Increased and normalized uptake of 18F-FDG in a case of bone periprosthetic infection treated by antibiotics

We report the case of a 69 years old man with left hip prosthesis, who presented clinical, biochemical and imaging signs of periprosthetic infection treated with linezolid, an antibacterial agent of the oxazolidinone class. Two weeks after this treatment, a fluorine-18-fluoro-2-deoxy-d-glucose positron emission to-mography/computed tomography (18F-FDG PET/CT) scan showed increased uptake in the skeleton and also increased uptake in several focal areas in the spine and near the prosthesis and the surgical wound on the left gluteus medius. Bone marrow biopsy was negative; meanwhile the antibiotic therapy, after four weeks of treatment was stopped due to red blood cells and platelets toxicity. Six weeks later, the patient developed high fever again and in order to revaluate the periprosthetic inflammation, he was resubmitted to 18F-FDG PET/CT which showed normal 18F-FDG uptake in the whole skeleton, including the prosthesis and the subcutaneous wound. Some focal areas of increased uptake in the lumbar spine were still detected. In the next 4 weeks the patient was under a "watch and wait" follow-up in a steady state. In conclusion: In the case we report, since we found no other reason, we consider that the increased uptake of the 18FFDG in the skeleton was due to an increased metabolic reaction of bone marrow to infection normalized after treatment. The myelosuppressive action of linezolid could be another factor. The persistent focal areas in the lumbar spine where due to age-related bone deformities including some Schmorl's nodes. The inflammation in the bone prosthesis and the subcutaneous wound responded almost totally to the antibiotic treatment we applied.