Geographic Polyostotic Thermal Osteonecrosis of the Foot and Ankle Caused by Fourth-Degree Burn: a Case Report

We report a case of extensive polyostotic osteonecrosis spanning several bones and joints at the deep margin of a fourth-degree burn. A 41-year-old female presented following an unwitnessed fall with loss of consciousness, with her left foot and ankle positioned close to a space heater for a prolonged period of time. Bone involved in the initial burn was unable to appropriately heal and remodel during recovery, leading to secondary fractures and osteoarthrosis. Subsequent computed tomography (CT) imaging of the left foot and ankle revealed relative sclerosis of bone deep to the site of fourth-degree burn in a distinctive contiguous pattern. The anterior talar dome was involved and went on to collapse by 17 months following the injury with additional secondary osteoarthrosis visible by 24 months. Magnetic resonance imaging (MRI) of the foot and ankle obtained 24 months after the initial injury demonstrated a striking pattern of marrow signal abnormality on both fluid-sensitive and T1-weighted images consistent with osteonecrosis, mirroring the same distribution of involvement seen by CT. This case is being reported to illustrate the unique geographic polyostotic pattern of osteonecrosis that can occur in the setting of a focal thermal injury and how the pattern of bony sclerosis at the depth of injury may be helpful in planning surgical fixation, arthrodesis, or arthroplasty procedures and in predicting future complications.