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排序方式: 共有132条查询结果,搜索用时 15 毫秒
1.
Attempts have been made to investigate the effect of slip time of nitinol artificial esophagus for forming neo‐esophageal stenosis after replacement of a thoracic esophagus with nitinol artificial esophagus in 20 experimental pigs. The pigs whose slip time was less than 90 days postoperatively had severe dysphagia (Bown's III) immediately after they were fed, and the dysphagia aggravated gradually later on (Bown's III–IV). The pigs whose slip time was more than 90 days postoperatively had mild/moderate dysphagia (Bown's I–II) immediately after they were fed, and the dysphagia relieved gradually later on (Bown's II‐I‐0). The ratios between the diameter of neo‐esophagus in different slip time and normal esophagus were 25% (at 2 months postoperatively), 58% (at 4 months postoperatively), and 93% (at 6 months postoperatively), respectively. The relationship between nitinol artificial esophagus slip time and neo‐esophageal stenosis showed a positive correlation. After replacement of a thoracic esophagus with nitinol artificial esophagus, the artificial esophageal slip time not only affected the original diameter of the neo‐esophagus immediately, but also affected the neo‐esophageal scar stricture forming process later on. The narrowing of neo‐esophagus is caused by overgrowth of scar tissue. But there is the positive correlation between artificial esophagus slip time and neo‐esophageal stenosis, so this can be a way of overcoming neo‐esophageal stenosis by delaying slip time of artificial esophagus.  相似文献   
2.
To date, ventricular assist devices (VADs) have become accepted as a therapeutic solution for end‐stage heart failure patients when a donor heart is not available. Newer generation VADs allow for a significant reduction in size and an improvement in reliability. However, the invasive implantation still limits this technology to critically ill patients. Recently, expandable/deployable devices have been investigated as a potential solution for minimally invasive insertion. Such a device can be inserted percutaneously via peripheral vessels in a collapsed form and operated in an expanded form at the desired location. A common structure of such foldable pumps comprises a memory alloy skeleton covered by flexible polyurethane material. The material properties allow elastic deformation to achieve the folded position and withstand the hydrodynamic forces during operation; however, determining the optimal geometry for such a structure is a complex challenge. The numerical finite element method (FEM) is widely used and provides accurate structural analysis, but computation time is considerably high during the initial design stage where various geometries need to be examined. This article details a simplified two‐dimensional analytical method to estimate the mechanical stress and deformation of memory alloy skeletons. The method was applied in design examples including two popular types of blade skeletons of a foldable VAD. Furthermore, three force distributions were simulated to evaluate the strength of the structures under different loading conditions experienced during pump operation. The results were verified with FEM simulations. The proposed two‐dimensional method gives a close stress and deformation estimation compared with three‐dimensional FEM simulations. The results confirm the feasibility of such a simplified analytical approach to reveal priorities for structural optimization before time‐consuming FEM simulations, providing an effective tool in the initial structural design stage of foldable minimally invasive VADs.  相似文献   
3.
This paper summarizes some of the key differences between self-expanding and balloon-expanding stents, aligning engineering and design differences with clinical performance. While neither type of stent can be considered universally superior, the differences are significant enough to make each type more appropriate in specific circumstances. Many of the differences concern long-term outcome, for which there is still insufficient data.  相似文献   
4.
气道狭窄已成为一种较为常见的呼吸系统疾病,临床上往往需要进行气道支架置入术以实现气道的快速扩张,缓解患者的呼吸困难。但支架置入后常会出现肉芽组织过度增生的现象,严重的会造成气道的再狭窄。基于"应力-生长"关系的理论,肉芽组织的过度增生可能与局部力学环境的改变相关,特别是支架对气道壁的应力刺激。为此,研究将针对镍钛合金网状气道支架置入术展开计算机数值模拟,以分析支架置入前后局部力学环境的改变。结果显示气道支架置入后,狭窄处壁面的局部应力环境发生了显著的改变,其壁面的扩张应力明显升高且应力集中的现象较为严重。我们认为显著改变的局部应力环境可能是造成气道肉芽组织过度增生的因素之一。  相似文献   
5.
Abstract

Surgical treatment of high or complex anal fistulas often renders unsatisfying results. This is the report of the first successful closure of such anal fistula using a special Nitinol clip and applicator, the OTSC® Proctology system (Ovesco AG, Tuebingen, Germany): A 54-year old female patient was suffering from a high transsphincteric anal fistula. After seton drainage of the fistula for ten weeks, the fistula track was debrided using a special fistula brush. After transanal clip release from the applicator, the internal fistula opening was adequately closed by the clip. Eight months after clip closure the fistula had healed and the clip was removed using the OTSC® Proctology Clip Cutter. Fistula closure using the OTSC® Proctology system represents a promising sphincter-preserving minimally invasive procedure.  相似文献   
6.
