**2. Epidemiology**

Total joint arthroplasties remain some of the most common orthopaedic procedures performed worldwide. It is estimated that by 2015, over 500,000 total hip arthroplasties and 1.3 million total knee arthroplasties will be done in the United States alone (Kim, 2008). The aggregate costs in 2007 totaled over \$15 billion (US Agency for Healthcare Research and Quality, 2007). Geerts et al. reported that VTE would occur in 40%-60% of the patients undergoing total joint arthroplasty if no prophylaxis was administered (Geerts et al., 2008). Despite appropriate chemophrophylaxis, one study noted asymptomatic proximal DVT found on ultrasound in 6.7% of THA and TKA patients at the time of transfer to a rehabilitation center (Schellong et al., 2005). As many as 80% of all clinical VTE events associated with arthroplasty patients occur within 3 months after surgery (Oster et al., 2004).

The costs of VTE are significant. Approximately 10% of the patients who develop VTE following THAs or TKAs require re-admission to the hospital within 3 months after their index surgery (Oster et al., 2004). The clinical sequelae are often significant and can include leg swelling, venous stasis ulcers, pulmonary hypertension, post-thrombotic syndrome, and recurrence (Heit, 2006). The one-year mortality following deep vein thrombosis (DVT) has been reported as high as 14.6%. Pulmonary embolism (PE) is associated with even higher mortality rate. Heit et al. reported as high as 52.3% in a recent cohort study (Heit et al., 1999).

Venous Thromboembolism in Orthopaedic Surgery 161

Academy of Orthopaedic Surgeons (AAOS) have each released separate guidelines

Controversies exist regarding the two major practice guidelines for VTE prophylaxis. The ACCP has been updating its recommendations every 3 years for over 25 years (Hirsh et al., 2008). The AAOS guidelines have been a more recent development. Though the two have many similarities, there are a few significant differences. A major area of disagreement involves the use of DVT as a surrogate for PE in arthroplasty patients. The AAOS guidelines do not emphasize the correlation between DVT and pulmonary embolism (Eikelboom et al., 2009). In fact, the AAOS guidelines are for the prevention of PE following joint arthroplasty. The ACCP recommendations focus on the prevention of both VTE and PE as the goal rather than PE alone in the AAOS guidelines. Both guidelines focus on a balance between the risk of bleeding and the efficacy of anticoagulation. They both define risk-to-benefit ratio for different agents. Some of the most clinically relevant differences between the two guidelines are presented in Table 1. Neither guideline has been universally accepted. A recent survey was conducted by the American Association of Hip and Knee Surgeons regarding the practice standards among its member surgeons. The data demonstrated that 74% of the hospitals had adopted the ACCP guidelines, while 68% of the surgeons preferred the AAOS

Furthermore, compliance with the current guidelines has been suboptimal. Many surgeons continue to under-appreciate the prevalence of VTE and remain concerned with postoperative bleeding. Additionally, patient factors can inhibit appropriate prophylactic treatment. Injectable agents are expensive. Moreover, some patients are not at ease or in compliance with their administration. Oral agents have the challenges including: titration,

The ACCP guidelines recommend the optimal duration of VTE prophylaxis to be 28 to 35 days following THAs, and 10 to 14 days following TKAs (Kolb et al., 2003). Currently, the mean length of hospital stay is between 3 to 4 days, therefore full compliance with this recommendation is difficult for both the patient and the provider. Several studies have reported that continuation of thromboprophylaxis beyond the hospitalization is efficacious and safe in the risk reduction of late VTE in surgical patients (Planes et al., 1996; Lassen et

Extended duration prophylaxis for VTE requires proper selection of pharmacological agent(s). The ideal anticoagulant should have the following characteristics: standard dosing with self-administration, no requirement for monitoring, established efficacy and safety profiles, acceptable tolerability in populations with co-morbid conditions, and few drugdrug or drug-foot interactions. The ACCP guidelines currently recommend warfarin, lowmolecular weight heparins (LWMH), and fondaparinux. They specifically recommend against using aspirin alone in the high-risk orthopedic patient population as there are

The AAOS guidelines recommend 2 to 6 weeks of prophylaxis with warfarin, 6 weeks using aspirin, or 7 to 12 days using LMWH or fondaparinux (AAOS 2007). The ACCP guidelines,

monitoring, and drug-drug, or drug-food interaction (Moyer et al., 2009).

al., 1998; Comp et al., 2001; Bergqvist et al., 2002; Rasmussen et al., 2006).

regarding the prevention of VTE. This can be confusing to the providers.

guidelines (Markel et al., 2010).

**4.1 Extended duration prophylaxis** 

insufficient evidence-based data.
