Surgery

360 motion preservation is not a single spinal device and/or procedure, but a concept, which includes many types of spinal devices and procedures. The name and concept is adapted from 360 fusion. The major difference between the two is that 360 motion preservation preserves the motion of the spine and 360 fusion leaves the patient in a permanently fixed position in the segments, where it is used.

Both concepts address severe conditions of the spine, such as degenerative scoliosis, where dorsal and ventral procedures are needed. The ventral procedures address the anterior vertebral column of the spine (the stack of vertebral bodies and discs) and the dorsal procedures address the posterior laminae column of the spine (the chain of laminae, which includes the facet joints).

Like a flat tire, which makes the steering and support of a car unstable, so does a flat (desiccated or herniated) disc make the spine vertically unstable. Therefore, an artificial disc replacement of some type, which will reestablish the height of the intervertebral disc space, is part of 360 motion preservation.

To extend our automobile analogy further the facet joints, like the tire rods of a car, guide and limit the movement of each spinal segment (the tires). It can be more directly said that the horizontal stability of the spine is the main responsibility of the facet joints. The facet joints limit the rotation of each spine level. When these joints are missing because of a procedure like a laminectomy or facectomy, or malfunctioning from disease, 360 motion preservation utilizes dorsal pedicle screws as anchoring points for posterior rod fixation, just like fusion. However, unlike fusion, the rods are longer and allow for movement. The rods use springs to help return the spine segment to a neutral position. The nature of these screws and rods can vary, so the correct application and sizing of the rods is critical to a good outcome.

The vertebral level of the spine can be thought as a triangle with apex of the triangle located in the vertebral column and the base of the triangle in the laminae. As we know from basic geometry and engineering, a triangle is the simplest and most reliable shape of form stability. With the relative abundance of bone in this area of the spine, it makes this an ideal anchoring site for screws. These screws are known as pedicle screws, because the screws, enter the laminae, go through the pedicles, which lie next to the spinal canal, and into the vertebral body, making for a very secure anchoring. See image below.

Degenerative scoliosis can present not only with a coronal C curve in the spine, but also with a severe C curve and/or rotation of the spine. In these cases, hybrid constructs are used, i. e. the use of 360 fusion and 360 motion preservation in combination and adjacent to each other. The ability to connect fusion segments with the motion segments, greatly enhances the stability of the spine. Therefore, where fusion levels are adjacent to motion levels, stability of the spine and motion levels can be enhanced, if the motion levels can be attached to the fusion levels. Again we must say that the correct selection of the screws and connectors must be made the surgeon.

Modern back surgery requires much more engineering than traditional back surgery. And the surgeon must look at each case’s individual characteristics more so than previously done in medicine.