"Everyone is concerned about preventing blood clots," he says, "but the risks of blood thinners far outweigh the benefits. A blood clot is not as much of an issue as paralysis that results from bleeding into the spinal cord or a severe stroke from bleeding into the brain. Patients think that because they're taking drugs, they won't have a problem, but that's not always the case."

Dr. Parvizi's study has been accepted for publication in The Journal of Arthroplasty.

Aspirin also can lower the risk of DVT and PE

In another study, Japanese researchers investigated the incidence of DVT and PE in total joint replacement patients treated with aspirin and mechanical prophylaxis, such as compression stockings and foot pumps.

Principal investigator Koh Shimizu, MD, an orthopaedic surgeon at Chiba Rosai Hospital in Japan undertook the study after a patient experienced severe cerebral bleeding from anticoagulation therapy. "This sad experience made me realize that the prevention of DVT and PE is absolutely necessary, but an excessive amount of anticoagulation is worse than doing nothing," he says.

Dr. Shimizu and his colleagues followed 1,500 patients prospectively for DVT for 10 days after total joint replacement.. All patients wore elastic stockings and were started on a foot pump, which provides intermittant compression, immediately after surgery. Two days later, each began a month-long regimen of 162 mg of daily aspirin, and continued taking a half dose for another three months. Venography, a test for DVT, was performed preoperatively and 10 days after surgery.

The overall incidence of DVT was 19.2 percent, with most clots occurring in knee replacement patients. One hip replacement patient developed mild PE, whereas no knee surgery patients did. There were no complications from the aspirin.

Dr. Shimizu says the incidence of DVT was far lower than in patients receiving no preventive treatment but admits it was higher than in people receiving anti-clotting therapy. "Strong anticoagulants containing LMWH [low-molecular-weight heparin] and warfarin increase hemorrhage and infection, although they can effectively decrease DVT and PE. Mild anticoagulants containing aspirin and [standard] heparin are safe, although the occurrence of DVT may be more frequent," he explains.

Although convinced of the safety and efficacy of aspirin therapy, Dr. Shimizu believes high-risk patients need stronger medications.

"In this study, gender, age, body mass index, preoperative venous abnormalities and preoperative range of motion were thought to be risk factors for DVT. Therefore, for patients with many risk factors – for example, older women who are overweight and have limited range of motion – we recommend the use of anticoagulant therapy. For these patients, mechanical prophylaxis should [also] be used more aggressively, since this has no side effects."

Benjamin C. Bengs, MD, an orthopaedic surgeon at UCLA Medical Center, points out that neither study is conclusive and that there are a number of conflicting studies on DVT prevention.

"These are just two of many articles on this subject, all of which have slightly different takes," Dr. Bengs says. [For instance], some studies say that aspirin is the equivalent, or almost the equivalent, of Coumadin [in its ability to prevent blood clots], but others show the contrary. There is a huge body of literature and a number of differing opinions, and I don't think that these studies alone allow [physicians] to change the standard of care."

However, he says, the studies help the ongoing effort to safely prevent blood clots after joint surgery.

"I think surgeons can take this new data plus guidance from the representative academies – the American College of Chest Surgeons and the AAOS – add their own clinical judgment, and proceed from there," Dr. Bengs says.