No abstract

Electromagnetically navigated in situ aortic fenestration for juxtarenal aortic stent grafts was feasible in a healthy animal model. Identified remaining challenges were: shortening the procedure to avoid long warm ischemia times, using an aortic aneurysm animal model, and improving the stability of the stent graft material.

BackgroundElectromagnetic tracking is a relatively new technique that allows real time navigation in the absence of radiation. The aim of this study was to prove the feasibility of this technique for the treatment of posterior pelvic ring fractures and to compare the results with established image guided procedures.MethodsTests were performed in pelvic specimens (Sawbones®) with standardized sacral fractures (Type Denis I or II). A gel matrix simulated the operative approach and a cover was used to disable visual control. The electromagnetic setup was performed by using a custom made carbon reference plate and a prototype stainless steel K-wire with an integrated sensor coil. Four different test series were performed: Group OCT: Optical navigation using preoperative CT-scans; group O3D: Optical navigation using intraoperative 3-D-fluoroscopy; group Fluoro: Conventional 2-D-fluoroscopy; group EMT: Electromagnetic navigation combined with a preoperative Dyna-CT. Accuracy of screw placement was analyzed by standardized postoperative CT-scan for each specimen. Operation time and intraoperative radiation exposure for the surgeon was documented. All data was analyzed using SPSS (Version 20, 76 Chicago, IL, USA). Statistical significance was defined as p< 0.05.Results160 iliosacral screws were placed (40 per group). EMT resulted in a significantly higher incidence of optimal screw placement (EMT: 36/40) compared to the groups Fluoro (30/40; p< 0.05) and OCT (31/40; p< 0.05). Results between EMT and O3D were comparable (O3D: 37/40; n.s.). Also, the operation time was comparable between groups EMT and O3D (EMT 7.62 min vs. O3D 7.98 min; n.s.), while the surgical time was significantly shorter compared to the Fluoro group (10.69 min; p< 0.001) and the OCT group (13.3 min; p< 0.001).ConclusionElectromagnetic guided iliosacral screw placement is a feasible procedure. In our experimental setup, this method was associated with improved accuracy of screw placement and shorter operation time when compared with the conventional fluoroscopy guided technique and compared to the optical navigation using preoperative CT-scans. Further studies are necessary to rule out drawbacks of this technique regarding ferromagnetic objects.

This work presents concepts for complex endovascular procedures using electromagnetic navigation technology (EMT). Navigation software interfacing a standard commercially available navigation system was developed, featuring registration, electromagnetic field distortion correction, breathing motion detection and gating, and state-of-the-art 3D imaging post processing. Protocols for endovascularly placed, in-situ fenestrated abdominal aortic stent grafts and an EMT guided transjugular intrahepatic portosystemic shunt (TIPSS) creation have been designed. A dedicated set of interventional devices was developed for each of the procedures: For aortic in-situ fenestration a combination of high-porosity stentgrafts, steerable catheters and electromagnetically navigated guidewires was used, for TIPSS a dual-navigated (sheath and stylet) TIPSS-device was designed and manufactured. The developed devices underwent phantom testing, in preparation for animal experiments to prove the feasibility of the approach. Once established, these systems could aid in performing these challenging interventional radiology procedures, exploiting the unique characteristics of electromagnetic navigation and solving multiple of the problems associated with these interventions being performed under X-ray fluoroscopy, such as lacking real-time 3D information or extensive exposure to ionizing radiation.