Do higher-than-average readmission and complication rates among hospitals performing large numbers of hip and knee replacements suggest below-average performance on the part of those facilities, or is the situation more nuanced than simple numbers can reveal?

In the Philadelphia area, several high-volume and reputable hospitals are defending their performance in light of new Medicare data showing that their readmission and complication rates for joint replacements are higher than the national averages.

For example, at Pennsylvania Hospital, which had an 8.2% readmission rate and a 4.7% complication rate, both higher than average, a hospital official told the Philadelphia Inquirer that the percentages may be misleading because a physician there had been willing to take on especially complicated cases.

Others say the numbers could reflect an abundance of caution, a more economically challenged patient population that finds it tougher to follow post-operative care instructions or simply better record-keeping.

The risk-adjusted Medicare formula is designed to take a large number of pre-existing conditions into account. But James Saucedo, lead author of a Northwestern University study that found that inconsistent record-keeping is often a factor in such data, told the Inquirer that busy urban hospitals may not have time to record all comorbidities. One result, he said, is that "institutions [that] we would expect to be among the best [are] going to look terrible."

However, Lisa Suter, associate director of the Yale University program that developed the Medicare analysis, says the numbers accurately reflect patient populations by "aggregating results over many, many patients at each hospital" and that they give "a very important sense of how sick that hospital's patients are."

Jim Burger