The effect of injectable biocompatible elastomer (PDMS) on the strength of the proximal fixation of endovascular aneurysm repair grafts: An in vitro study

Aortic aneurysm sac filling with AneuFix injectable polymer during endovascular aneurysm repair: feasibility and safety trial study protocol

INTRODUCTION

Type II endoleaks (T2ELs) following endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) can lead to aneurysm growth, compromising the stent graft seal and risking rupture. Preventing these endoleaks during EVAR involves filling the AAA sac around the stent graft to exclude the aneurysm and block any arteries causing the endoleak. This study investigates the feasibility and safety of using AneuFix, a biocompatible injectable polymer developed by TripleMed (Geleen, the Netherlands), for aneurysmal sac filling during EVAR in high-risk T2EL patients.

METHODS AND ANALYSIS

A feasibility, single-arm, single-centre clinical trial will initially include five patients with infrarenal AAA, eligible for EVAR, and at high risk for T2EL based on the number of patent lumbar arteries and the cross-sectional area of the aortic lumen at the level of the inferior mesenteric artery. Postevaluation by the Data Safety and Monitoring Board, the study cohort will extend to 25 patients. During EVAR and after stent graft deployment, the aneurysm sac is filled with AneuFix polymer using a filling sheath positioned parallel to the contralateral limb with the tip inside the aneurysm sac. Primary outcome is technical success (successful AAA sac filling). The secondary outcomes include clinical success at 6 and 12 months (occurrence of T2ELs and AAA growth assessed with CT angiography), intraoperative and perioperative complications, all endoleaks, adverse events, re-interventions, aneurysm rupture and patient survival.

ETHICS AND DISSEMINATION

This trial was approved by the Dutch Authorities (Central Committee on Research Involving Human Subjects, IGJ), Amsterdam University Medical Centre Ethical Commission, and adheres to the Declaration of Helsinki and European Medical Device Regulation. Results will be shared at (inter)national conferences and in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04307992.

An Injectable Neural Stimulation Electrode Made from an In-Body Curing Polymer/Metal Composite

Implanted neural stimulation and recording devices hold vast potential to treat a variety of neurological conditions, but the invasiveness, complexity, and cost of the implantation procedure greatly reduce access to an otherwise promising therapeutic approach. To address this need, a novel electrode that begins as an uncured, flowable prepolymer that can be injected around a neuroanatomical target to minimize surgical manipulation is developed. Referred to as the Injectrode, the electrode conforms to target structures forming an electrically conductive interface which is orders of magnitude less stiff than conventional neuromodulation electrodes. To validate the Injectrode, detailed electrochemical and microscopy characterization of its material properties is performed and the feasibility of using it to stimulate the nervous system electrically in rats and swine is validated. The silicone-metal-particle composite performs very similarly to pure wire of the same metal (silver) in all measures, including exhibiting a favorable cathodic charge storage capacity (CSCC ) and charge injection limits compared to the clinical LivaNova stimulation electrode and silver wire electrodes. By virtue of its simplicity, the Injectrode has the potential to be less invasive, more robust, and more cost-effective than traditional electrode designs, which could increase the adoption of neuromodulation therapies for existing and new indications.

Determination of coefficient of friction for self-expanding stent-grafts

Migration of stent-grafts (SGs) after endovascular aneurysm repair of abdominal aortic aneurysms is a serious complication that may require secondary intervention. Experimental, analytical, and computational studies have been carried out in the past to understand the factors responsible for migration. In an experimental setting, it can be very challenging to correctly capture and understand the interaction between a SG and an artery. Quantities such as coefficient of friction (COF) and contact pressures that characterize this interaction are difficult to measure using an experimental approach. This behavior can be investigated with good accuracy using finite element modeling. Although finite element models are able to incorporate frictional behavior of SGs, the absence of reliable values of coefficient of friction make these simulations unreliable. The aim of this paper is to demonstrate a method for determining the coefficients of friction of a self-expanding endovascular stent-graft. The methodology is demonstrated by considering three commercially available self-expanding SGs, labeled as A, B, and C. The SGs were compressed, expanded, and pulled out of polymeric cylinders of varying diameters and the pullout force was recorded in each case. The SG geometries were recreated using computer-aided design modeling and the entire experiment was simulated in ABAQUS 6.8/STANDARD. An optimization procedure was carried out for each SG oversize configuration to determine the COF that generated a frictional force corresponding to that measured in the experiment. The experimental pullout force and analytically determined COF for SGs A, B, and C were in the range of 6-9 N, 3-12 N, and 3-9 N and 0.08-0.16, 0.22-0.46, and 0.012-0.018, respectively. The computational model predicted COFs in the range of 0.00025-0.0055, 0.025-0.07, and 0.00025-0.006 for SGs A, B, and C, respectively. Our results suggest that for SGs A and B, which are exoskeleton based devices, the pullout forces increase upto a particular oversize beyond which they plateau, while pullout forces showed a continuous increase with oversize for SG C, which is an endoskeleton based device. The COF decreased with oversizing for both types of SGs. The proposed methodology will be useful for determining the COF between self-expanding stent-grafts from pullout tests on human arterial tissue.