Scoliosis surgery is a type of orthopedic surgery, the basic principle of which is to straighten a curved spine by inserting internal fixations (most commonly such as pedicle screws) into the spine, then attaching these screws with internal fixation rods, and then straightening the spine through orthopedic manipulations (including concave bracing, convex compression, de-rotation, bar force, etc.), the simplest example is a sapling growing crooked, we can put a stick next to it and We can put a stick next to it and tie a string to correct its growth (of course the process of scoliosis orthopedics is much more complicated than this). After the scoliosis is corrected, the spine surgeon will do an implant fusion, which involves removing the cortical bone from the surface of the vertebral body, exposing the cancellous bone surface, and then planting the broken bone and other bone grafting materials (such as allograft bone, artificial bone, etc.) that he or she removed during the surgery, in the hope that the part of the spine that was just fixed will grow and fuse together in the future and become one. This process usually takes 1.5 to 2 years to complete. So why do we need bone graft fusion after spinal orthopedics? Because scoliosis patients have severe deformation and structural abnormalities in the spine, and we straighten the spine with strong instrumentation, just as we straighten a bent rod, it will spring back and deform, and we need two internal fixation rods connected to screws to counteract this deformation force (both are locked by nuts). If we do not do implant fusion, then the internal fixation will be subjected to repeated bending and other forces during repeated daily activities, and it will be easy to break, screw pull-out, etc. In the early stage after scoliosis orthopedic surgery, the internal fixation is used to maintain the orthopedic shape, and when the bones grow together, the bony structure is used to maintain the orthopedic shape and bear the load, and the initial fusion is usually obtained in 3 months, and the process is completed in 1-2 years, after which the load on the internal fixation becomes much smaller. Therefore, the section of the spine after surgery is immobile both in the early and late stages, and even if the internal fixation is removed, it is still immobile because the bones grow together; instead, the orthopedic shape is often lost in part because of the reduced support after the internal fixation is removed. However, the part of the spine that is not yet fused still has mobility, and the hip joint plays a big role when bending over. So you can still bend after scoliosis surgery, but the operated portion of the spine is immobile, and if you want more mobility, you need to preserve more of the active spinal motion segments. Evaluating whether a scoliosis surgery was done well, from a professional surgeon’s point of view, depends not only on how straight it was straightened, but also on how much fusion there was and whether as many motion segments as possible were preserved to give the patient better motor function and quality of life.