Definition for Periprosthetic Joint Infection
The Workgroup convened by the Musculoskeletal Infection Society. The Journal of Arthroplasty 2011; 26(8): 1136-8
SICOT Associate Member & SICOT Newsletter Editorial Board Member – London, United Kingdom
Diagnosis of periprosthetic joint infection (PJI) remains a real challenge to the orthopaedic community. Currently, there is no single standard definition for PJI. This communication presents the diagnostic criteria that have been proposed by a workgroup convened by the Musculoskeletal Infection Society (MSIS). The diagnostic criteria were developed after the evaluation of available evidence. The role of every diagnostic test was examined, and the literature was reviewed in detail to determine the threshold for each test. It is hoped that the proposed definition for PJI will be adopted universally; bringing standardisation into a field that has suffered extensive variability and heterogeneity.
Definition of PJI Criteria
Based on the proposed criteria, a definite PJI exists when:
there is a sinus tract communicating with the prosthesis;
a pathogen is isolated by culture from 2 or more separate tissue or fluid samples obtained from the affected prosthetic joint;
4 of the following 6 criteria exist:
elevated serum erythrocyte sedimentation rate (30mm/h) and serum C-reactive Protein (CRP) concentration (10mg/L);
elevated synovial white blood cell count;
elevated synovial polymorphonuclear percentage (PMN%);
presence of purulence in the affected joint;
isolation of a microorganism in one culture of periprosthetic tissue or fluid;
greater than 5 neutrophils per high-power field in 5 high-power fields observed from histologic analysis of periprosthetic tissue at 400 times magnification.
As outlined by the authors correctly, the literature has suffered for long with no consensus on a definition for PJI, which has made communication and comparison of results between surgeons and various centres treating infection impossible. Additionally, a lack of consensus has often resulted in delayed diagnosis and commencement of treatment in a timely fashion which is key for any successful management plan.
Therefore, the MSIS convened a workgroup to review the evidence in the literature and provide a ‘gold standard’ definition for PJI against which new diagnostic tests for infection could be measured. It was also agreed that this definition will be reviewed regularly to adopt new diagnostic tests which may prove to become essential in the diagnosis of PJI. In fact, the International Consensus Group for PJI  has already made minor modifications to the diagnosis by removing purulence as a minor criterion and adding the leukocyte esterase strip test  as an alternative for synovial fluid WBC count. Hence, the diagnosis of PJI can be made with the presence of three out of five rather than four out of six minor criteria as outlined above. It is worth noting that PJI may still be present, even in the absence of sufficient criteria for infection, and a systematic diagnostic approach should therefore be combined with an individualised therapeutic strategy.
- Parvizi J, Jacovides C, Antoci V, Ghanem E. Diagnosis of periprosthetic joint infection: the utility of a simple yet unappreciated enzyme. J Bone Joint Surg Am. 2011 Dec 21;93(24):2242-8.