Limb lengthening is a common used callotasis technique. A dynamic axial fixator system with telescoping capabilities permits a slow distraction and becomes a proximal submetaphyseal corticotomy callus. In the last two years we realized seven limb lengthening in children under fourteen years old, five of them were unilateral dismetry and one of them an achondroplasic girl bilateral. Of them all we had six easy resoluting complications.