Bone loss, deficits, gaps, or non-unions are areas of missing bone that need to be healed with the help of a bone transport or vascularized membrane procedure. These surgeries can be performed using internal or external technology offered at the Canadian Limb Lengthening Centre. When bone is broken, it heals by first forming a callous (which is new bone that is still soft but will harden over time). Bone transporting uses this process of callous formation (or healing new bone) and stretches it gradually (a process called distraction osteogenesis) to fill the space where bone is missing. This is done using fixation devices that slowing stretch the new forming bone in order to make it long enough to fill the gap. Bone transport techniques can be used to fill very large bony defects (or gaps), anywhere from 2-16 or more centimeters.