At their meeting in June, the AAOS Board of Directors approved a new clinical practice guideline (CPG) on the diagnosis of periprosthetic joint infections.

Total joint arthroplasty is an effective means of improving function and decreasing morbidity in patients with degenerative arthritis. However, deep periprosthetic joint infection remains a major complication for both total hip arthroplasty (THA) and total knee arthroplasty (TKA) with an incidence of 1 percent to 2 percent at 2 years postoperatively and up to 7 percent after revision surgery. Infection is a common cause of revision arthroplasty; 15 percent of revision THAs and 25 percent of revisions TKAs are due to infection.

Although the incidence of infection appears to be small, the total number of joint arthroplasties being performed is on the rise. This will undoubtedly lead to a greater number of complex cases, with the presence of multidrug-resistant organisms in sick and immunocompromised patients.

Diagnosis is a challenge
To date, the orthopaedic surgeon’s biggest challenge has been to correctly diagnose periprosthetic joint infection preoperatively or intraoperatively so that effective treatment regimens capable of eradicating the inciting organism may be implemented. Much effort has gone into optimizing current modalities and creating new ones because no single test can reliably and solely identify such infections.

The preoperative workup for periprosthetic joint infections includes serology with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). These tests have a pivotal role in screening patients at risk, while joint fluid cell count and neutrophil differential have emerged as reliable indicators of infection.

In addition to cell count and differential testing, the aspirated fluid can be cultured for the presence of aerobic and anaerobic organisms. The technetium-Tc99m (99Tc) isotope bone scan, performed alone or combined with Indium-111 radioisotope, and the fluoro-deoxyglucose-positron emission tomography (FDG-PET) have been described in diagnosing periprosthetic joint infections, but with equivocal results.

Intraoperatively, gram staining of periprosthetic tissue samples has demonstrated poor sensitivity in detecting infection. A frozen section of periprosthetic tissue is frequently used to detect acute inflammation and the presence of neutrophils. Currently, the culture of an organism on solid media from multiple specimens obtained during surgery remains the “gold standard” for diagnosing periprosthetic joint infections. However, culture can fail to correctly identify an inciting organism, even in the presence of overwhelming clinical evidence indicating infection.

Guideline development
To develop the clinical practice guideline, the workgroup 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 workgroup 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 (in the absence of reliable evidence, the workgroup makes a recommendation based on clinical opinion).

The guideline includes 15 recommendations (Table 1). Seven of these are graded as strong, three as moderate, one as weak, one as inconclusive, and three are based on consensus. The work group proposes that patients be stratified into higher or lower probability of infection, based on the following criteria:

Higher probability of infection: One or more symptoms and at least one or more of the following: risk factors (supported by evidence or expert opinion); physical exam finding; early implant loosening/osteolysis (based on radiographic findings)

Lower probability of infection: Pain or joint stiffness only and none of the following: risk factors (supported by evidence or expert opinion); physical exam finding; early implant loosening/osteolysis (based on radiographic findings)

Risk factors identified and supported by the evidence include prior infection of the joint (knee), superficial surgical site infection (hip and knee), obesity (hip), extended operative time (greater than 2.5 hours, hip and knee) and immunosuppression (knee).

Risk factors supported by expert opinion (work group consensus) include recent (within 1 year) bacteremia or candidemia findings; metachronous prosthetic joint infection; skin disorders (psoriasis, chronic cellulitis, lymphedema, chronic venous stasis, skin ulcers); intravenous drug use; recent (within 3 years) infection or colonization with methicillin-resistant Staphylococcus aureus; active infection at another site.

In addition, the work group developed several algorithms illustrating the recommendations of the guidelines. Readers are encouraged to refer to these algorithms when reading the guideline, which is available at www.aaos.org/guidelines

Javad Parvezi, MD, served as vice chair of the workgroup that developed the clinical practice guidelines on the diagnosis of periprosthetic joint infections. He can be reached at parvj@aol.com

How the guidelines came to be
The Clinical Practice Guideline on the Diagnosis of Periprosthetic Joint Infections, adopted by the AAOS Board of Directors at their June 2010 meeting, 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. They included Craig Della Valle, MD, chair; Javad Parvizi, MD, FRCS, vice-chair; Thomas W. Bauer, MD, PhD; Paul E. DiCesare, MD; Richard Parker Evans, MD; John Segreti, MD; Mark Spangehl, MD; William C. Watters III, MD; Michael Keith, MD; Charles M. Turkelson, PhD; Janet L. Wies, MPH; Patrick Sluka, MPH; and Kristin Hitchcock. Special acknowledgement goes to research analysts Sara Anderson, MPH; Kevin Boyer; and Laura Raymond, MA.

Among the groups that participated in peer review of this guideline were the American Association of Hip and Knee Surgeons, the European Bone and Joint Infection Society, the Knee Society, the Musculoskeletal Infection Society, and the Society of Nuclear Medicine.

Funding 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 on June 18, 2010.

The methods used to prepare this guideline were rigorous, employed to minimize bias and to develop a set of reliable, transparent, and accurate clinical recommendations for diagnosing periprosthetic joint infections. These methods are detailed in the full guideline.

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