A spiral fracture is caused when force is applied to a bone in a twisting motion. According to the University of Texas Medical Branch, injuries where the end of an extremity is fixed while the rest of the limb remains in motion often result in this type of fracture.
Fractures occur when the physical force exerted on bones is greater than their strength. According to WebMD.com, fractures are very common for patients of all ages. Those at particular risk for fractures include the elderly and those who suffer from certain disorders and other diseases that may weaken the structure of their bones. Accidental spiral fractures of the tibia bone in the lower leg, often referred to as "torsion fractures'" or "toddler's fractures," are particularly common in preschool-age children who fall a short distance and land on an extended leg.
According to the American Academy of Orthopaedic Surgeons, spiral fractures derive their name from the shape of the breakage, which spirals around the shaft of the bone in a pattern similar to that of a spiral staircase. Depending on the amount of force applied causing the break, spiral fractures may be either stable or displaced, indicating whether the two ends of the bone are still in alignment with one another.