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From left: Bryan D. Springer, MD, speaks during the "Urban Legends of TKA" ICL as fellow presenters J. Bohannon Mason, MD; Raymond H. Kim, MD; and James A. Browne, MD, look on.


Published 6/1/2017
Peter Pollack

Evidence-based Medicine Meets "Urban Legends" of TKA

Annual Meeting ICL challenges efficacy of enduring practices
Evidence-based medicine is something we, as orthopaedic surgeons, are forced to examine more closely as we switch to a value-based healthcare system," explained Bryan D. Springer, MD, during an Instructional Course Lecture (ICL) on "The Urban Legends of Total Knee Arthroplasty (TKA)." "The question is: Do we really follow it? Evidence suggests that many of us practice evidence-based medicine less than 50 percent of the time. Many beliefs become so entrenched in our practice that we ultimately think that they are based in science, when in fact they might not be."

The ICL focused on the use of evidence in common TKA practice patterns, and attempted to dispel many enduring "urban legends" surrounding the procedure. Raymond H. Kim, MD, discussed myths primarily associated with the preoperative period, and J. Bohannon Mason, MD, looked at the intraoperative period. Finally, James A. Browne, MD, addressed the postoperative period.

Preoperative concerns
Myth: Autologous blood donation reduces the risk of allogeneic transfusion.

According to Dr. Kim, a 1999 study found that patients who had an immediate autologous transfusion postoperatively had fewer medical complications. However, he also pointed out that donating your own blood results in a 3 percent drop in hematocrit per unit. "Due to this orthopaedically induced anemia, such patients are actually at higher risk for requiring a transfusion, not only of their own blood, but of an allogeneic blood as well," he said. A second study involving 4,642 patients found that the percentage of patients at high risk of transfusion doubled after a preoperative autologous donation.

Myth: Tranexamic acid (TXA) increases the risk of thromboembolic complications.

"TXA inhibits fibrinolysis by blocking the lysine-binding site of plasminogen to fibrin," noted Dr. Kim. "TXA has been shown to significantly decrease blood loss, and in study after study, it has been demonstrated to not increase rates of deep vein thrombosis (DVT). It is inexpensive; about $54 for the intravenous version, and there is evidence to support the use of oral TXA. It's safe and very cost-effective."

Myth: Do not use a first-­generation cephalosporin in a patient with a non-anaphylactic reaction to penicillin.

Antibiotic prophylaxis significantly decreases infection rates, but some patients report a penicillin allergy. If the allergy is self-reported, "the cross-reactivity with cephalosporin is actually only 1 percent. Among patients with a confirmed penicillin allergy, the cross-reactivity is only 2.55 percent," noted Dr. Kim. "In the case of confirmed allergies to cephalosporins, the National Surgical Infection Prevention Project states that the antibiotic options are vancomycin or clindamycin."

However, vancomycin is less effective than cephalosporins against sensitive Staphylococcus strains, and its routine use may lead to vancomycin-resistant bacteria.

Myth: Serum white blood cell (WBC) count or gram stain are useful tests for diagnosing prosthetic joint infection (PJI).

In fact, both WBC count and gram stain are poor indicators of PJI. Dr. Kim recommends using criteria developed by the Musculoskeletal Infection Society: via a sinus tract that communicates with the prosthesis, or two positive cultures from the joint, or any four of the following minor criteria:

  • elevated erythrocyte sedimentation rate and C-reactive protein
  • elevated synovial WBC count
  • elevated synovial neutrophil percentage
  • positive histologic analysis of the periprosthetic tissue
  • intra-articular purulence
  • single positive culture
  • greater than 5 polymorphonuclear cells per high-power field at 400× magnification

Recently, the International Consensus Group on Periprosthetic Joint Infection added a positive leukocyte esterase test as a minor criterion. Alpha-defensin is another recent addition to the armamentarium of tests used to diagnose PJI.

Intraoperative concerns
Myth: Never use the skin knife below the fascia on a TKA.

"More than 50 percent of orthopaedic surgeons change the blade after the skin incision, out of concern that it would transfer bacterial flora deep into either the tissues or the implant," reported Dr. Mason. He noted that older studies did find a higher rate of contamination on skin blades compared to deep blades. However, more recent studies, using contemporary antiseptic techniques, found no statistical significance in the contamination among skin blades, deep blades, or control blades.

