NiTinol-based cutting edges for endovascular heart valve resection: First in-vitro cutting results

Machining of shape memory alloys based on Nitinol (NiTi) creates difficulties due to its ductility and severe strain hardening. In this experiment, different cutting edges and grinding parameters were tested to optimize cutting results on NiTi-based blades intended for endovascular heart valve resection. The cutting procedure was performed using two counter-rotating circular NiTi blades of different diameter. A rotating/punching process should be performed. Different shapes (glazed, waved, and saw tooth), different grinding techniques (manual, manual grinder, and precise milling cutter) and additionally various velocities (50 and 200 rpm) were tested on specific test specimens. Cutting forces were measured and cutting quality was examined using digital microscopy. Preliminary tests with rotating blades showed superior results using cutting edges for the punching process (150 N vs. 200 N; n=7). In a second step special test specimens were tested. Maximum cutting-force was 265 N±20 N (mean±SD; n=7). Subsequently different shapes were tested at 50 and 200 rpm using the rotating/punching method regarding alternate grinding techniques. Cutting forces were 27 N±7.7 N for glazed blades (n=7) at 50 rpm and 18 N±4.7 N at 200 rpm, waved blades (n=7) required a maximum force of 18 N±5 N at 50 rpm and 11 N±3.3 N at 200 rpm, whereas saw tooth blades (n=7) needed 17 N±12.7 N at 50 rpm and 9 N±1.2 N at 200 rpm. Precise cutting quality was only seen when using glazed blades sharpened under accurate conditions with a high-speed milling cutter. Although shape memory alloys based on Nitinol are difficult to process, and well-defined grinding parameters do not exist, acceptable results can be reached using high-speed milling cutters. Best cutting quality can be observed by using glazed blades, performing a rotating/punching process at high velocities. Lower cutting forces can be observed by using other shape-types, however this leads to lower cutting quality. Therefore, further investigations on blade-machining and velocity-testing seem to be necessary to create optimal cutting results.     

纤维支气管镜定位和X线引导置入镍钛合金支架治疗气道狭窄的比较

目的 比较纤维支气管镜定位（bronchofibmscope location,BFL）和X线引导下置入镍钛（NT）合金支架治疗良恶性病变所致气道狭窄的优缺点。方法 对各种原因导致的30例气道狭窄,随机选择16例用BFL置入NT支架,另14例采用X线引导的方法置入NT 支架,并比较两者放置的准确率、放置所需时间、术后感染率、住院时间和住院费用。结果 BFL放置支架的准确率与X线引导下放置NT支架的相同,但前者放置支架的时间、术后感染率、住院时间和住院费用都显著少于后者（P〈0．01）。结论 BFL无须气管切开,创伤、痛苦少,且可单人操作,适于基层医院开展,值得推广应用。     

Percutaneous trans-hepatic bilateral biliary stenting in Bismuth IV malignant obstruction