镍钛聚髌器与改良张力带钢丝治疗髌骨骨折的对比研究   总被引:1,自引:0,他引:1  
吴庭东  蒋毅  张满江 《北京医学》2010,32(4):304-306
目的比较镍钛聚髌器与改良张力带钢丝治疗髌骨骨折的临床疗效。方法78例髌骨骨折手术治疗患者,分为镍钛聚髌器组(42例)和改良张力带钢丝组(36例),术后随访6-14个月(平均10个月),根据术后X线片和关节功能恢复情况评定临床疗效。结果失访14例,其余患者骨折平均临床愈合时间为8周,其中镍钛聚髌器组优良率为94.3%,改良张力带钢丝组优良率为79.3%,临床疗效无显著性差异(P﹥0.05)。对于13例粉碎性骨折,镍钛聚髌器组中优6例,良2例,差1例;改良张力带钢丝组中优0例,良1例,差3例,前者效果明显优于后者(P﹤0.05)。结论镍钛聚髌器是治疗髌骨骨折的有效方法,尤其适用于粉碎性骨折。  相似文献   
7.
This article gives an overview of methods applied for surface treatment of nickel–titanium shape memory alloys in medical applications. The different methods are classified into the three major groups: removal, oxidation and coating. The principle behind each group of methods is explained and the pros and cons of the different methods are discussed.  相似文献   
8.
目的:探讨髌骨侧方腱膜丝线缝合加镍钛合金聚髌器(NT—PC)治疗髌骨粉碎性骨折的体会。方法:采用髌前横弧形切口,整复髌骨粉碎性骨折,用10#丝线行髌骨侧方骨折块间断缝合固定,再用NT—PC固定骨折端,早期进行功能锻炼。结果:治疗髌骨粉碎性骨折98例,骨折均获得骨性愈合,膝关节功能好,优良率96.9%。结论:髌骨侧方腱膜丝线缝合加NT—PC治疗髌骨粉碎性骨折,手术操作简便,不仅保留了髌骨,又能牢固固定骨折端,便于早期功能锻炼,疗效确切。  相似文献   
9.
Fatigue and durability of Nitinol stents   总被引:1,自引:0,他引:1  
Nitinol self-expanding stents are effective in treating peripheral artery disease, including the superficial femoral, carotid, and renal arteries. However, fracture occurrences of up to 50% have been reported in some stents after one year. These stent fractures are likely due to in vivo cyclic displacements. As such, the cyclic fatigue and durability properties of Nitinol-based endovascular stents are discussed in terms of an engineering-based experimental testing program. In this paper, the combined effects of cardiac pulsatile fatigue and stent-vessel oversizing are evaluated for application to both stents and stent subcomponents. In particular, displacement-controlled fatigue tests were performed on stent-like specimens processed from Nitinol microtubing. Fatigue data were collected with combinations of simulated oversizing conditions and pulsatile cycles that were identified by computer modeling of the stent that mimic in vivo deformation conditions. These data are analyzed with non-linear finite element computations and are illustrated with strain-life and strain-based constant-life diagrams. The utility of this approach is demonstrated in conjunction with 10 million cycle pulsatile fatigue tests of Cordis SMART Control® Nitinol self-expanding stents to calculate fatigue safety factors and thereby predict in vivo fatigue resistance. These results demonstrate the non-linear constant fatigue-life response of Nitinol stents, whereby, contrary to conventional engineering materials, the fatigue life of Nitinol is observed to increase with increasing mean strain.  相似文献   
10.
本文报告了弓形记忆加压接骨器的研制和57例临床应用结果。该器具有2个纵轴加压枝,2~8个半环固定枝。其超弹、记忆效应作用于上肢管状骨时,可为骨断端提供一种轴向的、动态的和持续的加压力(24~56kg)直至骨愈合。临床应用骨折31例,骨不连26例,术后弃用外固定,早期活动。随访4~32个月,平均13.7个月。骨折组术后平均2.2个月,骨折处为板状替代;骨不连组术后平均3.64个月,不连处为板状替代。两组均未发现术后感染、骨不连等并发症,其中46例于术后半年左右取出本器,随访中未见板状替代部再骨折。  相似文献   
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