Usefulness of a newly designed laser-cut metal stent with an anchoring hook and thin delivery system for EUS-guided hepaticogastrostomy in experimental settings (with video).

BACKGROUND AND AIMS: EUS-guided hepaticogastrostomy (EUS-HGS) is associated with high rates of adverse events. The present study evaluated the feasibility of a newly designed stent equipped with a dilatation and antimigration system for EUS-HGS in phantom and animal models. METHODS: The newly designed stent was a partially covered laser-cut stent with antimigration anchoring hooks and a thin tapered tip (7.2F). The feasibility of these stents for biliary obstruction was compared with that of conventional stents. Evaluated outcomes were resistance force to migration in phantom and ex vivo models, rates of technical success and adverse events, and histology in an in vivo model. RESULTS: The resistance forces on the distal (3.59 vs 1.73 N and 6.21 vs 1.74 N) and proximal (3.58 vs 1.5 N and 5.97 vs 1.67 N) sides in phantom and ex vivo models were significantly higher for hook stents than for conventional stents. Although EUS-HGS was successfully performed in all cases with both stents (100% [10/10] vs 100% [8/8]), the success rate of EUS-HGS without using a fistulous tract dilation device was significantly higher with hook stents (100% [10/10]) than with conventional stents (13% [1/8]). No adverse events occurred with either stent. Pathologic examination showed adhesion between the stomach and liver. CONCLUSIONS: The strong resistance to migration and the absence of the dilation step are important advantages of newly designed hook stents. These stents may therefore be feasible and safe for EUS-HGS.

Comparing the mechanical properties of a self-expandable metallic stent for colorectal obstruction: Proposed measurement method of axial force using a new measurement machine.

OBJECTIVES: Colorectal stenting is widely performed using self-expandable metallic stents (SEMSs), but the mechanical properties have not been evaluated. Therefore, we conducted an in vitro study to evaluate the mechanical properties of colorectal SEMSs. METHODS: Eighteen individual types and sizes of uncovered SEMSs were evaluated for their mechanical properties. Radial force was measured using a measurement machine. Axial force (AF) was measured by two methods: a conventional manual method and a new method using a measurement machine. The correlation of these two methods was evaluated. We also proposed an "AF zero border" that was defined as the angle at which the torque force disappeared. RESULTS: Radial force versus diameter curves and AF versus angle curves were influenced by the structure and the size of each stent. There was excellent correlation of AFs measured by the new and conventional manual method (y = 21.434x, R = 0.881, P < 0.0001). Colorectal SEMSs could be categorized into five subgroups according to the mechanical properties. Most hook-wired SEMSs had the AF of zero border. CONCLUSIONS: This is the first report to evaluate the mechanical properties of colorectal SEMSs, and these data may provide useful information for the clinical use and development of colorectal SEMS. Furthermore, the new measurement machine might standardize the measuring method of AF.

Endoscopic ultrasonography-guided choledochoduodenostomy using a newly designed laser-cut metal stent: Feasibility study in a porcine model.

BACKGROUND AND AIM: Endoscopic ultrasonography (EUS)-guided choledochoduodenostomy (EUS-CDS) is increasingly used in the treatment of malignant distal biliary obstruction. Standardized use of this technique requires improvements in instruments, including more convenient and safer devices. The present study was designed to evaluate the resistance force to migration (RFM) of a newly designed laser-cut metal stent and the feasibility of EUS-CDS using this stent. METHODS: This experimental study used a porcine model of biliary dilatation involving five male pigs. The new stent is a fully covered laser-cut stent with anti-migration anchoring hooks. The RFM of the new stents was compared with those of three commercially available covered metal stents using a phantom model. In the animal study, after ligation of Vater's ampulla with endoscopic clips, the dilated common bile duct was punctured under EUS guidance, followed by EUS-CDS using the new stent. One week after the procedure, the stents were removed endoscopically and the fistulas were assessed after the pigs were killed. Technical feasibility and clinical outcomes were evaluated. RESULTS: Among the four stents, the new stent had the highest RFM. Metal stent placement was successful in all five pigs, with no procedure-related complications occurring during and 1 week after endoscopic intervention. All stents remained in place without migration and were removed easily using a snare. At necropsy, fistulas were created between the bile duct and duodenum in all pigs. CONCLUSION: EUS-CDS using a newly designed metal stent was feasible and effective in this porcine model of biliary dilatation.

A novel, fully covered laser-cut nitinol stent with antimigration properties for nonresectable distal malignant biliary obstruction: a multicenter feasibility study.

BACKGROUND/AIMS: Stent migration occurs frequently, but the prevention of complications resulting from covered self-expandable metal stents (C-SEMSs) remains unresolved. We prospectively assessed a newly developed C-SEMS, a modified covered Zeo stent (m-CZS), in terms of its antimigration effect. METHODS: Between February 2010 and January 2011, an m-CZS was inserted into 42 patients (31 initial drainage cases and 11 reintervention cases) at a tertiary referral center and three affiliated hospitals. The laser-cut stent was flared for 1.5 cm at both ends, with a 1 cm raised bank located 1 cm in from each flared end. The main outcome of this study was the rate of stent migration, and secondary outcomes were the rate of recurrent biliary obstruction (RBO), the time to RBO, the frequencies of complications, and overall survival. RESULTS: Of the 31 patients with initial drainage, stent migration occurred in four (12.9%, 95% confidence interval, 5.1% to 29.0%), with a mean time of 131 days. RBO occurred in 18 (58%), with a median time to RBO of 107 days. Following previous C-SEMS migration, seven of 10 patients (70%) did not experience m-CZS migration until death. CONCLUSIONS: m-CZSs with antimigration properties effectively, although not completely, prevented stent migration after stent insertion.

Measurement of radial and axial forces of biliary self-expandable metallic stents.

BACKGROUND: Efforts to understand the properties of self-expandable metallic stents (SEMSs) through their mechanical properties have progressed. Among them, radial force (RF) is well known as an expanding force, but axial force (AF) has not been measured before. Correlations of these properties to clinical results are not well known. OBJECTIVE: We measured RF and AF of 14 different SEMSs and discussed the results in terms of clinical implications. DESIGN: Experimental study. SUBJECTS: Measurement of RF and AF of 14 different covered and uncovered SEMSs. METHODS: RF was measured with an RF measurement machine manufactured by Machine Solution, and AF was measured with in-house equipment. RESULTS: Measurements of RF in the process of expansion showed characteristic patterns closely related to the structures and materials of SEMSs. Results of AF measurement can be classified into 3 groups: high, medium, and low AF, depending on the type of SEMS. AF decreased with an increase of the length of stents. A plot of RF against AF revealed 3 distinguished RF/AF combinations and indicated the importance of understanding the properties by not only RF or AF individually but also by RF/AF combination. LIMITATIONS: In vitro study using measurement equipment. CONCLUSION: It was demonstrated that a combination of RF and AF is more effective than RF or AF individually in understanding the clinical implications of SEMSs. More work is needed to correlate mechanical properties with clinical results by designing model experiments.