Surgery for spinal stenosis with degenerative spondylolisthesis

Controversy continues about the best surgical option for patients with symptomatic lumbar spinal stenosis and concomitant degenerative spondylolisthesis. At the centre of this controversy is a debate on the efficacy of decompression alone versus decompression with fusion. In this context, durability has been defined as maintenance of clinical benefit without the need for additional intervention.1 The potential benefit of fusion surgery in terms of durability should be weighed against the risks of future reoperations because of adjacent segment disease. Previous randomised controlled trials and observational register studies did little to settle the controversy because the results were inconsistent.2345678910 Three previous randomised controlled trials (two from Scandinavia and one from Japan) reported findings favouring decompression without fusion,234 whereas one randomised controlled trial from the US reported findings favouring decompression with fusion.5 Specifically, the US randomised controlled trial reported significantly higher reoperation rates for patients managed with decompression without fusion.5

A meta-analysis aggregating the results of these four randomised controlled trials found no significant differences between the two treatment options in patient reported outcome measures, such as the Oswestry disability index or reoperation rates.6 Furthermore, two large studies of data from Scandinavia’s national registers found no significant differences in patient reported outcomes or reoperation rates after two years of follow-up when comparing decompression with or without fusion.78 By contrast, two studies analysing data from the US quality outcomes database found that decompression combined with fusion was associated with significantly better patient reported outcomes than decompression alone over two or five years,910 but no significant difference in reoperation rates.

In a welcome addition to this evidence, Kgomotso and colleagues reported five year results from the Norwegian degenerative spondylolisthesis and spinal stenosis (Nordsten-DS) trial(doi: 10.1136/bmj-2024-079771).11 The findings are important because this trial evaluated surgery for spinal stenosis with concomitant degenerative spondylolisthesis over five years. The authors found that decompression with no fusion was not inferior to decompression with fusion, with respect to patient reported outcomes and reoperation rates. The study primarily adds valuable data for patient reported outcomes: 84 (63%) of 133 patients in the decompression group and 81 (63%) of 129 patients in the fusion group met the primary outcome (an Oswestry disability index reduction of ≥30% from baseline to five year follow-up). The difference between the groups was 0.4 percentage points (95% confidence interval −11.2 to 11.9). Confident evaluation of differences in reoperation rates may require longer follow-up because other evidence suggests that the distribution of reoperations for adjacent segment disease after a spinal fusion is bimodal, with peaks in incidence after two and 10 years.12 A longer follow-up may not add further value to patient reported outcomes, however, other health related events may occur during a longer follow-up that could affect these outcomes. An important limitation of Kgomotso and colleagues’ study was that the patients were not masked to the treatment assignment, which, for example, may affect patients’ satisfaction with treatment. Furthermore, the study was not powered to compare differences in reoperation rates between the two treatment groups.

As Kgomotso and colleagues noted, only a few countries reported a change in surgical practice following earlier trials favouring decompression without fusion. In Sweden, for example, the rate of fusion surgery for patients with spinal stenosis and spondylolisthesis decreased from 75% in 2009 to less than 20% in 2018,13 whereas in the US, rates of decompression with fusion increased from 67% in 2016 to 90% in 2019.14 Changes to practice in countries such as the US may require the intervention of health leaders and policy makers in addition to new evidence.

The health economic consequences of fusion surgery are important from a policy maker’s perspective. Cost utility estimates are already available from a model based on data from the Nordsten-DS trial and reoperation rates reported by the aforementioned US randomised controlled trial,45 indicating that decompression with fusion is not cost effective compared with decompression alone in the surgical management of degenerative spondylolisthesis over a two year time horizon.15

Patient information and shared decision making are both undermined by the absence of consensus on how to surgically manage lumbar spinal stenosis with degenerative spondylolisthesis. While the US randomised controlled trial and quality outcomes database studies suggested that fusions can be beneficial for carefully selected patients, Kgomotso and colleagues’ findings also indicated that decision makers could work towards reducing the global rate for fusion surgery, perhaps aiming for a Scandinavian level of less than 20%.5910

In conclusion, Kgomotso and colleagues provided important five year evidence for the effectiveness of decompression without fusion with respect to patient reported outcomes. However, longer term studies are needed to finally settle the issue regarding differences in reoperation rates between decompression with or without fusion for spinal stenosis with degenerative spondylolisthesis.