Pediatric Subacute Osteomyelitis

  • Etiology: Staphylococcus aureus most common, subacute osteomyelitis which can persist for years before converting to frank osteomyelitis and resulting in a Brodie abscess
  • Imaging: radiolucent center with reactive sclerosis + surrounding granulation tissue, lucent channel extending to physis is pathognomonic, sclerotic rim on radiograph fades away
  • MRI: penumbra sign – central abscess fluid, enhancing high signal granulation tissue (penumbra), very low signal sclerotic rim of bone sclerosis (dark on all MRI sequences), low signal peri-lesional marrow edema
  • Clinical: may be afebrile with normal inflammatory marker levels, may present with draining abscess

Radiology Cases of Subacute Osteomyelitis with Brodie Abscess

MRI of subacute osteomyelitis / Brodie abscess
Sagittal T1 MRI without contrast of the knee (left) shows a small round low signal intensity lesion in the middle of the proximal tibia that is surrounded by low signal intensity peri-lesional marrow edema. Sagittal T1 MRI with contrast (center) better demonstrates the small round low signal intensity lesion and coronal T1 MRI with contrast (right) shows a faint enhancing ring (penumbra) around the lesion.