Novel Magnetic Countertraction Enhanced Performance in Colonic Endoscopic Submucosal Dissection: An Ex Vivo Crossover Study (With Video).

Endoscopic submucosal dissection (ESD) is technically demanding with the main limitation on the lack of effective countertraction. Existing countertraction methods such as clip-related techniques only provide unidirectional static traction force that may restrict their utility in complicated colorectal ESD. The magnetic countertraction system provides dynamic force by manipulating an external magnetic source. We designed a novel magnetic countertraction system with an internal magnet retractor introducible via the endoscopy channel and the external magnetic effector mounted on a robotic arm that could be easily manipulated. We evaluated the performance and safety of the system in an ex vivo randomized crossover study. ESD was performed on ex vivo porcine colon models with standardized 3 cm target lesions marked at gravity-dependent locations. Endoscopists performed the ESD in pairs, randomized to magnetic countertraction (MAG-ESD) or conventional ESD (C-ESD) first to minimize bias from the learning effect. During MAG-ESD, a flexible internal magnetic retractor was deployed via the endoscopic channel and anchored to the lesion margin. A robotic arm-mounted external permanent magnet (EPM) was positioned above the colon model to engage the retractor and provide dynamic countertraction. Seventy-two ESD (36 MAG-ESD and 36 C-ESD) were performed by 18 endoscopists. MAG-ESD significantly reduced procedure time by 20.4% (p = 0.0002) and workload (NASA-TLX mean difference: -19.81, 95% CI: -25.42 to -14.19). All procedures achieved en bloc resection. MAG-ESD had significantly fewer complications (OR = 0.782, 95% CI: 0.644-0.949), including lower rates of perforation and muscle injury. The novel magnetic countertraction system significantly improved procedural efficiency, reduced operator workload, and enhanced safety in ex vivo colonic ESD.