Sinus Tracts in Joint Infection Need More Than a Yes-or-No Diagnosis, Experts Argue

When an artificial joint becomes infected, one of the most alarming signs a surgeon can see is a small channel opening on the skin that drains fluid from deep around the implant. This passage, known as a sinus tract, is one of the most specific indicators of periprosthetic joint infection, or PJI, and it appears as a confirmatory criterion in every major diagnostic definition, from the Infectious Diseases Society of America to the Musculoskeletal Infection Society, the International Consensus Meeting, and the European Bone and Joint Infection Society. Yet according to an international team of bone infection specialists writing in the Journal of Bone and Joint Infection, the way medicine currently describes these tracts, as simply present or absent, is far too crude for the decisions that follow the diagnosis. The binary label, they argue, tells surgeons almost nothing about what they will actually face in the operating room.

The Viewpoint, led by Irene K. Sigmund of the Medical University of Vienna together with Marjan Wouthuyzen-Bakker, Tristan Ferry, Ricardo Sousa, Daniel Pérez-Prieto, Alex Soriano, Volker Alt, Willem J. Metsemakers, Martin Clauss, and Rihard Trebse, does not question the diagnostic value of the sinus tract. Its presence communicating with the prosthesis remains among the most reliable confirmatory signs of infection, and the authors accept that a binary criterion serves diagnosis well. Their concern lies further downstream: once the diagnosis is made, the same single word, sinus tract, is expected to guide treatment selection, patient counselling, study design, and the interpretation of clinical outcomes. In reality, they contend, two patients who both fulfil the diagnostic definition may represent fundamentally different reconstructive problems.

The clinical stakes are considerable. A sinus tract is frequently treated as a contraindication to debridement, antibiotics, and implant retention, the joint-preserving procedure known as DAIR, and in many centres it also influences whether a patient is considered for a one-stage revision, in which the infected implant is exchanged in a single operation. The 2013 IDSA guidelines recommend against both DAIR and one-stage revision when a sinus tract is present, favouring instead a two-stage exchange in which the implant is removed, antibiotics are given, and a new prosthesis is implanted only after the infection appears controlled. By contrast, the 2018 International Consensus Meeting stated that a complex sinus tract that cannot be excised together with the previous surgical scar should be regarded as a relative contraindication to one-stage exchange, without ever defining what complex means.

The most recent consensus effort reveals just how unsettled the field remains. The 2025 International Consensus Meeting concluded that one-stage revision may be considered in patients with a sinus tract provided that adequate soft-tissue coverage can be achieved at the conclusion of surgery. That recommendation achieved only moderate agreement, with 70.7 percent of delegates in favour and 24.7 percent against, a level of dissent that the authors read as direct evidence of ongoing uncertainty about the surgical implications of sinus tract characteristics. Collectively, these successive guidelines implicitly acknowledge that not all sinus tracts are clinically equivalent, yet no consensus exists on how their complexity should be defined or reported.

Existing classification systems for PJI severity do little to close this gap. The McPherson classification, developed in the late 1990s and early 2000s, recognizes a synovial-cutaneous fistula as one of the compromising factors in grading the local extremity, but it does not characterize different sinus tract phenotypes or offer standardized descriptors of complexity. The more recent JS-BACH classification and the PJI-TNM system, which borrows the staging logic of oncology, both incorporate soft-tissue involvement as an important component of disease severity, yet neither specifically characterizes sinus tracts. The result is a diagnostic vocabulary that can confirm infection with high specificity but cannot describe the local disease it has confirmed.

In practice, experienced surgeons already look far beyond the binary. When planning treatment, they weigh the extent of soft-tissue involvement, the condition of the surrounding tissues, whether the implant is exposed, the number of previous surgical procedures, and the overall complexity of reconstruction. The contrast the authors draw is stark. A patient with a single, small sinus tract, minimal soft-tissue involvement, and healthy surrounding skin differs substantially from a patient with multiple communicating fistulae, chronic drainage, extensive soft-tissue destruction, implant exposure, and a history of repeated operations. Both satisfy the diagnostic definition of a sinus tract, but they are unlikely to benefit from identical surgical strategies.

This definitional poverty may also explain a persistent puzzle in the literature. Studies of one- and two-stage revision in patients presenting with a sinus tract have reported strikingly conflicting outcomes: some demonstrate encouraging eradication rates, while others report substantially higher rates of treatment failure and reinfection. The authors suggest that a binary description may be insufficient to capture the complexity of disease relevant to surgical decision-making, and that unreported differences in sinus tract characteristics could be quietly driving the heterogeneity in results. Without standardized reporting, the studies cannot be meaningfully compared, and the true prognostic weight of any particular tract feature remains unknown.

To address this, the team proposes a set of standardized descriptors of sinus tract complexity, explicitly framed as a hypothesis-generating minimum reporting dataset rather than a validated classification or treatment algorithm. The descriptors cover the characteristics of the tract and the surrounding local disease, including the number of tracts, their location, their maturity, the degree of soft-tissue compromise, whether the implant is exposed, the history of previous surgical procedures, associated abscess formation, and osseous involvement such as cloaca formation, an opening in bone through which infection can drain. These features should be interpreted in the context of joint-specific anatomy and, where relevant, imaging and intraoperative findings, because the external appearance of a tract may underestimate the extent of underlying disease. In the absence of validated thresholds for duration or maturity, the authors recommend that future studies report these characteristics descriptively rather than applying arbitrary cut-offs.

The authors are careful to bound their claim. The descriptors are not additional diagnostic criteria and should not be read as an independent treatment algorithm; their individual prognostic significance remains to be established in prospective validation studies. Sinus tract complexity, moreover, is only one component of the multifactorial complexity of PJI. Surgical decision-making should never rest on tract characteristics alone but must always be interpreted alongside well-established factors including the type and chronicity of infection, host status, microbiology, vascularity, bone involvement, implant characteristics, soft-tissue condition, and overall reconstructive feasibility. The aim is not to replace existing classification systems but to complement them, potentially feeding into future staging systems that integrate sinus tract descriptors with assessments of soft-tissue coverage and the need for reconstructive procedures.

If the framework is validated, the payoff could be substantial: meaningful comparisons between studies, improved risk stratification, and a common language for describing sinus tract complexity across centres, allowing researchers to test how different sinus tract phenotypes interact with different treatment strategies. The Viewpoint distils its argument into a single sentence that captures the shift it seeks: diagnosis begins with identifying a sinus tract, but treatment requires understanding its complexity, in conjunction with the many other factors that contribute to the overall complexity of periprosthetic joint infection. For the growing population of patients living with joint replacements, that distinction could determine whether the first operation is the last.

Subject of Research: Standardized characterization of sinus tract complexity in periprosthetic joint infection

Article Title: Beyond the binary description of sinus tracts in periprosthetic joint infection

Article References: Sigmund, I. K., Wouthuyzen-Bakker, M., Ferry, T., Sousa, R., Pérez-Prieto, D., Soriano, A., Alt, V., Metsemakers, W. J., Clauss, M., & Trebse, R. (2026). Beyond the binary description of sinus tracts in periprosthetic joint infection. Journal of Bone and Joint Infection, 11(5), 651-654. https://doi.org/10.5194/jbji-11-651-2026

Image Credits: AI Generated

DOI: 10.5194/jbji-11-651-2026

Keywords: periprosthetic joint infection, sinus tract, one-stage revision, two-stage exchange, DAIR, EBJIS, IDSA, International Consensus Meeting, soft-tissue coverage, orthopaedic surgery, implant infection, classification systems