The Role of Fusion in Spinal Stenosis: What Claims Data Tell Us
The indications for fusion in lumbar spinal stenosis (SpS) remain controversial. Degenerative spondylolisthesis is the only degenerative lumbar condition where reasonably good evidence suggests outcomes are improved by adding fusion to decompression. Most surgeons also believe that fusion improves outcomes in degenerative scoliosis, though there is no high quality evidence demonstrating this is true. In the absence of spondylolisthesis or scoliosis, the literature suggests there is no clinical benefit to adding fusion to the decompression, though data indicate that fusion continues to be performed in the absence of sagittal or coronal plane deformity. In an attempt to look at this question on a large scale, Dr. Lad and colleagues used the MarketScan claims database to determine re-operation rates and costs associated with surgery for SpS in the absence of spondylolisthesis. Stenosis patients were classified as having undergone decompression alone or decompression and fusion, while the fusion patients were further stratified based on whether or not instrumentation was used. They had two year follow-up data on over 12,000 patients, of whom approximately 75% underwent decompression alone and 25% also underwent fusion. They found that the fused patients were younger and were more likely to have undergone multilevel laminectomies. Long-term re-operation rates were similar for the decompression alone and decompression + fusion groups, though the decompression alone group was more likely to undergo re-operation within the first year (4.2% vs. 3.2%, p = 0.01). The addition of instrumentation was associated with a somewhat higher re-operation rate (17.4% vs. 12.2% at longest follow-up, p = 0.11), though this was not significant. Not surprisingly, initial hospital costs were about three times higher for those undergoing decompression + fusion compared to those treated with decompression alone (approximately $35K vs. $12K), and the use of instrumentation resulted in about $10K increased upfront costs. There were no significant cost differences between the groups beyond the initial hospitalization.
The results of this study should come as no surprise to the spine community. Many papers have reported higher costs and complication rates in SpS patients treated with decompression + fusion compared to decompression alone, with no evidence indicating that the addition of fusion in patients without spondylolisthesis or scoliosis leads to better clinical outcomes. It was reassuring to see that 75% of SpS patients without spondylolisthesis did not undergo fusion. Given the limitations of claims data, the indication for fusion in the other 25% of the patients cannot be determined, though it is possible that these patients had scoliosis, instability or other indications for fusion not recorded in the database. The two major limitations of claims data are the lack of clinically important baseline information (i.e. how many levels were treated, were there neurological deficits, psychosocial factors, etc.) and patient reported outcome measures. The first problem can result in significant confounding that cannot be controlled for with statistical measures, and the second substantially limits the conclusions that can be drawn. For example, the authors indicated that the fusion patients underwent more multilevel procedures than the decompression alone patients, a confounder that could affect length of stay, complication rates, and re-operation rates. Re-operation rate is a problematic outcome measure as the choice to re-operate is a decision made by the patient and surgeon based on subjective criteria. It seems likely that aggressive surgeons who prefer decompression and instrumented fusion compared to decompression alone may also be more likely to re-operate. From a healthcare systems perspective, this paper supports limiting the use of fusion in SpS patients unless there are clear indications for fusion. This conclusion makes sense in the context of earlier studies that have shown no advantage to adding fusion to decompression in SpS patients without a clear indication for fusion.
Please read Dr. Lad’s paper in the May 20 issue. Does this paper affect how you see the role of fusion in spinal stenosis? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor