Thoracic spinal fusion is a surgery that joins two or more vertebrae in the middle back (T1-T12) using bone grafts and hardware (screws, plates) to create a single, solid bone, eliminating painful motion and stabilizing the spine. It treats instability from fractures, deformities (scoliosis, kyphosis), tumors, or degenerative conditions, aiming to reduce pain and improve function, with recovery involving longer periods of limited activity.