Adjunctive Fusion Bests Decompression Alone for Spondylolisthesis

Pauline Anderson

August 25, 2021

Researchers are learning more about the advantages of adding fusion to decompression surgery for patients with grade 1 lumbar spondylolisthesis.

In a study with more than 600 participants, researchers determined that those who underwent fusion plus decompression had significantly better disability scores at 24 months compared with those who underwent decompression alone.

Additional analysis showed that reoperation rates were relatively low for all participants.

Dr Andrew Chan

Although the reoperation rate was not significantly different between the two treatment groups, it was lower for those who underwent fusion, and it was "in the same direction" as the primary study outcome, said co-investigator Andrew K. Chan, MD, Complex Spine Fellow, Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina.

Still, "when surgeons choose the procedures they think is best for their patients, they achieve low reoperation rates overall for both types of procedures," Chantold Medscape Medical News.

The findings were presented at the American Association of Neurological Surgeons (AANS) 2021 Annual Meeting.

Vertebra Slips

Spondylolisthesis occurs when one vertebra slips out of place onto another, putting pressure on the nerve and causing lower back and leg pain.

Nonsurgical treatments can usually relieve symptoms. These include "a whole host of things to get patients through the pain," including muscle relaxants, neuroleptics, physical therapy, and spinal injections, Chan said.

Degenerative spondylolisthesis affects 13.6% of the US population. Most cases are asymptomatic. Chan noted that prevalence increases with age and that about 40% of individuals aged 60 to 69 years suffer from this condition.

Grade 1 spondylolisthesis, the lowest of four grades of slippage, is a common indication for surgery. However, the "age old" question has been whether fusion is necessary "or can we get away with a decompression procedure without fusion," said Chan.

During a decompression procedure, a surgeon removes structures that are compressing the nerve root. Fusion involves connecting screws by rods and bone grafts around the vertebrae so as to join or fuse the vertebrae together.

Previous research has been somewhat unclear as to which approach yields the best outcomes.

The current investigators used data from the Quality Outcomes Database Lumbar Spondylolisthesis Study Group, which includes data from 12 high-volume spine centers across the United States. To date, the registry has enrolled 608 patients who underwent single-segment surgery for grade 1 lumbar spondylolisthesis.

Of these, 140 underwent decompression, and 468 underwent decompression and fusion. About 85% had at least 24 months of follow-up.

Reduced Disability

In their primary analysis, which was published in April in the Journal of Neurosurgery: Spine, the researchers determined that at 24 months, outcomes were better for patients who underwent fusion.

Change in Oswestry Disability Index score was significantly greater in the fusion-plus-decompression group than in the decompression-only group (−25.8 vs −15.2, P < .001).

The new secondary analysis assessed reoperation rates. Researchers recorded reoperations related to the index surgery that were assessed at 30-day, 1-year, 2-year, and 3-year time points.

Chan noted that there were important baseline differences between the two groups. For example, those in the fusion group were younger (mean age, 59.9 years, vs 69.6 years) and had a higher proportion of women (60.7% vs 47.1%). They also had a lower rate of type 2 diabetes and a higher rate of depression.

Those in the fusion cohort also had more disability, back pain, and lower quality of life, and they less often had a motor deficit. Leg pain was similar in the two groups.

Regarding sociodemographics, patients in the fusion cohort were slightly less educated but were more likely to be employed.

Patient Selection Key?

Overall, the reoperation rate was 6.9% at 2 to 3 years (42 patients with 44 reoperations).

"It showed that when experienced spine surgeons across the US choose the procedure they think is best for patients, they have a pretty low reoperation rate overall," said Chan.

The reoperation rate was 9.3% for patients who underwent decompression alone and 6.2% for those who underwent decompression with fusion. The between-group difference did not reach statistical significant (P = .21), possibly because it was underpowered, Chan noted.

However, that could change with time. The investigators aim to follow these patients for 10 years, during which period the difference with fusion may become significant.

Chan emphasized the difference in timing for the reoperations for the two groups. The rate at 30 days was significantly higher for fusion (P = .02) and was significantly higher for decompression alone during the 30-day to 1-year time window (P = .01). There were no significant differences at other time points.

Results showed that of the 13 reoperations in the decompression group, six cases (4.3% of the total) required transition to fusion. Of the 29 patients who underwent reoperation in the fusion group, 13 (2.8% of total) needed revision fusion.

The researchers are now assessing the factors that should be considered when adding fusion. The "classical thinking" has been that fusion is needed if the spondylolisthesis is unstable or there is significant back pain, Chan said.

"Maybe we should start to think about what we can do to select the right patients for each type of procedure," he added.

"Real-World Data"

Commenting during the presentation session, John Ratliff, MD, professor, Department of Neurosurgery, Stanford University, Stanford, California, praised the research.

"This is a very well-executed retrospective study," said Ratliff, who was not involved with the research.

He noted that the analysis using the quality outcomes database examined only grade 1 spondylolisthesis and single-level surgery.

In addition, it is an observational study, not a controlled trial. "And that's a good thing. This is real-world data," Ratliff said.

He added that the overall reoperation rate was less than 7% and that only about 4% of cases in the decompression-only group required conversion to fusion.

"It shows a group of surgeons can effectively discern who does not need a fusion, as reoperation rates with conversion were very low," he said.

However, Ratliff said he would like to know more about the revision status of the study participants.

"It would be interesting to learn more about the patient factors driving this surgeon choice of procedure; that would be key to applying this data" to patient care, he concluded.

The study was funded by an educational grant from the Neurosurgery Research and Education Foundation that was sponsored by Medtronic and DePuy.

American Association of Neurological Surgeons (AANS) 2021 Annual Meeting. Abstract 300. Presented August 23, 2021.

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