Is Full Endoscopic Lumbar Discectomy Less Invasive Than Conventional Surgery? A Randomized MRI Study

Background: In the present randomized prospective study, we compared the surgical invasiveness using a quantitative volumetric analysis of postoperative paravertebral muscle signal intensity changes between transforaminal full endoscopic lumbar discectomy (FELD) and open discectomy (OD). Methods: We prospectively collected the data from 50 patients with a single-level lumbar foraminal herniation, invalidating radicular pain, and adequate imaging studies available (postoperative magnetic resonance imaging [MRI] <24 hours). These patients had been randomly assigned to FELD (n = 25) or OD (n = 25). Data were collected on age, sex, leg and back pain, complications, and follow-up time. Muscle segmentations were performed manually using 3DSlicer software on postoperative isovolumetric T1-weighted contrast-enhanced and T2-weighted short tau inversion recovery MRI scans. Both sequences were processed using multiplanar reconstruction in orthogonal planes. The clinical and demographic characteristics and volumetric data were then compared between the 2 groups. Results: We found a higher mean volume of paravertebral muscle signal alterations among the OD-treated patients in both T2-weighted short tau inversion recovery MRI (P ≤ 0.001) and T1-weighted contrast-enhanced MRI (P ≤ 0.001) scans than among the FELD-treated patients. No differences were found between the median preoperative and postoperative leg pain between the 2 groups (P = 1.000). The median scores for postoperative back pain were significantly lower for the FELD group (P ≤ 0.001), as was the median interval from surgery to autonomous mobilization (P = 0.001). Conclusions: We found a significant difference in signal intensity of the paravertebral muscles between the FELD and OD groups, reflective of the minor surgical invasiveness of endoscopic discectomy. FELD resulted in less trauma to the paraspinal muscles, possibly also reducing inflammatory cytokine release and, therefore, is a valuable tool for spinal surgeons.