Osteosarcoma is the most common primary malignancy in orthopedics. With the advent of neoadjuvant chemotherapy, the survival rate of osteosarcoma has increased to 70%, and limb preservation techniques, which can greatly improve the quality of survival, have gradually become one of the core techniques in the treatment of osteosarcoma. Currently, the limb preservation rate for osteosarcoma under neoadjuvant chemotherapy can reach 90%. Limb preservation in pediatric osteosarcoma has always been a hot spot and difficult research area because it involves the growth of children. For children’s limb preservation surgery, lengthenable prosthesis replacement and bone relocation surgery can be carried out in the form of lengthenable prosthesis: Meet the conditions: 1, children, with growth potential; 2, tumor involvement of the joint; 3, osteotomy length of at least 14cm to meet the need for lengthening shortcomings: domestic prosthesis workmanship problems; imported prosthesis higher cost, slightly longer production cycle osteosarcoma limb preservation surgery secondary lengthening surgery in the prosthesis lengthening 2cm postoperative Bone relocation technology: can complete the real sense of limb preservation, the application of their own bone to complete the repair of the defect after tumor removal meet the conditions: 1, the tumor is located in the backbone; 2, chemotherapy effect is good; 3, family cooperation (need family members to operate the extension pole and care 1-2 years) Disadvantages: early patient life is slightly inconvenient, high requirements for family members about 4 years after surgery to remove the frame (the longest time, generally 1-2 years).