This trial is investigating the use of bone marrow stem cells in creating new bone growth in surgery for bone lengthening. The trial is being conducted by Nagoya University Hospital. Prior to surgery for bone lengthening, bone marrow will be harvested from participants and stem cells isolated and expanded. These stem cells will then be introduced to the fracture site at the time of surgery. Participants will be monitored for complications and assessed for bone repair. The trial expects to enrol 30 subjects.