Pain Ther. 2026 Aug 1. doi: 10.1007/s40122-026-00872-5. Online ahead of print.
ABSTRACT
INTRODUCTION: Persistent postoperative low back pain remains a concern after unilateral biportal endoscopic (UBE) surgery, but the impact of surgery-related interspinous ligament edema is unclear. This study investigated whether magnetic resonance imaging (MRI)-detected interspinous ligament region edema (ISLRE) was associated with delayed pain recovery and persistent postoperative low back pain after UBE surgery.
METHODS: This retrospective cohort study included patients who underwent single-level UBE surgery between October 2021 and October 2024. On the basis of MRI within 3 days postoperatively, ISLRE was graded as grade 0 (no/minimal edema), grade 1 (localized edema), or grade 2 (diffuse or confluent edema involving most of the operated interspinous region). Clinical outcomes included visual analogue scale scores for low back pain (VAS-LBP), Oswestry disability index (ODI), and persistent postoperative low back pain, defined as 12-month VAS-LBP > 3. Multivariable linear and logistic regression analyses were performed to assess independent associations, and linear mixed-effects modeling was used to evaluate longitudinal pain recovery trajectories.
RESULTS: A total of 245 patients were included (grade 0: n = 117; grade 1: n = 74; grade 2: n = 54). Interobserver agreement for MRI grading was substantial (κ = 0.802). At 12 months, VAS-LBP scores increased progressively across edema grades (1.66 ± 1.20, 2.34 ± 1.45, and 3.54 ± 1.65 for grades 0-2, respectively; P < 0.001), while persistent postoperative low back pain occurred in 21.4%, 41.9%, and 68.5% of patients, respectively (P < 0.001). Compared with grade 0 edema, grade 2 edema was independently associated with higher 12-month pain scores (β = 1.78, 95% confidence interval [CI] 1.34-2.22; P < 0.001) and more than eightfold increased odds of persistent postoperative low back pain (odds ratio [OR] 8.90, 95% CI 4.01-19.76; P < 0.001). Linear mixed-effects modeling demonstrated significantly delayed pain recovery trajectories in higher-grade edema groups. Although statistically significant, the magnitude of ODI differences at 12 months was below the minimal clinically important difference (MCID) threshold, suggesting limited clinical relevance.
CONCLUSIONS: The extent of postoperative ISLRE, particularly grade 2 edema, may be useful for postoperative risk stratification and targeted patient management after UBE surgery.
PMID:42542473 | DOI:10.1007/s40122-026-00872-5
