Giant cell tumor of bone Giant cell tumor of bone is a low-grade malignant tumor that may originate from tissue fibroblasts. 90% of giant cell tumors of bone occur in long bones, almost always at the epiphyseal closure of the epiphysis, with femur, tibia, humerus, and radius bone ends being the most common, with only a few cases occurring before the closure of the growing cartilage. Etiology】 The etiology of this disease is unknown. Recent electron microscopic studies have revealed that the basal cells have two different appearances: one is fibroblasts and the other is histiocytes, so the hypothesis that the tumor originates from tissue fibroblasts is confirmed. The giant cells are derived from fused basal cells. Based on the histochemical and electron microscopic features, it is not yet possible to distinguish these giant tumor cells from normal osteoblasts, so some scholars believe that they are derived from osteoclasts. Clinical manifestations】 Pain is its main symptom, often with joint pain. Tumor close to joint cavity may cause joint function limitation and intra-articular exudation. When intra-bone lesion expands, there is often obvious swelling and thinning of bone cortex, which is prone to subtle fracture or pathological fracture, especially in the lower limbs, resulting in increased pain and loss of function. If the tumor penetrates the bone cortex and enters the soft tissues, there will be swelling of soft tissues, edema around the tumor, as well as superficial skin veins filling up in a reticular pattern and other signs. Auxiliary examination] 1. X-ray examination The tumor is mostly confined to the end of bone and epiphysis, with swelling and biased growth, thinning of cortex, but complete outline and no periosteal reaction. There are similar residual trabeculae in the septum and soap bubble-like changes. In the advanced stage of the disease, the bone cortex can be ruptured and soft tissue masses can be seen. 2.CT examination shows low-density osteolytic destruction, bone cortical expansion and thinning, bone shell wrapped around the low-density tumor parenchyma, there is often a deeper bone ridge in the inner surface of the shell. 3.MRI examination In MRI image, the boundary is clear, a few lesions have low signal ring at the edge, and most of the tumors show uniform low signal or medium signal in T1-weighted image. In T2-weighted images, the signal is often uneven, with mixed low, medium or high signal. 4.Pathological examination The tumor is composed of soft and brittle tissues, light brown in color and uniform, with hemorrhage, necrosis and cystic changes. It is confined to the bone, mostly eccentric and expansive. Microscopically, the tumor consists of fibroblastic and histiocytic stromal cells, with a large number of multinucleated giant cells distributed in each department. One or more nuclei of different sizes are often seen in the nuclei of the stromal cells, which are pleomorphic and often have nuclear divisions. Giant cells contain abundant, possibly vacuolated cytoplasm, in which a large number of nuclei gather, and these nuclei are similar to the nuclei of stromal cells. Diagnostic points】 1. There is often clinical joint pain, and when the tumor is close to the joint cavity, there is often obvious swelling, pain and functional impairment. X-ray shows eccentric, osteolytic and swelling bone destruction in the epiphysis, with clear boundary, sometimes with soap bubble-like changes and obvious encapsulation. 3.Pathological examination of the tumor consists of dense, uniformly sized mononuclear cells, with a large number of multinucleated giant cells distributed in each department, and stromal distribution of spindle fibroblast-like and round histiocyte-like cells. Differential diagnosis】 1. Bone cysts are mostly found in adolescents, with clinical manifestations of local soreness or pain, mostly without clinical symptoms, mostly occurring in the epiphysis or diaphysis of femur and humerus, with eccentric, osteolytic destruction, surrounded by osteosclerosis, prone to pathological fractures, with fractures mostly comminuted, with fracture pieces trapped in the capsule. The bone destruction of giant cell tumor is located at the epiphyseal closure of bone, with relatively high density, no surrounding osteosclerosis, thinning of bone cortex, deeper bone crest on the inner surface of the bone shell, and the bone shell wrapped around the low-density tumor parenchyma, unlike the bone cyst-like bone shell is intact, which can be easily distinguished by pathological examination. 