The Role of Labeled Leukocyte Bone Scintigraphy in the Diagnosis of Infected Prosthetic Joints

Background: Prosthetic joint infection is a major complication, leading eventually to revision arthroplasty. Although many of the complications of joint replacement surgery can be easily diagnosed, differentiating aseptic loosening from infection remains a daunting task. The American Academy of Orthopaedic Surgery guidelines strongly recommends erythrocyte sedation rate (E,S.R) and C-reactive protein (CRP) blood tests, as well as joint aspiration analysis, as supporting evidence for joint infection. Nuclear medicine modalities are suggested to be used in equivocal cases only. On the other hand, nuclear medicine procedures, and specifically labeled leucocytes are widely used in the diagnosis of joint infection across Europe.

Study Design and Methods: In this retrospective cohort study, the records of a total of 168 prosthetic hip or knee revision surgeries, in 130 patients, performed in our institution in the years 2013-2016 were reviewed.

47 patients were imaged using labeled leukocyte scintigraphy, nine of them more than once (two to four times). The scintigraphy result reports were correlated with outcome with respect to intra-/post-operative diagnosis of prosthetic joint infection.

Results: 45 of 47 scintigraphy tests were negative. One was equivocal, in a patient who had three prior negative labeled WBC scintigraphies. One was positive, but a later test in same patient was negative. Of these 47 patients, 11 were demonstrated intra- or post operatively as positive for infected prosthetic joint, including the two non-negative cases discussed. The remaining 36 patients went through revision surgery with no evidence of infection.

Conclusion: In our study population labeled leukocyte scintigraphy was not a sensitive test for diagnosis of a prosthetic joint infection and had a poor negative predictive value. We are currently designing a study aiming to assess the PET/CT technology using FDG-labeled leucocytes as a diagnostic tool for prosthetic joint infection.