002917004)the Guangxi Science and Technology Plan Project,China(No.AD16380019).
文摘This study aimed to evaluate the feasibility and safety of a novel stent manufactured by metal injection molding(MIM)in clinical practice through animal experiments.Vessel stents were prepared using powder injection molding technology to considerably improve material utilization.The influence of MIM carbon impurity variation on the mechanical properties and corrosion resistance of 316L stainless steel was studied.In vitro cytotoxicity and animal transplantation tests were also carried out to evaluate the safety of MIM stents.The results showed that the performance of 316L stainless steel was very sensitive to the carbon content.Carbon fluctuations should be precisely controlled during MIM.All MIM stents were successfully implanted into the aortas of the dogs,and the MIM 316L stents had no significant cytotoxicity.The novel intravascular stent manufactured using MIM can maintain a stable form and structure with fast endothelialization of the luminal surface of the stent and ensure long-term patency in an animal model.The novel intravascular stent manufactured using MIM demonstrates favorable structural,physical,and chemical stability,as well as biocompatibility,offering promising application in clinical practice.
