Biloine W. Young • Wed, Feb 1st, 2012
It has long been known that blood clots are a risk factor for patients undergoing replacement of their hips or knees. But just how great that risk is has been quantified by research out of the University Hospital of Lausanne, Switzerland.
Jean-Marie Januel, Ph.D., M.P.H., senior researcher at the Institute of Social and Preventive Medicine, has found that 1 in 100 patients who have knee replacement surgery and 1 in 200 who have hip replacement surgery will develop a blood clot while they are still in the hospital. The numbers do not reflect those patients who develop blood clots after leaving the hospital.
Called a venous thromboembolism, this is a situation in which a blood clot forms in one of the deep veins of the body and then breaks away, sometimes lodging in the lungs or brain. Surgeons routinely prescribe anti-clotting drugs to help prevent blood clots from forming following the surgical procedure.
Januel and his colleagues evaluated the results of 47 studies that included approximately 45,000 patients. Some of the studies were clinical trials; 21 studies involved patients who were having hip replacements; 20 included patients having their knees replaced; and six included patients who were having both done.
The researchers were surprised to find that the number of blood clots following knee replacement surgery were twice as high as were those for hips. According to Kathleen Doheny on WebMD, other studies have found that, when the period after the hospital stay is included, the clots after hip surgery occur with greater frequency than is reported in this study. The risk of blood clots is probably greater than the numbers reported because the risk persists beyond the period of the study. The Lausanne report is published in the Journal of the American Medical Association.