Comparative study of cylindrical vs circular ring magnets for colonic anastomosis in rats

Figure 1 Magnets. A: Front views of the cylindrical magnet and circular ring magnet; B: Side view of the magnets once attracted; C: Magnetic field viewing film showing the magnetic field distributions for the cylindrical magnets and circular ring magnets; D: The magnetic force curve.

Figure 2 Schematic of the surgical procedure. A: A magnet is inserted through the anus into the proximal portion of the colon; B: Another magnet is inserted through the anus to the distal end of the colon; C: The two magnets in the colon are attracted; D: The magnets are discharged after the side-to-side colonic anastomosis is established. DM: Daughter magnet; PM: Parent magnet.

Figure 3 Surgical procedure. A: For the cylindrical group, a cylindrical daughter magnet (DM) and cylindrical parent magnet (PM) were placed in the proximal and the distal end of the colon (black arrows); B: The two cylindrical magnets attracted together (yellow circle); C: For the circular group, a circular ring-DM and circular ring-PM were placed in the proximal and distal ends of the colon (black arrows); D: The two circular ring magnets attracted together (yellow circle); E: For the cylindrical–circular group, a cylindrical-DM and a circular ring-PM were placed in the proximal and distal ends of the colon, respectively (black arrows); F: The cylindrical-DM and circular ring-PM attracted together (yellow circle). DM: Daughter magnet; PM: Parent magnet.

Figure 4 Measurement of anastomotic parameters. A: Measurement of the burst pressure of the anastomosis; B: Measurement of the anastomotic diameter.

Figure 5 Anastomotic gross specimens. A-D: Gross specimen of colon anastomosis from the cylindrical group; E-H: Gross specimen of colon anastomosis from the circular ring group; I-L: Gross specimen of colon anastomosis from the cylindrical–circular ring group.

Figure 6 Representative images of histological staining of the colonic anastomosis. A and B: Hematoxylin & eosin (H&E) and Masson trichrome staining of the anastomosis in the cylindrical group; C: H&E and Masson trichrome staining of the necrotic tissue between the daughter magnet (DM) and parent magnet (PM) in the cylindrical group; D and E: H&E and Masson trichrome staining of the anastomosis in the circular ring group; F: H&E and Masson trichrome staining of the necrotic tissue between the DM and PM in the circular ring group; G and H: H&E and Masson trichrome staining of the anastomosis in the cylindrical–circular ring group; I: H&E and Masson trichrome staining of the necrotic tissue between the DM and PM in the cylindrical–circular ring group.

Figure 7 Finite element simulation analysis. A: Stress distribution after intestinal wall compression in the cylindrical group; B: Stress distribution after intestinal wall compression in the circular ring group; C: Stress distribution after intestinal wall compression in the cylindrical–circular ring group.