Fusion Adds Little to Laminectomy for Lumbar Stenosis

Janis C. Kelly

April 14, 2016

Patients whose lumbar spinal stenosis was treated with decompression surgery plus fusion ended up no less disabled than those who had decompression alone, but they did lose more blood, stay hospitalized longer, and have higher medical bills, according to two studies published in the April 14 issue of the New England Journal of Medicine.

Outcomes from these randomized controlled trials call into question the current enthusiasm for decompression plus fusion, now routinely performed in more than half of patients with surgically treated spinal stenosis in the United States (including 96% of those with degenerative spondylolisthesis).

Neither research group found that adding fusion improved scores on the Oswestry Disability Index (ODI), a disease-specific scale used to assess disability related to low back pain at 2 and 5 years after surgery. One study found a 5.7-point difference on the more general physical component summary score of the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), but that difference barely cleared the 5-point criterion for minimal clinical importance.

In an accompanying editorial, Wilco C. Peul, MD, PhD, and Wouter A. Moojen, MD, PhD, write, "The goal of surgery in lumbar spinal stenosis is to improve walking distance and to relieve pain by decompression of nerve roots. The addition of instrumented fusion — 'just to be sure' — for the treatment of the most frequent forms of lumbar spinal stenosis does not create any added value for patients and might be regarded as an overcautious and unnecessary treatment." Dr Peul and Dr Moojen are both from Leiden University Medical Center and Medical Center Haaglanden, The Hague, the Netherlands, and were not involved in either of the studies.

The aim of the first study, the Swedish Spinal Stenosis Study (SSSS), reported by Peter Försth, MD, PhD, from the Department of Surgical Science, Uppsala University, Sweden, and colleagues, was to determine whether combining fusion surgery with decompression surgery resulted in better clinical outcomes at 2 years than decompression surgery alone.

The trial included 247 patients with lumbar spinal stenosis at one or two adjacent vertebral levels who were randomly assigned either to decompression (laminectomy) alone or to decompression plus fusion surgery. About half of the patients also had degenerative spondylolisthesis, defined as presence of a vertebra that had slipped at least 3 mm past the vertebra below it.

Randomization was stratified for presence or absence of degenerative spondylolisthesis. The authors write, "Many spine surgeons view this sign of instability as a mandatory indication for fusion surgery."

The primary outcome in the Swedish study was the score on the ODI 2 years after surgery. The researchers also assessed patient-reported outcome measures, a 6-minute walk test, and a health economic evaluation, as well as 5-year data where available.

The second study was the Spinal Laminectomy versus Instrumental Pedicle Screw (SLIP) trial, reported by Zoher Ghogawala, MD, and colleagues in the United States. Dr Ghogawala is from the Alan L. and Jacqueline B. Stuart Spine Research Center, Lahey Hospital and Medical Center, Burlington, Massachusetts.

The SLIP researchers randomly assigned 66 patients, all of whom had symptomatic lumbar spinal stenosis and grade 1 degenerative spondylolisthesis, either to decompressive laminectomy alone or to laminectomy with posterolateral instrumented fusion. The authors note that in 2011, 465,000 spinal fusion procedures were performed in the United States, at a cost of $12.8 billion, the highest aggregate hospital costs of any surgical procedure performed in US hospitals.

Their study tested the hypothesis that lumbar laminectomy with instrumented fusion (rigid pedicle screws affixed to titanium alloy rods) would produce better outcomes on the SF-36 than laminectomy alone. The primary outcome measure was change in the SF-36 at 2 years. The SLIP trial included ODI score as a secondary outcome measure.

Neither study showed a significant difference in disability (measured by the ODI) associated with adding fusion to decompression surgery for spinal stenosis. In the SSSS, the mean ODI at 2 years was 27 in the fusion group and 24 in the decompression-alone group (P = .24). In the smaller SLIP study, the change in ODI at 2 years was −26.3 in the fusion group and −17.9 in the decompression-alone group (P = .06).

Furthermore, in SSSS, adding fusion had no effect on disability score in the group of patients expected to be most likely to benefit: those with degenerative spondylolisthesis.

Dr Peul and Dr Moojen comment that in the SSSS study, decompression with fusion "was associated with higher costs [an additional $6800,] but did not provide improvement with respect to the primary outcome measure, the ODI, or to any other clinical outcome, including walking distance."

Researchers in the SLIP study report that their primary outcome, the SF-36 at 2 years after surgery, increased by 15.2 for the fusion group vs 9.5 for the decompression-alone group, for a difference of 5.7 (P = .046).

The SF-36 physical component summary score increases continued to be greater in the fusion group than in the decompression-alone group at 3 and 4 years. However, the study sample size had been calculated with the assumption that 10% of patients would be lost to follow-up each year. By year 2, 14% of patients had been lost, and by year 4, 30% of patients were lost to follow-up. The authors write, "The interpretation of the differences observed at the 3-year and 4-year time points are weakened by the lower rates of follow-up. Future studies will benefit from larger sample sizes that also include valid disease-specific assessments as primary outcomes."

Adjunct fusion was also associated with other problems. Length of hospital stay for fusion vs decompression alone was 4.2 vs 2.6 days in the SLIP study (P < .001) and 7.4 vs 4.1 days in the SSSS study (P < .001). In the SLIP patients, mean blood loss was 513.7 mL for fusion vs 83.4 mL for decompression alone (P < .001).

According to Dr Peul and Dr Moojen, Dr Ghogawala and colleagues were correct to conclude that the difference in SF-36 score does not justify the associated higher costs or longer duration of surgery (289.6 vs 124.4 minutes).

The editorialists conclude, "Given that the disease-specific ODI is a better outcome measure for the treatment of spinal stenosis than the general SF-36, the fact that both trials showed that the improvements in the scores on the ODI did not differ significantly between the two surgical approaches suggests that the costlier approach of instrumented fusion does not add value for patients."

SSSS was supported in part by Johnson & Johnson. One coauthor reports receiving grant support from Medtronic. Another coauthor is an employee of and holds stock in Quantify Research. Among the SLIP study authors, one coauthor reports grant support from Stryker Spine and personal fees from AxioMed Spine and OrthoMEMs outside the submitted work. Another coauthor reports personal fees from the Agency for Health Research and Quality, Bayer, the Blue Cross Blue Shield Association, Pfizer, and Takeda outside the submitted work. The remaining authors have disclosed no relevant financial relationships. Dr Moojen has disclosed no relevant financial relationships. Dr Peul reports grant support from the European Committee FPU-7, ZonMw, Paradigm Spine, Medtronic, the Eurospine Foundation, and CVZ outside the submitted work.

N Engl J Med. 2016;374:1413-1434, 1478-1479. Försth article full text, Ghogawala article full text, Editorial full text

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