Deep venous thrombosis (DVT) is the end result of a complex interaction of events including the activation of the clotting cascade in conjunction with platelet aggregation. Patients undergoing major lower extremity orthopedic surgery, especially total joint arthroplasty (TJA), are at high risk for developing a postoperative DVT or a subsequent pulmonary embolus. Venous thromboembolic (VTE) prophylaxis, most commonly pharmacologic prophylaxis, has become the standard of care for patients undergoing elective TJA. However, the controversy between the efficacy of VTE prophylaxis and the increased risk for bleeding in the postoperative period continues to exist. This review addresses the controversy underlying VTE prophylaxis by outlining 2 guidelines and demonstrating the pros and cons of different DVT prophylaxis regimens based on the available evidence-based literature.
Deep venous thrombosis (DVT) is the end result of a complex interaction of events including the activation of the clotting cascade in conjunction with platelet aggregation. It has been clearly demonstrated that patients undergoing major lower extremity orthopedic surgery, especially total joint arthroplasty (TJA), are at high risk for developing a postoperative DVT or a subsequent pulmonary embolus (PE). In the arena of TJA, orthopedic surgeons are particularly concerned with proximal DVT and symptomatic or fatal PE.
Patients undergoing primary total hip arthroplasty (THA) or total knee arthroplasty (TKA) have exhibited rates of symptomatic PE as high as 20% and 8%, respectively when no prophylaxis has been administered. As a result, the use of venous thromboembolic (DVT and PE) prophylaxis, most commonly pharmacologic prophylaxis, has become the standard of care for patients undergoing elective TJA. The risk of fatal PE following primary hip or knee replacement has been consistently reported to be between 0.1% and 0.2%, regardless of the chemoprophylactic agent employed for prophylaxis.
Based on the necessity of postoperative venous thromboembolic (VTE) prophylaxis following TJA, the National Quality Forum endorsed a voluntary consensus standard for inpatient hospital care in the earlier part of this decade. The surgical care improvement project (SCIP) guidelines, a result of the consensus, require documentation of initiation of DVT prophylaxis in the time period extending from 24 hours before surgery to 24 hours following surgery. The rationale for the SCIP guidelines stemmed from the government’s emphasis on pay-for-performance (P4P) whereby physicians receive increased compensation as a function of meeting certain “standards of care.”
Despite several years of evaluating this question, the best prophylaxis for thromboembolic disease remains controversial. The use of pharmacologic prophylaxis has been adopted as the standard of care for treatment of these patients by many orthopedic surgeons at most centers across North America. However, the controversy between the efficacy of VTE prophylaxis and the increased risk for bleeding in the postoperative period continues to exist. In recent years, this debate has brought about the development of clinical guidelines to improve patient care, address key questions, define evidence-based recommendations, and promote future research. Clinical guidelines are not meant to represent a predefined protocol or absolute rules for treatment, and should never substitute for clinical judgment.
Dependent on the clinical guideline followed, from the American College of Chest Physicians (ACCP) or the American Academy of Orthopaedic Surgeons (AAOS), there are several recommended regimens available for treatment. Included in the options are low molecular weight heparins (LMWHs), synthetic pentasaccharides, adjusted-dose warfarin, aspirin, and mechanical prophylaxis. Several studies have evaluated the various modalities for DVT prophylaxis, and comparison studies have stratified the risks and benefits for each option.
The following review addresses the controversy underlying VTE prophylaxis by outlining 2 guidelines and demonstrating the pros and cons of different DVT prophylaxis regimens based on the available evidence-based literature.
American College of Chest Physicians guidelines
The ACCP was founded in 1935, and the first set of guidelines for venous thromboembolic prophylaxis (VTE) was published in 1986. The goal of these guidelines is to focus on the prevention of the overall rate of VTE. These guidelines are based on a review of prospective, randomized studies only. The guidelines have subsequently gone through several iterations with the most recent update in 2008. Inherent to these guidelines is that all primary THA and TKA patients are considered “high risk” regardless of patient age, activity level, and comorbidities.
