The spine is the upright longitudinal axis of the body and is also the center of nerve communication between the brain and the trunk. Most spinal lesions affect both of these functions. Surgical treatment is aimed at restoring the stability of the spine and its intrinsic form to the greatest extent possible, and relieving the nerve compression. Surgery inevitably reduces the stability of the spine, so spine surgeons often have to use internal fixation devices to fix the diseased spinal segment, including titanium plates, screws, and birdcage or threaded interbody fusion devices. These fusion devices can be filled with bone tissue removed by decompression during surgery, and can be used to fix and implant bone at the same time, avoiding the pain of bone removal by the patient.