Unifying Concepts

Diagnostic Criteria for Fracture-Related Infection (FRI)

Fracture-related infection (FRI) is a severe complication following bone injury and can pose a diagnostic challenge. There is a spectrum of clinical presentations of FRI and differentiating them from noninfected causes can be difficult. In the early postoperative period, classical clinical symptoms of infection, such as pain, redness, warmth, or swelling, overlap with features of normal fracture healing. Later, more subtle clinical presentations such as fracture nonunion or persistent pain can be attributable to both infective and noninfective conditions. The complexity and variety of FRI may have hindered the establishment of uniform diagnostic criteria.

Confirmatory criteria for FRI
1. Fistula, sinus or wound breakdown (with communication to the bone or the implant).
2. Purulent drainage from the wound or presence of pus during surgery.
3. Phenotypically indistinguishable pathogens identified by culture from at least two separate deep tissue/implant (including sonication-fluid) specimens taken during an operative intervention. In case of tissue, multiple specimens (≥3) should be taken, each with clean instruments (not superficial or sinus tract swabs). In cases of joint effusion, arising in a joint adjacent to a fractured bone, fluid samples obtained by sterile puncture may be included as a single sample.
4. Presence of microorganisms in deep tissue taken during an operative intervention, as confirmed by histopathological examination using specific staining techniques for bacteria or fungi.

Suggestive criteria for FRI
1. Clinical signs – any one of:

  • Pain (without weight bearing, increasing over time, new-onset)
  • Local redness
  • Local swelling
  • Increased local temperature
  • Fever (single oral temperature measurement of ≥38.3°C (101°F))

2. Radiological signs – any one of:

  • Bone lysis (at the fracture site, around the implant)
  • Implant loosening
  • Sequestration (occurring over time)
  • Failure of progression of bone healing (i.e. non-union)
  • Presence of periosteal bone formation (e.g. at localizations other than the fracture site or in case of a consolidated fracture)

3. A pathogenic organism identified by culture from a single deep tissue/implant (including sonication-fluid) specimen taken during an operative intervention. In case of tissue, multiple specimens (>3) should be taken, each with clean instruments (not superficial or sinus tract swabs). In cases of joint effusion arising in a joint adjacent to a fractured bone, a fluid sample obtained by sterile puncture is permitted.
4. Elevated serum inflammatory markers: In musculoskeletal trauma, these should be interpreted with caution. They are included as suggestive signs in case of a secondary rise (after an initial decrease) or a consistent elevation over a period in time, and after exclusion of other infectious foci or inflammatory processes:

  • Erythrocyte sedimentation rate (ESR)
  • White blood cell count (WBC)
  • C-reactive protein (CRP)

5. Persistent, increasing or new-onset wound drainage, beyond the first few days postoperatively, without solid alternative explanation.
6. New-onset of joint effusion in fracture patients. Surgeons should be aware that FRI can present as an adjacent septic arthritis in the following cases:

  • Implant material which penetrates the joint capsule (e.g. femoral nailing)
  • Intra-articular fractures



  1. Onsea J, Van Lieshout EMM, Zalavras C, Sliepen J, Depypere M, Noppe N, Ferguson J, Verhofstad MHJ, Govaert GAM, IJpma FFA, McNally MA, Metsemakers WJ. Validation of the diagnostic criteria of the consensus definition of fracture-related infection. Injury. 2022 Mar 12:S0020-1383(22)00209-1. [Medline]
  2. Govaert GAM, Kuehl R, Atkins BL, Trampuz A, Morgenstern M, Obremskey WT, Verhofstad MHJ, McNally MA, Metsemakers WJ; Fracture-Related Infection (FRI) Consensus Group. Diagnosing Fracture-Related Infection: Current Concepts and Recommendations. J Orthop Trauma. 2020 Jan;34(1):8-17. [Medline]
  3. Metsemakers WJ, Morgenstern M, McNally MA, Moriarty TF, McFadyen I, Scarborough M, Athanasou NA, Ochsner PE, Kuehl R, Raschke M, Borens O, Xie Z, Velkes S, Hungerer S, Kates SL, Zalavras C, Giannoudis PV, Richards RG, Verhofstad MHJ. Fracture-related infection: A consensus on definition from an international expert group. Injury. 2018 Mar;49(3):505-510. [Medline]


Created Mar 29, 2022.

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