Friday, November 6, 2009
Frequent readers of my blogs and articles will have read entries concerning disc bulges and herniations and also covering discogenic pain. Those topics concerning the intervertebral discs, along with various traumatic fractures of the spine, make up the vast majority of the spinal injuries involved in litigation. For that reason, most trial attorneys have at least a passing familiarity with these concepts. But there are other issues involving the spine that may be encountered from time to time. These include spondylolisthesis, spondylolysis, spondylosis and ankylosis, and involve different areas of anatomy including the pars interarticularis and the facets. Since these terms are more unusual, fewer attorneys are familiar with these concepts, so today I will provide you with a general overview so that you may be more comfortable when encountering these conditions in future cases.
First, let us begin by discussing the anatomy of the spine. The spine is made up of multiple individual bones called vertebrae that provide support for the weight of the upper body and provide protection for the spinal cord by surrounding it with an armor of bone from the skull all the way down to the pelvis. Each vertebra can be described as a ring with the large cylindrical vertebral body forming the anterior aspect of the ring and the laminae and spinous processes forming the posterior aspect of the ring. The vertebral bodies are aligned with one atop another forming a column providing the majority of the support for the spine. The laminae form a shield protecting the posterior aspect of the spinal cord. It is important to note that the region of the vertebrae where the posterior aspects join with the anterior aspects is called the pars interarticularis. Also there are joints where the posterior elements of each vertebra come together above and below, and these are called facets. Finally, we must understand that the spinal cord branches into nerve roots at each intervertebral level and that these nerve branches exit the spine through channels called foramen that run beneath the facets.
Now that we've covered the pertinent anatomy, let’s discuss the various pathologies that you might encounter when researching a spinal injury. Of course, as mentioned earlier, disc herniations and spinal fractures are the most common injuries you will come across, but there are other conditions you will see from time to time. Spondylolisthesis, sometimes referred to as anterolisthesis, is a defect in the alignment of the vertebral bodies allowing one vertebral body to slip forward over the vertebral body at the level beneath. In most cases the entire spine, above the level of the defect, is displaced anteriorly. In other words, if you have a spondylolisthesis at L5-S1, the L5 vertebral body will be displaced forward in relation to the sacrum (S1) but L5 will still maintain its proper alignment with L4 and the other vertebrae above. While it may be easy to imagine this change in relationship between the vertebral bodies, it is more difficult to visualize the changes in the posterior aspect of the spine that allow this displacement to occur. In order for the vertebra to move forward the posterior articulations at the facets must be either dislocated or weakened, or there must be a separation in the pars interarticularis (another condition called spondylolysis) allowing for a separation of the vertebra itself. While such a defect in the pars is generally a congenital or pre-existing condition, trauma can cause a worsening of the actual displacement resulting in the spondylolisthesis that is eventually diagnosed. Spondylolishesis is a problem because it can change the passageway for the spinal cord down through the spinal canal causing compression or stretching of the spinal nerves. It can also place tension of the exiting nerve roots at the specific level of displacement or may be associated with a disc herniation at the level of instability. Spondylolisthesis can be mild to severe and if symptomatic is generally treated with a spinal fusion procedure including bone grafts and fusion hardware.
The final pathology we will discuss is spondylosis (sometimes referred to as ankylosis). Basically, this is simply arthritis of the spine. This arthritis may develop over time following the trauma involved in a case, or it may be preexisting and exacerbated by the injury of your case. As with all forms of arthritis, spondylosis primarily affects the joint surfaces. This can include the endplates of the vertebral bodies adjacent to the discs in the anterior aspect of the spine, or the articular surfaces of the facet joints in the posterior aspect of the spine. As with other forms of arthritis, this condition can cause localized pain within the joints themselves or can cause overgrowths of bone (bone spurs or osteophytes) that can protrude into vital regions causing compressions of vulnerable nerves including the spinal cord and nerve roots. As we learned earlier, the foramen through which the nerve roots travel are adjacent to the facets, so overgrowth of arthritis in this area can narrow these foramen and impinge upon the nerve roots. Spondylosis can be treated with a variety of procedures ranging from simple steroid injections to widespread spinal fusion surgery, based on the severity of the condition. The key issue is to remember that although this is an arthritic condition, it can be still linked specifically to trauma.