Elastic stable intramedullary nailing system (ESIN) and flexible intramedullary nailing (FIN) are more recent surgical procedures that utilize internal fixation that has been shown to reduce the Healing Index and minimize complications. Similarly to the Ilizarov technique, the procedure is intended to correct deformities and elongate limb bones. This form of treatment is not suitable for the elongation of bones with a small shaft diameter or sections containing open growth zones. Patients with severe forms of Ollier disease also are not suited for surgery because of an increased risk of complications due to bone frame instability. Both the elastic stable intramedullary nailing system (ESIN) and flexible intramedullary nailing (FIN) use two bent elastic nails in order to allow for greater realignment and stability. This technique used in conjunction with a circular external fixator has been shown to significantly reduce Healing Index values in both monosegmental and polysegmental lengthening. Another advantage is that no fractures or deformities were found in later follow ups of 2 to 5 years.