FRI classification is helpful to compare patients for research and to guide clinicians in decision-making when treating patients with a standardized treatment strategy. There are several classifications (Cierny-Mader, BACH) that can help to understand FRI. However, these classification systems were developed before the destinction between FRI and oestomyelitis was made, limiting their usefullness in clinical practice especially in a low-resource setting.

A new FRI classification system was published in 2024 and is according to our experts most useful to guide personalized decision-making. This new system was based on simplicity, reproducibility and distinctness. It has been specifically created to be applicable in all clinical settings, as the highest prevalence of fracture-related infections is in LMICs.

This FRI classification system has three major elements and is easy to remember:

• Fracture
• Related patient factors
• Impairment of soft tissues

Complexity in each element is graded from 1 to 5, and this grading helps you consider possible treatment options.

It’s important to realize that the situation for a patient may change before a definitive treatment plan is made. For example, related patient factors can be optimized, or impairment of soft tissues can become more extensive following a primary surgical debridement.

Ideally, use this classification after surgical debridement in the OR when you can assess the situation adequately.

The Chapter 'Managing FRI' uses this classificatin system in the decision making when making an FRI treatment plan.

Why is time not a factor in FRI classification?

Historically, bone infection classification and treatment plans have been influenced by time to presentation, specifically the decisions to treat with debridement, antibiotics and implant retention (DAIR). However, there is very little evidence to support this choice, and more recent research has classified time from injury as an independent factor on treatment outcomes. In expert opinion, time from injury impacts the patient as a whole, but no cutoff is possible.

The passage of time may have a positive influence on FRI, as some bone healing may occur. For example, an F2 can become an F1, leading to better outcomes. On the other hand, it may create bigger issues, for example bone loss.