By Peter Pollack
Large study examines factors that may increase the risk of DVT and PE
“Knee arthroscopy is the most commonly performed orthopaedic procedure in the United States,” explained Diane L. Dahm, MD, at the annual meeting of the American Orthopaedic Society for Sports Medicine. “However, data on the risk of symptomatic venous thromboembolic events (VTEs), including deep vein thrombosis (DVT) and pulmonary embolism (PE), are limited, and most published studies include relatively small numbers.”
Fig. 1 Supporting the contralateral limb and using a sequential compression pump or compression stocking during arthroscopic knee procedures can help reduce the risk of VTE. Reproduced from Matava, MJ: Arthroscopy for Osteoarthritis of the Knee in Liberman JR, Berry DJ, and Azar FM (eds): Advanced Reconstruction Knee, American Academy of Orthopaedic Surgeons 2011, pp. 479-487.
With that in mind, Dr. Dahm and her colleagues conducted a case-matched, retrospective review of knee arthroscopies performed at a single institution over a 20-year period. They examined the records of 12,595 patients who underwent knee arthroscopy between 1988 and 2008. Overall, they identified 43 cases of symptomatic VTE—35 cases of DVT, 5 cases of PE, and 3 cases of DVT that progressed to PE. The overall incidence of VTE was 0.34 percent.
Classic factors and more
“We used a case control methodology to identify potential risk factors for VTE,” said Dr. Dahm. “A 2:1 matched control group was generated for knee arthroscopy cases performed by the same surgeon on the same day, or immediately preceding each case in which a VTE occurred. We excluded patients who were younger than age 18 at the time of surgery and those who had undergone another surgery within 3 months prior to knee arthroscopy.”
Dr. Dahm pointed out that the accepted “classic risk factors” for VTE include the following:
- age older than 65 years
- body mass index (BMI) greater than 30
- use of oral contraceptives or hormone replacements
- chronic venous insufficiency
- previous VTE
The research team also examined potential risk factors such as gender, alcohol use, anticoagulant use, history of malignancy, history of trauma to the involved lower extremity, and history of prior knee surgery.
“We also looked at surgical procedure details including the type of procedure, anesthesia type, tourniquet time, and length of surgery,” she said.
Procedure type not a factor
The researchers found that factors associated with an elevated risk for postoperative VTE included history of malignancy (P = 0.01), history of prior VTE (P = 0.02, odds ratio = 8.9), and the presence of two or more of the other “classic risk factors.”
“Patients having at least two of the following risk factors had significantly higher risk of VTE: age older than 65 years, BMI greater than 30, smoking, oral contraceptive or hormone replacement use, and chronic venous insufficiency,” explained Dr. Dahm. “For these high-risk patients, we recommend considering the use of chemoprophylaxis to prevent VTE following knee arthroscopy.”
Dr. Dahm pointed out that—based on the study data—the type of knee arthroscopy procedure performed had no effect on incidence of VTE. In addition, the team did not find the following factors to be significant: coronary artery disease, diabetes mellitus, alcohol abuse, a history of trauma, prior knee surgery, anesthesia type, length of surgery, or tourniquet time.
Limitations of the data, according to Dr. Dahm, include the study’s retrospective design, the fact that multiple surgeons performed the procedures, and the fact that only symptomatic VTEs were studied.
“We are most certainly underestimating the true incidence of VTE,” she said.
Dr. Dahm’s colleagues on the study team included Joseph A. Morgan, MD; Aaron J. Krych, MD; Jedediah H. May, MD; Bruce A. Levy, MD; and Michael J. Stuart, MD.
Disclosure information: Dr. Levy—VOT Solutions, Arthrex; Dr. Stuart—Arthrex, Stryker; Drs. Dahm, Morgan, Krych—no conflicts; Dr. May—no disclosure.
Peter Pollack is a staff writer for AAOS Now. He can be reached at firstname.lastname@example.org
- Based on this case-matched, retrospective study of more than 12,500 patients who underwent knee arthroscopy, the incidence of VTE after knee arthroscopy is less than 0.4 percent.
- Risk factors for the development of VTE after knee arthroscopy include a history of malignancy or prior VTE or the presence of two or more of the following: age older than 65 years, BMI greater than 30, smoking, oral contraceptive or hormone replacement use, and chronic venous insufficiency.
- Chemoprophylaxis should be considered for patients undergoing knee arthroscopy who are at high risk for the development of VTE.
August 2011 Issue
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