Postoperative Infections

In this chapter, the role of imaging and its findings in postoperative infection with an emphasis on arthroplasty are discussed. The time relative to the surgical procedure is of paramount importance. Early postoperative infections occurring within the first days, weeks, and up to 3 months are diagnosed clinically supported with laboratory results and rarely need imaging studies. In the chronic phase, defined as occurring 3 months or later relative to surgery, the infections are usually low grade, and are difficult to differentiate from other complications, especially aseptic loosening of an arthroplasty. In this clinical scenario, image-guided aspiration of (periprosthetic) fluid or synovial biopsy is indicated to allow not only culture but also analysis of the fluid. Next-generation sequencing is gaining importance in the analysis of synovial fluid. Other imaging studies, such as leucocyte scanning (111In-labeled white blood cell scintigraphy) in combination with colloid bone marrow scan or 3-phase bone scintigraphy, and MRI may be warranted to increase specificity in specific situations that will be discussed.