Objective:

To assess whether adding fusion to decompression improves 12-month outcomes for patients with degenerative lumbar spondylolisthesis and whether patient characteristics modify comparative effectiveness.

Approach:

• Design and population: Cohort study using target trial emulation, combining the Norwegian Registry for Spine Surgery and the NORDSTEN-DS randomized trial. It included 2,252 patients aged 18–80 years: 1,446 treated with decompression alone and 806 with decompression plus fusion.
• Outcomes and analysis: Primary outcomes were disability (Oswestry Disability Index [ODI]) and subsequent spine surgery within 12 months. Inverse probability weighting adjusted for measured baseline differences; prespecified subgroup analyses examined sex, age, smoking, BMI, back pai…

Key Findings:

• Adjusted mean 12-month ODI scores were 22.3 after decompression alone and 20.0 after fusion; the difference did not establish a clear advantage for fusion.
• There were no clear group differences in back or leg pain, quality of life, treatment satisfaction, or subsequent surgery (estimated risks 7% with decompression alone and 6% with fusion).
• Perioperative complications were estimated at 5% with decompression alone and 9% with fusion. Decompression alone was associated with operations about 85 minutes shorter and hospital stays 1.9 days shorter.
• No clear evidence showed that prespecified patient characteristics modified comparative effectiveness.
• In a post hoc exploratory analysis, men with BMI ≥30 kg/m² had worse disability outcomes after fusion; the estimated ODI difference favored decompression alone by 12.8 points. The authors said this finding requires further investigation.

Interpretation:

The authors reported that patient subgroups did not have differential effects from adding fusion to decompression at 12 months. Findings were consistent with previous randomized trials reporting limited additional benefit from fusion for degenerative lumbar spondylolisthesis.

Limitations:

• Most patients were treated in routine practice rather than randomly assigned, leaving possible residual confounding, including from unmeasured differences in vertebral slippage severity.
• ODI outcomes were missing for about 17% of patients at 12 months, although sensitivity analyses produced similar findings.
• The study may have lacked power to detect small subgroup effects, was based on patients treated in Norway, and had only 12 months of follow-up.

Sources:

• Annals of Internal Medicine