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The new guidelines suggest the use of pharmacologic agents and/or mechanical compressive devices for the prevention of VTE in patients undergoing elective hip or knee arthroplasty, but do not make a specific recommendation on the type of agent or the duration of the prophylaxis.


Published 10/1/2011
Michael A. Mont, MD

Board approves VTED prevention guidelines

Guidelines address identification of at-risk patients and prophylaxis against VTED

At their meeting on Sept. 24, 2011, the AAOS Board of Directors approved a new clinical practice guideline (CPG) on the prevention of venous thromboembolic disease (VTED) in patients undergoing elective hip or knee arthroplasty (THA/TKA). The new CPG replaces AAOS guidelines introduced in 2007 on a similar topic (Prevention of Symptomatic Pulmonary Embolism in Patients Undergoing Total Hip or Knee Arthroplasty) and is substantively different from the previous guideline.

For example, the new guideline includes deep venous thrombosis (DVT) as an outcome, which was not the case with the previous guideline. The new CPG also compares the recommendations to both the previous guideline and to recommendations from other organizations, including the American College of Chest Physicians, the Agency for Healthcare Research and Quality, and the National Institute for Health and Clinical Excellence.

The new guideline has 10 recommendations (and 4 additional subcategorized recommendations) covering various aspects of patient screening, risk factor assessment, and prophylactic treatment against VTED, as well as on the use of postoperative mobilization, neuraxial anesthesia, and vena cava filters (Table 1).

Significance of VTED
VTED can lead to various major complications and is the most common reason for emergency readmissions following THA and TKA. Among these complications are the development of symptomatic DVT, bleeding, and pulmonary embolus (PE), the latter possibly being fatal. Although the incidences of symptomatic DVT and PE are low, the incidence of asymptomatic DVT has been estimated to be 20 percent or higher in patients undergoing primary hip and knee arthroplasty.

Unfortunately, despite the numerous studies in this area, the risk of VTED has remained static over the past 20 years. Thus, as the number of THA and TKA procedures increases, a commensurate increase in the number of these complications can be anticipated.

As a result, prophylaxis against VTED is required by healthcare agencies and payers. Even the federal government has become involved. For example, one of the quality measures mandated by the Centers for Medicare & Medicaid Services is the Surgical Care Improvement Project guideline on VTE and PE prophylaxis. However, the controversy over the most appropriate agents, as well as their timing and duration of administration, continues.

The 2007 AAOS guideline recommendations on prophylaxis differed from those in the 2008 update of the American College of Chest Physicians guidelines. This led to many questions concerning the most appropriate prophylactic regimen. The new guideline suggests prophylaxis, but does not recommend a specific strategy.

Guideline development
To develop the CPG, the work group first formulated a set of preliminary recommendations that specified what should be done in whom, when, where, how often, or for how long. These were intended to function as the questions for systematic review by the AAOS research team.

Once all relevant published articles were assembled and graded by level of evidence, the work group then provided a final recommendation of strong (good quality evidence), moderate (fair quality evidence), weak (poor quality evidence), inconclusive (insufficient or conflicting evidence), or consensus (when the condition in question can result in loss of life or limb and in the absence of reliable evidence, the recommendation is based on clinical opinion).

For a strong recommendation, a minimum of two high-quality studies were needed. A minimum of two moderate-quality studies were required for a moderate grade, and a minimum of two low-quality studies were needed for a weak grade.

Of the 10 main recommendations in the guideline, one is graded as strong, three as moderate, one as weak, one as inconclusive, and four are based on consensus.

Risk stratification
Screening of patients who may or may not be at risk for VTED has been controversial. The guideline recommends further assessment of patients who have had a previous venous thromboembolism. Patients should also be assessed for known bleeding disorders such as hemophilia and for the presence of active liver disease. However, no clear evidence was found for routine assessment of any other potential risk factors.

Prophylaxis against VTED
The guideline recommends that THA and TKA patients with a prior history of VTE receive pharmacologic prophylaxis and mechanical compressive devices for prevention of VTED. Mechanical compressive devices should be used for patients with a history of a bleeding disorder and/or active liver disease. Either or both pharmacologic and mechanical prophylaxis can be used for patients who are not at elevated risk (beyond that associated with the surgery itself) of VTED or bleeding. Patients should also discontinue antiplatelet agents (eg, aspirin, clopidogrel) before undergoing elective hip or knee arthroplasty.

