Limb lengthening surgery uses the principles of bone regeneration (distraction osteogenesis) to pull the bones apart and create new bone. Gradual Lengthening with circular external fixation, relies on a customized apparatus that is surgically attached to the limb. The external portion of the apparatus encircles the leg, allowing for adjustments to be made. Bone has the capacity to regenerate in response to injury. When the apparatus lengthens the bone a cascade of signals activates cellular behavior resulting in enhanced formation of bone.