The New New Hip

With its ball-and-socket arrangement, the hip appears to be a structurally simple joint. But to the patient, and to his orthopedic surgeon, a disease-damaged hip often presents appalling problems. Surgeons have for years been inserting workable mechanical substitutes, but too often the substitute has failed, either because of faulty wearing surfaces, or because of infection that later requires the removal of the whole artificial joint.

A vastly improved artificial hip has now been devised. Using a replacement hip of his own design and a unique sterilization technique, Surgeon John Charnley, 59, of England's Wrightington Hospital at Wigan, has performed 4,000 hip operations and cut the infection rate among his patients from 4% to .5%. Two major U.S. medical centers, New York's Hospital for Special Surgery and Hollywood Presbyterian Hospital, are now performing the operations.

Behind His Back. When a hip joint is damaged, the ball of bone at the head of the femur may rub against the roughened surface of the socket in the hip proper (see diagram), causing severe and immobilizing pain. Replacing the head of the femur with a stainless steel ball (just under an inch in diameter for the average patient) is relatively easy. The difficulty is to secure the ball to the femur. In early operations, the shaft holding the ball was screwed into the femur. Charnley was dissatisfied with the method because the shaft sometimes came loose. A dentist friend proposed that he "cement" it in with methyl methacrylate, a plastic used for years in dentistry. "My friend couldn't have suggested anything better," says Charnley. "It was a tremendous advance. The prosthesis [artificial part] now remains permanently, rigidly fixed to the bone."

That was only half of the mechanical problem. The ball must rotate in a socket, which in most such hip operations had been made of steel. Charnley disliked the steel-to-steel joint because it must be lubricated solely by body fluids, which are often inadequate. A plastic socket would require no lubrication. But what plastic? He tried Teflon, only to have it break loose and damage nearby bone. "One day," he says, "a salesman turned up with a sample of high-density polyethylene. I sent him away, telling him that we knew that polyethylene was useless. I hadn't heard of high-density polyethylene, but luckily my lab technician had, and behind my back he told the salesman to leave a sample. We tested its wearing properties, and the results were fantastic."

Since late 1962, Charnley has used the polyethylene socket, which is also cemented in place with methyl methacrylate. In an intensive follow-up of his first 500 cases, Charnley has found the cement holding perfectly. The polyethylene, originally 10 mm. thick, wears away at the rate of about 1 mm. in five years. "No discomfort should be noticed until at least 50% has worn away," he says, "and if that happens, we can always replace the socket."

Need to Shout. There remained the danger of infection, especially severe in hip surgery because so much tissue must be exposed. With Charnley's new plastic techniques, the infection rate was 4%. That was too high by his standards. Then he devised an elaborate suction system for his operating room. Each member of the surgical team was fitted with a flexible tube, long enough to permit free movement, that ran up his back and was connected to a narrow steel tube that encircled the face and had holes through which his exhaled breath was drawn away. "It makes communication harder and people have to shout a bit," Charnley concedes. "But we don't sweat nearly so much and work is much less exhausting." It must be, because Charnley now schedules six operations a day, four days a week. Each one takes 1 1/4 hours.

In Los Angeles last month, surgeons at Hollywood Presbyterian Hospital who had studied Charnley's methods demonstrated their technique in a space-age adaptation of an operating room. The entire area around the operating table was covered with a plastic "greenhouse," into which ultra-filtered air flowed from above, fast enough to change the air completely ten times a minute. Within it, three surgeons, Doctors John Toma, Charles Bechtol and Charles Hutter, were dressed in space suits with helmets, like those worn by astronauts on the moon. The scrub nurse, who handles sterile instruments, was similarly attired. Their patient was Margaret Fales, 59, a credit manager, who had been so crippled that walking was unbearably painful. By last week Miss Fales was free of the pain that had driven her to surgery; her hips were a bit stiff in the morning and she tired by afternoon--but she could walk.

At a recent surgical staff meeting in Los Angeles, other former patients of Charnley and his disciples demonstrated their agility. A woman of 65, who had replacements for both hips, walked with neither pain nor limp. A former R.A.F. pilot, 46, handicapped for more than 20 years by a World War II injury, did a little "gogo" dance.

This file is automatically generated by a robot program, so reader's discretion is required.