Engineering Goals for Future Thoracic Endografts—How Can We Make Them More Effective?

Endovascular treatments for catastrophic aortic conditions have gained increasing popularity over the past 20 years. Originally developed for abdominal aortic aneurysms (EVAR), treatment has been modified for use in thoracic aortic repair (TEVAR). As expanding numbers of patients with increasingly intractable conditions and more hostile anatomies are treated, endovascular stent designs are maturing to be suitable for these more demanding situations. This article discusses the engineering considerations that apply to changing stent graft designs for current and evolving thoracic applications. The biological parameters that differentiate thoracic from abdominal aortic environments are outlined. Factors concerning materials, sealing mechanisms, deployment, stent frame architecture, and migration resistance are described, and eagerly awaited potential future developments are summarized.     

Simulated Bench Testing to Evaluate the Mechanical Performance of New Carotid Stents

Our group recently developed a novel covered carotid stent that can prevent emboli while preserving the external carotid artery (ECA) branch blood flow. However, our recent in vitro side‐branch ECA flow preservation tests on the covered stents revealed the need for further stent frame design improvements, including the consideration to crimp the stent to a low profile for the delivery of the stent system and having bigger cells. Hence, the current work aims to design new bare metal stents with bigger cell size to improve the crimpability and to accommodate more slits so that the side‐branch flow could be further increased. Three new stent designs were analyzed using finite element analysis and benchmarked against two commercially available carotid stents in terms of their mechanical performances such as crimpability, radial strength, and flexibility. Results indicated that the new bare metal stent designs matched well against the commercial stents. Hence our new generation covered stents based on these designs can be expected to perform better in side‐branch flow preservation without compromising on their mechanical performances.     

Treatment of Otosclerosis with a Superelastic Nitinol Piston: First Results

Stapedotomy with implantation of an alloplastic prosthesis is a well-established therapy for the treatment of otosclerosis. Since the middle of 2008, a new Nitinol prosthesis with memory function and superelastic properties has been available which is expected to make fixation on the long process of the incus much easier. The advantage of this prosthesis is that heat-induced wire crimping is no longer necessary and damage to the incus caused by heat is avoided. Since May 2008, laser-assisted stapedotomy with implantation of a Nitinol prosthesis was performed in 21 patients suffering from otosclerosis. The prostheses used for all patients had a size of 4.5 mm × 0.4 mm. The patient collective consisted of 14 women and 7 men with a mean age of 53.4 years. Pre- and postoperatively, an ENT examination was carried out followed by an audiological evaluation of the hearing result. In addition, the properties of the prosthesis (“proper fitt”, “handling”, and “overall rating”) were evaluated intraoperatively by means of a test protocol. The Nitinol prosthesis was implanted successfully in all 21 patients. The mean air-bone gap for the frequencies from 0.5 to 4 kHz was 9.83 dB postoperatively. Intraoperatively, the fit of the prosthesis was rated as “good to very good”, the handling as “good” and the overall rating of the system was “good to very good”. Our patient collective showed good postoperative hearing results. Due to simple intraoperative handling, especially placing the Nitinol prosthesis in position, the critical work step of crimping is no longer necessary.     

Nitinol medical devices and implants

Superelastic Nitinol is now a common and well-known engineering material in the medical industry. While the greater flexibility of the alloy drives many of its applications, there are also a large number of lesser-known advantages of Nitinol in medical devices. This paper reviews 7 of these less-obvious but very important reasons for Nitinol's success, both past and future. Several new medical applications will be used to exemplify these points, including the quickly-growing and technologically-demanding stent applications. Stents are particularly interesting because they take advantage of the thermoelastic hysteresis of Nitinol.     

The OTSC® Proctology clip system for anal fistula closure: First prospective clinical data

Abstract

Introduction: Anorectal fistulas represent a troublesome condition for both patient and surgeon. The OTSC® Proctology clip system is a new device for transanal anorectal fistula closure. Material and methods: The OTSC® Proctology system was evaluated in a prospective clinical study undertaken in two surgical proctological centers. Ten patients (three women, seven men; median age 55 years, range 25-73 years) with nine transsphincteric and one suprasphincteric fistulas were enrolled into the study. Results: The median operation time was 30 minutes (range 20-45 minutes). There were no intraoperative technical or surgical complications. Postoperatively, no patient reported intolerable discomfort, immoderate pain or foreign body sensation in the anal region. At follow-up examination six months after surgery, nine out of ten patients had no clinical signs or symptoms of their previous fistula and were considered as healed (success rate 90%). In one patient persistency of the fistula was noted due to spontaneous early clip detachment on the third postoperative day. Discussion: These first data demonstrate the efficacy of the OTSC® Proctology system in the treatment of anal fistulas. Currently, more patients were enrolled into this prospective study to allow further evaluation of this new device and to assess its future role in relation to established surgical strategies for anorectal fistulas.     

