By Joshua Weaver, MD

Assistant Professor of Clinical Neurology, Weill Cornell Medical College

SYNOPSIS: For patients with symptomatic lumbar stenosis and single-level spondylolisthesis who were refractory to conservative treatment, there was no significant difference between outcomes in those who underwent decompression surgery with instrumented fusion vs. decompression surgery without fusion.

SOURCE: Austevoll IM, Hermansen E, Fagerland MW, et al. Decompression with or without fusion in degenerative lumbar spondylolisthesis. N Engl J Med 2021;385:526-538.

Low back pain radiating to the legs often is caused by degenerative lumbar stenosis from disc bulges and overgrowth of the facet joints and ligaments causing compression of the nerve roots. Spondylolisthesis, or misalignment of the spine in which one vertebra has slipped forward from the vertebra below it, also commonly can contribute to stenosis and pain. If this pain does not improve with medication and physical therapy, surgical decompression may be performed to relieve symptoms. Surgical techniques vary widely, with some techniques involving instrumented fusion of the vertebral bodies (e.g., with screws, rods, or cages), and other techniques that are less invasive and do not require fusion. In 2016, the authors of two studies compared decompression with or without fusion in lumbar stenosis, finding slightly different results. Subsequent analyses of these studies led to ambiguous conclusions and persistent questions regarding the superiority of one technique over the other.1,2

In this trial, 267 people with low back pain radiating to the legs that was refractory to conservative treatment for three months who had lumbar spinal stenosis and at least 3 mm of spondylolisthesis at the stenotic level were randomized into two groups: decompression-alone and decompression with fusion. The decompression alone group underwent a posterior decompression that was bilateral, ipsilateral, or ipsilateral with crossover to the contralateral side. The fusion group underwent posterior decompression with implantation of various hardware at the discretion of the surgeon.

Demographic characteristics were similar among the two groups. Outcomes were measured at three months, one year, and two years. The primary outcome was a reduction in a disability score (Oswestry Disability Index [ODI]) by 30% or more from baseline by two years. Secondary outcomes included mean change in the ODI score, a claudication scale, functional impairment scale, satisfaction with treatment score, numeric rating scale for leg and back pain, and a quality-of-life scale.

For the primary outcome, 71.4% in the decompression-alone group and 72.9% in the fusion group showed a reduction of at least 30% in the ODI score, showing noninferiority of decompression alone compared to decompression with fusion. Similarly, no significant difference was found in the secondary outcomes of improvement in claudication, functional impairment, leg and back pain, satisfaction, or quality of life. Duration of surgery, length of hospitalization, and blood loss during surgery were significantly less in the decompression-alone group. There was a trend toward the patients in the decompression-alone group needing re-operation by two years compared to the fusion group, although this was not statistically significant.

COMMENTARY

Although studies from 2016 have suggested similar outcomes in different surgical techniques for lumbar stenosis (decompression with fusion vs. decompression without fusion), there has remained a debate over which type of surgery is superior. This recent study adds to the body of evidence indicating surgical decompression without fusion is not inferior to surgical decompression with fusion. This is important, since minimally invasive surgery without fusion is less complicated, less invasive, cheaper, and possibly safer than surgery involving fusion.

There were important limitations to this study. It is difficult to generalize this study to all patients with lumbar stenosis since it was limited to those with spondylolisthesis at one level. Some experience this degenerative condition at multiple levels, and some live with lumbar stenosis without any spondylolisthesis. Patients with severe neural foraminal stenosis were excluded in this study, although it is not uncommon for patients to experience this condition along with spondylolisthesis. Patients with prior fusion surgeries were excluded. Twenty percent of patients included exhibited dynamic instability of the spondylolisthesis on flexion/extension imaging, but these patients were lumped with the total group, and subgroup analysis on surgery type (fusion vs. decompression without fusion) in this subgroup could not be conducted since this study was not powered adequately to do so.

Regardless, this is a valuable study that highlights the fact that in cases of single-level spondylolisthesis and lumbar stenosis, a less invasive surgical approach produces similar outcomes to more invasive fusion surgery. In general, less invasive approaches are favored because of reduced risk of complications and faster recovery. This is an important discussion clinicians can have both with their patients and their colleagues regarding treatment options. However, surgical treatment options often are quite nuanced and involve many factors, including number of levels of spondylolisthesis, presence of scoliosis, presence of significant neural foraminal stenosis, presence of dynamic instability with various movements of the spine, history of osteoporosis, baseline activity levels, and history of prior surgical fusion, among others.

Many of these conditions may lead a surgeon to choose fusion as an empirically superior alternative to decompression without fusion. Future studies should include these subgroups for further characterization. Comparison of specific minimally invasive decompression surgical techniques and hardware types for fusion surgeries need to be studied in more detail, too.

REFERENCES

  1. Försth P, Olafsson G, Carlsson T, et al. A randomized, controlled trial of fusion surgery for lumbar spinal stenosis. N Engl J Med 2016;374:1413-1423.
  2. Ghogawala Z, Dziura J, Butler WE, et al. Laminectomy plus fusion versus laminectomy alone for lumbar spondylolisthesis. N Engl J Med 2016;374:1424-1434.