Percutaneous Endoscopic Lumbar Discectomyfor L5–S1 Disc Herniation: Transforaminalversus Interlaminar Approach

Background: Percutaneous endoscopic lumbar discectomy (PELD) is a minimally invasive spinal technique. The unique anatomic features of the L5–S1 space include a large facet joint, narrow foramen, small disc space, and a wide interlaminar space. PELD can be performed via 2 routes, transforaminal (TF-PELD) or interlaminar (IL-PELD). However, it is questionable that the decision of the endoscopic route for L5–S1 discs only depends on the surgeon’s preference and anatomic relation between iliac bone and disc space. Thus far, no study has compared TF-PELD with IL-PELD for L5–S1 disc herniation. Objective: The goal of this study was to compare the radiologic features and results of TF-PELD and IL-PELD. We have clarified the patient selection for the PELD route for L5–S1 disc herniation. Study Design: Retrospective evaluation. Methods: Thirty consecutive patients each were treated with TF-PELD and IL-PELD for L5– S1 disc herniation in 2 institutes, respectively. Radiological assessments were performed pre- and postoperatively. The disc type, disc size, location, migration, disc height, foraminal height, iliolumbar angle, iliac height, and interlaminar space were analyzed. Clinical data were compared with a 2-year follow-up period. Pre- and postoperative pain was measured using a visual analog scale (VAS; 0 – 10) and functional status was assessed using the Oswestry Disability Index (ODI; 0 – 100%) and the time to return to work. Results: In the 2 groups, the mean VAS scores for back and leg pain, as well as the ODI, were significantly improved. The mean time to return to work was 4.9 weeks with TF-PELD and 4.4 weeks with IL-PELD. Incomplete removal, resulting in the need for subsequent open surgery, occurred in one case (3.3%) of TF-PELD and in 2 cases (6.6%) of IL-PELD. Postoperative dysesthesia developed in 2 patients (6.7%) after IL-PELD; however, there was no dysesthesia after TF-PELD. Recurrence occurred in 3.3% with TF-PELD and in 6.7% with IL-PELD during the 2-year follow-up. A significant difference between groups was demonstrated in terms of disc type, location, and migration. The prevalence of axillary disc herniation (20 cases, 66.7%) was higher than that of shoulder disc herniation (10 cases, 33.3%) in the IL-PELD group. On the other hand, in the TF-PELD group, shoulder disc herniation (20 cases, 66.7%) was more prevalent than the axillary type (10 cases, 33.3%; P = 0.01). A higher number of patients in the TF-PELD group had central disc herniation (10 cases, 33.3%) compared with that in the IL-PELD group (2 cases, 6.7%; P = 0.01). Eleven cases (36.7%) of high grade migration were removed using IL-PELD and one case (6.7%) was removed using TF-PELD (P = 0.01). TF-PELD was used to remov only 3 cases of recurrent disc herniation. There were no significant differences of radiologic parameters between the iliac bone and L5–S1 disc space between the 2 groups. Limitations: This study has a relatively small sample size and a short follow-up period. Conclusion: This study demonstrated that TF-PELD is preferred for shoulder type, centrally located, and recurrent disc herniation, while IL-PELD is preferred for axillary type and migrated discs, especially those of a high grade. Key words: PELD, L5-S1 disc herniation, transforaminal, interlaminar