Bone cyst is a neoplastic lesion that is confined to the long bone epiphysis in children and adolescents. It occurs in the femoral neck, upper femur and upper humerus. The cyst gradually moves towards the diaphysis with age. The wall of the cyst is a fibrous envelope and the cyst is filled with yellow or brown fluid. The lesion causes bone destruction and predisposes to pathological fractures. The disease is generally easy to diagnose. However, the recurrence rate of postoperative bone cysts is high, and the management of combined pathological fractures remains controversial, often with clinical complications of delayed healing and nonunion of the fracture. Factors associated with postoperative recurrence of bone cysts: typing of cysts Bone cysts occurring at or near the epiphyseal plate are called active bone cysts; bone cysts occurring at the epiphysis or the diaphysis and leaving the epiphyseal plate are called stationary bone cysts. neer refers to bone cysts located within 5 mm of the epiphyseal plate as active bone cysts and bone cysts more than 5 mm from the epiphyseal plate as stationary bone cysts. The active type has a tendency to recur. Treatment Whether the cyst scraping is complete and whether the bone graft is adequate is one of the important factors of recurrence. The cyst window or slot should not be too small so that the cyst contents can be scraped thoroughly, especially the ends of the fibrous envelope and cystic cavity and the depression of the bone crest, and the bone crest is removed with a round grinding drill if necessary. Subsequently, the residual cavity wall is cauterized with 95% alcohol and the bone graft must be filled densely without leaving a dead cavity. Preferably, granular bone grafting is used. Age The younger the age, the more likely the cyst will recur. There are two main treatment methods for bone cysts with pathological fractures, one is conservative treatment until the pathological fracture heals and then treat the bone cyst, and the other is treating the cyst and fracture together. 1.After the fracture is healed, the lesion tissue is clearly demarcated from the normal tissue and can be easily and completely removed. Bone scab grows in large amount, bone cortex is thicker, bone strength increases, and windowing or grooving is expanded without worrying about delayed fracture healing. After pathological fracture, the capsule fluid flows out of the capsule cavity, which naturally reduces the pressure in the capsule cavity and significantly improves bone marrow blood flow. On the one hand, it reduces the exudate and decreases the content of inflammatory factor interleukin, thus reducing the inflammatory factor stimulating osteoclasts causing bone resorption, on the other hand, the improvement of bone marrow blood flow stimulates the osteogenic system and promotes new bone formation. 2, the cystic bone cortex itself is thin and the bone strength is low. Local normal bone loss after fracture, such as immediate lesion removal, on the one hand, is likely to cause massive bone loss, aggravate local blood transport destruction, resulting in delayed healing or even non-healing of the fracture, and also occur bone defects leading to bone shortening. Moreover, after the lesion is removed, the bone strength is significantly reduced and must be strengthened with external braces or internal fixation. On the other hand, the local tissue swelling and cystic fluid flow mixed with blood crust during fracture, and the boundary between tumor-like tissue and normal tissue is not clear, so it is not easy to remove the lesion completely and cause normal bone loss during lesion removal. The treatment of bone cyst is mainly divided into two kinds of conservative treatment and surgical treatment. Conservative treatment includes hormone injection, autologous red bone marrow injection; surgical treatment includes drilling and drainage, lesion scraping and bone grafting. Some patients with bone cysts can heal spontaneously after pathological fractures occur. It is now generally accepted that conservative treatment is preferred for bone cysts with pathological fractures. If the cyst remains after the fracture heals, surgery should be performed.