Infected bone defects are a common complication of severe open fractures and infected fractures especially in those with associated skin defects. Long canal bone defect more than 6 cm, traditional autologous or allogeneic bone grafting, which requires a long crawling replacement process, is often disturbed by a variety of factors during its own reconstruction and bone non-healing or bone graft resorption occurs, making the treatment more difficult and the disability rate higher. Previously, the accepted treatment principle was: complete cure of infection – repair of skin defects – cancellous bone grafting. However, the treatment period is long, the success rate is low, the infection is prone to recurrence, and the joint function recovery is poor. mowlent reported the successful application of bone grafting in the infected cavity in 1944, and many scholars in China and abroad have also reported the application, but the efficacy is still uncertain, and the wound repair is also difficult, and there are still people who end up amputating their limbs because the infection is not cured. Practice has proved that the key to the treatment of bone defects is whether the infection can be completely cured, and only after the infection is completely cured can the bone defect repair be effective. The main reasons for the failure to cure the infection are incomplete debridement, poor drainage, and failure to recognize the importance of stabilizing the fracture end to cure the infection, or the lack of understanding and mastery of a fracture fixation method that can both effectively stabilize the fracture end and facilitate the treatment of infection. This group of cases demonstrates that the application of osteotomy lengthening with compression fixation, combined with thorough focal debridement and proper surgical dressing changes for the treatment of infected bone defects, has the following advantages. The advantages of external bone fixation technique: 1. Bone segment lengthening and compression fixation can be performed simultaneously or separately. Bone segment lengthening is a simple method for repairing bone defects, and the efficacy is precise. Compression fixation provides a reliable guarantee for the healing of the broken bone. The overall fixation does not affect the joint and facilitates the rehabilitation of joint function. 2. The form of spatial fixation, away from the foci of infection through the needle, does not increase the local damage, does not increase the chance of spreading infection, creating favorable conditions for complete healing of infection. Firm and stable bone break end, so that the trauma has a stable environment, conducive to trauma repair. It can ensure unobstructed drainage and facilitate wound dressing change. 3.Limb and skin lengthening techniques can treat limb shortening and skin defects at the same time. Indications and contraindications: 1. Indications: hematogenous osteomyelitis infection has been cured and traumatic osteomyelitis inflammation has been limited in the lower limb bone defects. Open fractures of the long bones of the lower extremities combined with wound infection, the inflammation has been limited to the bone defect. Large bone defect and soft tissue defect of open fracture of lower leg. 2. Contraindications: Inflammation and extensive scarring at the osteotomy and extension of bone segment less than 6 cm are not suitable for surgery. Selection of surgery 1.Simultaneous lengthening and compression fixation (the speed of compression fixation is the same as lengthening): suitable for tibial defect, fibula intact, complete debridement and skin defect below 3cm. 2. Phase I compression fixation (bone break is fixed by direct compression during surgery): applicable to those with both tibial and fibular defects, bone defect below 2cm, infection has been cured, and there is no blood flow obstruction in the distal limb after compression. 3. Rapid gradual compression fixation (the speed of compression fixation is faster than the speed of lengthening): tibia and fibula are defective, bone defect and wound is greater than 6cm, infection is basically cured, and there is no blood flow obstruction after compression. Principles of infected wound management: thorough lesion debridement, adequate drainage and regular surgical dressing changes are the key aspects to cure the infection. Selective use of antibiotics in the wound is also a proven measure for treating infection, but it is only effective when used on the basis of thorough debridement. This group of cases illustrates that on the basis of thorough lesion debridement, maintaining a certain gap in the bone break end early on does not aggravate the infection. On the contrary, unobstructed drainage without residual inflammatory lacunae is necessary to ensure unobstructed drainage, making measures to treat infection such as surgical dressing changes of the wound more effective, and is the key to complete cure of infection and prevention of recurrence. In addition, the stability of the broken bone end is also an important biological factor that must be noted to promote wound healing and prevent the spread of infection. When using this method to treat infected bone defects, the following issues should be noted: ① no systemic symptoms of infection toxicity ② basic control of wound infection, infection foci are limited and stable ③ no inflammation or scarring at the osteotomy extension ④ no inflammatory edema in the soft tissue around the bone defect ⑤ pressure fixation should be observed at all times when the distal limb blood flow, and pressure should be stopped or slowed down when blood flow is found to be impaired ⑥ attention should be paid to the lack of inflammation in the injured limb and pinhole when extending Reaction, once found should be promptly dealt with, in serious cases should stop lengthening, systemic application of antibiotics. The application of bone segment lengthening and compression fixation, combined with thorough lesion removal and correct surgical dressing change, treatment of infected bone defects in the long bones of the lower limbs, simple method, precise efficacy, infection does not recur, can treat skin defects and limb shortening at the same time, and no need for ex situ extraction, no foreign body in the body, good recovery of limb function, has the value of promoting application.