Nonunion is one of the common postoperative complications of bone fracture, also known as fracture nonunion, which is a manifestation of the cessation of the healing function of the fracture end under the influence of certain conditions. 1986, the FDA defined nonunion as “at least 9 months after injury and fracture, with no tendency to further healing for 3 months”, but there is no universally accepted definition. In 1986, the FDA defined nonunion as “an injury or fracture that is at least 9 months old and has not had a tendency to heal for 3 months”, but there is no universally accepted definition for nonunion. Despite the variety of treatments for fractures and the maturity of the techniques, nonunion still occurs in 5-10% of patients with fractures. In 1976, Weber-Cech categorized bone nonunion into Hypertrophic nonunions, Oligotrophic nonunions and Atrophic nonunions. The treatments for atrophic nonunions include internal and external fixation, bone and bone marrow transplantation, physiotherapy and biotherapy, etc. More than 90% of atrophic nonunions can be treated by a single surgical method, and 80% of cases have a good prognosis, i.e., the fracture is well healed and there is no obvious limb unequal in length or limb functional limitation. With the continuous progress of orthopaedic technology, the treatment methods of bone nonunion have been gradually improved and upgraded, and are summarized as follows: 1. Early biophysical therapy 1.1 Electrical stimulation Since the study of bone piezoelectricity phenomenon began in 1950, there have been a lot of experimental and clinical studies showing that electrical stimulation has therapeutic value for bone nonunion, and the clinical observation shows that electrical stimulation is obvious for hypertrophic type of nonunion, and the effect is poorer for atrophic type of nonunion and bone defects. Scott et al. treated 21 cases of long bone osteochondrosis through double-blind controlled trial, all patients used the same electrical stimulator, but the control group had no current release, as a result, 6 out of 10 patients in the test group were cured, and 11 cases in the control group were not cured. Since electrical stimulation does not correct deformity and limb shortening, it is now mainly used in patients with hypertrophic metaphyseal bone nonunion without deformity, bone defect and limb shortening. 1.2 Ultrasound stimulation Low intensity ultrasound can stimulate bone healing by producing low level pressure on tissues through high frequency sound waves, Nolte PA found that low intensity ultrasound can promote cartilage ossification and bone scab formation, thus accelerating fracture healing.Gebauer used low intensity pulsed ultrasound to treat 17 cases of delayed bone healing or bone nonunion after limb lengthening, and all of them were cured in 3-12 months. The results of this study are summarized in the following table. At present, there are various explanations for its mechanism of action, favoring the joint participation of multiple mechanisms, but the specific mechanism still needs further research. 1.3 Extracorporeal high energy shock wave (ESW) Extracorporeal high energy shock wave (ESW) is a commonly used method for the treatment of urinary stones, and has been used for more than 10 years for the treatment of osteoarthritis.The mechanism of ESW may be related to the stimulation of bone marrow osteoclasts, Wang et al. experimentally found that ESW can improve the growth and differentiation of rabbit bone marrow osteoclasts, and proposed that this effect may be related to the stimulation of bone marrow osteoclasts, and that it may be related to the stimulation of bone marrow osteoclasts. Wang et al. experimentally found that ESW could increase the growth and differentiation of rabbit bone marrow osteoblasts and suggested that this effect might be related to TGF-β1.The greatest advantage of ESW is that it is non-invasive and can be performed on outpatients. Although there is a lot of literature on the therapeutic effect of ESW on osteogenesis imperfecta, Bieder- mann analyzed the literature and found that there is no clinical evidence that ESW has a therapeutic effect on osteogenesis imperfecta. 1.4 Hyperbaric oxygen therapy In 1966, Coulson proposed that Hyperbaric oxygen therapy (HBOT) could improve the prognosis of bone fracture through animal experiments. There are many scholars through animal experiments proposed that hyperbaric oxygen can promote bone regeneration and remove diseased and dead bone; Kerwin through the study of the rabbit model of osteoarthritis proposed that hyperbaric oxygen can promote the generation of bone, but can not promote the regeneration of blood vessels, and can not improve the X-ray and histological manifestations of osteoarthritis. Although some people have suggested that hyperbaric oxygen can improve the efficacy of osteogenesis imperfecta through clinical trials, there is no controlled trial to support or oppose the therapeutic effect of hyperbaric oxygen. 2, local injection therapy 2.1 percutaneous autologous bone marrow transplantation As early as 1869 Conjon has observed that the autologous bone marrow allograft has osteogenic effect, due to the limitations of the research conditions at that time, this study was not carried out until 1976 Friedenstein et al. proved that the bone marrow in addition to hematopoietic stem cells, but also contains spindle-shaped fibroblastic colony-forming units, which are dormant for a long time in vivo. Cells in vivo in a dormant state for a long time, in vitro under the appropriate conditions of stimulation can enter the cell cycle, thus forming similar to the bone and cartilage fragments of the cell colony. 