Introduction: Despite successful union after intramedullary nailing of open femur fractures with bone loss or significant comminution, the discrepancy in leg length can lead to a significant impairment for the patient. Lengthening over a femoral nail is a described technique in such clinical scenarios. Corticotomy around an existing intramedullary nail (IMN) was introduced to address lengthening of the limbs without changing or removing any previously implanted IMN. Osteotomy around an existing IMN is a challenging technique that requires careful handling to avoid inadvertent damage to the IMN. Case description: Two patients with open type IIIA shaft of femur fractures who presented with bone loss following trauma underwent debridement and IMN fixation. After nailing, the patient was placed on a fluoroscopic table to enable an anteroposterior and lateral radiograph of the femur. Under image guidance, a rail frame was applied and we used a novel technique of osteotomy for lengthening of the femur using a Gigli saw. In both cases, the bony union was achieved by the end of 1 year. Conclusion: Lengthening over the IMN using a lengthening device helps in correcting limb length discrepancy as well as aids in achieving optimal bony union at the same time. The use of our novel corticotomy technique helps to minimize the damage to the intramedullary device. The existence of the nail minimizes the time required for the external frame since during the consolidation phase the nail supports the regenerate bone.