Bypass surgery made easier

Cincinnati, OH--Thanks to an 18-member development team at Ethicon Endo-Surgery Inc. (EES), a Johnson & Johnson Co., patients now have an alternative to the long incision typically used to extract veins for coronary heart bypass surgery. The vein harvesting operation normally takes place simultaneously with the coronary bypass operation.

The new procedure designed by the EES team, called the Endopath^TM system, consists of four primary devices that physicians can employ in conjunction with an endoscope:

- Subcu-Dissector(R), used to create operative space (tunnel) in the subcutaneous tissue of the leg.

- Subcu-Retractor(R), used to maintain the operative space.

- Vessel Dissector(R), used in the blunt dissection of tissues.

- Allport Clip Applier(R), used to clip the vein branches following dissection.

"Our innovative devices will revolutionize this surgical procedure," boasts John Love, project team leader for the EES team that developed the vessel harvest instruments.

The EES team performed this achievement in a "record time" of 18 months from initial discussions to market. Critical to the design of the devices was materials selection. Therefore, early in the design process, the engineering team got valuable "in-house" assistance from Dow Plastics, Midland, MI.

Visitors to the Medical Design and Manufacturing West show to be held next month (Feb. 11-13) in Anaheim, CA, can view the system first-hand at Dow Plastic's Booth 1047.

Powerful potential. The importance of the new system cannot be underestimated. From 550,000 to 600,000 patients worldwide undergo coronary artery bypass grafting each year. The worst pain for some patients who face the surgery is actually in the leg, from which the surgeons remove a vein to bypass the diseased coronary arteries.

The vein harvesting project began in October 1994 when three different groups of customers came to EES to voice their dissatisfaction about the current vein harvesting methods, according to Michael F. Clem, EES's manager of emerging surgical procedures. "There are sometimes clinical complications in the way saphenous vein harvesting is done today, which is a single, long incision down the leg," says Clem, a doctor of veterinary medicine, summing up the group's concern. Among the customers were plastic surgeons, peripheral vascular surgeons, and a general surgeon.

Their concerns were reinforced by the addition of cardiovascular surgeons and surgical assistants to the group. The meetings helped define what the difficulties of the vein harvest procedure were, followed by brainstorming sessions to outline possible solutions.

Clem adds that the project involved much more than the financial reward that might ensue for EES. "We wanted to look at it from the standpoint of caring about the patient," he explains. "We were informed that about 10% of patients who undergo open vein surgery suffer from major complications." Depending on who you talk to, complications can involve as few as 1% of the patients treated to more than 40%.

One of the problems is that after a four- or five-day stay at the hospital, the surgeons send the patients home. A week later, when they go back to their cardiologist or general-practice physician, complications can show up. "My understanding is that a lot of these complications occur after discharge," says Clem.

Before investing in the project, EES looked carefully at the business potential, costs, and patient benefits involved with designing a new vein harvesting procedure. Study results looked promising.

With this incentive as a positive driving force, EES decided to give the project the go ahead. Enter Gary Knight, EES senior design engineer, as project leader. In the lab and at the model shop, Knight and Clem, plus Steve Black, model maker at EES, developed several system prototypes. The goal, says Knight, was to create a new prototype every week. "We pretty much hit that mark on average over the next three months," Knight recalls.

Helping to make this possible were assists from EES's 3-D CAD solid-modeling programs and 3-D rapid prototyping. For this project, the designers relied on Pro/ENGINEER from Parametric Technology Corp., Waltham, MA, to design the models. (EES is in the midst of switching to Milford, OH-based SDRC's I-DEAS software.)

"Once the solid models were iterated, we turned the CAD files over to Steve and our model shop to produce the sterolithographic models," Knight notes. "Within a week's time we were able to go from an idea on paper to molded urethane parts using 3-D CAD, SLA (3D Systems, Valencia, CA), or SLS (DTM Corp., Austin, TX), and rubber molds."

Disposability decisions. Serious discussions ensued during the design stages as to whether or not to make the instruments reusable or disposable. With medical costs continuing to spiral, hospitals are looking for ways to cut expenses wherever possible, especially in the operating room. Some panel members considered that the ability to reuse the vein-harvesting equipment would cut costs, as well as be more environmentally sound.

However, a reusable device also has some drawbacks. For instance, the initial cost of reusable devices is significant, and resterilization and repackaging would have to be included. And, a reusable device would make the design far less flexible when adding improvements to the instruments. In addition, all materials used in a disposable system are environmentally sound and can be incinerated in the typical fashion.

The decision: make them single-use, disposal devices.

As noted, the vein harvesting procedure works in conjunction with an endoscope. In a typical operating-room setting, the endoscopic equipment encompasses a one-chip or newer three-chip camera; a 5 mm x 300 mm, 30-degree endoscope; fiber-optic light source; and video equipment that lets the surgeon follow the path of the endoscope as it travels along the route of the vein, while also providing a video record of the procedure.

Materials input. Karen L. Winkler, senior applications development engineer at Dow Plastics, helped the EES engineers work through the intricacies of materials selection.

The discussions entailed how best to incorporate standard engineering plastics in products that compete in a high-end, value-driven business. Criteria behind the choice also included the need for a rigid material that could withstand stress under operating conditions, as well as one that would easily flow into the 20-inch mold and properly free the ribbed construction of the handles. Moreover, the materials had to stand up to gamma radiation and ethylene oxide sterilization procedures.

In sessions with Knight; Dave Stefanchick, staff design engineer; and James L. Millward, EES' supplier manager-material technology--and using results from mold-flow analyses--the team settled on four Dow materials:

- Isoplast(R) 2540 40% glass-filled thermoplastic urethane for the vessel dissector's 20-inch-long, gray rod.

- Calibre(R) 5201 20% glass-filled polycarbonate for the clip applier's, dissector's, and retractor's white handles and cover.

- Calibre MegaRad(R) 2081 clear-grade polycarbonate for the dissector's and retractor's blunt-tip spoon, allowing the surgeon to view the endoscopy as the device tunnels its way along the vein.

- Pellethane(R) 2363 80A thermoplastic polyurethane elastomer for a scope retaining clip that permits most en-doscopic devices to be inserted intoeach instrument's handle.

Each instrument's shaft and the ferrule that holds the assembly together consist of 304 stainless steel.

Clear-cut decision. EES got FDA clearance to market the system last February. A few weeks later, the Louisville-based Jewish Hospital became the first facility in the nation to remove a vein through the new videoscopic procedure. The hospital is the 8^th largest heart center out of 850 across the U.S.

As of last count, more than 2,000 such operations have been performed at 100 hospitals since the system was introduced. Many others are joining the fold all the time, EES officials note. As the procedure becomes more readily available, "more patients will be pressuring their doctors to adopt the new harvesting method," asserts Dr. W. Peter Geis, director of the Minimally Invasive Surgical Training Institute at Baltimore's St. Joseph Medical Center.

Both surgeons and the EES team members see the cost and time to perform the procedure shrinking as more of the devices enter the market and more surgical personnel are trained in their use. For example, it takes 30 to 45 minutes to perform the open leg surgery, and could take as much as an hour to close the incision.

The procedure also gets high marks from Dr. Peter P. McKeown, associate professor of surgery at the University of South Florida College of Medicine in Tampa, who was one of the first to perform the operation. He feels the procedure "will become the standard of care in one or two years." And that forecast should be welcome news for the hundreds of thousands of future patients who face coronary artery bypass surgery.