A 62-year-old diabetic man has a neuropathic plantar ulcer over the first metatarsal head. Plain radiographs show no bony abnormality, but the ulcer base probes onto bone and local signs of infection are present. Which investigation is most appropriate to confirm or exclude underlying osteomyelitis at this stage?
- A Repeat plain radiograph after 4 weeks
- B Ultrasound of the forefoot
- C Technetium-99m bone scan alone
- D MRI of the foot ✓
Explanation
When plain radiographs are normal but clinical suspicion of osteomyelitis persists, MRI is the imaging modality of choice, showing marrow oedema and cortical involvement earlier than radiographs with high sensitivity and specificity. Serial radiographs take weeks to show lytic change and delay diagnosis. Technetium bone scan is sensitive but nonspecific in a neuropathic, possibly Charcot-prone foot, and labelled leucocyte scanning is reserved for problem cases. Ultrasound cannot assess bone marrow. A positive probe-to-bone test plus raised inflammatory markers further raises pretest probability.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.