Surgery by Numbers

Originally Published MDDI June 2002

MEDICAL DESIGN EXCELLENCE AWARDS 2002

Ancure Endograft System

Submitted by Stirling Design (Aptos, CA); manufactured by Guidant Corp. (Menlo Park, CA)

Miniaturizing devices and minimizing the invasiveness of surgeries have been key trends in the medical sector over the past decade. The Ancure Endograft System applies these concepts for the first time to the treatment of abdominal aortic aneurysms, potentially life-threatening bulges of the aorta.

Previously, patients had to undergo grueling surgery. Deep abdominal incisions extending from the breastbone to the pubic bone were needed to access the aorta, and numerous organs had to be moved out of the way, then replaced once a blood-diverting polyester sheath was attached to the weakened aortic wall. The patient's recovery process was lengthy, and patients spent an average of six days in the hospital following surgery.

In contrast, clinical trial results show a reduced morbidity rate and patients who are able to go home 24 to 48 hours after surgery when treated with the Ancure Endograft System. With the system, a surgeon inserts a catheter into the patient's body through the femoral artery, guides it through the artery up to the aorta, positions the device, and deploys the implant. A balloon on the catheter is used to seal the implant to the aorta.

Guidant started developing the system years ago, and while some other minimally invasive techniques have now come on the market, Guidant's remains unique for several reasons.

"Ours is the only device that uses a unibody construction," explains Anne Mueller, product development engineer for Guidant. The product resembles a Pocket Fisherman—fitting comfortably into surgeons' hands and eliminating sharp edges that might catch on drapery or other items in the operating room. "The graft implant also features hooks that 'anchor'—which is where the product name came from—the graft to the vessel. Finally, the device incorporates tabs that surgeons activate in numerical order to perform the procedure."

Guidant's original graft system had two handles and was fairly complicated to use. The company hired Stirling Design to improve the device's industrial design, ergonomics, and user interaction, and Phillips Plastic Corp. (Hudson, WI) to design new molding and manufacturing processes.

"Our greatest challenges were miniaturizing the parts and making the device more user-friendly," recalls Loren Stirling, principal of Stirling Design. "Our task was to design the surgeon's end of the delivery device to be as ergonomic, uncomplicated, and friendly as possible."

Working together, the three companies consolidated the original product's two handles into one and simplified the steps for use. The number of parts used in the device was reduced by 25%, which cut manufacturing costs by 88%. The relatively large (up to 26 mm) diameter of the graft-and-attachment system was designed to collapse to 23 French for delivery into the body.

The next hurdle was to make a complicated procedure less so. Stirling and his counterparts at the other companies brainstormed ideas and decided to number the procedure steps on the device so that surgeons couldn't perform any of the steps out of order.

"There are a number of steps involved: positioning the graft material; deploying, then setting, the hooks at both ends of the material; then backing the delivery hardware out of the area," Stirling says. "Surgeons are basically transformed into artists building a boat in a bottle. They guide the graft material by watching it on an x-ray monitor as it moves along the artery. (There are trace markers on the graft implant.) We created a foolproof method of deployment by numbering each step and requiring surgeons to remove safety tabs before proceeding from one step to another. It's impossible to skip a step. This concept was important from a human factors standpoint."

Also important to the entire process was the collaboration that occurred among the firms involved. "Everyone approached the design from a different perspective—from a design engineering viewpoint, surgeon usage perspective, and manufacturer's view," Stirling says. "The conclusions we came to in concert made for a solution that best meets the patients', the surgeons', and the manufacturer's needs."

Copyright ©2002 Medical Device & Diagnostic Industry