AIM: To investigate the clinical efficiency of percutaneous trans-hepatic bilateral biliary metallic stenting for the management of Bismuth IV malignant obstructive disease.METHODS: Our hospital’s database was searched for all patients suffering from the inoperable malignant biliary obstruction Bismuth IV, and treated with percutaneous bilateral trans-hepatic placement of self-expandable nitinol stents. The indication for percutaneous stenting was an inoperable, malignant, symptomatic, biliary obstruction. An un-correctable coagulation disorder was the only absolute contra-indication for treatment. Bismuth grading was performed using magnetic resonance cholangiopancreatography. Computed tomography evaluation of the lesion and the dilatation status of the biliary tree was always performed prior to the procedure. All procedures were performed under conscious sedation. A single trans-hepatic track technique was preferred (T-configuration stenting) and a second, contra-lateral trans-hepatic track (Y-configuration stenting) was used only in cases of inability to access the contra-lateral lobe using a single track technique. The study’s primary endpoints were clinical success, defined as a decrease in bilirubin levels within 10 d and patient survival rates. Secondary endpoints included peri-procedural complications, primary and secondary patency rates.RESULTS: A total of 35 patients (18 female, 51.4%) with a mean age 69 ± 13 years (range 33-88) were included in the study. The procedures were performed between March 2000 and June 2008 and mean time follow-up was 13.5 ± 22.0 mo (range 0-96). The underlying malignant disease was cholangiocarcinoma (n = 10), hepatocellular carcinoma (n = 9), pancreatic carcinoma (n = 5), gastric cancer (n = 2), bile duct tumor (n = 2), colorectal cancer (n = 2), gallbladder carcinoma (n = 2), lung cancer (n = 1), breast cancer (n = 1) or non-Hodgkin lymphoma (n = 1). In all cases, various self-expandable bare metal stents with diameters ranging from 7 to 10 mm were used. Stents were placed in Y-configuration in 24/35 cases (68.6%) using two stents in 12/24 patients and three stents in 12/24 cases (50%). A T-configuration stent placement was performed in 11/35 patients (31.4%), using two stents in 4/11 cases (36.4%) and three stents in 7/11 cases (63.6%). Follow-up was available in all patients (35/35). Patient survival ranged from 0 to 1763 d and the mean survival time was 168 d. Clinical success rate was 77.1% (27/35 cases), and peri-procedural mortality rate was 5.7% (2/35 patients). Biliary re-obstruction due to stent occlusion occurred in 25.7% of the cases (9/35 patients), while in 7/11 (63.6%) one additional percutaneous re-intervention due to stent occlusion resulting in clinical relapse of symptomatology was successfully performed. In the remaining 4/11 patients (36.4%) more than 1 additional reintervention was performed. The median decrease of total serum bilirubin was 60.5% and occurred in 81.8% of the cases (27/33 patients). The median primary and secondary patency was 105 (range 0-719) and 181 d (range 5-1763), respectively. According to the Kaplan-Meyer survival analysis, the estimated survival rate was 73.5%, 47.1% and 26.1% at 1, 6 and 12 mo respectively, while the 8-year survival rate was 4.9%. Major and minor complication rates were 5.7% (2/35 patients) and 17.1% (6/35 patients), respectively.CONCLUSION: Percutaneous bilateral biliary stenting is a safe and clinically effective palliative approach in patients suffering from Bismuth IV malignant obstruction.     

In vitro comparison of three percutaneous atrial septal defect closure devices for endothelialisation and haemocompatibility

Central illustration. Endothelial progenitor cell (EPC) extraction, culture and characterisation, and adhesion, proliferation and haemocompatibility testing on three devices. ASD: atrial septal defect; NS: not significant; PC: positive control.

     

Radicular Pain due to Subsidence of the Nitinol Shape Memory Loop for Stabilization after Lumbar Decompressive Laminectomy

A number of dynamic stabilization systems have been used to overcome the problems associated with spinal fusion with rigid fixation recently and the demand for an ideal dynamic stabilization system is greater for younger patients with multisegment disc degeneration. Nitinol, a shape memory alloy of nickel and titanium, is flexible at low temperatures and regains its original shape when heated, and the Nitinol shape memory loop (SML) implant has been used as a posterior tension band mostly in decompressive laminectomy cases because the Nitinol implant has various characteristics such as high elasticity and a tensile force, flexibility, and biological compatibility. The reported short-term outcomes of the application of SMLs as posterior column supporters in cervical and lumbar decompressive laminectomies seem to be positive, and complications are minimal except for the rare occurrence of pullout and fracture of the SML. However, there was no report of neurological complications related to neural compression in spite of the use of the loop of SML in the epidural space. The authors report a case of delayed development of radiating pain caused by subsidence of the SML resulting epidural compression.     

Minimally invasive surgical clip closure of anorectal fistulas: current status of OTSC Proctology

Abstract

OTSC Proctology is a minimally invasive sphincter-preserving technique for the surgical treatment of anorectal fistulas. It is based on a super-elastic Nitinol clip which closes the internal fistula opening to allow healing of the fistula tract. A systematic search of the literature was undertaken to identify publications about OTSC Proctology. All studies and reports identified were reviewed and evaluated to determine the feasibility, efficacy and safety of clip surgery. The assessment of all available studies with a total of more than 200 surgical cases strongly suggests that the clip procedure is safe and effective with a low rate of complications. The technique rendered convincing short and long term results with an overall healing rate of approximately 63%. Best results were achieved when OTSC Proctology was used as first-line treatment (healing rate 74%) and for cryptoglandular fistulas (healing rate 64%). However, its future clinical role for IBD-associated recurrent and anorecto-vaginal fistulas remains to be determined, due to a relatively low number of these patients in the evaluated studies. OTSC Proctology is part of the novel armamentarium for the treatment for anorectal fistulas, which is based on high-technology devices. They can be repeatedly used and even combined without causing irreversible sphincter damage.