Intramedullary nailing is a commonly used method for the treatment of closed fractures of long tubular bones of the limbs. Intramedullary nail fixation for long diaphysis fractures is beneficial to fracture healing, reduces the failure rate of internal fixation, reduces the infection rate, reduces the amount of blood loss, and allows for early activity, especially for severe comminuted fractures with the incomparable advantages of steel plates. For long tubular bone fractures such as femur and tibia, intramedullary nail fixation is currently the preferred treatment method, which significantly improves the fracture healing rate and greatly reduces various complications compared with previous plate fixation. However, from the recent literature, the incidence of bone nonunion after intramedullary nailing treatment is 0.5%-3% for various reasons, and most of them are hypertrophic bone nonunion. Hypertrophic nonunion indicates that there is local new bone formation at the fracture end, osteogenic potential, good blood circulation in the fracture area, the main reason for nonunion is that the internal fixation is not secure, the fracture end is more mobile, there is shear stress, and the newborn repair tissues can not fight against the shear stress, fracture, and can’t form a continuous bone scab. If the fracture end stress is too large or the fracture end gap is too wide, it is difficult to form a bridging connection. In addition, premature weight-bearing functional activities may lead to the early formation of bone scab breakage, absorption, while inappropriate functional exercise, easy to make the fracture ends between the shear stress is not conducive to fracture healing. Improper choice of internal fixation, such as choosing too thin and too short main nails (locking nails closer to the fracture line), too few distal locking nails (only 1 nail) or abandoning locking nail fixation due to the difficulty of placing locking nails, all result in insufficient stability of the fracture ends, and also contribute to the occurrence of hypertrophic osteochondroma. There are many treatment methods for bone nonunion after intramedullary nail fixation: expanding the marrow to replace the intramedullary nails and refix or removing the intramedullary nails and replacing them with plate fixation, retaining the intramedullary nails with additional plate fixation, changing to dynamization, and so on. Meanwhile, bone grafting is performed to promote the healing of large bone defects and atrophic bone nonunion. Taiwan orthopedic surgeon Ueng et al. found that rotational instability was the main cause of non-healing after intramedullary nail fixation of femoral stem fractures. The first report of non-infectious nonunion after intramedullary nail fixation of femoral stem fracture using preservation of the original intramedullary nail, additional side plate and combined bone grafting was reported with a healing rate of 100% . Under the premise of preserving the original intramedullary nail, this technique firstly ensures the axial stability and anti-buckling stability, and then the additional side plate enhances the rotational stability of the fracture end, which provides the crucial mechanical factors for local fibrocartilage calcification and promotes the initial connection of the bone scab. In recent years, scholars have reported that 100% bone healing has been achieved with this method. In the treatment of hypertrophic bone nonunion after interlocking intramedullary nail internal fixation, the longitudinal stabilizing factor of the original intramedullary nail is retained, and the insufficiency of interlocking intramedullary nail in reducing the shear stress of the fracture end is solved through the additional plate, which provides a better mechanical stability and ensures stable bone contact at the fracture end. It provides a good foundation for the healing of bone nonunion. Mechanical stability allows calcification of the fibrocartilage at the fracture end, which is then penetrated by neovascularization, ultimately bridging and shaping the bone at the site of the nonunion. For large non-union gaps, autologous iliac bone grafting is used, as the bone grafting material autogenous bone is most appropriate. For the bone nonunion gap less than 5 mm, the bone scabs chiseled on the access side can be trimmed and planted around it, which simplifies the surgical operation, shortens the surgical time, and avoids the damage and sequelae in the donor area. The addition of a smaller lateral plate does not require too much periosteum stripping, so the damage to the blood flow of the fracture end is actually not great, and the original intramedullary nail does not need to be removed, which does not result in the waste of internal fixation, and reduces the economic burden of the patient. Surgery has little interference with neighboring joints, simple operation, reliable fixation, and allows early postoperative active and passive functional exercises. The recovery of joint function is good. The main indication for this treatment is hypertrophic bone nonunion after intramedullary nail fixation of lower limb fracture, which is not suitable for atrophic bone nonunion and infected bone nonunion, and requires that the original internal fixation has not been broken.