2.Chondroblastoma The age of prevalence is 10～20 years old, the symptoms are late and mild, the main symptoms are intermittent pain and swelling of adjacent joints, muscle weakness. x-ray shows small round, 2～4cm low density shadow in the center of secondary ossification with clear boundary, surrounded by reactive bone to form sclerotic margin, dotted calcification is visible in the lesion. The tumor cells are chondroblasts with “paving stone” arrangement. The onset of giant cell tumor is mostly at the epiphyseal closure of the bone, which is different from the epiphyseal onset of chondroblastoma. There is no surrounding osteosclerosis, thinning of bone cortex, and deeper bone crest on the inner surface of the bone shell, and there is no calcification in the lesion area, so the difference in pathology is even greater. 3.Aneurysmal bone cyst is an isolated, swelling, hemorrhagic, multi-room cyst with clinical manifestations of local swelling, pain and dysfunction of the affected area. x-ray shows osteolytic and eccentric bone destruction of the long bone epiphysis, protruding outward like balloon expansion, with a thin bone shell on the cyst surface. The main differentiation point with giant cell tumor of bone is that the latter bone destruction is located at the epiphyseal closure of the bone, with relatively high density, no surrounding osteosclerosis, thinning of bone cortex, deeper bone crest on the inner surface of the shell, bone shell encircling the low-density tumor parenchyma, bone shell like worm-like, mottled, and no fluid-fluid flat within the lesion. Pathological examination is easy to identify. Treatment and rehabilitation】 1. Non-surgical treatment (1) Radiotherapy: For inoperable lesions, such as vertebrae and other parts of the body where surgery is not easy to complete, or those who cannot be operated for other reasons, radiation therapy can be considered, or radiation therapy for 2 months followed by surgery to facilitate complete removal of the lesion and reduce intraoperative bleeding. Low-level dose (45Gy) radiotherapy can be used and completed within 4-5 weeks, which can kill microscopic lesions and enable long-term control of lesions. (2) Chemotherapy: Systemic chemotherapy has little or no effect on giant cell tumor, but local application has been reported. For sarcoma transformed by giant cell tumor of bone, the most common method is to expand resection combined with chemotherapy. 2.Surgical treatment (1) Scraping plus local adjuvant therapy: It is suitable for smaller tumors that do not break through the bone cortex. In addition to articular cartilage, the inner wall of tumor attachment should be completely removed until the normal bone tissue. Then inactivate the tumor wall with carbolic acid and alcohol for 3 times, and finally fill the bone cavity with bone cement (Figure 4-6-1). Liquid nitrogen, high-power laser vaporization, argon knife charring, microwave, etc. can also be applied for inactivation. When the subchondral bone has been destroyed or is very thin, in order to keep the bone cement from contacting with the cartilage, a layer of 1~2M thick autologous bone is implanted under the cartilage and then filled with bone cement. If the tumor destruction is severe or the lesion is located in a mechanically stressed area (e.g., femoral neck) then autologous or allograft bone needs to be applied to restore bone integrity (Figure 4-6-2). For lesions involving the spine (including 1 to 2 sacral segments), tumor scraping with internal fixation is feasible (Figure 4-6-3). (2) Expanded tumor resection, combined fibula and iliac bone grafting with anastomosis of blood vessels: This procedure was invented and adopted by Luoyang Orthopedic Hospital in Henan Province, and is mainly applicable to cases of periprosthetic osteoblastoma with subchondral bone destruction not exceeding 2/3 of the articular surface and one side of the bone cortex remaining intact, with Enneking surgical stage Ia; radiological imaging Campanicci ‘s classification was I-II; pathology Jaffe’s classification was I-II. The method of tumor resection and reconstruction of the upper tibia: epidural anesthesia was used, and the surgery was performed in two groups simultaneously. In one group, a medial or lateral incision was made at the upper tibia according to the tumor site, and the tumor was separated within the normal tissue, and the tumor was removed as a whole 4-5 cm from the lower edge of the tumor, preserving the articular cartilage and the uninvaded and damaged bone cortex on one side. If the tumor is damaged to the tibial tuberosity, the patellar ligament will be cut down and protected, and the tibial tuberosity will be removed. Repeated flushing with saline was performed. In the other group, the contralateral iliac bone block was excised, and the peroneal flap with peroneal artery and vein was freed and excised, with the appropriate length determined by the size of the