Low-Molecular-Weight Heparin May Be Preferred to Compression Stockings After Knee Arthroscopy

In patients undergoing knee arthroscopy, low-molecular-weight heparin (LMWH) for 1 week was more effective in reducing the occurrence of deep venous thrombosis and other vascular complications vs graduated compression stockings, according to the results of an assessor-blinded, randomized controlled trial reported in the July 15 issue of the Annals of Internal Medicine.

"Knee arthroscopy, the most common orthopedic operation worldwide, carries a definite risk for deep venous thrombosis; however, postsurgical thromboprophylaxis is not routinely recommended," write Giuseppe Camporese, MD, from the University Hospital of Padua in Padua, Italy, and colleagues from the Knee Arthroscopy Nadroparin Thromboprophylaxis Study Group.

The goal of this study was to compare use of LMWH vs graduated compression stockings in adults having knee arthroscopy with regard to the prevention of deep venous thrombosis and complication rates.

At the Abano Terme Clinic and University Hospital of Padua, 1761 consecutive patients undergoing knee arthroscopy between March 2002 and January 2006 were randomized to wear full-length graduated compression stockings for 7 days (n = 660) or to receive a once-daily subcutaneous injection of LMWH (nadroparin, 3800 anti-Xa IU) for 7 days (n = 657) or for 14 days (n = 444).

The primary efficacy endpoint was the combined incidence of all-cause mortality, asymptomatic proximal deep venous thrombosis, and symptomatic venous thromboembolism. Combined incidence of major and clinically relevant bleeding events was the primary safety endpoint. After the second interim analysis, the data and safety monitoring board prematurely stopped the 14-day heparin group.

At the end of the assigned prophylactic regimen, or earlier if indicated, all patients had bilateral whole-leg ultrasonography examinations, and all patients with normal findings were observed for 3 months. None of the patients was lost to follow-up.

In the stockings group, the 3-month cumulative incidence of asymptomatic proximal deep venous thrombosis, symptomatic venous thromboembolism, and all-cause mortality was 3.2% (21/660 patients) vs 0.9% (6/657 patients) in the 7-day LMWH group (absolute difference, 2.3 percentage points; 95% confidence interval [CI], 0.7 - 4.0 percentage points; P = .005) and 0.9% (4/444 patients) in the prematurely stopped 14-day LMWH group.

In the stockings group, the cumulative incidence of major or clinically relevant bleeding events was 0.3% (2/660 patients) vs 0.9% (6/657 patients) in the 7-day LMWH group (absolute difference, -0.6 percentage point; 95% CI, -1.5 to 0.2 percentage points) and 0.5% (2/444 patients) in the 14-day LMWH group.

Limitations of this study were that it was not double blind or double dummy, ultrasonography was used to determine the incidence of deep venous thrombosis, nearly half of the events making up the composite efficacy outcome measure were distal deep venous thromboses, it excluded patients who were having prolonged procedures or had risk factors for thromboembolism, and stockings instead of placebo were used because of local prophylaxis policies.

"In patients undergoing knee arthroscopy, prophylactic LMWH for 1 week reduced a composite endpoint of asymptomatic proximal deep venous thrombosis, symptomatic venous thromboembolism, and all-cause mortality more than did graduated compression stockings," the study authors write. "We believe that withholding prophylaxis after knee arthroscopy exposes these predominantly young patients to a small but definite risk for venous thromboembolism."

In an accompanying editorial, Russell D. Hull, MBBS, MSc, from Foothills Hospital in Calgary, Alberta, Canada, notes the need for a better understanding of the harms of prophylaxis.

"The [findings encourage] the use of LMWH thromboprophylaxis in knee arthroscopy patients undergoing meniscectomy," Dr. Hull writes. "The aggregate evidence supports this recommendation. A clear answer about thromboprophylaxis in nonmeniscectomy patients - which includes diagnostic arthroscopy patients - awaits further research to precisely define the incidence of DVT [deep venous thrombosis] according to the type of arthroscopic procedure."

The study authors have disclosed no relevant financial relationships. Dr. Hull has disclosed various financial relationships with sanofi-aventis, LEO Pharma, GlaxoSmithKline, Bayer, and Pfizer.

Ann Intern Med. 2008;149:73-82, 137-139.