Jay Parvizi

Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Total Hip and Knee Arthroplasty

Venous thromboembolic disease (VTED) can lead to multiple major complications and is the most common reason for readmissions following total knee arthroplasty1. These complications include symptomatic deep-vein thrombosis (DVT), bleeding (as a result of prevention or treatment interventions), and pulmonary embolus (PE), the latter of which is sometimes fatal. Although the incidences of symptomatic DVT and PE are low, the incidence of asymptomatic DVT has been estimated to be 20% to 40% in patients undergoing primary total hip and total knee arthroplasty2. Unfortunately, this risk of symptomatic VTED has remained static over the past twenty years. Thus, as the number of total hip and total knee arthroplasty procedures increases, a commensurate increase in the number of these complications can be anticipated. These facts underscore the tremendous importance of this topic in our field, in which close to one million joint arthroplasty procedures are being performed each year in the United States3. The recommendations from the recently updated American Academy of Orthopaedic Surgeons (AAOS) guideline for Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty are published in this issue of The Journal. These supersede a guideline that was first released by the AAOS in 2007 on a similar topic4. This update of the 2007 AAOS guideline was required in order to maintain inclusion in the Agency for Healthcare Research and Quality National Guideline Clearinghouse. The updated guidelines were developed by a panel that included orthopaedic surgeons with subspecialty interests in adult reconstructive surgery as well as a hematologist with a subspecialty concentration in coagulation disorders. The panel was supported by the AAOS evidence-analysis team, which included expert methodologists and evidence-analysis specialists. All AAOS guidelines are created to guide physicians through a series of diagnostic and treatment decisions in an effort to improve the quality of care. It should be noted that guidelines cannot be a substitute for appropriate decision-making in individual cases. Final decisions concerning a test or treatment must be based on all of the available data presented by a patient, patient preferences, and the resources available. This guideline was based on the best available published research. It was developed to minimize bias, to promote reproducibility, and to enhance transparency. Preliminary recommendations were first developed by the work group; subsequently, the preliminary recommendations were then thoroughly researched by the AAOS evidence-analysis team. On the basis of the assembled evidence, which included an extensive array of forest plots developed by the AAOS research staff (which are available with the full document posted on the AAOS web site5), the work group provided a final recommendation of strong, moderate, weak, inconclusive, or consensus (the work group opinion when there was an absence of reliable evidence). A minimum of two high-quality studies were needed for a strong recommendation, a minimum of two moderate-quality studies were needed for a moderate grade, and a minimum of two low-quality studies were needed for a weak grade. In the present guideline, all articles pertinent to VTED between 1970 and 2010 were evaluated. The group considered recommendations concerning preoperative evaluation, diagnosis, treatment, and postoperative prevention of VTED. These outcomes were based on a model in which seven outcomes were deemed critical and most relevant: all-cause mortality, death from bleeding, death from PE, periprosthetic joint infection, reoperation due to bleeding, reoperation for any reason within ninety days after surgery, and symptomatic PE. It should be noted that DVT was only considered a surrogate measure due to the poor correlation between acute DVT and PE. The guideline is accompanied by >800 pages of supporting documentation, but fortunately one can quickly read the shorter version of the ten recommendations with their accompanying eight-page rationale in less than fifteen minutes as an encapsulation of most of the concepts evaluated6 (see Appendix). Of the main recommendations in the guideline, one was graded as strong, three were graded as moderate, one was graded as weak, four were graded as inconclusive, and five were based on consensus (note that in three of the ten numbered recommendations, there were multiple parts so that the total number of recommendations is actually fourteen). In summary, the guideline addresses a number of controversial issues and provides the following guidance: the practitioner does not need to perform routine ultrasonographic screening and the practitioner should further assess patients for a history of previous venous thromboembolism, known bleeding disorders, and liver disease. However, there was no clear evidence that