tumor. The iliac bone is placed flat under the cartilage surface, the top is tightened against the cartilage, the medial side of the iliac bone (concave side) faces the articular cartilage, the contact between the iliac bone and the cartilage surface is poorly filled with cancellous bone, the fibular flap is folded in two, one is inserted in the medullary cavity, the other is fixed near the backbone, the two fibulae support the iliac flap embedded under the cartilage in parallel, the fibulae and the in situ bone are fixed with screws, the iliac bone and the in situ bone are fixed with a Kristen pin, if the tumor destroys the tibial tuberosity, the patellar ligament is fixed to the fibula. If the tumor disrupts the tibial tuberosity, the patellar ligament is fixed to the fibula. After fixation, the peroneal artery and vein were anastomosed to the recipient area, the artery to the anterior tibial artery, and the vein to the saphenous vein. If there is a dead space, the medial or lateral head of the gastrocnemius muscle is freed to fill the dead space, and the bone is fixed in a cast for 8 to 12 weeks after surgery, and the implant is gradually weight-bearing and functional knee exercises are performed after healing (Figure 4-6-4). Tumor resection and reconstruction method of the lower femur: The resection and reconstruction method is similar to the tumor of the upper tibia, with the lateral side of the iliac bone (convex side) facing the articular cartilage, the artery anastomosing with the descending branch of the external rotor femoral artery, and the vein anastomosing with the saphenous vein (Figure 4-6-5). (3) Tumor segment resection: Tumor segment resection should be extensive, including the tissue around the reactive bone shell. Artificial joint reconstruction (Figure 4-6-6), autologous bone reconstruction (Figure 4-6-7), or joint fusion can be applied after tumor resection. After extensive resection (including the original biopsy or the passing area of surgery), the local recurrence rate can be reduced to almost zero. (4) Amputation: It is indicated for very few cases where the tumor has extensively invaded the soft tissue and neurovascular bundle. The surgical method of giant cell tumor of bone is the most important factor to determine the postoperative recurrence, and the surgical staging of giant cell tumor of bone is also of great value to accurately evaluate the effect of surgery. For the treatment of giant cell tumor of bone, various surgical methods can be used depending on the condition. For small lesions, the method of scraping out the lesion and autologous bone grafting can be used, but the removal of the lesion must be complete. This method has a high recurrence rate and a high malignancy rate. Surgical indications for segmental resection are that the tumor has extensively destroyed the lesioned bone, pathological fractures have occurred, and the lesion is located in non-essential bone. Amputation may be considered for malignant giant cell tumors of bone, or for those with significant malignancy, and for those with extensive soft tissue invasion. For lesions involving the spine (including 1~2 sacral segments), tumor scraping with internal fixation is feasible. If the lesion is located in the spine or sacroiliac joint and cannot be removed surgically, it may lead to death once it becomes malignant. Pulmonary metastases are rare, including those that have developed into sarcomas. The incidence of sarcomatous transformation after radiation therapy for giant cell tumor of bone is generally considered to be about 8%. It is important to follow up closely after surgery. Local recurrence or metastasis of giant cell tumor rarely occurs more than 3 years after surgery, so especially in the first 3 years after surgery, the primary tumor and lung fields should be monitored. If it is postoperative recurrence or metastasis, all should be completely removed by surgery again without losing time. Difficulties and countermeasures】 Postoperative recurrence of giant cell tumor of bone is a difficult clinical problem to solve. In cases of recurrence or malignancy, resection should be performed. Since the resected bone segment is often an important part, such as knee, shoulder, hip, wrist, ankle, etc., it may lead to complex joint reconstruction and/or loss of important functions of the related limb. For those who have serious functional impact, we can use fibula to reconstruct the joint function through anastomotic vascular graft. For the osteoblastic tumor around the knee joint, we choose the extra-articular route to perform marginal or extensive resection, and apply the combined graft of iliac bone and fibula with anastomosis, which shows better results biologically and mechanically.