B Singh, BR Mittal, A Bhattacharya
Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India

A Aggarwal, ON Nagi
Department of Orthopaedic Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India

AK Singh
Department of Radiopharmacy, Institute of Nuclear Medicine and Allied Sciences, New Delhi, India

The use of radiolabelled antibiotics is fast emerging as a promising diagnostic test for the detection of infective lesions, because of their specific binding to the bacterial component. Ciprofloxacin is a broad-spectrum antibiotic that has been used as a radio-labelled antibiotic in both the diagnosis of infections in rabbits and in clinical trials on humans. The diagnosis of skeletal microbial infections remains a challenge, especially in orthopaedic patients with implants. We present a case report of a patient with undiagnosed and unrelenting pain in the lower third of the left leg, which had persisted for 6 months. A novel scintigraphy, which was developed in-house using a 99mTC ciprofloxacin single vial kit, was used for diagnosing the active bacterial infection. A 99mTC methylene diphosphonate bone scan was also performed to locate precisely the site of the lesion. Gradually increasing concentrations of both the radiotracers confirmed the presence of active bacterial infection in the distal third of the left tibia. Follow-up scanning after antibiotic therapy showed the disappearance of the pooling of 99mTC ciprofloxacin, indicating a good response. Therefore, 99mTC ciprofloxacin has good diagnostic and prognostic applications in deep-seated covert skeletal microbial infections. However, the persistence of a focal concentration detected by the 99mTC methylene diphosphonate scan was attributed to the inflammatory and not the infective pathology.