Taking aspirin to prevent blood clots after knee surgery may be a safe and effective alternative to currently recommended treatments that are often costlier and riskier, according to preliminary results from a study presented today at the 75th Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS). The study found that patients taking aspirin had less risk of developing blood clots than patients taking other blood-thinning drugs. They also faced a similar risk compared to patients receiving injectable drugs.

“Given the modern, less invasive techniques that orthopaedic surgeons are using now for total knee replacement, aspirin should be reconsidered a viable alternative to recommended therapies,” said Kevin J. Bozic, MD, MBA. Dr. Bozic is lead author on the study and associate professor in residence at the University of California, San Francisco Department of Orthopaedic Surgery and Philip R. Lee Institute for Health Policy Studies. Currently, clinical practice guidelines for preventing blood clots (venous thromboembolism) after total knee replacement do not recommend aspirin use.

This study suggests otherwise. Dr. Bozic and his team compared data from more than 93,840 patients who underwent knee replacement surgeries at some 300 hospitals between October 2003 and September 2005. Researchers compared the risk of:

• blood clots
• mortality
• surgical-site bleeding
• infection in patients receiving aspirin versus guideline-approved therapies

The study found that aspirin patients had:
• fewer risk factors for blood clots prior to surgery
• lower odds for blood clots compared to patients on warfarin
• similar odds compared to patients receiving injectable therapies to prevent clots
• no difference in bleeding risks or mortality

“Not only have surgical techniques changed, but patients undergoing knee surgery today are more likely to be younger and healthier than when the current treatment guidelines were developed,” said Dr. Bozic. “Aspirin is a simple, inexpensive and commonly used drug with few side effects, so it’s a very attractive alternative.”

The study concludes that more research needs to be conducted to help physicians determine which patient characteristics and treatment factors are best suited for aspirin use to prevent blood clots in knee replacement patients.

Most patients who undergo total knee replacement are between the ages of 60 and 80, but orthopaedic surgeons evaluate patients on an individual basis. Recommendations for surgery are based on a patient’s pain and disability, not age. Total knee replacements have been performed successfully at all ages, from the teenager with juvenile arthritis to the elderly patient with degenerative arthritis. This study shows significance as more than 533,000 knee replacements were performed in 2005.

Disclosure: Dr. Bozic and his co-authors received research grants from the Orthopaedic Research and Education Foundation and California Healthcare Foundation, and the Patient Safety Research and Training Grant from the Agency for Healthcare Research and Quality.

Source: American Academy of Orthopaedic Surgeons (AAOS)