Full-endoscopic lateral recess decompression: How much space do we need?

Purpose: To explore the relationship between intraoperative assessments made during full-endoscopic lateral recess decompression and the resulting clinical and radiographic outcomes. Methods: This was a prospective cohort study. Intraoperative measurements of the distance between the nerve root and the medial part of the facet joint were used to categorise patients into two groups: those with a space > 3.5 mm and those with a space < 3.5 mm after decompression. Clinical outcomes were evaluated using the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS) for back and leg pain at baseline and at 1, 3, 6, and 12 months postoperatively. Magnetic resonance imaging (MRI) scans were reviewed to assess the grading of lateral recess stenosis pre-operatively and post-operatively. Statistical analyses used t-tests and Chi-square tests. Results: Sixty-eight patients underwent interlaminar endoscopic decompression. The cohort was divided into two groups: 34 patients with a decompressed space > 3.5 mm and 34 patients with a space < 3.5 mm. Significant improvements were observed in all clinical outcomes for both groups, including VAS scores for back and leg pain and ODI scores postoperatively (P < 0.0001) with no significant differences at the 1, 3, 6, and 12-month follow-ups between the two groups. Radiographic assessments indicated a significant improvement in lateral recess stenosis in the > 3.5 mm group (P = 0.026). Conclusion: The intraoperative space between the nerve root and the medial part of the facet joint should exceed 3.5 mm during full-endoscopic decompression to ensure improved clinical outcomes and postoperative radiographic results. Faculty of Medicine, Chulalongkorn University Institutional Review Board Certificate of Full Board Approval No. 0335/2025. Thai Clinical Trials Registry ID TCTR20241219004.