The Use of 99mTc-Recombinant Human Annexin V Imaging for Differential Diagnosis of Aseptic Loosening and Low-Grade Infection in Hip and Knee Prostheses

The aim of this study was to assess the pattern of annexin V uptake in hip and knee prostheses suspected of being infected. Methods: A total of 7 patients undergoing revision surgery for hip or knee prostheses were studied; 5 patients had total hip replacements, and 2 had total knee replacements. Infection was confirmed by pathology, culture results, laboratory evaluation, and clinical follow-up. All patients also underwent a bone scan before surgery. Results: Annexin V scan findings were positive in 5 patients and negative in 2. Annexin V uptake was either focal (n = 4) or linear (n = 1). There were 4 true-positive, 2 true-negative, 1 false-positive, and no false-negative annexin V studies. Annexin V uptake was either more extensive or less extensive than, and usually was incongruent with, 99m Tc-methylene diphosphonate uptake. Conclusion: Our findings suggest that annexin V imaging shows greater uptake with infection than with aseptic loosening and has a high negative predictive value for prosthetic infection.