A 52-year-old diabetic man has a warm, swollen first metatarsophalangeal joint. A three-phase Tc-99m MDP bone scan shows focally increased flow and blood pool activity, and delayed images show intense uptake localized specifically to the first metatarsal head. The most likely diagnosis is:

• A Acute osteomyelitis ✓
• B Cellulitis alone
• C Degenerative arthropathy without infection
• D Reflex sympathetic dystrophy

Explanation

Osteomyelitis produces focal abnormality in all three phases, with the delayed bony phase uptake precisely centred on bone. Cellulitis shows diffuse soft tissue hyperaemia on flow and blood pool images but no focal skeletal uptake on delayed views, which is the discriminating feature here. Degenerative change causes isolated delayed-phase uptake without hyperaemia, and reflex sympathetic dystrophy gives diffuse periarticular uptake around the whole affected region.

Reference: Mettler, Essentials of Nuclear Medicine Imaging, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.