Electromagnetic tool for the endoscopic creation of colon anastomoses-development and feasibility assessment of a novel anastomosis compression implant approach

Abstract

Background: Colorectal anastomoses are among the most commonly performed interventions in abdominal surgery, while associated patient trauma is still high. Most recent trends of endoscopic anastomosis devices integrate magnetic components to overcome the challenges of minimally invasive surgery. However, the mutual attraction between magnetic implant halves may increase the risk of inadvertently pinching healthy structures. Thus, we present a novel anastomosis device to improve system controllability and flexibility.

Methods: A magnetic implant and an applicator with electromagnetic control units were developed. The interaction of magnetic implants with the electromagnets bears particular challenges with respect to the force-related dimensioning. Here, attraction forces must be overcome by the electromagnet actuation to detach the implant, while the attraction force between the implant halves must be sufficient to ensure a stable connection. Thus, respective forces were measured and the detachment process was reproducibly investigated. Patient hazards, associated with resistance-related heating of the coils were investigated.

Results: Anastomosis formation was reproducibly successful for an implant, with an attraction force of 1.53 [Formula: see text], resulting in a compression pressure of [Formula: see text]. The implant was reproducibly detachable from the applicator at the anastomosis site. Coils heated up to a maximum temperature of [Formula: see text]. Furthermore, we were able to establish a neat reconnection of intestinal bowel endings using our implant.

Discussion: As we achieved nearly equal compression forces with our implant as other magnetic anastomosis systems did (Magnamosis™: 1.48 N), we concluded that our approach provides sufficient holding strength to counteract the forces acting immediately postoperatively, which would eventually lead to an undesired slipping of the implant halves during the healing phase. Based on heat transfer investigations, preventive design specifications were derived, revealing that the wall thickness of a polymeric isolation is determined rather by stability considerations, than by heat shielding requirements.

Keywords: Anastomosis; Electromagnet; Endoscopic; Implant; Surgery.

Fig. 1

a Schematics of the anastomosis device comprising a two part applicator (1, 2), an implant (4, 5) and an endoscope overtube (7). Electromagnets (3) are used for control of implant de- and attachment from/to applicator heads. A flexible endoscope is used as carrier unit (8) for the system. At the aboral side, a soft magnet segment protrudes from the implant, into the electromagnetic coil (6). b Detailed schematics of the electromagnet mechanisms and implant units on both sides. Coil windings (1), continuous soft magnetic core (2), split soft magnetic core (3), implant comprising soft magnets (4), implant comprising hard magnets (5). Components positioned at the endoscope tip, i.e., closer to the patient’s mouth, are described by the term “oral” and system units positioned at the endoscope shaft, i.e., toward the patient’s anus, are described by the term “aboral”

Fig. 2

Schematics of the surgical procedure. Step 1: Starting configuration and positioning in the oral and aboral lumen. Step 2: Implant closure to achieve bowel reconnection; Step 3: Repulsion of permanent magnetic segments in the oral implant by establishment of a repulsive magnetic field (electromagnets); Step 4: Rejection of soft magnets in the aboral implant by establishment of a repulsive magnetic field (electromagnets)

Fig. 3

Schematics of the application device and implant units. Numbers indicate the most important parts, described on the side bar of (a) Applicator prototype mounted on a flexible endoscope within a mechanical trainer

Fig. 4

a Applicator and implant prototype mounted on the experimental setup b Oral applicator and implant unit (permanent magnets) c Aboral applicator and implant unit (soft magnets)

Fig. 5

a Experimental setup to measure forces acting between implant halves using a measurement force gauge (1), fixed on a slide to axially move it along a force rail (2). Implant dummies (4) were mounted on a metal bar (3) and fixed to the force gauge. b Each sample pair (6) is mounted on the implant dummy (4), to measure the adhesion force with respect to the tissue pair thickness. c In the second step, the sample pair is mounted on the applicator (7) to test the feasibility of the magnetic implant (8) detachment mechanism