Many hospitals are hard-pressed to tell people needing a hip replacement how much their procedure is likely to cost, according to a new study. Even when they can cite prices, going rates for the procedure may vary from hospital to hospital by a factor of 10, researchers found.

“It was very frustrating,” said Jaime Rosenthal, a student at Washington University in St. Louis who led the new research, which was reported in JAMA Internal Medicine. “You got transferred to all these different people. You had to leave messages, call back.”

According to the U.S. Centers for Disease Control and Prevention, about 327,000 Americans had a hip replaced in 2009.

The surgery is especially common among the elderly, who are covered by Medicare. Still, about half of all hip replacements in the U.S. are done on people younger than 65, some of whom may not have private insurance.

For the new study, Rosenthal called 122 hospitals: two per state and two in Washington, plus the top 20 orthopedic hospitals listed in U.S. News and World Report rankings. During each call, Rosenthal pretended to have a 62-year-old grandmother who needed a hip replaced but didn’t have insurance, and she asked for the total price of the procedure.

Just 45 percent of the top 20 hospitals and 10 percent of other hospitals could provide a complete cost for the hospital and doctor fees for a hip replacement, after up to five phone calls.

When Rosenthal called both the hospital and affiliated doctors separately, her team was able to put together the prices of procedures at 60 percent of top hospitals and 63 percent of others.

Those totals ranged anywhere from $11,100 to $125,798, Rosenthal and her colleagues reported.

She said some hospitals gave her reasons for a higher price — such as a private room — but for others, it wasn’t clear what went into the cost of care.

“It just points to the fact that most of us in the health system don’t have any idea what the costs really are,” said medical ethicist Ezekiel Emanuel from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, who co-wrote a commentary published with the new study.

Often, only the hospital’s billing office knows how much a patient is charged for a procedure such as a hip replacement, researchers noted.

Some of the variation in costs has to do with how hospitals factor in overhead to each patient’s bill, Emanuel said. And the cost of a hip prosthesis can vary four- or five-fold across the country, he added.

Jeanne Pinder, founder of ClearHealthCosts, said a 10-fold difference in price isn’t unusual, even within a single geographic area.

“I always recommend that people ask,” Pinder said.