Surgery for Degenerative Spondylolithesis; A Brief Review


In a recent article we talked about degenerative spondylolisthesis, what it is, whom it affects, and how it develops. In this article I would like to talk about the treatments for spondylolisthesis, with a focus on surgery, and the evidence behind the outcomes of surgical treatment. More in depth discussion of the evidence behind surgical treatment of spondylolisthesis can be found in a JAAOS article by Dr. Frank Eismont.

First, lets talk about who surgery is typically intended for. This article presumes that you already have a documented diagnosis of degenerative spondylolisthesis. If you belong to this group, surgery is typically reserved for patients with debilitating symptoms that have attempted non-operative or conservative treatment, such as NSAIDs and physical therapy, and continue to have debilitating symptoms.

Surgery has been shown to have better outcomes in patients with radicular pain or neurogenic claudication. Radicular pain, is sharp/electrical/shooting pain that shoots down your leg. It is caused by compression, inflammation, or irritation of the nerve roots as the exit the spinal cord. Neurogenic claudication is a condition where the patient experiences leg pain with walking, that is relieved by sitting, or bending over. Patients often describe this pain as improving when they are using a shopping cart or are using stationary bike, both activities where the lower back is flexed forward.

Neurogenic claudication is thought to result from lumbar (low back) spinal stenosis, which can be a component of degenerative spondylolisthesis.

Now, lets talk about the evidence behind surgical treatment for patients that fit the above description. Surgical treatment for degenerative spondylolisthesis is arguably most intensively studied topic in spine surgery.

The Spine Patient Outcomes Research Trial (SPORT) was a prospective, multicenter trial that cost over $15 million to carry out. This was one of the most expensive trials in all of orthopaedics. This study compared operative versus non-operative treatment for patients with degenerative spondylolisthesis. In order to discuss what this trial showed, we need to get into a little bit of the statistics-related details.

When a randomized trial is carried out two types of analyses are done, one is the intention-to-treat analysis and the other is the as-treated analysis. The intention-to-treat analysis compares the groups that followed the strict randomization scheme and excludes the patients that crossed over from one into the other. For example, if a patient was randomized to the non-operative arm of the study but then decided to have surgery because their symptoms were so severe, this patient would be excluded in intention-to-treat analysis. The as-treated analysis compares groups based on which treatment they actually received, regardless of where the patients were initially randomized.

The SPORT trial had a significant amount of crossover. It is inherently difficult to carry out a randomized trial comparing surgical versus non-operative treatments. At the center of this issue is the fact that strict randomization cannot be enforced, if a patient that was randomized to the non-operative arm of the study decides to have surgery the physicians cannot (and should not) prevent him from doing so.  Due to the high crossover rate, the intention-to-treat analysis of the sport trial did not show any difference between the operative and non-operative groups.

The as-treated analysis however showed a clear benefit from surgery. At the 4-year follow up mark 67% of the patients that underwent surgery reported a significant improvement in symptoms compared to 21% of patients that did not undergo surgery. The surgery that is typically offered for degenerative spondylolisthesis is a decompression and fusion of the involved segments. The decompression procedure is typically a laminectomy, which involves removing the spinous process and surrounding bone in order to unroof the spinal canal and take the pressure off the spinal cord.

Fusion typically involves rods and screws that immobilize the spinal segments involved, and aid in bone overgrowth of the joints in the spinal column. The surgical details regarding types of fusion, which can be done with versus with out rods and screws, and the evidence behind different surgical treatments are beyond the scope of this article. I hope this is a useful review of the evidence behind surgery for degenerative spondylolisthesis!

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