Have you ever seen an artificial bone that “grows”? You must think it’s strange, since it’s artificial bone, how can it “grow”? The advantage of this lengthenable prosthesis is that it can be artificially lengthened periodically as the child grows, allowing the affected limb to grow in tandem with the healthy limb. Osteosarcoma is known to be the “ultimate killer” of children and adolescents, and was previously treated by brutal amputation. With the improvement of adjuvant chemotherapy, the long-term survival rate can reach 70%, and limb preservation surgery has become the main procedure for bone tumors instead of amputation. Complete bone tumor resection and artificial prosthesis replacement limb preservation surgery has been commonly performed. In recent years, due to the emergence of new types of extendable artificial bone joint prostheses, children with bone cancer can also achieve limb preservation and no more amputation and disability. History: According to the literature, the history of artificial prosthesis replacement can be traced back to the fourth century AD, when cases of shoulder joint replacement were performed with ivory. With the advancement of material science and modern surgical techniques, artificial joint replacement started to develop in the middle of the 20th century, and artificial prosthesis replacement surgery for bone tumors in adults can achieve better results. However, for children, due to immature bone development, the affected limb after surgery will not grow or grow slowly due to epiphyseal defect, resulting in unequal limb length and limp, which affects aesthetics and daily life and work. This prompted doctors to search for and invent a prosthetic device that could be continuously lengthened, and in 1976, this idea was realized and applied clinically. However, in the early days, the treatment was not satisfactory due to the material and design of the lengthening device, and surgery was required for each lengthening, so there were many complications, and the failure of the surgery was related to the design and biocompatibility of the prosthesis. With the development of science and technology, the “growable” prosthesis has been improved, since 1990, there has been a remote-controlled lengthenable artificial prosthesis, through the external electromagnetic field force in the prosthesis to generate heat, so that the lengthenable prosthesis spring device automatically extended lengthening, each time an average of 10 mm, each extension time only 20 seconds. Each lengthening time is only about 20 seconds. As the child grows taller each year, the preserved limb becomes progressively shorter, at which point the surgeon can lengthen the artificial bone of the limb several times, making the limb as long as a normal limb, with a magic effect, and without the need for multiple surgeries and anesthesia, and saving money. There are no acute complications during lengthening, only mild discomfort and oral analgesics, and the overall results are satisfactory, thus giving a strong impetus to the development of lengthenable prostheses. Indications and contraindications for lengthenable prosthesis replacement: The lengthenable artificial bone joint prosthesis is mainly used for aggressive bone tumors and most malignant bone tumors with a wide range of destruction in the extremities of children and adolescents, as a replacement for bone defects after bone cancer resection. The indications also require: no systemic metastases or only isolated and resectable metastases; the bone tumor does not invade important nerve and vascular tissues; there is sufficient skin and soft tissue to cover the prosthesis when the tumor is resected and reconstructed; there is no other more suitable method to reconstruct the function of the limb. It should be especially emphasized that bone tumor resection and lengthenable prosthesis replacement must be performed with the cooperation of effective chemotherapy, and the surgery should strictly abide by the principles of surgical resection of tumor, and complete and total removal of tumor. Local limb preservation cannot be done at the cost of reducing survival rate, otherwise the meaning of limb preservation will be lost. The main contraindications are important nerve and blood vessel invasion, advanced tumor or high-dose radiotherapy resulting in poor local soft tissue blood supply conditions and local infection. Artificial bone arthroplasty is not suitable for young patients with high exercise intensity, soft tissue resection with a tendency of prosthesis instability or obese patients. Complications of lengthenable prosthesis replacement and its treatment: With the common development of bone tumor limb preservation and the prolongation of patient survival, lengthenable artificial prosthesis may also have some long-term complications, such as prosthesis loosening, sinking, fracture, infection, etc., which are caused by extensive soft tissue resection, difficulty in prosthesis fixation and damage to biomechanical structure due to increased postoperative stress. The surgeon will deal with each case accordingly. In conclusion, the “growing” artificial bone is a wonder among the lengthenable prosthesis replacements and is an important method of limb preservation and reconstruction for children with bone tumors. It is an important method of limb preservation and reconstruction for children with bone tumors. Children can resume functional activities of the limbs at an early stage, and the recent results are very satisfactory, and the long-term results are improving. Many achievements have been made in the research and application of artificial joint materials, and the research of lengthenable prosthesis is getting more and more attention from all over the world. We believe that there will be a new generation of lengthenable prosthesis which is more ideal, safe and long-lasting.