Accuracy of diagnostic imaging techniques in patients with a suspected fracture-related infection

Post-operative infections after fracture treatment are one of the most severe
and challenging complications in trauma and orthopaedic surgery. The complete
spectrum of infections (e.g. acute, chronic, superficial or deep, with or
without bone involvement, with or without implants in situ) following surgical
fixation of a closed or open fracture are referred to as *fracture-related
infections* (FRI). The reported incidence of FRI generally varies between 2-4%,
but may increase up to 45%, depending on the comorbidities (diabetes, vascular
disease, smoking) and the extent of the injury (presence of contaminated open
fractures, concomitant soft tissue injuries, need for emergency damage control
surgery). Fracture-related infections result in multiple re-operations, long
antibiotic treatment, immobilization, inability to work and restrictions to
participate in social activities. The personal impact for a patient, suffering
from a FRI, is significant. The treatment of an FRI can take several months or
even years.

A fast and accurate diagnosis of fracture related infection would aid in
optimal clinical decision making for this condition. However, consensus about
the best diagnostic imaging modality for diagnosing fracture related infections
is lacking in our current practice (6). Commonly requested imaging modalities
for bone infections are a conventional magnetic resonance imaging (MRI), white
blood cell (WBC) and fluorodeoxyglucose positron emission tomography (FDG-PET).
The aforementioned techniques all have their capabilities and limitations to
discriminate bacterial infections from inflammatory response due to the
traumatic soft tissue damage and/or fractures, soft tissue reaction induced by
the operative treatment of the injuries, and foreign body reactions due to
implant placements (7). However, there is no literature, nor a uniform
agreement regarding the best imaging technique that should be used to (early)
detect and determine the extent of FRI*s. We recently conducted a systematic
review on the accuracy of diagnostic imaging modalities for FRI, but were
hampered by limited literature, heterogeneous patient populations and outdated
imaging techniques (8). A proper prospective and sufficiently powered trial
that compares these different imaging techniques for diagnosing FRI*s has never
been carried out. Because, we as applicants of this study (trauma surgeons,
orthopedic surgeons, nuclear physician, radiologist) are closely involved in
treating patients with fracture-related infecties, we took the effort to
improve the knowledge about this condition by initiating this trial.

The primary aim of our *Imaging of Fracture-related Infections trial (IFI
trial)* is to assess the diagnostic accuracy of all commonly requested medical
imaging techniques (WBC scintigraphy, FDG-PET/CT and MRI). The secondary aim is
to establish whether there are factors such as recent surgery, use of
antibiotics, patient comorbidities and/or in situ implants that influence the
diagnostic accuracy of these imaging modalities. Secondary goals are also to
determine the quality of life the medical costs that arise from
fracture-related infections.

This study is a multicenter prospective cohort study. All patients, who will be
included in the IFI trial, will undergo three imaging techniques, namely a WBC
scintigraphy, an FDG-PET/CT and an MRI, in order to determine the most accurate
imaging strategy for diagnosing fracture-related infections.

The extent of burden and risks for patients participating in the study is
considered to be low. All imaging techniques used in this study (leucocyte
scintigraphy, FDG-PET and MRI) are well established diagnostic techniques
worldwide.