“Quis custodiet ipsos custodes?” (“Who will guard the guards themselves?”) (Juvenal, Roman poet and satirist [55 to 127 a.d.], Satire VI1)
The decision about which thromboprophylactic measure to use with patients undergoing total joint arthroplasty has always been contentious. The choice is made no easier by the myriad of pharmacological and mechanical prophylactic options that currently exist. Consequently, reaching a consensus on which method of prophylaxis is optimal is extremely challenging and, at best, highly controversial. The argument is most heated regarding high-risk patients or patients with bleeding risks.
In an attempt to provide some direction in this area, the American Academy of Orthopaedic Surgeons (AAOS), as the preeminent provider of musculoskeletal education, has produced guidelines on the prophylaxis of venous thromboembolic events in patients undergoing total joint arthroplasty2. These guidelines are based on the interpolation of results reported in the literature. However, it is one thing to promulgate guidelines and another thing entirely to validate their utility for an unselected patient population. In this study, Lewis et al. demonstrated the clinical effectiveness of the AAOS clinical guidelines by reporting on a large, prospective series of patients, utilizing risk stratification as well as pharmacological and/or mechanical prophylaxis. In doing so, they highlighted a number of unresolved dilemmas that surgeons face in using thromboprophylaxis in an elective setting, particularly with the high-risk patient or in cases in which bleeding is a major concern.
In considering these dilemmas further, let us look to the legal profession for some insight and perspective. Lady Justice is an allegorical personification of the moral force in the judicial system. Her effigy is most often depicted blindfolded, carrying a set of scales in her right hand and a double-edged sword in her left; the icons are a symbolic representation of objectivity, the balance of support for and opposition to a case, and the positive and negative aspects of a decision. These principles are equally applicable to medicine and have particular resonance when considering the thorny subject of the optimal thromboprophylactic measure in elective orthopaedic surgery. Our choice of prophylactic measure should not be determined by anecdotal experience or convention. It must be based on objective measures with the highest level of evidence available. We must continue to weigh the risks and benefits of treatment. At the same time, it is important for us to be aware that in particularly high-risk cases, the consequence of treatment, including death or substantial morbidity, may tip the scales toward a more conservative approach. We need to be cognizant that our intervention may also have consequences beyond its intended target and that the effect of this intervention may be detrimental—for example, a postoperative hematoma following thromboprophylaxis.
So, what have we learned from this study? First, we now know that the AAOS clinical guidelines are not only useful but they work. We recognize that the ninety-day incidence of venous thromboembolic complications is significantly greater in patients undergoing total knee arthroplasty (1.46%) than in those undergoing total hip arthroplasty (0.56%), albeit with a different thromboprophylactic regimen. Total knee arthroplasty patients were managed postoperatively with 325 mg of enteric-coated aspirin twice daily for six weeks, whereas total hip arthroplasty patients were managed with subcutaneous injections of 40-mg enoxaparin sodium once daily for ten days followed by oral administration of 325-mg enteric-coated aspirin for four weeks. We realize that a personal history of blood clots is significantly associated with complications, but a family history and a personal history of malignancy is not. Further, we understand that the risk ratio is significantly elevated in high-risk total knee arthroplasty patients compared with high-risk total hip arthroplasty patients (risk ratio = 3.5), despite equivalent prophylaxis with enoxaparin sodium for twenty-eight days. We have also learned that the insertion of an inferior vena cava filter in the high-risk total knee arthroplasty group was statistically associated with the occurrence of venous thromboembolism, supporting the view of the limited role of a filter in preventing emboli.
“Common sense is not so common.” (Voltaire, Dictionnaire Philosophique, 17643)
This manuscript also provides a harrowing example and salient reminder of the consequence of noncompliance with thromboprophylaxis. The authors relay the story of the death of a fifty-year-old female patient who underwent bilateral total knee arthroplasty. She was placed in a high-risk group but refused to take enoxaparin sodium because of a needle phobia. Warfarin use was recommended as an alternate method of prophylaxis, but the patient failed to comply with the prescription. Three weeks later, after a long car trip, she died of a likely pulmonary embolism. Thankfully, patient compliance with orally administered medication is typically very good. A recent report by Carrothers et al., had noncompliance rates as low as 4% with oral administration of thromboprophylactic medication4. If ever a “bogey-man” tale is required to convince your patients of what might happen if they do not take their medication, this particularly tragic saga offers a very poignant and compelling example.
Clinical governance is defined as patient safety and patient satisfaction measured against objective standards. These standards have been set and exemplified through the presentation of data gathered from national joint registries5,6. With the publication of this manuscript, we now know that the AAOS clinical guidelines for the prophylaxis of venous thromboembolic events in patients undergoing total joint arthroplasty not only meet objective standards but also are clinically effective. As these guidelines are adopted more widely and become the standard of care, it is likely that the practice of risk stratification will be employed routinely and the dilemma of how to most effectively manage high-risk patients will be further resolved.
1. Juvenal. The sixteen satires. Green P, translator. London: Penguin Books; 1999.
2. Mont MA, Jacobs JJ. AAOS clinical practice guideline: preventing venous thromboembolic disease in patients undergoing elective hip and knee arthroplasty. J Am Acad Orthop Surg. 2011 Dec;19(12):777-8.
3. Voltaire F. Philosophical dictionary. London: Penguin Books; 2004.
4. Carrothers AD, Rodriguez-Elizalde SR, Rogers BA, Razmjou H, Gollish JD, Murnaghan JJ. Patient-reported compliance with thromboprophylaxis using an oral factor Xa inhibitor (Rivaroxaban) following total hip and total knee arthroplasty. J Arthroplasty. 2014 Apr 24. Epub ahead of print.
5. Pedersen AB, Mehnert F, Johnsen SP, Husted S, Sorensen HT. Venous thromboembolism in patients having knee replacement and receiving thromboprophylaxis: a Danish population-based follow-up study. J Bone Joint Surg Am. 2011 Jul 20;93(14):1281-7.
6. Guijarro R, Montes J, San Román C, Arcelus JI, Barillari G, Granero X, Monreal M. Findings from the Spanish National Discharge Database. Venous thromboembolism and bleeding after total knee and hip arthroplasty. Thromb Haemost. 2011 Apr;105(4):610-5. Epub 2010 Dec 21.