Device may overcome problems of magnetic guidance

September 16, 2013

A recently developed instrument may improve the adjustment capabilities of a magnetic coupling system being investigated for use in laparoscopic procedures.

Nashville, TN-A recently developed instrument may improve the adjustment capabilities of a magnetic coupling system being investigated for use in laparoscopic procedures, according to data presented at the AUA annual meeting in San Diego and subsequently published in Surgical Innovation (2013; 20:385-94).

Magnetic Anchoring and Guidance Systems (MAGS), introduced 5 years ago by Jeffrey A. Cadeddu, MD, and colleagues at the University of Texas Southwestern Medical Center, Dallas, can be seen as another technological step toward minimizing trauma and morbidity in laparoscopic procedures. The concept underlying the technology is to reduce the number of ports and incisions associated with a surgical procedure by anchoring surgical instruments, such as cameras, intracorporeally with extracorporeal magnets, just as a bar magnet on one side of a sheet of paper can hold a paper clip in place on the other side.

However, there are challenges with the MAGS equipment design that S. Duke Herrell, MD, associate professor of urologic surgery at Vanderbilt University Medical Center, Nashville, TN, and his colleagues in Vanderbilt’s School of Engineering are bent on resolving.

Dr. Herrell explained that the current camera system is rendered relatively immobile when anchored by the external magnet and that moving it to change the visual field requires often-forceful manipulation of the patient’s abdominal wall.

“To get the camera’s field of vision changed and held, physical force has to be applied. Pushing on a patient’s abdomen, with force that must be held, is not a good solution,” Dr. Herrell told Urology Times.

To resolve this issue, a team consisting of Pietro Valdastri, PhD, Dr. Herrell, and colleagues are developing a dichotomous segmented instrument. One segment, the tail or anchoring module, consists of two magnets that allows the instrument to be fixed in place intracorporeally by external magnets. The second segment is a camera embedded in a structure called the Local Magnetic Actuator.

“The secondary magnet system can move the camera through a range of about 80 degrees vertically via magnetic force. It simply ‘levitates’ its position,” Dr. Herrell explained.

The system is a 95-mm long, 12.7-mm wide cylindrical device that weighs about 20 grams.

The system’s function and flexibility were demonstrated in nephrectomies performed in four fresh tissue cadavers (three male, one female). The procedures were successfully conducted by first author Ryan Pickens, MD, using two ports for working instruments only.

“It might be said that it is easy to perform a nephrectomy in a cadaver because it doesn’t bleed. On the other hand, the technology allowed us exposure and visualization, and allowed us to perform dissection and identify and get to the vessels in a manner similar to what would be done in a live human,” said Dr. Herrell.

Further modifications anticipated

At this stage of development, an assistant remotely controls the camera, but Dr. Herrell envisions a system that would be controlled by the operating surgeon, perhaps by a foot pedal. He also anticipates employing advanced camera technology. The team used fundamental technology in these initial experiments to control costs. The authors said they feel they have accomplished their goals and hope to move to a clinical setting within the next year or two.

“The problem with current laparoendoscopic single-site (LESS) procedures is that the tools do not allow triangulation, and in instances the camera can block your vision. There are geometric complexities involved,” Dr. Herrell said. Placing a camera internally, anchoring it with external magnets, and being able to manipulate it externally with full field control would substantially reduce some of these geometric challenges.

Dr. Herrell said he anticipates this technology will be an integral part of the drive toward instrument miniaturization as well as fewer and smaller incisions.

“We have also been working on developing and incorporating microlaparoscopic instruments and procedures. Instead of 5-mm instruments, we can use 3-mm instruments. It is possible to imagine a scenario in which an operation that usually requires four or five 12-mm incisions may only require one 12-mm incision. This would significantly reduce the trauma of the operation, which is the goal of minimally invasive procedures,” he said.

Dr. Herrell has an investment interest in Veran Medical Technologies and is a consultant/adviser to Aesculap, Inc.UT

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