But according to Mayo thrombosis expert John Heit, MD, of the Mayo Clinic in Rochester, MN, the study published in Wednesday's Journal of the American Medical Association, is deeply flawed for several reasons, and thus misstates the actual VTE risk. Explaining his reasoning in an opposing clinical review in the same issue, Heit said the risk of VTE extends as long as 91 days after surgery, far beyond the few days the patients remain hospitalized and the period of this study.
In a large California data set from between 1991 and 1993, for example, the 91-day cumulative incidence rates for symptomatic VTE were 2.8% for knee replacement patients and 2.1% for hip replacement patients, he writes.
"The authors did everything correctly," Heit says in a phone interview. "But the study has serious limitations that really make the results difficult to interpret and potentially not all that applicable to current day practice."
The percentages in their study are "too low for the entire period of risk, which is three months after hip replacement and a month and a half after knee replacement. And it's probably too high for the current duration of hospitalization, which is only three or four days. So I don't think they're very helpful for counseling the patient or to be used as a benchmark for quality improvement."