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Published 4/1/2017
Terry Stanton

Symposium Addresses “All Things Infection”

An overflow crowd packed a large San Diego Convention Center room during the 2017 AAOS Annual Meeting for the symposium “All Things Infection: All You Need to Know,” featuring a panel of 12 surgeons and researchers who shared their expertise on periprosthetic joint infection (PJI) and related issues.

“It's great to see the room full—it shows there is strong interest in addressing this important topic,” said panelist Craig J. Della Valle, MD. Symposium moderator Javad Parvizi, MD, FRCS, opened with an overview of current recommendations arising from the 2013 International Consensus Meeting (ICM) on PJI and those of the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO). (The CDC is poised to release a set of prevention guidelines, and the WHO offers 29 recommendations on 23 topics.)   “Surgical site infections (SSIs) are an immense burden on health care, providers, and patients,” Dr. Parvizi said. Yet much of the accepted knowledge about them is “based on thin science, if any at all.” Most SSIs are caused by contamination of an incision with microbes from the patient's own skin. The skin can contain more than 1 million bacteria per square centimeter, while as few as 10 microbes per square centimeter can cause an SSI. “If we can reduce the number of microorganisms, we can reduce the risk of infection,” Dr. Parvizi said. The ICM, CDC, and WHO offer guidance for measures before, during, and after surgery. Patient optimization involves a number of health and lifestyle issues, including systemic or local infection, immunosuppressive state (such as HIV), uncontrolled diabetes/hyperglycemia, chronic disease (anemia, liver, renal, etc.), malnutrition, obesity, affective disorders, smoking, excessive alcohol consumption, and intravenous drug use. explained how his institution, NYU Langone Medical Center, Hospital for Joint Diseases (HJD), is establishing a perioperative surgical home (POSH) concept for preventing infections. According to Dr. Iorio, for medically complex patients, it is critical to use “an integrated optimization, testing, and clearance center” that uses “a risk coordinator, patient's internist, or a hospital-affiliated center associated with a total joint–specific education and comorbidity identification process.” He also noted that preoperative optimization of risk factors for suboptimal outcomes is the best method of prevention.” HJD has incorporated a transdepartmental approach—involving anesthesia, internal medicine, smoking cessation, pulmonary, cardiology, endocrine, nutrition, bariatrics, physical therapy, and psychiatry—to decrease perioperative morbidity and mortality and decrease readmissions, Dr. Iorio said. The POSH approach “allows for risk stratification of knee arthroplasty candidates and clinical treatment to mitigate modifiable risk factors in high-risk patients as part of the preoperative evaluation process.” Currently, it is a surgeon-directed initiative, Dr. Iorio said, but he hopes that oversight will be transferred to a risk stratification coordinator. “In today's bundled payment and quality-driven environment, it is no longer economically feasible to simply accept increased risk in poorly managed patients,” Dr. Iorio said. “We have chosen to take an active role in managing modifiable risk factors and will delay surgery until these risk factors are controlled. Surgeons, primary care physicians, internists, and specialty physicians involved in the pre-admission clearance process can all participate in decreasing these risk factors preoperatively. Our concept of a perioperative orthopaedic surgical home to optimize patients preoperatively has led to decreased complications and readmissions as well as better outcomes.” Detection tips, CPGs
John Segreti, MD, an infectious disease specialist, offered a primer on diagnosing infection and “strategies to isolate the bug.” He noted that molecular methods detect bacteria with the same accuracy as culture, but they do not provide antibiotic susceptibility information. Culturing should be done at least 2 weeks after the patient has ceased taking antibiotics, asserted Dr. Segreti, who noted that a single dose of prophylactic antibiotics does not alter intraoperative culture results in PJI. Detection should target both aerobic and anaerobic bacteria, while fungi and mycobacteria are rare enough that they generally do not merit testing in most regions. Gram staining is not reliable, Dr. Segreti said, as intraoperative Gram staining was found to have a sensitivity of 27 percent and a specificity of 99.9 percent. Dr. Della Valle summarized the AAOS Clinical Practice Guidelines (CPGs) on diagnosing PJI.  