1987 Friedenstein et al. found that the walled mononuclear cells cultured in a plastic dish can be differentiated into osteoblasts, chondrocytes, adipocytes, myoblasts and so on in certain conditions, such mononuclear cells is the Bone marrow mesenchymal stem cells. In 1986, Connolly et al. reported for the first time the use of autologous bone marrow percutaneous injection to cure a 31-year-old patient with infected tibial bone nonunion, 85ml of bone marrow was extracted from the posterior superior iliac crest and injected into the posterior lateral tibial fracture, and the fracture was confirmed to be healed by imaging after 6 months. Later, this method was widely accepted by scholars and used to treat various kinds of delayed bone healing, bone nonunion, bone defects.In 1993, Garg et al. used this method to treat 20 patients with bone nonunion of long bones, injecting 15-20 ml of bone marrow into the end of the fracture, repeating the procedure once after 3 weeks, with the affected limb immobilized in a plaster cast, and 17 cases of the patients were cured in 3-7 months. cure. 2.2 Injectable bone growth factor Animal experiments have shown that some cytokines can promote osteogenesis when injected into bone defects or fracture sites. These cytokines include bone-forming protein family (BMP), TGF-β family, platelet growth factor (PDGF), growth factor (GF) and so on. After Urist et al. discovered in 1965 that bone matrix contains Bone Morphogenetic Protein (BMP), which can induce ectopic osteogenesis, researchers have confirmed through a large number of animal experiments and clinical applications that BMP can induce irreversible differentiation of mesenchymal stromal cells into bone, cartilage, ligaments, tendons, and neural tissues. Currently, there are more than 14 types of BMP family members and the number is still increasing, among which BMP-2 and BMP-7 have been used in clinical applications. In a clinical trial conducted in 18 hospitals in the U.S., Friedlaender et al. grouped together to treat 124 cases of tibial malunion with autologous bone graft and bone-forming protein-1 (OP-1, BMP-7), and found that the results of the two were comparable, and the latter is less traumatic and avoids a series of complications of autologous bone grafting such as infections, neurovascular injuries, etc. Johnson et al. combined bone grafting and BMP injection to treat 30 cases of tibial malunion, and found that the results of BMP-2 and BMP-7 were similar. Johnson et al. combined bone grafting and BMP injection to treat 30 cases of femoral osteogenesis imperfecta, 24 cases were cured, they think this combination can not only stimulate the growth of bone, but also promote the bone shaping. pecina et al. treated 20 cases of osteogenesis imperfecta patients, the results are satisfactory. chen et al. proved through the test that the bone-forming protein-1 on the infected bone defects can also have a stimulating effect on bone formation. 3, surgical therapy At present, surgery is still the most important treatment for bone grafting. 3, Surgical therapy At present, surgery is still the most important and effective method of treating osteogenesis imperfecta, including lesion excision, internal fixation, external fixation, bone grafting and the combined application of various methods. The choice of surgery is mainly based on the type of osteoarthritis and the patient’s general and local conditions. In general, for hypertrophic bone nonunion, because of the large amount of bone scab formation at the fracture end, the surrounding blood supply is rich, and the healing ability is strong, only solid fixation and compression at the fracture end are needed to achieve the purpose of healing; while for atrophic bone nonunion, there is almost no bone scab formation at the fracture end, the fracture end is sclerotic, ossification, and the bone defect is formed, and there is no blood supply in the surrounding area, and the potential of healing is very small, and the environment of the fracture end has to be improved, and the combination of bone grafting and fixation is necessary to deal with it. The environment of the fracture end must be improved, and the fracture must be treated with a combination of bone grafting and fixation. 3.1 Internal and external fixation The choice of internal and external fixation depends on the type of nonunion, the condition of bone and soft tissue, the size and location of the fracture end, and the amount of bone defect. Internal fixation methods mainly include steel plate fixation and intramedullary nail fixation, which have their own advantages and disadvantages and indications: steel plate fixation is suitable for hypertrophic bone nonunion, but osteoporosis should be applied with caution, and when it must be applied, polymethylmethacrylate can be injected into the medullary cavity to strengthen the fixation, but it will increase the difficulty of the operation; intramedullary nails, especially interlocking intramedullary nails are suitable for the long bones of bone nonunion such as humerus, femur and tibia, but the treatment of pediatric bone nonunion should be cautious. Caution should be exercised when treating pediatric bone nonunions, as they may interfere with bone growth and development. External fixation includes cast external fixation, Ilizarov external fixator, single arm brace etc. Bost first combined internal fixation and one side external fixation to lengthen the femur in 1956 and later this method was used to treat bone defects. Combined internal and external fixation can achieve lengthening of the bones, especially the femur and tibia, when osteogenesis imperfecta is accompanied by severe bone defects. Non-interlocking intramedullary nails can control angulation, but the external fixation must be removed only after the fracture is stabilized; interlocking intramedullary nails can compensate for this disadvantage. The main advantages of combined internal and external fixation are the control of angulation displacement and fracture of new bone, and the shortening of the duration of external fixation in patients. In addition, in order to minimize pin tract infection, contact between internal and external fixation should be avoided. 