Chapter 7. Summary and conclusions

1. Three-phase bone imaging is useful in the diagnosis of hip prosthesis infections, as negative results in the dynamic arterial and soft-tissue phases exclude infection reliably in the majority of suspected cases. The bone-metabolic phase of imaging is also useful for comparison with leukocyte images in both hip and knee prostheses.

2. In addition to earlier images, 24-hour images are needed for reliable diagnosis of hip and knee prosthesis infections with ^99mTc-labelled leukocyte/bone imaging, and comparison of the 2- to 4-hour images with the 24-hour images is necessary.

3. In addition to earlier images, 24-hour images are needed for reliable diagnosis of hip and knee prosthesis infections with ^99mTc-ciprofloxacin imaging, and comparison of the earlier images with the 24-hour images is necessary. However, it does not seem necessary to obtain both 1-hour and 4-hour images, and in clinical practice, imaging between 3 and 4 hours post-injection would appear sufficient.

4. The results with ^99mTc-labelled leukocyte/bone imaging are slightly superior to ^99mTc-ciprofloxacin imaging in the diagnosis of hip and knee prosthesis infections. ^99mTc-labelling of leukocytes is time-consuming and includes a potential risk of disease transmission by misadministration, which could be avoided by the use of ^99mTc-ciprofloxacin. The ^99mTc-ciprofloxacin imaging procedure is less time-consuming than the combined ^99mTc-labelled leukocyte/bone imaging procedure.

5. A suitable method for everyday clinical practice in suspected hip prosthesis infections would include screening of the patients with three-phase bone imaging and confirmation of abnormal results in the arterial and soft-tissue phases with ^99mTc-leukocyte imaging, including 24-hour images. In suspected knee prosthesis infections, ^99mTc-labelled leukocyte imaging, including 24-hour images, could be done first, and no additional studies would be needed in negative cases. In positive cases, bone-metabolic imaging could be used for the confirmation of possible infections. Based on the literature, bone marrow imaging is also advantageous in comparison with leukocyte imaging. ^99mTc-ciprofloxacin imaging appears to be a promising method in suspected hip and knee prosthesis infections. Further research with larger patient populations is warranted to verify the validity of this technique.