A guide to shape memory and superelasticity in Nitinol medical devices

Shape memory and superelasticity properties of Nitinol have allowed the development of many novel medical devices. The intent of this paper is to approach the shape memory effect from the perspective of the attributes of a simple, yet elegant Nitinol device, the Homer Mammalok? needle localizer. Manufacturing methods, deformation behavior and temperature dependence of the device will be briefly reviewed.     

Posterior Cervical Fixation with a Nitinol Shape Memory Loop for Primary Surgical Stabilization of Atlantoaxial Instability: A Preliminary Report

Objective

To evaluate a new posterior atlantoaxial fixation technique using a nitinol shape memory loop as a simple method that avoids the risk of vertebral artery or nerve injury.

Methods

We retrospectively evaluated 14 patients with atlantoaxial instability who had undergone posterior C1-2 fusion using a nitinol shape memory loop. The success of fusion was determined clinically and radiologically. We reviewed patients'' neurologic outcomes, neck disability index (NDI), solid bone fusion on cervical spine films, changes in posterior atlantodental interval (PADI), and surgical complications.

Results

Solid bone fusion was documented radiologically in all cases, and PADI increased after surgery (p<0.05). All patients remained neurologically intact and showed improvement in NDI score (p<0.05). There were no surgical complications such as neural tissue or vertebral artery injury or instrument failure in the follow-up period.

Conclusion

Posterior C1-2 fixation with a nitinol shape memory loop is a simple, less technically demanding method compared to the conventional technique and may avoid the instrument-related complications of posterior C1-2 screw and rod fixation. We introduce this technique as one of the treatment options for atlantoaxial instability.     

应用国产封堵器闭合室间隔缺损修补术后残余漏

目的 评价应用国产封堵器治疗室间隔缺损修补术后残余漏的可行性和疗效.方法 11例患者,经胸超声心动图测量室间隔缺损术后残余漏直径为3～9 mm,平均(5.82±2.09)mm.经股静脉通过6～9 F鞘管送入封堵器,在X线透视和超声引导下完成操作.结果 左心室造影8例为膜部瘤型,3例为漏斗型.造影显示单出口6例,多出口5例,缺损口直径3～9 mm,平均(6.09±1.58)mm.应用封堵器直径(8～12)mm.10例患者应用1个封堵器完全封堵.1例残余漏有4个漏口,应用2个封堵器后仍有少量残余分流.升主动脉造影均无主动脉瓣返流.1例术后第3天发生完全性房室传导阻滞,应用氢化可的松治疗2周后完全恢复.术中X线透视时间8～30 min,平均(16.91±4.23)min.术后随访1个月～4年,1例残余分流仍存在.全部患者无血栓栓塞、溶血、感染性心内膜炎,无封堵器移位,无主动脉瓣反流等并发症.结论 经导管封堵治疗室间隔缺损修补术后残余漏疗效可靠,操作安全.     

Successful rigid endoscopic removal of an esophageal subtotally covered nitinol stent 11?months after initial placement

Formation of granulation tissue and stricture at the stent’s ends are well-known long-term complications of esophageal subtotally covered externally self-expandable metal stents (SEMS). Removal is associated with an increased risk of mucosal injury, severe bleeding, mediastinis, and consecutive stenosis. We report on a case of successful endoscopic removal of an esophageal SEMS 11 months after original placement to cover an iatrogenic esophageal perforation created during rigid esophagoscopy in a patient with cancer of unknown primary (CUP) syndrome. This case shows that safe SEMS late removal is achievable and at the same time illustrates the disadvantages of using SEMS for benign esophageal pathology. Particularly in cases of accidental esophageal injury during endoscopy, esophageal SEMS placement should be considered as a therapeutic option only if conventional surgery is contraindicated.