The SLIP trial is the first RCT directly comparing laminectomy plus instrumented fusion versus laminectomy alone for grade I degenerative lumbar spondylolisthesis with stenosis. It answers whether adding fusion to decompression produces superior outcomes — and at what cost.
For years, surgeons debated whether fusion was truly necessary on top of decompression for stable grade I spondylolisthesis, with only retrospective and non-randomized data (including Herkowitz's influential 1991 series) pointing toward fusion. The SLIP trial finally provides class I evidence: fusion wins on quality of life and dramatically reduces reoperation risk.
When you see a patient aged 50-80 with grade I degenerative spondylolisthesis (3-14 mm), stable on flexion-extension films, and symptomatic stenosis, the default should be laminectomy plus instrumented fusion if the patient can tolerate the increased blood loss and operative time. For elderly or medically frail patients (ASA III or higher, osteoporosis), the tradeoff shifts: decompression alone is a legitimate option, but counsel the patient that roughly 1-in-3 will need reoperation for instability.
All reoperations in the decompression-alone group were at the index level for instability, while all reoperations in the fusion group were at adjacent levels — a reminder that fusion trades index-level instability risk for adjacent-segment disease risk. The SLIP trial should be read alongside the contemporaneous Swedish RCT (Forsth 2016, same NEJM issue), which found no benefit of fusion for lumbar stenosis without spondylolisthesis, reinforcing that the fusion indication is specific to the spondylolisthesis subset.
The SLIP trial is the first RCT directly comparing laminectomy plus instrumented fusion versus laminectomy alone for grade I degenerative lumbar spondylolisthesis with stenosis. It answers whether adding fusion to decompression produces superior outcomes — and at what cost.
For years, surgeons debated whether fusion was truly necessary on top of decompression for stable grade I spondylolisthesis, with only retrospective and non-randomized data (including Herkowitz's influential 1991 series) pointing toward fusion. The SLIP trial finally provides class I evidence: fusion wins on quality of life and dramatically reduces reoperation risk.
When you see a patient aged 50-80 with grade I degenerative spondylolisthesis (3-14 mm), stable on flexion-extension films, and symptomatic stenosis, the default should be laminectomy plus instrumented fusion if the patient can tolerate the increased blood loss and operative time. For elderly or medically frail patients (ASA III or higher, osteoporosis), the tradeoff shifts: decompression alone is a legitimate option, but counsel the patient that roughly 1-in-3 will need reoperation for instability.
All reoperations in the decompression-alone group were at the index level for instability, while all reoperations in the fusion group were at adjacent levels — a reminder that fusion trades index-level instability risk for adjacent-segment disease risk. The SLIP trial should be read alongside the contemporaneous Swedish RCT (Forsth 2016, same NEJM issue), which found no benefit of fusion for lumbar stenosis without spondylolisthesis, reinforcing that the fusion indication is specific to the spondylolisthesis subset.