A Novel “Flying Owl Sign” to Predict Favorable Patient-Reported Outcomes Following Full-Endoscopic Lumbar Discectomy

Study designA retrospective case-control design.ObjectiveThis study proposed a novel MRI finding termed the "Flying owl sign" to characterize a specific type of lumbar disc herniation (LDH) and examined the correlation between this image finding and the patient-reported outcomes (PROs) following full-endoscopic lumbar discectomy.MethodsA retrospective case-control study was conducted involving LDH patients who underwent full-endoscopic lumbar discectomy in our institution. The propensity score matching method was employed to categorize patients into a "Flying owl sign" group and a control group. Multivariable logistic regression analysis was performed to evaluate the relationship between the "Flying owl sign" and the PROs.ResultsA total of 431 patients who underwent full-endoscopic lumbar discectomy between November 2015 and October 2022 in our institution were enrolled. After a mean follow-up of 32.24 ± 8.60 months, 377(87.47%) patients were satisfied (NASS score of 1 or 2). 10.21% (44/431) patients exhibited "Flying owl sign", and experienced significantly greater improvements in VAS(<i>P</i> = 0.022), higher patient satisfaction index (<i>P</i> = 0.016), and a lower incidence of residual low back pain (<i>P</i> = 0.013) than the control group. Propensity score matching produced a final study cohort of 88 patients. The multivariate analysis revealed that "Flying owl sign" was a protective factor for satisfaction (OR = 3.544, <i>P</i> = 0.018).ConclusionThe presence of "Flying owl sign" reflected a specific LDH type, which was the combination of giant disc herniation and the integrity of the posterior longitudinal ligament. "Flying owl sign" correlated with improved postoperative efficacy and satisfaction in patients with LDH, and may contribute to reducing residual low back pain rates.