Pediatric Subacute Osteomyelitis

  • Etiology:
    — Is intraosseous abscess
    — Staphylococcus aureus most common
    — Subacute osteomyelitis can persist for years before converting to frank osteomyelitis and resulting in a Brodie abscess
  • Imaging Radiograph:
    — Radiolucent center with reactive sclerosis and surrounding granulation tissue
    — Lucent channel extending to physis is pathognomonic
    — Sclerotic rim on radiograph fades away
  • Imaging 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
  • DDX:
  • Complications:
  • Treatment: Antibiotics
  • Clinical:
    — May be afebrile with normal inflammatory marker levels
    — May present with draining abscess

Radiology Cases of Subacute Osteomyelitis with Brodie Abscess

Radiograph and MRI of Brodie abscess
Oblique radiograph of the foot (left) shows a lesion in the base of the first metatarsal which has an oval radiolucent center with surrounding reactive sclerosis. Sagittal T2 MRI of the foot (above right) shows an oval hyperintense lesion surrounded by a very low signal intensity rim and hyperintense marrow edema throughout the first metatarsal. Sagittal T1 MRI with contrast (below right) shows rim enhancement (penumbra) around the lesion.
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.