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Sqeaking ceramic hip joint

Josephine

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That Must Be Bob. I Hear His New Hip Squeaking.
By Barnaby J. Feder May 11, 2008

The first time a patient’s artificial hip squeaked, he was bending down to pick up something. He said he looked up, expecting to see an animal. Another patient 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.

Another patient said his friends look with embarrassment or concern at their floorboards when he walks though their homes.

As all three patients - and many others – discovered their artificial hips were made of ceramic materials that were promoted as being much more durable than older models. But for reasons not yet fully understood, their hips started to squeak, raising questions about whether the noises herald more serious malfunctions.

“There is something amiss here,” said Dr. Douglas E. 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. 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. 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 United States in 2003, squeaking was extremely rare.

Now, tens of thousands of ceramic hips later, from Stryker and other makers that entered the field, many patients say their squeaking hips are interfering with daily life. One study in the Journal of Arthroplasty found that 10 out of 143 patients who received ceramic hips from 2003 to 2005 (7%) 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 discussed the matter 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 that the joints are wearing out prematurely that could force patients to undergo the very operation they had hoped to avoid by choosing ceramics.

Already, many patients have sued Stryker, the pioneer and market leader, which some doctors say has been slow to take their patients’ concerns seriously. The Food and Drug Administration 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 that some did not meet its sterility specifications. Stryker says that 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% of implants.

Whatever the actual frequency, some investigators who have looked at the problem say the squeaking seems to be associated with extreme flexing of the ceramic implants, but exactly 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 have encountered, like the sensation that the hip disengages slightly when a patient walks.

While there have been no reported cases of serious mishaps, some surgeons fear that the ceramic material might shatter at some point, 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 M. Bried, a surgeon in Poway, California. Ceramic materials have been used since the 1960s. Dr. Bried said he was concerned that squeaking might be “a harbinger of something similar.” and had advised patients to consider getting the hip replaced “sooner rather than later.”

Stryker says such fears are overblown but doctors who have removed ceramic hips say they find dark stripes that indicate accelerated wear on the ceramic heads. But durability tests have suggested that even those extracted hips would have outlasted conventional metal-and-plastic replacement joints, according to researchers.

“There is no evidence that the wear associated with squeaking would lead systems to fail,” said Dr. James A. D’Antonio, an orthopedic surgeon outside Pittsburgh, who was a chief investigator on the clinical trials that led to regulatory approval for Stryker’s Trident.

Dr. D’Antonio, whose longstanding role in Stryker’s product development efforts earned him $1.1 million in consulting payments from the company last year, said he had implanted 400 Tridents since the clinical trials began in 1996. He said that only four of his patients had noticed squeaks and that none of them were able to reproduce them in his office.

But Dr. Fabio Orozco, a surgeon at the Rothman Institute, a major orthopedics group in Philadelphia, said that a recently completed review of about 1,500 Rothman patients with ceramic hips had found that the squeaking condition occurred in 49 of them, or about 3 percent.

May 9, 2008
Anatomy of a Squeak
Some patients who have received artificial hips with ceramic components have complained that the hips make a squeaking sound. The exact cause of the squeaking is unknown, but “stripe wear” found on used ceramic parts suggests that the noise may begin when these parts rub together. The audible squeak may be the resulting harmonic vibration of the metal shell or stem

ceramic squeak.JPG
 

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