Fatigue fracture of the sacrum in a child.

Fatigue fractures involving the sacrum are extremely rare, and to our knowledge no occurrence of such a fracture in a child has been reported in the English-language literature. These fractures may mimic primary bone tumours or infection, and it is important to make an accurate diagnosis so that unnecessary biopsy can be avoided. We report a fatigue fracture of the sacrum in an 11-year-old child following prolonged aerobic exercise.