They note that risk stratification is generally based on consensus opinion rather than strong evidence and assigns “higher probability” or “lower probability” to a patient's risk profile. “It's something we intuitively do every day,” he said. Examples of higher probability for infection include prior history of infection, obesity (for hips), inflammatory arthritis, early implant loosening (<5 years), and early osteolysis. the cpg strongly recommends obtaining erythrocyte sedimentation rate (esr) and c-reactive protein (crp) values, as these tests are ubiquitous and inexpensive, have a high sensitivity, and are of low risk to patients. they are an excellent screening tool because if both results are negative, the risk of pji is low. the guidelines also strongly recommend aspiration if esr crp levels are elevated, or “if suspicion is high.” the guidelines note that joint aspiration is probably the best test. the cutoff point for synovial fluid white blood cell count is 3,000> μL and is 80 percent for the percentage of neutrophils in the differential. “The patient must be off antibiotics for at least 2 weeks” before aspiration, Dr. Della Valle said.” Plain radiographs rarely show evidence of infection, although suspicion may be raised if rapid loosening occurs after arthroplasty. Nuclear medicine studies may be considered a second-line option, and a negative scan can predict the absence of infection. The CPG states that evidence is insufficient to recommend MRI and CT imaging. Echoing Dr. Segreti, Dr. Della Valle noted that the CPG strongly recommends against intraoperative Gram staining. On the other hand, intraoperative frozen sections can be quite useful for diagnosis “if you have a good pathologist with an interest and knowledge in examining them and if you are skilled in selecting samples.” The CPG recommends against giving a patient antibiotics “until you make a diagnosis and get cultures from the joint,” Dr. Della Valle said. This practice reduces the risk of false-negative cultures, whereas giving antibiotics prematurely causes confusion over diagnosis and makes antibiotic selection more difficult. Following the guidelines—specifically, in regard to ESR and CRP tests and aspiration with cell count—will “make the diagnosis for you in 90 percent of cases,” noted Dr. Della Valle. The early infection trauma challenge
Addressing the topic of early infection in trauma cases, Paul Tornetta III, MD, defined early infection as occurring in a fracture that is fixed and acutely closed and that arises prior to union. “The ones that come back 'early infected' are the most challenging,” he said, noting that these clinically apparent infections are not necessarily culture-positive. According to Dr. Tornetta, some points to consider include whether the implant is a nail or plate—and, if it's a plate, is the fixation stable, and is the alignment acceptable? “Those are prerequisites for leaving the nail or plate in place,” Dr. Tornetta said. “How is the soft-tissue envelope? Is there anything in there that is dead?—because that has to come out.” The primary issues with early infection are whether to retain hardware, the length of antibiotic administration, and measures to encourage healing. The success rate for retention of hardware is around 70 percent. Smoking is a predictor for failure, nails fare worse than plates when retained, and lower extremities do worse than upper extremities, Dr. Tornetta said. Addressing differences between nails and plates, Dr. Tornetta said, “With a nail, if you have an obvious infection, you need to assume it is an intramedullary infection. This calls for a local incision and drainage in addition to reaming the canal. Definitive nailing is done after infection is resolved. Take the nail out and ream the canal once it's healed, because a fair number of patients will reinfect.” Plates, he said, “are a little bit different. You want to retain them if they are stable and if there is acceptable alignment; otherwise, they have to go.” Culture-specific antibiotics should be prescribed after treatment—until union occurs. “Sometimes this is 6 months or longer, and you should consider removal of the plate once you've got union, because 30 percent of these patients will reinfect,” Dr. Tornetta said. Dr. Tornetta said he scrubs the plate down with chlorhexidine after initial débridement, with the bristle side of the brush to provide mechanical cleaning. Afterward, he changes out his instrument, and swaps out any screw that is not rigidly tight. He also “slathers” the plate with a vancomycin paste he prepares from powder and saline solution (1.25 cc of saline solution per gram of powder). Also presenting at the symposium were Matthew P. Abdel, MD; Thorsten Gehrke, MD, Fares S. Haddad, FRCS; Frederick A. Matsen III, MD; Edward M. Schwarz, PhD; Bryan D. Springer, MD; and Alexander R. Vaccaro, MD, PhD, MBA. Terry Stanton is the senior science writer for AAOS Now. He can be reached at tstanton@aaos.org
The POSH approach Richard Iorio, MD,