It will be some time before the first man with an artificial heart walks down the street on artificial legs, breathing through an artificial lung, his blood coursing through long stretches of artificial artery, his metabolic poisons filtered by an internal artificial kidney, while he admires the landscape through artificial corneas in eyes filled with a chemical fluid the consistency of molasses. It may be that no one man will ever enjoy all these advantages of alloplasty-surgery in which foreign materials are used to replace the body's natural parts. But it will not be long before many people are fitted with one or more of these devices.
For thousands of years, repair surgery was limited to such obvious and available materials as wood, bone and ivory-which the body is usually quick to reject. Then doctors turned to refined metals. But the current mush rooming of alloplasty had to await the proliferation of synthetic plastics. Most of the materials now favored are the polymers (basically familiar molecules in unfamiliar, complex arrangements), such as nylon, Dacron and Plexiglas. But even more widely useful are the silicones,* which may be solid or as gooey as engine oil.
In Brain & Heart. Even the hypersensitive brain is amenable to surgery and the implantation of certain plastics. Only ten years ago, a child who was born with or soon developed the condition known as hydrocephalus (water on the brain) was doomed to mental retardation or early death. Today, more than 80,000 youngsters have their brain-drain problem solved by an implanted Silastic tube.
The duct of Silastic (trade name for medical silicones made by Michigan's Dow Corning Corp.) is 18 in. to 24 in. long, only 1/16-in. thick. It is led under the skin, behind the ear and down the neck to a point where it is spliced into the internal jugular vein. The excess brain fluid is thus dripped into the bloodstream, where the body readily disposes of it. Another Silastic preparation, which looks like a sheet of waxed paper, serves to correct a different type of brain problem: when part of the brain's parchmentlike covering, the dura mater, is damaged or destroyed, the brain tissues and fluids are kept from bulging or leaking out by a Silastic sheet backed with Dacron.
In a still more delicate sealing-off operation, Tufts University's Dr. Bertram Selverstone opens the skull of a patient who has an aneurysm on a brain artery. To seal or prevent a rupture, he sprays the artery with a plastic mixture which gives it a dry, thin coating like Saran wrap. Then Dr. Selverstone sprays on a second coat, using a new, quick-setting epoxy resin. The double coat has the desired toughness. And more than 100 patients are living with blowout patches in their brains.
Muscular and robust as it is, the heart is less tolerant of foreign materials. Washington Surgeon Charles Hufnagel overcame this intolerance in 1952, when he implanted the first artificial aortic valves, made of a Plexiglas ball in a Plexiglas sleeve. The ball has since been replaced by Silastic.