This is a prospective study done on 40 patients presented with lower limb length discrepancies ‎between March 1993 and September 2003. After correction of apparent shortening by ‎correcting associated deformities like flexion deformities of the knee, bone lengthening for the ‎remaining true shortening ranging from 3cm – 10.5 cm was done. The "Z" corticotomy involves ‎cutting the cortex in Z manner with preservation of the periostieum and medullar cavity as much ‎as possible, followed by manual distraction.‎
‎ The advantages of Z corticotomy in comparison to transverse corticotomy or transverse ‎osteotomy are; That there is no need for internal fixation by plate and screws, no need for bone ‎graft to enhance osteogenesis, the chances of mal-alignment of the distracted fragments are ‎minimal as the limbs of the Z – corticotomy maintaining the alignment during the distraction, ‎and the stability of the external fixate is very important for the extent of ontogenesis but this ‎was compensated by doing Z corticotomy. ‎