Recent RCTs comparing decompression alone to decompression and fusion for degenerative spondylolisthesis (DS) reached somewhat contradictory conclusions, though these studies made it clear that not all DS patients need to be fused.1,2 However, it remains unclear who does need a fusion. Some studies have suggested that patients with a mobile listhesis, maintained disk height, and sagittally aligned facet joints are at increased risk for progression of listhesis following decompression without fusion, though no large study has confirmed this.3 In order to better understand if baseline radiographic findings can predict failure of decompression alone in DS, Dr. Schar and colleagues from Switzerland retrospectively reviewed a case series of 161 patients undergoing unilateral or bilateral laminotomy (midline sparing surgery) for spinal stenosis. Approximately one third of the patients had at least one level with a spondylolisthesis, and no patients underwent a fusion at the index procedure. Patients with greater than 3 mm of motion on flexion-extension radiographs were excluded. At a median four-year follow-up, 15% of patients had undergone reoperation, 72% of which were for recurrent stenosis and 28% of which were for adjacent segment stenosis. Of the 56 patients with listhesis, 18% underwent a revision surgery for recurrent stenosis. Only 4% of patients without listhesis underwent a reoperation for recurrent stenosis. Disk height and facet angle were not associated with risk of reoperation. The authors did not report patient reported outcomes (PROs).
This is a nice retrospective cohort study that demonstrated that the presence of a "stable," low-grade listhesis is a risk factor for reoperation following midline-sparing decompression. The study also failed to identify any radiographic risk factors for reoperation other than the presence of listhesis. The authors argue that an 18% reoperation rate at 4 years is acceptable and may be preferable to outcomes following fusion. However, this study lacks a fusion comparison group and really does not provide any information to guide the decision about whether or not to perform a fusion for a DS patient. The results do suggest that the reoperation rate using this technique in the absence of listhesis is very low. In order to answer the question about which DS patients benefit from fusion, a study needs to include a large number of DS patients treated decompression alone or decompression and fusion. Such a study would need to include baseline patient characteristics and radiographic studies, PROs, and reoperation rates. This would allow for subgroup analyses to be performed to compare outcomes between decompression alone and decompression and fusion for patients with different baseline characteristics and radiographic findings. More complex is determining the best decompression (i.e. midline laminectomy vs. midline-sparing laminotomy) or fusion (i.e. uninstrumented vs. instrumented vs. interbody) technique. These studies would need to include a much larger number of patients than have been assembled in prior studies in order for the subgroups to be large enough. Until such a study exists, surgeons will need to consider the available data and discuss the pros and cons of including a fusion when deciding on surgical technique with their patients. Given the technical difficulty, increased complication rate, and likely worse outcomes for a revision decompression as compared to a decompression and fusion for adjacent segment degeneration, it may make sense to fuse healthy patients who can tolerate the operation.
Please read Dr. Schar's article on this topic in the February 15 issue. Does this change your opinion about the need for fusion in DS? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
1. Forsth P, Olafsson G, Carlsson T, et al. A Randomized, Controlled Trial of Fusion Surgery for Lumbar Spinal Stenosis. The New England journal of medicine 2016;374:1413-23.
2. Ghogawala Z, Dziura J, Butler WE, et al. Laminectomy plus Fusion versus Laminectomy Alone for Lumbar Spondylolisthesis. The New England journal of medicine 2016;374:1424-34.
3. Blumenthal C, Curran J, Benzel EC, et al. Radiographic predictors of delayed instability following decompression without fusion for degenerative grade I lumbar spondylolisthesis. J Neurosurg Spine 2013;18:340-6.