Spinal Anatomy Coding

In a discussion about spinal anatomy, one of my coworkers once said, “It’s not so much that the spinal column is three-dimensional, it’s more five-dimensional.” I think that is an apt description of the vertebral segments that stack one on top of the other to compose the spinal column.  It is critical for coders to have a thorough understanding of spinal anatomy when assigning ICD-10-PCS and CPT codes to spinal fusion procedures.  In this blog post, we will walk through a brief primer on spinal anatomy.

The spine is composed of bone and soft tissue.  Let’s start with the bones.

No Bones About It

When you look at an individual vertebral segment from the top down, you see a ring of bone that surrounds and protects the spinal cord.  This ring is composed of the vertebral body on the anterior side, which is opposite the spinous process with the transverse processes on each side.  The laminae (singular form: lamina) connect the spinous process to the transverse processes and pedicles connect the transverse processes to the vertebral body.

The anatomy of the spine, though, is not complete until each vertebral segment is stacked one on top of the other to create the spinal column.  And once you flip a spinal segment over to look at it from the lateral aspect, you see additional bony protrusions.  These bony protrusions, called facets or articular processes, allow each vertebral segment to fit in a puzzle-like fashion with the segments above and below it.  They also prevent the individual bones of the spine from twisting out of place.

The Softer Side of the Spine

The vertebral discs (also called intervertebral discs or disks) are the shock absorbers of the spine.  They are located between each vertebral body and prevent bone-on-bone contact.  Intervertebral discs are prone to injury and disease.  Some of the most common disc diseases are shown here and include disc degeneration, bulging, and thinning.  Because of their proximity to the spinal cord and nerve roots as they exit the spine, disc disorders can cause extreme pain.

Columns and Approaches

When coding spinal fusion procedures, there is a lot of mention about anterior and posterior fusions as well as anterior and posterior approaches.  And while these may sound interchangeable, they refer to two different things.

An anterior fusion is performed on the anterior column, or front part of the spine – the part that lies in front of the spinal cord.  Anterior fusions involve fusing the vertebral bodies of two or more segments together since the vertebral body is the portion of the spine anterior to the spinal cord.  Posterior fusions occur in the part of the spinal column that is behind, or posterior to, the spinal cord.  Posterior fusions involve fusing the facet joints or the posterolateral gutter of the spine.

An anterior approach is performed when the surgical approach is through the front, or sometimes side, of the body.  Anterior approaches may be necessary for anterior fusion and involve dissection of the visceral organs to reach the intervertebral space.  Posterior approaches are performed for anterior or posterior fusion and involve making an incision in the back with the same level of dissection necessary for an anterior approach.