Prophylactic strategies, agents, and timing
Comparing different prophylactic strategies is difficult; few placebo-controlled trials can be found, in part because the establishment of prophylaxis as the standard of care was readily accepted before evidence-based comparative data were available.

The new CPG does not recommend specific pharmacologic agents and/or mechanical devices. The work group had defined critical outcomes of interest as PE, major bleeding, symptomatic DVT, and all-cause mortality. Unfortunately, reports using these outcomes were rare, and the number of placebo-controlled trials was limited. Therefore, the group had to rely on the analysis of any DVT as a surrogate measure to evaluate the relative efficacy of the prophylactic strategies. In addition, several pharmacologic agents were not found to consistently reduce the occurrence of DVT.

In addition, the work group recommends that patients and physicians discuss the appropriate duration of prophylaxis for each individual situation, given the paucity of data on nearly all of the prophylactic modalities. This discussion is consistent with current practice.

Early mobilization, neuraxial anesthesia, and filters
In the absence of reliable evidence related to VTED, the consensus of the guideline work group is that early mobilization is a low-cost, minimal risk measure for patients after elective THA and TKA.

The use of neuraxial anesthesia (such as intrathecal, epidural, and spinal) can help limit blood loss, but was not found to affect the occurrence of VTED.

No clear evidence was found about whether inferior vena cava filters could prevent PE in patients who have a contraindication to chemoprophylaxis and/or known VTED.

In addition to the clinical practice guideline (CPG) on the prevention of venous thromboembolic disease in patients undergoing elective hip or knee arthroplasty, the AAOS Board of Directors also approved a second CPG during its September meeting. The CPG on the treatment of supracondylar fractures, a collaborative effort between the AAOS and the Pediatric Orthopaedic Society of North America, will be featured in next month’s AAOS Now. The guideline is available on the AAOS website, at www.aaos.org/guidelines

A link to the complete guideline can be found at www.aaos.org/guidelines

Michael A. Mont, MD, served as vice-chair of the work group that developed the CPG on preventing VTED in patients undergoing elective hip and knee arthroplasty.

Disclosure: Dr. Mont—Stryker; Johnson & Johnson; Joint Active Systems, Inc.; Salient Surgical; TissueGene; National Institutes of Health (National Institute for Arthritis and Musculoskeletal and Skin Diseases & National Institute of Child Health & Human Development); Wright Medical Technology, Inc.

How the guidelines came to be
The Clinical Practice Guideline on Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty, adopted by the AAOS Board of Directors in September 2011, was developed by a multidisciplinary volunteer work group that included orthopaedic surgeons who practice in a variety of settings, along with assistance from the AAOS guidelines unit. Members of the work group included Joshua J. Jacobs, MD, chair; Michael A. Mont, MD, vice-chair; Lisa N. Boggio, MS, MD; Kevin J. Bozic, MD, MBA; Craig J. Della Valle, MD; Stuart B. Goodman, MD; Courtland G. Lewis, MD, Adolph J. Yates, Jr., MD; William C. Watters III, MD; Charles M. Turkelson, PhD; Janet L. Wies, MPH; Patrick Donnelly, MA; Nilay Patel, MPH; Patrick Sluka, MPH, and Kristin Hitchcock, MSI. Disclosure information for each of the work group members is included in the guideline document.

The following are among the groups that gave explicit consent to be listed as peer reviewers of this guideline:

  • American Academy of Family Physicians
  • American Association of Hip and Knee Surgeons
  • American College of Chest Physicians (ACCP)
  • American Society of Regional Anesthesia and Pain Medicine
  • American Surgical Association/Society of Surgical Chairs
  • International Society on Thrombosis and Haemostasis
  • The Joint Commission on Accreditation of Healthcare Organizations

Input and feedback from the ACCP was especially helpful in finalizing the document. Participation in the AAOS peer review process does not constitute an endorsement of this guideline by the participating organization. Funding for the guideline was provided solely by the AAOS.

The guideline is based on a systematic review of the current scientific and clinical information on accepted approaches to treatment and/or diagnosis. The entire process included a review panel of internal and external committees, public commentaries, and final approval by the AAOS Board of Directors in September 2011.

The methods used to prepare this guideline were rigorous and employed to minimize bias and develop a set of reliable, transparent, and accurate clinical recommendations for preventing venous thromboembolic disease in patients undergoing elective hip and knee arthroplasty. These methods are detailed in the full guideline.

The development of AAOS evidence-based clinical practice guidelines is overseen by the Guidelines Oversight Committee and the Evidence-Based Practice Committee. The full guideline is available at www.aaos.org/guidelines