**1. Introduction**

Metastatic bone cancer is the most common malignancy in the bone tumor. The life expectan‐ cy of patients has been increasing considerably over the recent years since the development of cancer management, but the occurrence chance of bone metastasis also increased. The inci‐ dence rate ranges from 20% to 85%, varying by type of cancers. Bone metastasis is the major cause to deteriorate the life quality of patients due to severe pain, walking difficulty, and

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pathologic fracture.Pathologic fracture is inducedin around10% of bone metastasis, andis lifethreatening to patients.

The treatment of metastatic bone tumor includes the combination of modality including medication, radiation therapy, and surgery to reduce pain and prevent bone destruction. Recently, the use of bisphosphonate and denosumab was reported as an inhibition of osteolytic microenvironment factors. Radiation therapy is the most frequently used and effective method for palliation but has limitation of bone strengthening.

Generally, patients need operation for the prevention of pathologic fracture, especially on the weight-bearing bones like vertebrae, pelvis, and femur as well as long tubular bone of extremity. The early surgical management before the fracture is important and has many benefits: avoiding terrible pain and complications, relatively easy surgery, reducing rehabili‐ tation time and life-threatening condition. The surgical methods for bony metastasis include curettage and bone cement (PMMA, polymethyl methacrylate) augmentation, internal fixation with plate or intramedullary (IM) nail, arthroplasty, and prosthesis reconstruction. The surgical treatment method is chosen by multidisciplinary teamwork. The most appropriate surgical option should be selected under the consideration of patient's age and life expectancy, general condition, response of medical treatment, and even preoperative life quality, because major surgery lead to stop or delay of chemotherapy and radiation therapy, and many accompanied complications.

Recently, various minimally invasive surgical methods that can be performed without general anesthesia and large incision have been introduced for metastatic bone tumor: ethanol injection, cryoablation, radiofrequency (RF) ablation, cementoplasty, etc. The percutaneous bone cement (PMMA, polymethyl methacrylate) injection is known as cementoplasty or osteoplasty, and has been shown favorable outcomes in the vertebral body and the flat bones such as pelvis, scapula, and sternum. However, solitary bone cement injection without metallic fixation at the long bone still has high risk of pathologic fracture.

A new novel surgical technique will be introduced in the concept of percutaneous metallic fixation and simultaneous bone cement injection. For this technique, the unique implant, multihole injection screw and nail, is developed. This implant has a hollow in the center and perforated side holes allowing the material injection to the bony lesion. This minimally invasive surgical method showed good result in the respect of pain relief, mechanical stability, surgical risk, rehabilitation period, hospital stay, surgical cost, and local tumor suppression. The injection material can be various, including chemotherapeutic agent, anti-osteolytic agent, and accelerate bone healing agent as well as PMMA bone cement. Recently, the MR-guided focused ultrasound surgery (MRgFUS) is introduced. MRgFUS is an external ablation which showed effectiveness in reducing pain from bone metastases. However, MRgFUS lacks restoration for mechanical stability.

This chapter will introduce the diverse developing minimally invasive surgical methods and suggest future direction for better management of patients with metastatic bone tumor.
