Abstract

A variety of radiopharmaceuticals and imaging techniques are currently available for scintigraphic imaging of infections. However, comparisons on the clinical value of such techniques have been limited, especially in prosthesis infections.

This series included 138 cases with suspected prosthesis infections – 94 in hip and 44 in knee prostheses of patients whose final diagnoses were based on clinical, operative and microbiological findings, and who underwent three-phase bone, ^99mTc -leukocyte and ^99mTc-ciprofloxacin imaging in the Department of Clinical Chemistry, Oulu University Hospital and in the Laboratory, L?nsi-Pohja Central Hospital, during the years from 1993 to 2001.

The normal arterial and soft-tissue phase images of three-phase bone imaging practically excluded infection in hip prostheses, whereas these techniques frequently yielded false positive findings in patients with knee prostheses, resulting in specificity of 23% or less. In combined ^99mTc-leukocyte/bone imaging, diagnostic accuracy was 80–86% at two- to four-hour images and 87–98% at 24-hour images. The ^99mTc-ciprofloxacin images showed unspecific accumulation of tracer in the one-hour and four-hour images, which disappeared in the 24-hour images in most hip and knee prostheses. ^99mTc-ciprofloxacin imaging yielded almost as good diagnostic accuracy as combined ^99mTc-leukocyte/bone imaging.

In conclusion, in suspected hip prosthesis infections, normal findings in three-phase bone imaging exclude infection, whereas abnormal results in the arterial and soft-tissue phases should be confirmed with ^99mTc-leukocyte imaging using 24-hour images. Contrary-wise, in suspected knee prosthesis infections, ^99mTc-leukocyte imaging with 24-hour images is the first-line examination, and abnormal results in 24-hour images should be confirmed by using ^99mTc-bone-metabolic imaging. ^99mTc-ciprofloxacin yielded almost equally good results as ^99mTc-leukocyte/bone-metabolic imaging, but unfortunately, the tracer is not commercially available, although it has been patented.