Each year approximately 200,000 Americans undergo total hip replacement surgery. Statistics reveal that between 400 and 800 people develop a fatal pulmonary embolism in the first three months following this procedure. A pulmonary embolism is a blood clot which forms in a leg vein, breaks off, and travels to the lungs.
Another complication experienced by some total hip replacement patients is localized swelling and pain in the leg when a clot forms and causes decreased flow of blood to the heart. The aforementioned complications occur more often following hip surgery than any other type of surgery.
Blood Clot Assessment
An assessment of various factors which affect blood clot formation following hip replacement surgery was presented in the December 14, 2000 New England Journal of Medicine. A research team led by Dr. Richard H. White of the University of California, Davis, School of Medicine and Medical Center, analyzed the medical records of California Medicare patients who underwent hip replacement surgery between 1993 and 1996. The 91 day post-op period was reviewed and a comparison was made between 297 patients who had been re-hospitalized for formation of a blood clot and 592 patients who had not been re-hospitalized because of clot formation.
Blood Clot Formation
The research team assessed the impact of pneumatic compression, anticoagulant therapies, and body mass index (BMI) on clot formation. It was found that:
- Overweight patients with a BMI of 25 or more were 2 1/2 times as likely to be hospitalized for blood clots than the control group.
- Pneumatic compression was of most benefit to patients of average weight. Pneumatic compression (an external device consisting of inflatable cuffs for the purpose of massaging and compressing the legs to prevent blood from pooling in the veins and an increased risk of clot formation) did not reduce the risk of blood clots in overweight patients.
- Patients of normal weight who used pneumatic compression were 30 percent as likely to be re-hospitalized for blood clots as patients not treated with pneumatic compression.
- Patients of all weight categories who were treated with anticoagulant drug therapy after going home were only 60 percent as likely to have symptomatic clots as those patients not receiving the therapy.
Certain groups of patients benefit more from certain treatments. The studies point out the importance of pneumatic compression in patients with BMI under 25 and the importance of anticoagulant drug therapy after hospital discharge but future studies are needed to analyze the ineffectiveness of pneumatic compression in patients with BMI over 25.
Prevention of Perioperative Deep Venous Thrombosis And Pulmonary Embolism. B. Todd Sitzman, M.D., M.P.H., December, 1998.
Avoiding Blood Clots After Hip Replacement Surgery, Newswise, 12/14/00.
Predictors of Rehospitalization for Symptomatic Venous Thromboembolism after Total Hip Arthroplasty, NEJM, 12/14/00, Vol. 343, No.24.