other potential risk factors increase the rate of VTED or bleeding. Pharmacologic and/or mechanical prophylaxis can be used for patients who are not at elevated risk for VTED or bleeding; however, based on the dearth of available evidence for the seven critical outcomes specified above, there is no recommendation for a specific pharmacologic agent and/or mechanical device. The use of neuraxial anesthesia (such as epidural and spinal anesthesia) can help to limit blood loss but was not found to affect the occurrence of VTED. There are many similarities between the 2007 AAOS guideline and the present update, with the most notable being the focus on patient-centered outcomes such as symptomatic PE as opposed to the surrogate outcome of venographically or ultrasonographically documented DVT. In addition, both the 2007 and 2011 guideline processes involved a detailed and comprehensive systematic review of the literature. Since 2007, the AAOS guideline-development process has evolved, in part in response to the 2011 Institute of Medicine (IOM) report entitled “Clinical Practice Guidelines We Can Trust.”7 The 2011 AAOS VTED guideline meets or exceeds nearly all of the IOM’s eight categories of standards for a trustworthy guideline (transparency, management of conflicts of interest, appropriate group composition, systemic review procedure, rating strength of recommendations, articulation of recommendations, external review, and updating). It is also worth noting that the recommendations in the 2007 AAOS guideline on prophylaxis differed from the 2008 update of the American College of Chest Physicians (ACCP) guideline. This led to many questions concerning the most appropriate prophylactic regimen. Like the AAOS, the ACCP has updated its 2008 guideline; the updated ACCP guideline is due to be released in early 2012. It is anticipated that there will be some convergence of the recommendations from the two different organizations, although the specific language of the ACCP guideline is not known at the time of submission of this Editorial. During the peer-review process of the 2011 AAOS guideline, methodologists on the ACCP work group provided valuable input and commentary that were incorporated into the final recommendations. Cooperation and collaboration of these two organizations, where possible, has been helpful to the process and will be helpful in future updates of these guidelines. Prophylaxis against VTED following primary hip and knee arthroplasty is now used as a quality measure by regulatory 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 (SCIP) guideline on VTE and PE prophylaxis. However, the controversy over the most appropriate agents, as well as their timing and duration of administration, continues. As the SCIP updates its quality measures, representatives from the AAOS will work to have the 2011 AAOS VTED guideline incorporated into these measures so that compliance with the AAOS guideline will meet the requirements of the SCIP measures. If successful, this will address one of the limitations of the 2007 guideline. It should be noted that there can be individual exceptions to some of the recommendations. For example, the work group believed that the majority of patients should be kept off of antiplatelet agents (e.g., aspirin, clopidogrel) prior to joint arthroplasty, but there may be exceptions (for example, if the patient has a stent for coronary artery disease) when a hematologist, cardiologist, or internist might believe that the risks of withholding antiplatelet agents outweigh the benefits8. Furthermore, the consensus recommendation that antiplatelet agents be discontinued prior to joint arthroplasty does not apply to the use of aspirin begun in the immediate preoperative period as part of a multimodal prophylaxis regimen. This guideline is not being offered as the final word in VTED prophylaxis; in the final analysis, the limitations in the guidelines represent limitations in the available evidence. There is much research that needs to be conducted to allow for more definitive guidance regarding VTED prophylaxis when these guidelines are updated within the next four years.

Corrosion and Tribology of Materials Used in a Novel Reverse Hip Replacement

Total hip arthroplasty has been utilized for the past 50 years as an effective treatment for degenerative, inflammatory and traumatic disorders of the hip. The design of these implants has generally followed the anatomy of the hip as a ball and socket joint with the femoral head representing the ball and the acetabulum representing the socket. We describe a novel hip arthroplasty design in which the “ball” is located on the acetabular side and the “socket” is located on the femoral side. The results of extensive biomechanical testing are described and document wear and corrosion characteristics that are at least equivalent to standard designs. These results support clinical assessment as the next step of the evaluation.