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Surgical Endoscopy

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01-01-2011

Maximizing coupling strength of magnetically anchored surgical instruments: how thick can we go?

Authors: Sara L. Best, Richard Bergs, Makram Gedeon, Juan Paramo, Raul Fernandez, Jeffrey A. Cadeddu, Daniel J. Scott

Published in: Surgical Endoscopy | Issue 1/2011

Abstract

Background

The Magnetic Anchoring and Guidance System (MAGS) includes an external magnet that controls intra-abdominal surgical instruments via magnetic attraction forces. We have performed NOTES (Natural Orifice Transluminal Endoscopic Surgery) and LESS (Laparoendoscopic Single Site) procedures using MAGS instruments in porcine models with up to 2.5-cm-thick abdominal walls, but this distance may not be sufficient in some humans. The purpose of this study was to determine the maximal abdominal wall thickness for which the current MAGS platform is suitable.

Methods

Successive iterations of prototype instruments were developed; those evaluated in this study include external (134–583 g, 38–61 mm diameter) and internal (8–39 g, 10–22 mm diameter) components using various grades, diameters, thicknesses, and stacking/shielding/focusing configurations of permanent Neodymium-iron-boron (NdFeB) magnets. Nine configurations were tested for coupling strength across distances of 0.1–10 cm. The force-distance tests across an air medium were conducted at 0.5-mm increments using a robotic arm fitted with a force sensor. A minimum theoretical instrument drop-off (decoupling) threshold was defined as the separation distance at which force decreased below the weight of the heaviest internal component (39 g).

Results

Magnetic attraction forces decreased exponentially over distance. For the nine configurations tested, the average forces were 3,334 ± 1,239 gf at 0.1 cm, 158 ± 98 gf at 2.5 cm, and 8.7 ± 12 gf at 5 cm; the drop-off threshold was 3.64 ± 0.8 cm. The larger stacking configurations and magnets yielded up to a 592% increase in attraction force at 2.5 cm and extended the drop-off threshold distance by up to 107% over single-stack anchors. For the strongest configuration, coupling force ranged from 5,337 gf at 0.1 cm to 0 gf at 6.95 cm and yielded a drop-off threshold distance of 4.78 cm.

Conclusions

This study suggests that the strongest configuration of currently available MAGS instruments is suitable for clinically relevant abdominal wall thicknesses. Further platform development and optimization are warranted.

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Title: Maximizing coupling strength of magnetically anchored surgical instruments: how thick can we go?
Authors: Sara L. Best
Richard Bergs
Makram Gedeon
Juan Paramo
Raul Fernandez
Jeffrey A. Cadeddu
Daniel J. Scott
Publication date: 01-01-2011
Publisher: Springer-Verlag
Published in: Surgical Endoscopy / Issue 1/2011
Print ISSN: 0930-2794
Electronic ISSN: 1432-2218
DOI: https://doi.org/10.1007/s00464-010-1149-0

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Maximizing coupling strength of magnetically anchored surgical instruments: how thick can we go?

Abstract

Background

Methods

Results

Conclusions

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Abstract

Background

Methods

Results

Conclusions

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