These guidelines have become commonplace in the evaluation of health care systems on behalf of hospitals, insurance companies, and attorneys. The recommendations were classified as Grade I (strong recommendation, with benefits outweighing risk, burden, and cost) or Grade II (recommendation with less certainty). Each class of recommendation was further substratified: (A) randomized controlled trials with consistent results and a low level of bias, (B) randomized controlled trials with inconsistent results or a major methodological design flaw, and (C) observational studies. The use of LMWH, fondaparinux (pentasaccharide), and warfarin (with an adjusted international normalized ratio [INR] between 2.0 and 3.0) all received a Grade IA recommendation for preventative treatment of total hip and knee arthroplasty; aspirin or low-dose unfractionated heparin received a Grade IA rating against their use for prophylaxis in patients following TJA. The use of intermittent pneumatic compression devices received a Grade IB rating for prevention in patients undergoing TKA.
These guidelines also address the duration of prophylaxis. During the first iteration, the ACCP guidelines from 1998 and 2001 recommended 7 to 10 days of prophylaxis that coincided with the length of hospital stay (Grade IA recommendation). In 2004, the guidelines were revised to recommend out of hospital prophylaxis for 28 to 35 days (Grade IA) but excluded patients undergoing TKA. With additional revisions, the 2008 guidelines currently recommend duration of prophylaxis with LMWH, fondaparinux, and warfarin for up to 10 days following THA and TKA (Grade IA), and up to 35 days following THA (Grade IA) or TKA (Grade IIB).
As with any guidelines being used to guide physicians in medical decision making, the risk versus benefit must be assessed. Implementation of the current ACCP guidelines has been associated with certain disadvantages, as reported in the orthopedic literature. Burnett and colleagues reported a 4.7% readmission rate, 3.4% irrigation and debridement rate, and 5.1% rate of prolonged hospitalization following 10 days of LMWH after TJA. Parvizi and colleagues have shown that patients with a wound hematoma or persistent wound drainage are at higher risk for a postoperative deep joint infection. As a direct consequence of the concerns for postoperative bleeding risk and potential for infection, orthopedic surgeons may prefer a more risk-averse method by which to prevent thromboembolic phenomena following TJA, especially because the rate of PE is similar regardless of the chemoprophylaxis agent used.
American Academy of Orthopedic Surgeons guidelines
A work group from the AAOS in conjunction with the Center for Clinical Evidence Synthesis (Tufts New England Medical Center) proposed a new set of guidelines for the prevention of symptomatic and fatal PE in patients undergoing elective TJA. The AAOS guidelines are a synthesis of an expert consensus as well as an analysis of 42 articles published since 1996, and focus on the prevention of symptomatic PE. The clinical outcomes of choice for evaluation included symptomatic and fatal PE, death, and major bleeding episodes following TJA. Consensus recommendations included the use of regional anesthesia, mechanical prophylaxis for all patients, rapid postoperative mobilization, and adequate patient education. Each patient required a preoperative evaluation for a determination of “standard” and “high” risk potential. The choice of a specific chemoprophylaxis agent was based on the individual risk-benefit profile for PE and bleeding complication.
Each recommendation was graded using the following system: (A) good evidence (level I studies with consistent findings) for recommending intervention, (B) fair evidence (level II or III studies with consistent findings) for recommending intervention, and (C) poor-quality evidence (level IV or V) for recommending intervention ( Table 1 ). Of the total number of recommendations from this set of guidelines, only 4 of them were derived from a systematic review of the literature. Additional general consensus recommendations are listed in Table 2 .
| Level I | High-quality randomized trial |
| Level II | Cohort study (good control) |
| Level III | Case-control study |
| Level IV | Uncontrolled case series |
| Level V | Expert opinion |
| General Recommendation | Level of Evidence | Grade |
|---|---|---|
| Assess all patients preoperatively with regard to their risk (standard vs high) of pulmonary embolism | Level III | Grade C |
| Assess all patients preoperatively with regard to their risk (standard vs high) of bleeding complications | Level III | Grade C |
| Consider vena cava filter placement for patients who have a known contraindication to anticoagulation therapy | Level V | Grade C |
| Consider intraoperative or immediate postoperative mechanical compression | Level III | Grade B |
| Consider regional anesthesia for the procedure (in consultation with anesthesia team) | Level IV | Grade C |
| Consider use of mechanical prophylaxis postoperatively | Level IV | Grade C |
| Rapid patient mobilization | Level V | Grade C |
| Routine screening for thromboembolism is not recommended | Level III | Grade B |
| Educate the patient about symptoms of thromboembolism | Level V | Grade B |
For patients at standard risk for both PE and major bleeding complications, the recommendation is as follows: aspirin, LMWH, pentasaccharide, or warfarin (INR goal of ≤2.0). This recommendation is based on level III evidence and was given a grade of B or C.
