What’s Best for Lumbar Spinal Stenosis?

Edward C. Benzel, MD

Two new multicenter randomized trials have come to slightly different conclusions about the effectiveness of laminectomy alone versus laminectomy plus instrumented fusion for lumbar spinal stenosis. The studies, one from the U.S. and one from Sweden, were simultaneously published in the April 14 New England Journal of Medicine.

Consult QD asked a co-author of the U.S. study, Edward C. Benzel, MD, to help sort out the conclusions. A Q&A with Dr. Benzel, a neurosurgeon in Cleveland Clinic’s Center for Spine Health, follows the study recaps below.

RELATED: Confusion Around Fusion: What’s Best for Lumbar Spinal Stenosis? (Revisited)

The studies in brief

The U.S. study is known as the SLIP trial (Spinal Laminectomy versus Instrumented Pedicle Screw) and enrolled 66 patients (mean age 67; 80 percent women) with stenosis and spondylolisthesis from five hospitals, including Cleveland Clinic. Patients underwent either standard bony decompression or decompression plus posterolateral instrumented fusion across the level of listhesis, with a bone graft harvested from the iliac crest.

The primary outcome measure was the generic physical component summary score of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) at two years after surgery. The secondary outcome measure was the Oswestry Disability Index (ODI), commonly used to assess disability related to low back pain.

At one year, SF-36 outcomes did not differ significantly between the groups. However, at two, three and four years after surgery, patients in the fusion group had a significantly greater increase in the SF-36 physical component summary score than did those in the decompression-alone group. Differences between groups in disability amelioration were not significant at any time points.

In the Swedish study, 247 patients with or without spondylolisthesis were randomly assigned to one of the two procedures. The authors concluded that the combined procedure did not improve the primary outcome measure, the ODI or any other clinical outcome, including walking distance.

Q: Dr. Benzel, how do you interpret the findings from these studies?

We demonstrated a very slight advantage with lumbar fusion accompanying laminectomy in patients with a grade 1 spondylolisthesis. The general practice across the U.S., but not in Sweden or my own practice, is to perform a fusion along with laminectomy in this patient population.

The Swedish study demonstrated that fusion accompanying a laminectomy did not provide an advantage or superior outcomes in their patient population. There is debate about whether the two patient populations are comparable. In the Swedish study, the population was more heterogeneous, not restricted to those with spondylolisthesis, while our trial was restricted to patients with spondylolisthesis and complaints related to lumbar stenosis.

We are a bit at odds with our Swedish colleagues if you look at this from a superficial perspective, but we are truly not at odds from an overall, big-picture perspective.

Q: How would you characterize the combined procedure’s “slight advantage” for a patient you were counseling on surgical options?

Patients across the board face a risk of instability following decompression, but the risk level varies. In counseling a patient, I would look at overall imaging parameters and the patient’s complaints to determine if there’s high risk for progressing to spondylolisthesis or a further slip. If so, I would recommend a fusion. On the other side of the coin, if I recommend fusion, I know that down the road there may be more problems related to the fusion, such as adjacent segment degeneration requiring further surgery.

Q: How should this study influence management of patients with degenerative spondylolisthesis in the U.S.?

Even though we showed a slight benefit with fusion, our study, combined with the Swedish study, will probably cause surgeons to exercise more restraint in recommending fusion surgeries to accompany decompression for lumbar stenosis.

Both operations are effective in the short term. However, we must understand that there may be a downside to a fusion procedure in the long run. Which approach will ultimately prove to be best? I don’t know.

What should be gleaned from our study is the notion that fusion is appropriate in selected cases. The decision really depends on symptoms and the imaging findings. How much back pain is there? How much leg pain? And from an imaging perspective, is the spondylolisthesis at high risk of progressing?

This study attempted to simplify things, but in reality it’s not a simple decision. Even though our study included only patients with spondylolisthesis, it was heterogeneous in that it included some patients at low risk for further instability and others at high risk.

Q: What characterizes a patient who is at high risk?

He or she would have a mobile slip, as demonstrated on flexion-extension X-rays or from supine to standing position — i.e., comparing an MRI (supine position) and a standing X-ray. He or she would have a normal disk interspace height, as compared to a more stable collapsed disk space. We find that with collapse of the disk, the patient is often more stable. So more advanced degenerative changes are associated with a greater degree of stability. And then you must consider the patient’s complaints. If there’s no back pain, I may not be inclined to do a fusion.

X-rays demonstrating an L4-5 slip in a patient with lumbar stenosis.

Q: How were these two studies noteworthy?

These are the first two major randomized, prospective, multi-institutional studies looking at fusion versus nonfusion for lumbar stenosis.

Randomized surgical trials are very, very difficult and laden with bias from both the patient and physician perspective. Our trial was unique in that we used a 10-member expert panel to review cases before enrollment. It was a check-and-balance system that helped eliminate bias in recommending enrollment while increasing the enrollment rate.

Q: Where should future studies focus?

Future studies should look at developing protocols to help surgeons identify which patients are stable and likely to never need a fusion and which patients are probably unstable and could benefit from a fusion.

We also must consider cost. Fusion costs more and involves a longer operating time and hospitalization. Is the small benefit from the combined procedure worth the cost? We don’t know, but we need to answer this question. We plan to conduct an analysis of our data from the SLIP trial.

Performing these operations minimally invasively is more expensive, but it yields lower infection rates and reduces recovery times. It must be noted, however, that efficacy is unproven.

Q: How would you sum up?

This is a very common operation in the U.S., and ours was the first comparative-effectiveness trial to look at the need or lack of need for fusion. Our study addressed the issue of equipoise by using an expert panel as a check-and-balance system.

My take-home is this: Surgeons should exercise caution when recommending a fusion to accompany a decompression operation for lumbar stenosis, and they should carefully scrutinize indications. Both operations are effective in the short term, so we need to work on sorting out which patients should or should not have a fusion. We really don’t know yet. I don’t think we settled that.

Dr. Benzel participated in a New England Journal of Medicine-sponsored online discussion with other authors of both studies. The transcript is available here.