Myth: Implant survival is enhanced with antibiotic cement fixation.

Although reducing PJI is the main justification for using antibiotic cement, Dr. Mason pointed to other concerns, such as allergic reactions, the potential for antibiotic local induction, resistance, systemic toxicity, and possibly changes in the mechanical properties of the cement. "Registry data on THAs suggest a lower infection rate and improved survivorship in cemented THAs in which antibiotic cements were used," he said. However, a 2013 meta-analysis found only a very slight risk ratio favoring antibiotic cement, while a 2014 meta-analysis covering 26,791 patients found no evidence for a decreased rate of deep infection.

From an economic perspective, Dr. Mason noted that justifying the routine use of antibiotic cement is difficult. A 2014 study calculated that, depending on the type of antibiotic used and using prevention of infection as the outcome measure, the cost per case of infection prevented ranged from $2,000 to more than $100,000.

Myth: Running fascial sutures will restrict knee flexion and are more likely to fail.

"TKA arthrotomies are traditionally closed in extension, but no evidence supports this practice," said Dr. Mason. "Closing in flexion has been shown to increase flexion motion, require less outpatient physiotherapy, and result in less loss of isokinetic muscle strength and a more anatomic patella tracking.

"Subcutaneous closures are advocated by many as superior for wound healing. Running sutures for fascial closure are often considered inferior to interrupted closure, and interrupted skin closure is often advocated as more secure than running closure. But none of these statements are supported by current meta-analytic data," he said.

Postoperative concerns
Myth: Drains help promote healing and decrease infection risk.

Dr. Browne traced this myth to a 1949 article in The Journal of Bone & Joint Surgery, which claimed that the use of drains materially reduced postoperative pain and disability. But, as with many papers in 1949, no data supported this statement.

Arguments against the use of drains include increased blood loss, interference with mobilization, added cost, potential for foreign body retention, and a theoretical portal for infection. However, he noted that recent data suggest that use of drains may reduce ecchymosis and help reduce early (within the first 12 hours postoperative) drainage.

Dr. Browne noted that a recent Cochrane review found that using drains results in increased blood loss and need for transfusion. The AAOS Clinical Practice Guideline on Surgical Management of Osteoarthritis of the Knee finds strong evidence for not using a drain with TKA, because there is no difference in complications or outcomes.

Myth: Patients with a hemoglobin level less than 10 g/dL or a hematocrit level less than 30 percent benefit from a transfusion (the 10/30 rule).

"The Transfusion Trigger Trial for Functional Outcomes in Cardiovascular Patients Undergoing Surgical Hip Fracture Repair randomized 2,016 hip fracture patients to a liberal approach (hemoglobin ≤ 10 g/dL) or a restrictive strategy (hemoglobin < 8 g/dL). It found no benefit to a liberal approach, even among elderly patients with multiple comorbidities," reported Dr. Browne.

Myth: Patients should not fly for 12 weeks after TKA due to the risk of venous thromboembolism (VTE).

In short flights of less than 4 hours, DVT has a very weak correlation with VTE, noted Dr. Browne. The risk increases for flights longer than 4 hours, and particularly for those longer than 8 hours.

A retrospective cohort study of 1,465 consecutive total joint arthroplasty patients, 220 of whom flew home at a mean 2.9 days after surgery, found no difference between flyers and nonflyers in terms of DVT, pulmonary embolism, or overall VTE, reported Dr. Browne. "The absolute risk, if it does exist, is almost certainly quite low. At our institution, we take reasonable precautions; most of these patients are on some form of chemoprophylaxis, and we have them wear compression stockings and mobilize every hour if they are traveling longer distances in the early postoperative period," he said.

"In our surgical experience, we carry many things that we've learned from authoritative sources and assumed to be true," observed Dr. Mason. "However, orthopaedic studies are often underpowered or inadequately constructed to answer the question. In practical terms, we perform surgeries and we're successful, the odds of an adverse event are small, and the numeric event clustering and/or unlinked associations may lead us to incorrect conclusions. In that instance, our knowledge is no longer knowledge, but manifest variance of opinion."

Peter Pollack is the electronic content specialist for AAOS Now. He can be reached at ppollack@aaos.org


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