Microendoscopic Posterior Decompression for L5-S1 Foraminal and Extraforaminal Lesions: A Comparative Study of...

Introduction Foraminal and extraforaminal nerve root compression at the lumbosacral junction (L5/S1) is an underrecognized cause of lumbar radiculopathy. The L5 nerve root traverses a narrow space between the transverse process and the sacral ala and may be compressed by migrated disc fragments or fibro-osseous structures. Although lumbar disc herniation (LDH) and foraminal or extraforaminal stenosis (FES) at L5/S1 are often evaluated together, their mechanisms differ. This study aimed to compare postoperative clinical outcomes between patients with L5-S1 foraminal and extraforaminal disc herniation and those with stenosis who underwent microendoscopic posterior decompression. Materials and methods This retrospective observational study included consecutive patients who underwent microendoscopic posterior decompression for isolated L5/S1 foraminal or extraforaminal lesions between 2015 and 2019. All procedures were performed by a single surgeon. Patients were classified into the LDH or FES group based on preoperative MRI and CT findings, with final confirmation by intraoperative findings. Patients with previous lumbar surgery at the index level, radiographic instability or spondylolisthesis requiring fusion, and multilevel symptomatic lesions were excluded. Functional outcomes were assessed using the Oswestry Disability Index (ODI), with achievement of the minimal clinically important difference (MCID; ≥13-point improvement) at 12 months as the primary endpoint. Leg and low back pain were assessed using the numeric rating scale (NRS). Results Forty patients completed 12-month follow-up (LDH, n = 19; FES, n = 21). ODI improvement was greater in the LDH group than in the FES group (median ΔODI, -24.4 (IQR, -36.0 to -10.9) vs. -17.8 (IQR, -22.2 to -2.2); p = 0.031). MCID achievement rates were comparable between the groups (73.7% in LDH and 61.9% in FES; p = 0.511). Improvements in leg pain and low back pain NRS did not differ significantly between the groups (p = 0.369 and p = 0.201, respectively). Conclusions Microendoscopic posterior decompression for L5/S1 foraminal or extraforaminal lesions resulted in similar rates of clinically meaningful improvement in LDH and FES. However, functional recovery was greater in LDH, suggesting that patients with FES may require different postoperative expectations regarding the degree and time course of functional recovery.