The concept of spinal segments The basic functional unit for maintaining spinal stability is the motor segment, which includes the two adjacent spinal segments and the intervertebral discs, synovial joints, and ligamentous structures between them. That is, a segment is equal to the upper and lower vertebral body parts, an intervertebral disc, the corresponding small joints, ligaments (three long and two short), etc. For example, when a vertebral body is fractured, depending on the severity of the fracture, one gap (two vertebral bodies or two vertebral bodies) can be fixed, or two gaps (three vertebral bodies or three vertebral bodies) can be fixed, and so on!