Sequential use of technetium 99m MDP and gallium 67 citrate imaging in the evaluation of painful total hip replacement.

Fourteen patients with 20 total hip joint replacements were studied for 14 painful prosthetic hips. Clinical examination, plain film radiographs and 99Tcm-MDP bone scans failed to differentiate between infection and mechanical loosening of a prosthesis. Sequential use of 99Tcm-MDP and 67Ga-citrate bone scans were performed in an attempt to discover underlying infectious process. Increased focal uptake of both radiopharmaceuticals over the same hip indicated an infectious process responsible for prosthetic loosening. There were no false positive gallium examinations. Sequential use of 99Tcm-phosphate compounds and 67Ga-citrate is recommended for differentiation between mechanical loosening of a prosthesis and loosening of a prosthesis secondary to an infectious process.