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Surgeons Look Back at Results of Fusion for Spondylolisthesis

There's help for patients who have low back and leg pain from isthmic spondylolisthesis in the form of spinal fusion. But this condition can affect different levels of the lumbar spine. And surgeons want the best results for each patient with the least invasive techniques. That's why these surgeons took a look back at the results of their patients with this diagnosis after two different types of fusions. The unique thing about the study was not just that they looked at two different types of surgical techniques, but that they compared them at two different lumbar levels (L4-L5 and L5-S1).

Isthmic spondylolisthesis refers to a defect in the vertebral bone. A crack in the pars interarticularis (supportive column) of the vertebra causes a separation of the main body of the bone from the back half where the spinal cord and spinal nerve roots are located. The vertebral body shifts forward over the stable vertebra below. The result is a pulling, traction pressure on the nerve tissue and neurologic symptoms. X-rays taken from a side view show characteristic changes that identify this condition.

Nerve tissue is highly sensitive so a shift of this type usually causes significant low back and/or leg pain. The pain is worse when extending the spine because the shift in the bone is the greatest in this position. Forward flexion moves the vertebra back toward a more neutral position, which takes pressure off the spinal nerves. When rest, improved postural alignment, and exercises don't help, then surgery to stabilize the segment may be needed.

Fusion is the most successful surgery. But there are different ways to do a spinal fusion. Different techniques can be used along with different approaches. For example, an anterior approach means the surgery is done from the front, posterior approach from the back, and lateral or transforaminal from the side. Often a combination of two different directions gives the surgeon the angle needed to avoid tissue trauma and potential problems or complications.

In this study, the surgeons compared the anterior lumbar interbody fusion (ALIF) to the transforaminal lumbar interbody fusion (TLIF) in patients with a single-level unstable spondylolisthesis. Interbody fusion means they remove the disc and replace it with a metal cage filled with bone chips. Screws were also used to hold everything together and in place until healing and complete fusion occurs.

Essentially there was one diagnosis but four separate groups. Group one had a L4-L5 spondylolisthesis treated with ALIF. Group two had the same level involved but was treated using the TLIF procedure. Group three had a L5-S1 level spondylolisthesis and ALIF. Group four had a L5-S1 level spondylolisthesis treated with the TLIF procedure.

What they wanted to know was whether it's better to use one approach over another based on the spinal level affected. Results were compared using both X-rays and patient symptoms and function. It's important to use both types of measures because doctors know that X-ray findings don't always match patient performance and level of satisfaction. X-rays show the amount of slip or grade before surgery and the rate of reduction after. Patient pain, function, and return-to-work status were measured using well-known tests such as the visual analog scale (VAS) and the Oswestry Disability Index (ODI).

By comparing results using both techniques at two different levels, the surgeons found that results were better for alignment using the ALIF at the L5-S1 level. Functional results were equal using ALIF at either level. But the TLIF approach seemed to have better functional results when used at the L4-L5 level even though there was no difference in alignment based on X-rays. Everyone in all four groups returned to their normal level of daily and work activities.

Surgeons have many things to consider when approaching surgery for these patients. Other studies have shown the importance of restoring the anatomy to as near normal as possible for the best long-term results. The results of this study may actually support those findings. For example, getting better results with the ALIF at the L5-S1 level may be related to the fact that the angle of the disc here is so steep. It's more difficult for the surgeon to prepare the disc space here for the cage when using the TLIF approach.

The authors consider the results of their research still somewhat preliminary. They want to follow-up with patients and see how the results hold up over time. They also want to consider the psychosocial effects of clinical outcomes for each group. For now they concluded that ALIF was superior to TLIF at the L5-S1 level. TLIF was superior to ALIF at the L4-L5 level. The addition of this new data may help surgeons when making decisions about surgical strategies for patients with unstable lumbar spondylolisthesis. Finding the least invasive, safest, yet most effective treatment for this problem is the goal. Recognizing that one surgical procedure may not be ideal for all levels is important.

Jin-Sung Kim, MD, et al. Which Lumbar Interbody Fusion Technique is Better in Terms of Level for the Treatment of Unstable Isthmic Spondylolisthesis? In Journal of Neurosurgery: Spine. February 2010. Vol. 12. No. 2. Pp. 171-177.


*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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