Spinal ligaments are lengths of connective tissue that join individual bones of the spine as well as stabilize the vertebral segments of the spine. Made of densely bundled fibers of collagen and elastin, they may be intrasegmental, or found between adjacent vertebrae, or they may be intersegmental, meaning that they link multiple vertebrae and thereby stabilize entire sections of the spine. Intrasegmental spinal ligaments include the interspinous ligaments, the intertransverse ligaments, and the ligamentum flavum. Among the intersegmental ligaments are the anterior longitudinal ligaments, the posterior longitudinal ligaments, and the supraspinous ligaments.
The intrasegmental spinal ligaments run vertically between individual vertebrae. Each vertebra consists of a body, the solid, weight-bearing portion of the bone; the vertebral foramen, the ring-shaped portion through which the spinal cord passes; and several processes projecting off the back and sides of the bone to which muscle tendons and ligaments attach. The intertransverse ligaments are those spinal ligaments that extend between the transverse processes. These are the paired processes that angle sideways off the posterior side of each vertebra.
Located closer to the vertebral foramen are the paired interspinous ligaments. These run between the spinous processes projecting downward and backward off the posterior side of each vertebra. Their anterior or front border is continuous with the fibers of the ligamentum flavum, another intrasegmental ligament that spans the laminae, the bony bridge that makes up the rear wall of the vertebral foramen and from which the processes project. Together they help hold the vertebrae in an extended or upright position, maintaining the space between them and preventing compression on the spinal nerves.
Continuous with the rear border of the interspinous ligament is the supraspinous ligament, which similarly links the spinous processes. It is an intersegmental ligament, meaning that in addition to connecting adjacent vertebrae it spans a segment of up to four vertebrae, lending strength and stability to entire sections of the spine. As the most posterior spinal ligament, for instance, it helps prevent excessive spinal flexion, or forward bending.
Another type of intersegmental ligament is the longitudinal ligament, of which there are two pairs. The anterior longitudinal ligament is a broad, flat ligament that covers the anterior aspect or front side of the vertebral body and extends almost the full length of the vertebral column. A similar ligament is found running down the posterior or rear side of the body of each vertebra; this is the posterior longitudinal ligament. It also runs all the way down the spinal column. These spinal ligaments reinforce the stability of the spinal column, resist excessive flexion and extension of spinal segments, and protect the spinal cord from compression forces.