Limb-length discrepancies and extremity deformities are among the most common non-traumatic orthopaedic conditions for which children are hospitalised. There is a need to develop new treatment options for lower-limb length discrepancy in order to ameliorate treatment outcomes, avoid or reduce rates of complication and provide early rehabilitation. The authors report on the basic principles, experimental and clinical data, advantages, problems and complications of a combined technique associating the Ilizarov method and flexible intramedullary nailing (FIN) in limb lengthening and deformity correction in children. They describe features of the use of hydroxyapatite-coated intramedullary nails in patients with certain metabolic bone disorders and in cases where bone consolidation has been compromised. The advantages of bone lengthening using a combined technique (circular fixator plus FIN) are a lower healing index, quicker distraction-consolidation, a reduced rate of septic and bone complications, the ability to correct deformities gradually and the increased stability of bone fragments during the external fixation period and after frame removal.