Diagnosing periprosthetic joint infections: where to start, what to look for

While a periprosthetic joint infection (PJI) is more likely to occur within the first two years of implantation, any artificial joint is at an increased risk of developing infection over its lifetime. Diagnosing PJI is not always straightforward—patients may not have obvious symptoms. Detection of infection requires a multi-disciplinary approach characterized by good communication and weighted problem-solving based on the right information. What signs of infection should a clinician be on the lookout for? What combination of testing, imaging, and cultures is recommended? Part 2 of this article series examines the complexities of PJI diagnosis.

Periprosthetic joint infection (PJI) is a growing problem [1, 2]. Even if rates of infection hold steady, the simple fact that more joints are being replaced translates into a higher number of PJI cases [3–6]. The prevalence of multi-drug resistant PJIs is also a “worrisome” trend [7]. The microorganisms that tend to colonize artificial joints grow in biofilms that present a challenging host of problems in terms of diagnosis and treatment [8–10].

The complex nature of PJIs necessitates a multidisciplinary approach to coordinate decision making. The weighted evaluation of the information gathered at each step of diagnosis and treatment requires cross-disciplinary collaboration and communication [11]. See Part 1 of this article series for further elaboration of PJI risk factors and pre-, intra-, and postoperative infection prevention strategies. Part 3 examines treatment options for acute and chronic PJI.

In addition to the increased economic cost related to PJI [12], there is an often unacknowledged personal cost for surgeons who may feel responsible. In qualitative telephone interviews with orthopedic surgeons, Mallon et al chronicled “a significant emotional impact on surgeons who report a collective sense of devastation and personal ownership, even though prosthetic joint infection cannot be fully controlled for.” [13]

Most common pathogens in PJI

A 2014 study on the most common PJI pathogens compared 898 cases from an infection referral center in Germany to 772 cases at a similar institution in the US. A higher number of virulent and resistant organisms were identified as the source of infection in the US center. The organisms that were identified were: coagulase-negative Staphylococcus, Staphylococcus aureus, Streptococcus spp, Enterococcus spp, anaerobes, fungi, and mycobacteria. Additionally, they found polymicrobial and culture-negative infections [14]. Other causative agents are gram-negative bacteria (such as Klebsiella spp, Pseudomonas aeruginosa), and Cutibacterium spp [15].

This is a long list of suspects, each with unique biomarkers, culturing requirements, antibiotic susceptibility, and antibiotic dosing specifications and delivery pathways (intravenous vs oral). However, it is worth mentioning that there are also other infection-causing microorganisms rarely associated with PJI and this uncommonness may prolong or complicate their identification—they are not routinely tested for [16–19]. Testing for rare microorganisms has been recommended, particularly in persistent cases [18, 20].

Did you miss AO Recon’s webinar on periprosthetic joint infection (PJI)?

In June 2019, AO Recon gathered an online community of close to 200 surgeons for an interactive information session and Q&A led by Olivier Borens, Head of Septic Surgery and Head of Traumatology at the Centre Hospitalier Universitaire Vaudois (Lausanne, Switzerland) and chat moderator Andrej Trampuz, Infectious Diseases Consultant in Septic Surgery at Charité–Universitätsmedizin (Berlin, Germany) on the topic of infection after joint arthroplasty.

Biofilm: the orthopedic surgeon’s nemesis

When microbes grow as a biofilm they multiply into slimy, multi-layered, sometime multi-species, complex, synergistic communities. The microorganisms (bacteria and fungi) adhere to each other as well as surfaces, such as prosthetic joints, chemically communicating with each other. Bacteria in a biofilm share available nutrients and gain protection from hostile environmental threats such as antibiotics and the body’s immune defenses through a variety of strategies [21]. It is hypothesized that biofilm formation evolved as a survival strategy during the time of primitive Earth [22].

As they mature, biofilms, such as those formed by common PJI-causing Staphylococcus spp, can develop extracellular barriers, making it difficult for the body’s immune cells to penetrate, and even deactivate those that do manage to get through [23]. And most importantly in terms of PJI, biofilms are less sensitive to antibiotics via several inherent biological mechanisms [9]. Figure 1 highlights the intensifying complexity of a biofilm through its stages of maturity—it can be more straightforward to diagnosis and treat an infection before it forms a biofilm. Figure 1 also illustrates the persistence of biofilms, which when associated with PJI make them more difficult to predict, diagnose, and treat [24].

However, early PJI detection is not always possible and once you have a suspicion of infection there is no single test that can reliably be used to diagnose it, which means that a combination of diagnostic testing must be employed and interpreted [25–28].

Read the full article with your AO login

  • Signs and symptoms
  • Reconnaissance: know your adversary
  • Imaging
  • Laboratory testing
  • Synovial fluid aspiration
  • Microbiology
  • Sonication
  • Molecular methods
  • Tissue histology
  • Diagnose PJI if at least one of these criteria is satisfied
  • What you’ve been waiting for
  • Conclusion
  • References

Part 1 | Preventing PJI: how to lower infection rates

Part 3 | Treating PJI: adopting an individualized approach

Additional AO resources on this topic

Access videos, tools, and other assets to learn more about this topic.


Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Olivier Borens

University Hospital Lausanne
Lausanne, Switzerland

Nora Renz

Inselspital—University Hospital Bern
Bern, Switzerland

Andrej Trampuz

Charité—University Medicine Berlin
Berlin, Germany

This issue was created by Word+Vision Media Productions, Switzerland.



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