For patients at elevated risk for PE and standard risk for major bleeding complications, the recommendation is as follows: LMWH, pentasaccharide, or warfarin (INR goal of ≤2.0). This recommendation is based on level III evidence and was given a grade of B or C.
For patients with standard risk of PE and elevated risk of major bleeding complications, the recommendation is as follows: aspirin, warfarin (INR goal of ≤2.0), or none. This recommendation is based on level III evidence and was given a grade of C.
For patients with elevated risk of both PE and major bleeding complications, the recommendation is as follows: aspirin, warfarin (INR goal of ≤2.0), or none. This recommendation is based on level III evidence and was given a grade of C.
The most important concept that is fundamental to the AAOS guidelines for thromboembolic prophylaxis is that the risk versus benefit for each individual patient must be assessed in the preoperative period. The general recommendations presented in Table 2 are a result of the work group’s consensus, and address a majority of the perioperative issues with prophylaxis. For patients with elevated risks for PE, major bleeding complication, or both, these guidelines provide an effective manner by which to treat these patients in the postoperative period following TJA. However, a weakness inherent to the AAOS guidelines is the inability to accurately assess the preoperative risk for DVT/PE. In reality, based on the nature of TJA, arthroplasty patients may not truly be considered low risk. In addition, there are studies to demonstrate rates of VTE as high as 72% following the administration of aspirin, thus raising the question of whether the use of aspirin is adequate as a thromboprophylaxis agent.
American Academy of Orthopedic Surgeons guidelines
A work group from the AAOS in conjunction with the Center for Clinical Evidence Synthesis (Tufts New England Medical Center) proposed a new set of guidelines for the prevention of symptomatic and fatal PE in patients undergoing elective TJA. The AAOS guidelines are a synthesis of an expert consensus as well as an analysis of 42 articles published since 1996, and focus on the prevention of symptomatic PE. The clinical outcomes of choice for evaluation included symptomatic and fatal PE, death, and major bleeding episodes following TJA. Consensus recommendations included the use of regional anesthesia, mechanical prophylaxis for all patients, rapid postoperative mobilization, and adequate patient education. Each patient required a preoperative evaluation for a determination of “standard” and “high” risk potential. The choice of a specific chemoprophylaxis agent was based on the individual risk-benefit profile for PE and bleeding complication.
Each recommendation was graded using the following system: (A) good evidence (level I studies with consistent findings) for recommending intervention, (B) fair evidence (level II or III studies with consistent findings) for recommending intervention, and (C) poor-quality evidence (level IV or V) for recommending intervention ( Table 1 ). Of the total number of recommendations from this set of guidelines, only 4 of them were derived from a systematic review of the literature. Additional general consensus recommendations are listed in Table 2 .
| Level I | High-quality randomized trial |
| Level II | Cohort study (good control) |
| Level III | Case-control study |
| Level IV | Uncontrolled case series |
| Level V | Expert opinion |
| General Recommendation | Level of Evidence | Grade |
|---|---|---|
| Assess all patients preoperatively with regard to their risk (standard vs high) of pulmonary embolism | Level III | Grade C |
| Assess all patients preoperatively with regard to their risk (standard vs high) of bleeding complications | Level III | Grade C |
| Consider vena cava filter placement for patients who have a known contraindication to anticoagulation therapy | Level V | Grade C |
| Consider intraoperative or immediate postoperative mechanical compression | Level III | Grade B |
| Consider regional anesthesia for the procedure (in consultation with anesthesia team) | Level IV | Grade C |
| Consider use of mechanical prophylaxis postoperatively | Level IV | Grade C |
| Rapid patient mobilization | Level V | Grade C |
| Routine screening for thromboembolism is not recommended | Level III | Grade B |
| Educate the patient about symptoms of thromboembolism | Level V | Grade B |
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