Low Molecular Weight Heparin Better than Graduated Compression Stockings for Preventing Venous Thrombosis in Knee Arthroscopy

Henry I. Bussey, Pharm.D., FCCP, FAHA
September, 2008

Low molecular weight heparin (LMWH) prophylaxis for 7 days should be offered to low risk patients who are undergoing knee arthroscopy with meniscectomy - that is the conclusion of the authors of the largest study ever performed in preventing venous thromboembolism (VTE) in knee arthroscopy; and that is the conclusion of the insightful editorial by Russell Hull.

Following arthroscopy, patients in this Italian study were randomly assigned to full leg graduated compression stockings (GCS at 30 to 40 mm Hg) [n= 660], low molecular weight heparin (LMWH, nadroparin 3800 anti-Xa units once daily for 7 days) [n = 657], or the same dose of nadroparin for 14 days [n = 444]. The 14 day regimen was discontinued for safety reasons at the 2nd interim analysis. Bilateral full-leg ultrasonography was done at the completion of the prophylaxis period and/or as indicated. Suspected pulmonary embolism (PE) was evaluated by V/Q scan, which was followed by chest CT if the V/Q results were "non-diagnostic". Patients with normal findings were followed for 3 months. The primary results, as presented in the attached table, indicated that the LMWH was superior to GCS in preventing thrombosis without a significant increase in major and clinically relevant bleeding.

Additional key considerations:

1. The study was not double-blind or double-dummy, but the evaluators were blinded to the treatment.
   
   
2. PE occurred in all groups and the biggest difference was in distal DVT
   
   
3. Patients who under went meniscectomy had a higher rate of VTE and benefited more from LMWH prophylaxis.
   
   
4. The patients in this study were relatively low risk in that those having prolonged procedures and/or those who had risk factors for thromboembolism were excluded; and the mean age was approximately 42 years. Whether higher risk patients require more aggressive and/or prolonged prophylaxis remains undertermined.
   
   
5. LMWH was started 8 hrs after the procedure (earlier than what is often done for other orthopedic procedures)

The accompanying editorial by Russell Hull highlights the previous low grade recommendations found in various guidelines which are necessarily based on very limited data. Hull goes on to agree that the new findings encourage the use of LMWH prophylaxis for 7 days in "low risk" knee arthroscopy patients undergoing meniscectomy. For those not under-going meniscectomy the benefit is less clear; and for those at higher risks, the best regimen remains uncertain.

References

1. Camporese G, et al. Low-molecular-weight heparin versus compression stockings for thromboprophylaxis after knee arthroscopy: a randomized trial. Ann Intern Med. 2008 Jul 15;149(2):73-82.
2. Hull RD. Thromboprophylaxis in knee arthroscopy patients: revisiting values and preferences. Ann Intern Med. 2008 Jul 15;149(2):137-9.