DAVID S. HOTTER
Government mandates aimed at cutting the cost of medical services make plastics the natural choice for devices used during in-home treatment or in hospitals. Engineers use polymers to slash manufacturing costs and streamline devices. The results are equipment that patients can use in the home and affordable disposables.
Medical plastics represent a $4.5 billion market worldwide. Of this number, $3.9 billion is commodity resins and $570 million is engineered resins. Commodities are growing 1 to 2%, while high-performance plastics grow at a rate between 6 and 8%.
The medical industry is similar to the automotive marketplace. Ten years ago plastics weren’t a major player in car designs; yet today they are well accepted. Plastics are in their infancy in medical devices today. The result is niche companies producing high-margin products using advanced resins and manufacturing processes.
Medical costs are rising as the population ages and people live longer. To counteract these costs, government is trying to reduce long-term hospital care, turning instead to out-patient surgery and acute-care facilities. John Dykstra, medical marketing manager at Phillips Plastics Corp., Prescott, Wis., explains, “New technologies are aimed at letting patients or medical professionals other than doctors administer medications more carefully and accurately, rather than requiring doctor visits. Cutting doctor and hospital visits is critical, especially with the limited amount of money allocated to patients through managed health care — whether they see doctors once a day or once a year.”
Instead of sending blood samples to labs, clinic workers or patients themselves run tests using portable machines to test blood and report results quickly. “Portable instruments let medical workers get test results to patients and doctors faster, and eliminate test mix-ups in the lab,” adds Nancy Hermanson, medical market technical leader for Dow Plastics business group of Dow Chemical Co., Midland, Mich.
Another way plastics help rein in health-care costs is by reducing the length of hospital stays. Endoscopic surgeries — in which doctors operate through small incisions rather than opening large skin sections — cause less trauma and therefore promote speedy recovery. They let doctors perform procedures on an outpatient basis or as day surgery. Equipment used in these surgeries are small with complex features, making plastics a popular replacement for metals.
For example, Ethicon Endo-Surgery, a Johnson & Johnson Co. located in Cincinnati, developed the first endoscopic vein-harvesting system used for coronary bypass surgery. The device is made almost entirely from thermoplastics supplied by Dow Plastics. During bypass surgery, the doctors use the instrument to extract the great saphenous vein from the patient’s leg. In the past, this was done via an incision made from the groin to the ankle. Now the procedure involves four 1-in. incisions for endoscopic instruments and fiberoptic cameras. The vein is then grafted between the aorta and coronary artery to bypass blockages.
Smaller incisions mean quicker recovery. “Anyone who has had bypass surgery tells you it’s their leg that hurts; they never complain about chest pain. Patients now complain their chests hurt, not the leg, which Ethicon views as a success,” says Hermanson.
CRACKING DOWN ON DESIGNS
Health-care reform is also forcing device manufacturers and material suppliers to cut costs. Engineers must show that new devices are not only better but also more cost effective than what they’re replacing. Doug Powell, medical industry specialist for Bayer Corp., Pittsburgh, explains, “As material suppliers, we must develop products that add value and slash manufacturing costs or reduce costs associated with disposables. Plastics give engineers design and processing flexibilities.”
One example of such technology is Bayer’s development of the first lipid-resistant polycarbonate for luers, tubing connectors, Y-site medication ports, and stopcocks. “Medical workers found that connectors were cracking when exposed to intravenous fluids such as lipid emulsions. To prevent leaks, they replaced parts every 24 hr, even though guidelines recommended 72 hr. With Makrolon DP1-1805, connectors last over 72 hr, reducing consumption by two-thirds,” Powell says. Besides reducing consumption, the polycarbonate resin replaces high-priced alternatives such as polyurethane, polyetherimide, and polysulfone, and is easier to mold.
In addition to letting manufacturers create small, complex designs, plastics can also be compounded to increase performance qualities such as lubricity, strength, and conductivity. “Bushings and bearings made from glass-reinforced, lubricated resins resist sterilization and let doctors operate them more smoothly,” explains George Forczek, marketing development manager, LNP Engineering Plastics Inc., Exton, Pa. “And static-conductive plastics help ground instruments used near explosive gases such as ether.”
With devices getting smaller and smaller, materials for components must meet more stringent demands including compatibility with other materials and resistance to repeated sterilization. In extremely demanding designs, engineers turn to high-end plastics such as polyketones to mold smaller components. “Designers choose polyketones when they can’t get the needed performance from polyesters, nylons, thermoset polyimides, and stainless steels,” says Dan Lazas, Victrex, general manager, Victrex USA Inc., West Chester, Pa.
An example is catheter tubing for minimal-invasive surgery, made from PEEK to maintain rigidity and toughness, and prevent kinking in thin-walled tubing.
However, PEEK isn’t used for disposable or lower-priced products because it’s expensive and must be processed at high temperatures. But PEEK increases components durability and allows them to be sterilized more severely. For example, medical workers use PEEK catheters twice instead of once before throwing them away because they stand up to sterilization.
Polymers represent another way to cost-effectively augment and improve existing designs. Thermoplastic elastomers, for example, are used for their soft feel. Nancy Boschert, marketing technical service representative for Advanced Elastomer Systems, Akron, Ohio, explains, “TPEs improve existing plastic designs and are combined with plastics to replace metals. Elastomers make it more comfortable for surgeons to hold instruments up to 8 hr without cramping or developing carpal tunnel syndrome.”
As medical-equipment designers become more familiar with plastics, they will find more-demanding applications for engineered resins. With continued cost pressures on equipment manufacturers, some of the focus will be on part processing. “Complex geometries are common when parts are consolidated. It is important that such designs are also easy to release from molds to maintain high parts-per-hour rates,” says Bayer’s Powell. “Mold-release sprays are one option, but they cause scrap parts for the first few shots and parts often require cleaning. We are developing grades with mold-release qualities built into the resin to address these concerns. Not only do the resins eliminate release sprays, they also let workers mold parts cooler and shorten cycle times. One customer reduced cycle time by 46%.”