Degenerative spondylolisthesis, where one vertebra slips slightly forward over the one below it, is one of the most common reasons patients hear the word fusion. The logic sounds airtight: the bone has moved, so bolt it down. But for stable, low-grade slips, a growing body of published research asks a different question: what if you relieve the nerve compression through a small tube and leave the spine alone? Here is what five recent studies found.
Study 1: 43 patients, one year on, 95 percent good or excellent
A 2024 study in Neurosurgery Practice followed 43 patients with spinal stenosis and grade I spondylolisthesis treated with full-endoscopic decompression alone, no fusion, no hardware. At a minimum of one year, 95 percent rated their outcome good or excellent. Meaningful slip progression appeared in just 7 percent, and only one patient, about 2 percent, went on to need a fusion. Strikingly, the number of patients with radiologic instability fell after surgery, from 22 to 12.
Study 2: stability preserved in 96.9 percent of cases
A 2025 cohort in Scientific Reports tracked 32 patients with grade I slips for 12 months after endoscopic decompression through the interlaminar window. Leg pain scores dropped from 7.1 to 1.4 out of 10, disability scores fell by more than two thirds, and exactly one patient developed new radiographic instability. Segmental stability was preserved in 96.9 percent of cases.
Study 3: the slip does not change the result
A 2026 study in Brain and Spine, the journal of the European neurosurgical societies, compared outcomes in 36 patients and found that having a stable low-grade slip did not worsen the results of endoscopic decompression. The slip percentage was statistically unchanged at final follow-up, while the space available for the nerves nearly doubled.
Study 4: two years out, the spine holds
A 2021 study in Pain Research and Management followed 28 patients with stable degenerative spondylolisthesis for an average of 25 months after interlaminar endoscopic decompression. Pain and disability scores improved significantly, disc height and slip percentage showed no significant change, and one patient ultimately required fusion.
Study 5: early evidence at higher grades
Most of this research covers grade I slips, the mildest kind. A 2025 case series in the Journal of Surgical Case Reports pushed further: three patients over age 75 with stable grade II and III slips, treated with facet-sparing endoscopic decompression alone. All went home the same day and maintained their improvement without slip progression at 6 to 18 months. Three patients is a starting point, not a conclusion, but it shows where surgeons are testing the boundary.
What this evidence is, and what it is not
Honesty about evidence quality matters more in medicine than anywhere else. These are cohort studies and case series, not large randomized trials. They involve carefully selected patients: stable slips, mostly grade I, with leg-dominant symptoms and imaging that matches the complaint. They do not show that fusion is obsolete, and they do not apply to unstable slips, higher grades in most patients, deformity, or fractures, where fusion remains the standard of care.
What they do support is narrower and still important: if your spondylolisthesis is stable and low grade, decompression alone through an endoscope is a legitimate, studied option, and a surgeon proposing fusion should be able to explain why your spine specifically needs the hardware. That conversation starts with your imaging.