The first time John Johnson's artificial hip squeaked, he was bending down to pick up a pine cone in his yard in Thomasville, Ga. Johnson looked up, expecting to find an animal nearby.
Susan O'Toole, a nutritionist at Montefiore Medical Center in the Bronx, who first squeaked going up stairs after getting home from her hip-replacement surgery in 2005, said she thought the banister she was gripping needed repair.
Edward Heary, an apprentice appraiser in Hatboro, Pa., said clients sometimes look with embarrassment or concern at their floorboards when he walks though their homes.
As all three patients — and hundreds of others — discovered once they pinpointed the source of the noises, they had become guinea pigs in an unfolding medical mystery. Their artificial hips are made of ceramic materials that were promoted as being much more durable than older models. But for reasons not fully understood, their hips started to squeak, raising questions about whether the noises herald more serious malfunctions.
"There is something amiss here," said Douglas Padgett, chief of adult reconstructive and joint-replacement service at the Hospital for Special Surgery in New York. More than 250,000 Americans get total hip implants each year, a procedure that generally costs close to $45,000.
Hip replacements have a success rate of more than 90 percent, based on patients' achieving relatively pain-free mobility after recovery periods that range from a few months to a year.
Annoying ... dangerous?
Any artificial hip can occasionally make a variety of noises. But until Stryker, a medical-products company, began marketing highly durable ceramic hips in the U.S. in 2003, squeaking was rare.
Tens of thousands of ceramic hips later — from Stryker and other manufacturers — many patients said squeaking hips are interfering with daily life. One study in the Journal of Arthroplasty found that 10 patients of 143 who received ceramic hips from 2003 to 2005, or 7 percent, developed squeaking. Meanwhile, no squeaks occurred among a control group of 48 patients who received hips made of metal and plastic.
"It can interrupt sex when my wife starts laughing," said one man, who talked on the condition that he not be named.
Beyond annoyance and embarrassment, many patients and their surgeons fear that the squeaky ceramic hips may signal the joints are wearing out prematurely. That could force patients to undergo the very operation — a second replacement of the same hip joint — they had hoped to avoid by choosing ceramics.
Dozens of patients have elected to endure subsequent surgeries to replace the noisy hips. Some sued Stryker, the pioneer and market leader, which some doctors said has been slow to take patients' concerns seriously.
Last fall, the Food and Drug Administration (FDA) issued a warning to Stryker, saying it had failed to take the steps needed to prevent squeaking and other problems. Clouding things further, Stryker last year recalled ceramic hip parts made at its factory in Cork, Ireland, after determining some did not meet its sterility specifications.
Stryker officials said none of the problems underlying the recall or the warning letter from the FDA reflect problems that cause squeaking, which it contends occurs in less than 1 percent of implants.
Whatever the frequency, some investigators said the squeaking seems to be associated with extreme flexing of the ceramic implants, but how is unclear. In X-rays, many of the squeaking hips appear to be perfectly aligned.
Nor is there a clear relationship between squeaking and hip pain or other conditions some patients say they encountered, such as the sensation that the hip disengages slightly when a patient walks.
Some patients squeak even they are walking normally, like O'Toole or Michael Mueller, of Scottsdale, Ariz. Mueller is so frustrated with squeaks, pain and popping noises for which he blames his ceramic hip that he has displayed his problem on YouTube.
Company responds
While there have been no reported cases of serious mishaps, some surgeons fear the ceramic material might shatter, leaving a patient with so many inflammatory shards in the hip that a doctor could never find them all.
"Catastrophic failure has been a concern in the past, with older ceramic components," said Dr. James Bried, a surgeon in Poway, Calif. Ceramic materials have been used since the 1960s.
Bried, who implanted Mueller's hip last year, said he was concerned the squeaking might be "a harbinger of something similar."
Stryker says such fears are overblown.
"It is important to keep this in perspective," said Aaron Kwittken, a spokesman for Stryker. "Published research shows squeaking is rare compared with other total-hip-related risks like infection, dislocation and leaving patients with uneven leg length."
Durability is paramount with artificial hips. Patients worry they will outlive their artificial hips and require a second, more extensive and even more expensive procedure at an age their bodies may be less able to cope with the trauma.
Ceramic hips were promoted as lasting much longer than the 15 years or so for conventional artificial joints made of steel and plastic.
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