3.2 Bone grafts Bone grafts can play the roles of inducing osteogenesis, scaffolding, and providing bone-forming cells, and various bone grafts can fulfill one or more of these roles. Bone grafts can be categorized into autogenous bone, allogeneic bone, xenogeneic bone and artificial bone according to the source of the material. Autogenous bone is the best material for bone grafting because it has both osteoinductive activity and scaffolding effect, and contains bone marrow cells, which have the best osteogenic effect, and does not cause immune reaction and disease transmission, but its source is limited, and bone extraction increases the pain of the patient, which is especially unsuitable for children and the elderly. Allogeneic bone grafting is also a limited source of bone grafting material, which has the risk of spreading infectious diseases such as hepatitis and AIDS, and involves ethical issues. Allogeneic bone transplantation has been emphasized in recent years, such as Kiel bone composite autologous red bone marrow transplantation has been reported to achieve satisfactory results, and the re-combination of allogeneic bone developed domestically has opened up a new prospect for the clinical application of allogeneic bone. Artificial bone, especially bioceramic class in orthopedics application has received attention, but pure artificial bone implantation can only play the role of scaffolding, but not induced osteogenic activity. Autologous bone grafts can be divided into non-vascularized bone grafts and vascularized bone grafts. Clinically, autologous bone is mostly harvested from the ilium, tibia, and fibula, which provide cancellous, cortical, and whole bone, respectively. Non-vascularized bone graft lacks blood supply and most of the cells die; vascularized autologous bone graft, with its own blood supply system, will not undergo osteonecrosis and resorption, and only has to heal with the recipient bone, and its repair process is similar to that of a fresh fracture without the need to undergo a creeping substitution. Vascularized bone grafts can be used to treat recalcitrant and severely infected osteochondroses, and can ensure local blood supply to the fracture site, but require microsurgical support. The earliest application is vascularized rib bone graft, later appeared with vascularized fibula, iliac bone graft, Crow and Sawaizumi respectively with vascularized second metacarpal bone proximal graft treatment of navicular bone and distal radius intractable bone not unite success, with vascularized composite osteomyocutaneous flap transplantation can be skin, muscle, bone defects in one-time repair. 4, the treatment of children’s osteoarthritis Children are in the period of growth and development, osteoblasts and osteoclasts are abundant and active, blood circulation is vigorous, fracture healing is rapid, scab formation is early, osteoarthritis is extremely rare, and the treatment is also relatively easy. At present, the literature on pediatric osteoarthritis is relatively small, and the case reports are mainly based on the diagnostic criterion of pediatric osteoarthritis, which is usually 6 months after the fracture has not healed, and the children’s osteoarthritis reported in the literature are mainly in the hand navicular bone, the long tubular bone, and the clavicle, etc. In addition, there are also reports on osteoarthritis in pathologic fracture. Hand navicular osteochondral nonunion is more common in adults, children’s navicular fracture accounts for about 0.4% of forearm fracture, 2.9% of wrist fracture, the occurrence of osteochondral nonunion is even rarer.Garcia-Mata reported four cases of navicular nonunion, all of them are due to poor diagnosis of navicular fracture or poor fixation, he pointed out that when the center of the navicular ossification is not fully appeared, the cartilage fracture of the navicular bone is easy to miss the diagnosis, which leads to delayed treatment, and eventually lead to osteochondral nonunion. He pointed out that the cartilage fracture of navicular bone was easily missed when the center of ossification of navicular bone was not fully appeared, which led to delayed diagnosis and eventually led to nonunion. He treated 4 children with bone grafting and refixation, and the results were good, and the movement of wrist joint was good, and there was no sequela found.Fujioka reported that in a case of a child with simultaneous fracture of navicular bone and cephalad bone, nonunion occurred in navicular bone after 2 months of plaster fixation, which showed that the navicular bone was indeed special. Chloros used autologous iliac bone graft and Herbert screw for internal fixation to treat 12 children with navicular osteoarthritis, with good healing of the osteoarthritis and good wrist function. Bone nonunion of long tubular bone is also rare in children, Liow treated 9 children with tibial bone nonunion, all of them were resected surgically, 2 of them were applied with single-arm external fixation bracket, 7 of them were applied with circular external fixation bracket, and the average follow-up was 66 months, and the fracture was healed and functioned well.Ropars reported a case of 13-year-old child with clavicle nonunion, who had suffered from 3 clavicle fractures, and finally developed nonunion, Ropars utilized bone pins, and then the bone pins were used in the treatment. Between 1998 and 2001, Gebauer performed 112 limb lengthening surgeries with the Ilizarov stent, of which 19 had delayed healing or bone nonunion and 17 were successfully treated with ultrasound stimulation. In conclusion, there are various treatment options for bone nonunion, and the best treatment option should be chosen according to the specific type. Surgery is still the most important treatment for bone nonunion, and with bone marrow transplantation and bone grafting, satisfactory results can often be achieved. Various kinds of biophysical therapies and the application of bone growth factors have opened up new ways for the treatment of bone nonunion, but the mechanism and therapeutic effect of these therapies need to be further researched and explored; children’s bone nonunion is relatively rare, and good results can be achieved through bone grafting or internal and external fixation.