A Comparative Study of the Efficacy of Unilateral Dual-Channel Endoscopic Targeted Resection of the S1 Superior Articular Process Tip versus MIS-TLIF in the Treatment of High-Level L5-S1 Extremely Lateral Disc Prolapse

Technical Summary: UBE vs. MIS-TLIF for High-Level L5-S1 Lateral Disc Herniation

Problem Statement
The treatment of extreme lateral lumbar disc herniation (EFLDH) at the L5-S1 level, particularly in patients with a "high iliac crest" (where the iliac crest extends beyond the midpoint of the L5 pedicle), presents a significant surgical challenge. In these anatomical variants, conventional transforaminal endoscopic approaches are physically obstructed by the iliac crest, forcing steep puncture angles that increase the risk of nerve root injury and reduce success rates. Conversely, traditional minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), while effective, involves extensive muscle dissection, facet joint resection, and permanent fusion. This results in greater trauma, loss of segmental mobility, and potential long-term complications such as adjacent segment disease. There is a lack of large-scale data comparing a motion-preserving endoscopic decompression technique against fusion for this specific complex pathology.

Methodology
This retrospective cohort study analyzed 450 patients treated between July 2022 and December 2024 at the General Hospital of Northern Theater Command. Patients were divided into two groups based on the surgical intervention performed by the same senior surgeon:

• UBE Group (n=300): Underwent Unilateral Biportal Endoscopy (UBE) with targeted resection of the tip of the S1 superior articular process (SAP) for simple decompression. The procedure utilized a posterior-to-anterior working trajectory through two small incisions (1 cm each) to bypass the iliac crest obstruction. The core technique involved using a diamond burr to resect 5–8 mm of the SAP tip to release the "pincer-like" compression on the L5 exit nerve root, followed by removal of the herniated disc.
• MIS-TLIF Group (n=150): Underwent standard minimally invasive transforaminal lumbar interbody fusion involving partial facet resection, discectomy, cage implantation, and percutaneous pedicle screw fixation.

Key Contributions

• Anatomical Solution: The study demonstrates that the UBE posterior-to-anterior trajectory effectively circumvents the physical obstruction of a high iliac crest, a limitation that hinders standard percutaneous endoscopic lumbar discectomy (PELD).
• Motion Preservation Strategy: It validates a "de-fusion" approach where targeted resection of only the SAP tip (approx. 6.8 mm) achieves adequate decompression while preserving the structural integrity and load-bearing function of the majority of the facet joint.
• Large-Scale Comparison: This is the first study to systematically compare UBE decompression against MIS-TLIF in a large cohort (450 patients) specifically for L5-S1 extreme lateral herniation with high iliac crests, moving beyond small case reports.

Results

• Perioperative Outcomes: The UBE group demonstrated significantly superior perioperative metrics compared to MIS-TLIF, including:
  • Intraoperative blood loss: 35.6 mL vs. 185.3 mL.
  • Postoperative hospital stay: 3.2 days vs. 5.8 days.
  • Fluoroscopy usage: 4.2 times vs. 8.5 times.
  • Postoperative drainage: 28.4 mL vs. 156.7 mL.
  • Note: Operative time was slightly longer in the UBE group (68.5 min vs. 58.2 min).
• Clinical Efficacy:
  • Long-term: At 12 months and final follow-up, there were no statistically significant differences between the two groups in Visual Analog Scale (VAS) scores for back/leg pain, Oswestry Disability Index (ODI), or modified MacNab excellent/good rates (94.0% for UBE vs. 92.7% for MIS-TLIF).
  • Early Recovery: The UBE group showed significantly faster pain relief and functional recovery in the early postoperative period (3 days to 3 months).
• Radiographic Findings: Both groups achieved significant enlargement of the intervertebral foramen (approx. 51–54% increase in area). Dynamic X-rays confirmed that the UBE group maintained segmental stability without exceeding instability thresholds (angle change <10°, displacement <3 mm), whereas the MIS-TLIF group showed significantly reduced mobility due to fusion.
• Safety: The overall complication rate was lower in the UBE group (4.7%) compared to MIS-TLIF (8.0%), though the difference was not statistically significant (P=0.158). UBE complications were primarily transient nerve irritation, while MIS-TLIF included risks related to internal fixation and incisional infection.

Significance and Claims
The authors claim that for L5-S1 extreme lateral disc herniation complicated by a high iliac crest, UBE-guided targeted resection of the SAP tip is a viable and superior alternative to MIS-TLIF for patients without pre-existing instability. The study concludes that:

1. Comparable Long-Term Efficacy: Simple decompression via UBE achieves long-term clinical outcomes equivalent to fusion.
2. Minimally Invasive Advantage: UBE offers significant benefits in reducing trauma, blood loss, radiation exposure, and hospital stay, while facilitating faster early recovery.
3. Functional Preservation: By avoiding fusion, the technique preserves segmental mobility and potentially reduces the risk of adjacent segment degeneration.
4. Paradigm Shift: The authors propose upgrading UBE from an "alternative option" to a "preferred option" for this specific anatomical presentation, redefining the treatment paradigm to prioritize "non-fusion and functional preservation."

The paper acknowledges limitations, including its retrospective nature, single-center design, and a follow-up period (average 18.5 months) that may be insufficient to assess very long-term fusion-related complications, recommending future prospective randomized controlled trials.