To investigate the application and clinical effect of using autologous fibula graft combined with knee fusion in the treatment of aggressive giant cell tumor of the distal femur. Methods In five cases of invasive giant cell tumor of the distal femur with bone defects after whole-block resection, knee fusion with free fibula graft combined with plate internal fixation was used to reconstruct lower limb function. Results All patients were followed up for 20-80 months, with MSTS scores of 21-27, bone healing time of 6-18 months, no graft resorption or fracture, no lesion recurrence, and return to normal work labor. Conclusion Whole tumor resection combined with fibular graft knee fusion is a good option for the treatment of aggressive giant cell tumor of the distal femur. The distal femur is one of the favored sites of bone tumors, especially the incidence of giant cell tumor of bone is high, and it is the first favored site of giant cell tumor of bone, which is characterized by its active biological behavior, rapid and destructive growth, easy local recurrence, and 0.5% possibility of primary malignancy [1], and there are more treatment methods, our department has treated 5 cases of aggressive giant cell tumor of bone in the distal femur since 2004 to 2009 ( From 2004 to 2009, five cases of invasive osteomegaloblastic tumor of the distal femur ( Campanacci grade III) were treated by whole-block resection and reconstructed by knee fusion using free fibula graft combined with plate internal fixation, and the functional follow-up of the lower limbs was satisfactory. 1. Clinical data 1.1 General information 5 cases, 1 male and 4 female, aged 31-47 years, 2 cases on the left and 3 cases on the right, all cases underwent X-ray, CT, MRI and CT chest examination of the affected limbs. All cases were routinely diagnosed by preoperative puncture pathology. X-rays were graded as grade III according to the Campanacci radiological grading system to clarify the extent of the lesion and the relationship between the neurovascular and tumor lesions, and to compare the full-length frontal and lateral radiographs of the contralateral fibula to exclude abnormal changes in the bone donor area of the fibula. Imaging examination was performed to clarify the extent of soft tissues invaded by the tumor, including the vascular nerve bundle and the joint surface, and the degree of intramedullary invasion, so as to determine the length of resection. 1.2 Surgical method Firstly, the ipsilateral or contralateral fibula was excised according to the preoperative measurement results, and the lower fibula was preserved at least 8 cm in length to avoid affecting the stability of the ankle joint, and the proximal free fibula was preserved in wet saline gauze. According to the tumor site, an anterolateral/anterior medial incision was chosen through the lower middle thigh, and the incision line included 1 cm of tissue around the puncture point. The femoral artery was carefully and safely separated or protected during the operation, and all the invaded muscle tissue was excised with a safe border outside the joint as far as possible, and the tumor segment was osteotomized according to the preoperative measurement of the border, and the osteotomy length was 10-15 cm, and the joint surface of the tibial plateau was excised. After inactivating the wound with 95% alcohol and distilled water, an autologous free fibula was implanted to bridge the defect area, and if the patella was not invaded, the patella was cut into bone strips for bone grafting, with a length of 12 to 18 cm, and fixed with long plate screws. Postoperatively, the long leg plaster brace was fixed for 12 weeks, and the wound was removed after 2 weeks. 2. Results The postoperative pathological results of all cases were consistent with the preoperative diagnosis, and there were no tumor cells at the edge of the osteotomy of the tumor segment. All patients were followed up for 20~40 months, with disappearance of pain symptoms, no wound infection, bone healing time of 6~18 months, no graft resorption or fracture, satisfactory walking function, and return to normal work labor with MSTS score of 21~27 (70~90%) (Figure 1). All patients did not have lesion recurrence or lung metastasis. The distal femur is the most common site for giant cell tumor of bone, and surgery is the first choice for focal invasive benign giant cell tumor of bone. Complete scraping of the lesion and bone grafting through a larger bone window is only applicable to Campanacci grade I-II tumors with undamaged bone cortex, and in patients with Campanacci grade II-III GCT, the tumor recurrence rate after scraping of the lesion is as high as More than 50%, prone to joint surface collapse, which seriously affects joint function or even requires amputation, and brings complicated reconstruction problems and reduced function, so its function is worse than the efficacy of applying extensive resection plus reconstruction at the beginning, therefore, for Campanacci grade II~III tumors with strong aggressiveness, which are more prone to lung metastasis, a reliable and reasonable method is to remove the whole tumor The reliable and reasonable method is to remove the whole tumor, which can greatly reduce the chance of tumor recurrence and provide a chance for complete cure of the tumor. There are many reconstruction methods after resection of Campanacci grade II~III tumors, and there is no satisfactory and unanimously accepted reconstruction method after extensive resection of benign and malignant tumors. For patients who are eligible for limb preservation, the common method of limb preservation is tumor prosthesis replacement. The indication for extensive tumor resection arthrofusion is aggressive GCT of the distal femur with a large soft tissue mass, and resection of the invaded soft tissue is the key to obtain good surgical borders, which is also an indication for tumor prosthesis replacement, but arthrofusion is also a good option, and internal fixation with a fibular graft plate can achieve good results. In this study, five patients with stage III giant cell tumor of bone underwent extensive resection of the fibular graft for knee fusion. All patients were followed up for 20-40 months with disappearance of pain symptoms, no wound infection, bone healing time of 6-18 months, bone healing rate of 100%, no graft resorption or fracture, satisfactory walking function, and return to normal work labor with MSTS score of 21-27 (70-90%). All patients did not have lesion recurrence or lung metastasis. The fused knee had better stability and allowed heavy work, with no difference in function compared to the prosthetic replacement in terms of walking, work efficiency, and movement. There were no local recurrences during the follow-up period in this group, and we believe that any reasonable treatment must ensure no recurrence of the lesion for 5 years after the initial surgery. Therefore, complete eradication of the primary lesion in the initial surgery is the main method to reduce recurrence. In this group, the bone giant cell tumor was Campanacci grade III with extensive soft tissue masses, and the scope of resection of the tumor segment should include marginal resection of the soft tissue in the reaction area, including the normal tissue at least 3 cm away from the lesion, complete removal of the soft tissue lesion to prevent tumor recurrence, and application of imaging findings to guide the plane of osteotomy. The osteotomy plane was guided by the application of imaging results, and the bone was osteotomized 3~5 cm away from the tumor, and sent to pathological examination as usual. We believe that for GCT patients with Campanacci grade III distal femur, the diseased tissue should be resected as completely as possible to reduce the recurrence rate while maintaining the maximum function of the lower limb, and the use of whole resected tumor free fibula graft fusion internal fixation is also a good choice.