A new definition for periprosthetic joint infection created

Issue: November 2011

ByJavad Parvizi, MD, FRCS

Javad Parvizi

Have you ever asked a medical student or resident to define periprosthetic joint infection? Most students would define it as a condition in which an infecting organism is present in the prosthetic joint. Although this is technically correct, it implies that isolation of an organism, i.e. a “positive culture” would be the “gold standard” for periprosthetic joint infection.

No one disputes that isolation of an organism is extremely important aspect for confirmation of periprosthetic joint infection (PJI). However, all of us in clinical practice dealing with PJI realize that there is a relatively large number of patients (5% to 8%) suffering from PJI in whom an organism cannot be isolated (culture negative), and conversely, there are some patients (again 5% to 8%) with no sign of PJI in whom cultures obtained may isolate a pathogen (false positive). Thus, positive culture is not a true “gold standard” for defining PJI, a fact that most of us live with on a daily basis. The question that arises is what then defines PJI?

One should not attempt to obtain an answer to this question from the literature. There are no single accepted criteria for PJI currently. Furthermore, some of these definitions even disagree with each other. There are almost as many definitions or criteria for PJI in the literature as there are published studies. It appears that institutions and investigators use a “self-selected” criteria for defining PJI. The existence of different diagnostic criteria or definition for PJI has made it complex to interpret the literature related to PJI. This complexity or frustration is experienced by hospitals attempting to report surgical site infections to the National Healthcare Safety Network, the surveillance arm of the Center for Disease Control and Prevention (CDC).

Recently, the Musculoskeletal Infection Society convened a workgroup and tasked them with evaluation of the literature to propose a diagnostic criteria. The workgroup consisted of orthopedic surgeons, infectious disease specialists, musculoskeletal pathologists and representatives from the CDC. The intention of this proposal was to have a “gold-standard” definition for PJI that can be universally adopted by all physicians, surveillance authorities (including the CDC), medical and surgical journals, the medicolegal community and all involved in management of PJI. Using this definition, clinicians can be confident in their diagnosis and therefore provide appropriate treatment. Additionally, adoption of this definition for research purposes will allow for consistency between studies and potential improvement of the quality of the published body of evidence. These definitions will be adopted and published by most major orthopedic journals. The CDC has also expressed interest in adopting these definitions for surveillance purposes.

Based on the recommendations of the workgroup, definite PJI is present when:

There is a sinus tract communicating with the prosthesis; or
A pathogen is isolated by culture from two separate tissue or fluid samples obtained from the affected prosthetic joint; or
When four out of the following six criteria exists: 1) elevated serum erythrocyte sedimentation rate or serum C-reactive protein concentration, 2) elevated synovial white blood cell count, 3) elevated synovial neutrophil percentage, 4) presence of purulence in affected joint, isolation of a microorganism in one culture of periprosthetic tissue or fluid; or 5) greater than five neutrophils per high power field in five high power fields observed from histological analysis of periprosthetic tissue at 400 times magnification.

However, PJI may be present if less than four of these criteria are met.

Moving forward, these definitions should be embraced by all to bring harmony into a field that has experienced much variation and inconsistency.

References:

Berbari E, Mabry T, Tsaras G, et al. Inflammatory blood laboratory levels as markers of prosthetic joint infection: A systematic review and meta-analysis. J Bone Joint Surg Am.2010;92(11):2102-2109.

Della Valle CJ, Sporer SM, Jacobs JJ, et al. Preoperative testing for sepsis before revision total knee arthroplasty. J Arthroplasty. 2007;22:90-93.

Ghanem E, Parvizi J, Burnett RSJ, et al. Cell count and differential of aspirated fluid in the diagnosis of infection at the site of total knee arthroplasty. J Bone Joint Surg Am.2008;90(8):1637-1643.

Parvizi J, Ghanem E, Menashe S, et al. Periprosthetic infection: what are the diagnostic challenges? J Bone Joint Surg Am. 2006;88 Suppl 4:138-147.

Parvizi J, Jacovides C, Zmistowski B, Jung KA. Definition of periprosthetic joint infection: is there a consensus? Clin Orthop Relat Res. 2011. Available at: http://www.ncbi.nlm.nih.gov/pub med/21751038 [Accessed July 14, 2011].

Trampuz A, Hanssen AD, Osmon DR, et al. Synovial fluid leukocyte count and differential for the diagnosis of prosthetic knee infection. Am J Med. 2004;117(8):556-562.

Javad Parvizi, MD, FRCS, editor of Infection Watch, can be reached at the Rothman Institute, 925 Chestnut St., 5th Floor, Philadelphia, PA 19107; 267-339-3617; email: parvj@aol.com.

Disclosures: Parvizi is a consultant to Stryker.