Preclinical Evaluation of Photoacoustic Imaging as a Novel Noninvasive Approach to Detect an Orthopaedic Implant Infection

Introduction: Diagnosing-prosthetic joint infection (PJI) poses significant challenges, and current modalities are fraught with low sensitivity and/or potential morbidity. Photoacoustic imaging (PAI) is a novel ultrasound-based modality with potential for diagnosing PJI safely and noninvasively. Materials: In an established preclinical mouse model of bioluminescent Staphylococcus aureus PJI, fluorescent indocyanine green (ICG) was conjugated to beta-cyclodextrin (CDX-ICG) or teicoplanin (Teic-ICG) and injected intravenously for 1 week postoperatively. Daily fluorescent imaging and PAI were used to localize and quantify tracer signals. Results were analyzed using 2-way analysis of variance. Results: Fluorescence clearly localized to the site of infection and was significantly higher with Teic-ICG compared with CDX-ICG (P = 0.046) and ICG alone (P = 0.0087). With PAI, the photoacoustic signal per volumetric analysis was substantially higher and better visualized with Teic-ICG compared with CDX-ICG and ICG alone, and colocalized well with bioluminescence and fluorescence imaging. Conclusion: Photoacoustic imaging successfully localized PJI in this proof-of concept study and demonstrates potential for clinical translation in orthopaedics.