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Which Surgical Fusion Method is Best for Degenerative Spondylolisthesis?
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Posted on: 10/22/2009
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There are different reasons to fuse the spine and different ways to do the fusion procedure. Surgeons are studying the results of fusion techniques to get an idea of which one works best for each problem. In this study, patients who had a spinal fusion for degenerative spondylolisthesis with one of three fusion methods are compared. Two of the fusion techniques used instrumentation such as screws or metal plates and screws. The third method used bone grafting without instrumentation. Outcomes were measured in terms of pain and physical function for up to four years.
Spondylolisthesis is a condition in which one of the vertebral bones slips forward over the one below it. Spondylolisthesis alters the alignment of the spine. As the bone slips forward, the nearby tissues and nerves may become irritated and painful. In older adults, degeneration of the disc and facet (spinal) joints can lead to spondylolisthesis. Spondylolisthesis from degeneration usually affects people over 50 years old. This condition occurs in African Americans more often than in whites. Women are affected more often than men.
In this study, almost 400 patients with degenerative spondylolisthesis who had a fusion procedure to correct the problem were included. Data from patients' charts was gathered from 13 spine centers in 11 different states. The three fusion techniques included 1) posterolateral in situ fusion (PLF), 2) posterolateral instrumented fusion with pedicle screws (PPS), and 3) posterolateral instrumented fusion with pedicle screws AND a 360-degree interbody fusion (fusion all the way around the spinal column at the affected level). The 360-degree approach was also referred to as PPS Plus.
Let's take a little closer look at the anatomy to understand this condition and why a fusion procedure is needed. Each vertebra has a main body of bone with a circle or arch of bone that attaches to the back of the vertebral body. When the vertebrae are stacked on top of each other, these bony rings create a hollow tube. This tube, called the spinal canal, surrounds and protects the spinal cord as it passes through the spine.
Two sets of bones form the spinal canal's bony ring. Two pedicle bones attach to the back of each vertebral body. Two lamina bones complete the ring. The place where the lamina and pedicle bones meet is called the pars interarticularis, or pars for short. There are two such meeting points on the back of each vertebra, one on the left and one on the right. The pars is thought to be the weakest part of the bony ring. This is where a tiny fracture in the bone called spondylolysis can develop. When the two sides of the fracture separate, the condition becomes a spondylolisthesis.
Without a fusion to hold the structures together, the vertebral body shifts farther and farther forward, putting pressure on the spinal cord and spinal nerve roots. The affected individual suffers from significant low back pain, leg pain, muscle weakness and atrophy, and sometimes even paralysis. So, back to the purpose of this study: which one of these surgical methods works best?
Well, to find out, the authors measured pain and physical function using two main tools. The first was the SF-36 bodily pain and physical function test. The second was the Oswestry Disability Index (ODI). Both are well-known and reliable measures of outcomes after treatment. They specifically wanted to know if patients had better health after surgery (compared to before treatment) and how did the patterns of symptoms, function, and health change after surgery (comparing the results of one procedure to another)? Patient satisfaction with final symptoms and care was also evaluated.
By following patients at six weeks, three months, two years, and finally, four years, they were able to see a pattern of results. At first, the posterolateral (noninstrumented) method had the best results. About one-fifth of the patients (21 per cent) had this procedure done. Of the two instrumented procedures, the posterolateral instrumented fusion (56 per cent of the patients) had better results at first (six weeks, three months). But by the end of the second year, patients in the 360-degree group (17 per cent of the patients) had better pain relief and less disability. Fusion rates were equal between the two instrumented techniques. The posterolateral fusion group had the lowest fusion rate. They did not find any differences in patient satisfaction from one group to another with care received or symptoms. This was true at all measuring points in time.
The most striking finding was what they found at the end of the four-year period: no difference in results between the three fusion groups. Any of the differences observed early after surgery were not maintained over time. These findings are important because statistics show that more and more older adults on Medicare are having back surgery and specifically spinal fusion. With the rising costs of health care, it's necessary to find safe, effective, and cost-reducing ways of treating common age-related conditions like degenerative spondylolisthesis.
The authors concluded that there wasn't an obvious winner among these three fusion techniques. They all produced about the same results when looking at pain, physical function, and patient satisfaction. With only a few minor postoperative complications, there was no harm done to the patients having each type of fusion. Fusion rates were slightly higher for patients who had instrumentation. These results are consistent with what other researchers have reported about fusion rates in previous studies of spinal fusion.But as far as naming one method the best in terms of outcomes, they couldn't do it.
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References:
William A. Abdu, MD, MS, et al. Degenerative Spondylolisthesis. Does Fusion Method Influence Outcome? Four-Year Results of the Spine Patient Outcomes Research Trial. In Spine. October 1, 2009. Vol. 34. No. 21. Pp. 2351-2360.
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*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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