# Interlaminar Versus Transforaminal Full-Endoscopic Lumbar Discectomy for L4–L5 Disc Herniation: Operative Time, Radiation Exposure, Complications, and Learning Curve

## TL;DR

This study compares two endoscopic techniques for treating L4-L5 disc herniation, finding similar long-term outcomes but differences in learning curve and radiation exposure.

## Contribution

The study provides a detailed comparison of interlaminar and transforaminal endoscopic discectomy techniques at the L4-L5 level, focusing on learning curves and radiation exposure.

## Key findings

- Both IELD and TELD showed significant and sustained improvements in patient-reported outcomes.
- TELD had shorter operative times after proficiency was achieved and was increasingly performed under conscious analgesia.
- TELD required higher radiation exposure during early adoption and remained numerically higher than IELD in later phases.

## Abstract

Background

L4-L5 disc herniation is a common cause of radiculopathy, yet the optimal full-endoscopic lumbar discectomy approaches: interlaminar endoscopic lumbar discectomy (IELD) or transforaminal endoscopic lumbar discectomy (TELD), remain debated due to level-specific anatomical constraints. This study compared operative efficiency, radiation exposure, complications, and clinical outcomes between IELD and TELD at the L4-L5 level.

Methods

A retrospective analysis of 131 consecutive L4-L5 full-endoscopic discectomies (42 IELD, 89 TELD) performed between 2021 and 2023 was conducted. Operative time, fluoroscopic dose-area product, anesthesia type, complications, and patient-reported outcomes (VAS, ODI) were recorded at baseline, 3 months, and 12 months. Temporal trends and learning-curve patterns were evaluated.

Results

A marked shift from IELD to TELD occurred over the study period, with TELD accounting for 90% of cases by 2023, and conscious analgesia was used in 94%. Operative time improved for both techniques, plateauing at 47 minutes for IELD and 42 minutes for TELD. Radiation exposure declined substantially for both approaches, decreasing from 160 to 120 µGym² for IELD and from 280 to 180 µGy·m² for TELD; however, TELD remained numerically higher than IELD in the late phase. All complications (five total) occurred early in the study period, with none recorded after 2022. Both approaches produced significant improvements in VAS and ODI scores, with comparable long-term clinical outcomes between groups.

Conclusions

Both IELD and TELD produced significant and sustained improvements in VAS and ODI, with no differences in long-term clinical outcomes. TELD showed a steeper learning-curve pattern and shorter operative times after proficiency was achieved, and it was increasingly performed under conscious analgesia. Fluoroscopy dose declined substantially over time for both approaches; however, TELD required higher radiation exposure during early adoption and remained numerically higher than IELD in late phases. Approach selection at L4-L5 should therefore prioritize anatomy, surgeon experience, and perioperative goals rather than expectations of superior long-term outcomes.