Prevention and treatment of implant-related infections are associated with an ongoing array of unmet challenges. This edition of AAOS Now discusses topics related to infections in orthopaedics, including biofilm and pre-closure Betadine baths. In line with the theme, this article examines two recently published articles on fracture-related infections (FRIs) that highlight and summarize key points for orthopaedic surgeons and other clinicians who treat FRIs.

Defining FRI
The earliest publication defining FRIs is a 2018 article from Metsemakers et al in Injury titled “Fracture-Related Infection: A Consensus on Definition from an International Expert Group.” The FRI acronym was agreed upon during two FRI consensus meetings convened in 2016 and later in 2018 in Switzerland. The FRI consensus meeting included more than 20 delegates from the AO Foundation and the European Bone and Joint Infection Society, who collectively proposed a consensus definition for FRI.

The consensus group recognized that the majority of published trials in fracture care did not use a standardized definition of FRI. Metsemakers et al stated, “The intention of establishing this definition of FRI was to offer clinicians the opportunity to standardize clinical reports and improve the quality of published literature.”

Diagnosing FRI
Another noteworthy article regarding FRI was published in 2020 in the Journal of Orthopaedic Trauma, titled “Diagnosing Fracture-Related Infection: Current Concepts and Recommendations.” In that article, Govaert et al wrote, “There is a spectrum of clinical presentations of FRI, and differentiating them from noninfected causes can be difficult.”

In terms of FRI diagnosis, Govaert et al suggested beginning an infection workup as Sir William Osler indoctrinated years ago, by starting with the medical history and clinical examination to establish the clinical suspicion of an FRI. From there, the clinician should ascertain the presence of confirmatory or suggestive criteria. These metrics are similar to the major and minor criteria of other infection-classification systems. For example, a fistula, sinus, wound breakdown, or purulent drainage (i.e., presence of pus) is FRI confirmation. Suggestive criteria include elevated inflammatory serum markers (i.e., erythrocyte sedimentation rate, complete blood count, C-reactive protein) and clinical and systemic signs such as redness or fever. Other suggestive criteria include joint effusion and persistent, increasing, or new-onset wound drainage. These criteria may then lead to surgical exploration where tissue samples for culture would confirm an FRI diagnosis.

The consensus group also concluded that the presence of pathogens identified by culture is not an absolute requirement for FRI for patients receiving chronic antibiotic suppression. A second key recommendation from the consensus group is that caution is warranted when interpreting the results of serum inflammatory markers in FRI, as their predictive value is low.

In terms of imaging modalities, CT, MRI, three-phase bone scan (BS), fluorodeoxyglucose (FDG) positron emission tomography (PET), and white blood cell (WBC) scintigraphy remain the more common options. The Govaert et al publication states that specificity for BS is so low (0 to 10 percent) that BS is not recommended in the workup of FRI. Rather, hybrid imaging (single-photon emission CT/CT, PET/CT, PET/MRI) may be preferred by the treating surgeon because it allows for better anatomic details. FDG is a glucose analog, and this variation of PET was developed in 1976 to monitor cancer patients, as cancer cells have increased uptake of glucose. The FDG tracer helps localize foci of cancer cells and other glucose-dependent cell types.

In addition to surgical site infection (SSI), periprosthetic joint infection (PJI), and FRI, one may also encounter the acronym IFF, which stands for infection after fracture fixation. It is worth noting while discussing FRI that the infection guidelines for PJI from the Centers for Disease Control cannot be extrapolated to fracture cases.

Summary
Clearly, infection in orthopaedics is a growing problem. Surgeons have evolved from talking about SSIs to PJIs and now FRIs. A number of recent publications present the work of the two FRI consensus group meetings. Hopefully, defining FRI will render future studies on FRI easier to evaluate, thereby improving infection prevention, diagnosis, and treatment.

Daniel R. Schlatterer, DO, MBA, FAAOS, is the former chairman of the orthopaedic surgery residency program and former chief of orthopaedic trauma at WellStar Health System in Atlanta, Georgia. He is a member of the AAOS Now Editorial Board.

References 

1. Metsemakers WJ, Morgenstern M, McNally MA, et al: Fracture-related infection: a consensus on definition from an international expert group. Injury 2018;49:505-10.
2. Govaert GAM, Kuehl R, Atkins BL, et al: Fracture-Related Infection (FRI) Consensus Group: diagnosing fracture-related infection: current concepts and recommendations. J Orthop Trauma 2020;34(1):8-17.