The Clinical Usefulness of 99mTc HMPAO Leukocyte/99mTc Phytate Bone Marrow Scintigraphy for Diagnosis of Prosthetic Knee Infection: A Preliminary Study

Purpose

The preferred radionuclide imaging procedure for diagnosing prosthetic joint infection is combined radiolabeled leukocyte/^99mTc sulfur colloid bone marrow scintigraphy, which has an accuracy of over 90 %. Unfortunately, sulfur colloid is no longer available in South Korea. In this study, we evaluated the usefulness of ^99mTc phytate, a substitute for ^99mTc sulfur colloid, when combined with radiolabeled leukocyte scintigraphy in suspected prosthetic knee infections.

Methods

Eleven patients (nine women, two men; mean age 72 ± 6 years) with painful knee prostheses and a suspicion of infection underwent both ^99mTc HMPAO leukocyte scintigraphy (LS) and ^99mTc phytate bone marrow scintigraphy (BMS). The combined images were interpreted as positive for infection when radioactivity in the LS at the site of clinical interest clearly exceeded that of the BMS (discordant); they were interpreted as negative when the increased activity in the LS was consistent with an increased activity in the BMS (concordant). The final diagnosis was made with microbiological or intraoperative findings and a clinical follow-up of at least 12 months.

Results

Five of eleven patients were diagnosed as having an infected prosthesis. The overall sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the combined LS/BMS were 100 %, 83 %, 83 %, 100 % and 91 %, respectively.

Conclusion

We find that combined ^99mTc HMPAO LS/^99mTc phytate BMS shows comparable diagnostic performance to other studies utilizing sulfur colloid. Combined ^99mTc HMPAO LS/^99mTc phytate BMS is therefore expected to be an acceptable alternative to combined radiolabeled LS/^99mTc sulfur colloid BMS for diagnosing prosthetic knee infections.