A malunion fracture is when a broken, or fractured, bone does not line up correctly during the healing process. Such a deformity is called a malunion. A malunion may occur when a large space between the two ends of the broken bone are filled with new bone. How a malunion may present can differ, but usually a malunion can be described as either rotated, crooked or shorter than it was before. Malunions can affect the daily life of the patient, and to fix them, surgery will usually be required.