Hip prostheses generally last between 10-15 years, said Joshua Farber, MD, vice chair of clinical affairs at Indiana University Hospital in Indianapolis. Then a series of complications can occur. Dr. Farber studied 45 patients who had pain in their replaced hip, using both plain film x-rays and MDCT to diagnose the problem. MDCT was 100% accurate in detecting bone loss near the prosthesis, said Dr. Farber. That compares to a 67% accuracy rate for plain films. MDCT had an added benefit for these patients, in that it could pinpoint exactly where the bone loss had occurred so the surgeon could more easily repair the problem, said Dr. Farber.
MDCT was 100% accurate in detecting fractures near the prosthesis, compared to 94% for plain films. In addition, MDCT was 61% accurate in detecting whether the prosthesis had come loose, compared to 54% for plain films. The ability to diagnose acetabular component loosening on MDCT was influenced by the experience of the radiologists reading the exam, said Dr. Farber. "When the most experienced radiologist read the exam, the accuracy rate was 72%."
Dr. Farber noted that they are currently comparing MDCT to plain film to determine which is a better test for diagnosing wear on the plastic liner between the metal components of the prosthesis and particle disease (as the prosthesis wears down, particles get into the tissues near the prosthesis and can cause an inflammation).
"As the population ages, we are seeing more of these types of patients. The increase in obesity also plays a role in the increase in hip replacements," Dr. Farber said. "At my institution we now do MDCT examinations on a majority of these patients. We recommend that, at the very least, MDCT should be performed if a patient has a plain film x-ray and the x-ray is questionable. MDCT also should be performed if surgery is needed since it provides a much better guide than plain film for the surgeon," Dr. Farber said.
The study will be presented on May 5 at the American Roentgen Ray Society Annual Meeting in Miami Beach, FL.
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