Percutaneous Endoscopic Lumbar Discectomy for L5–S1 Disc Herniation: Transforaminal versus Interlaminar Approach

Background: Percutaneous endoscopic lumbar discectomy (PELD) is a minimally invasive spinaltechnique. The unique anatomic features of the L5–S1 space include a large facet joint, narrowforamen, 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 theendoscopic route for L5–S1 discs only depends on the surgeon’s preference and anatomic relationbetween iliac bone and disc space. Thus far, no study has compared TF-PELD with IL-PELD for L5–S1disc herniation.Objective: The goal of this study was to compare the radiologic features and results of TF-PELD andIL-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- andpostoperatively. The disc type, disc size, location, migration, disc height, foraminal height, iliolumbarangle, iliac height, and interlaminar space were analyzed. Clinical data were compared with a 2-yearfollow-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 thetime to return to work.Results: In the 2 groups, the mean VAS scores for back and leg pain, as well as the ODI, weresignificantly improved. The mean time to return to work was 4.9 weeks with TF-PELD and 4.4 weekswith IL-PELD. Incomplete removal, resulting in the need for subsequent open surgery, occurred in onecase (3.3%) of TF-PELD and in 2 cases (6.6%) of IL-PELD. Postoperative dysesthesia developed in 2patients (6.7%) after IL-PELD; however, there was no dysesthesia after TF-PELD. Recurrence occurredin 3.3% with TF-PELD and in 6.7% with IL-PELD during the 2-year follow-up. A significant differencebetween groups was demonstrated in terms of disc type, location, and migration. The prevalence ofaxillary 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 highernumber of patients in the TF-PELD group had central disc herniation (10 cases, 33.3%) compared withthat in the IL-PELD group (2 cases, 6.7%; P = 0.01). Eleven cases (36.7%) of high grade migrationwere removed using IL-PELD and one case (6.7%) was removed using TF-PELD (P = 0.01). TF-PELDwas used to remov only 3 cases of recurrent disc herniation. There were no significant differences ofradiologic 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, especiallythose of a high grade.Key words: PELD, L5-S1 disc herniation, transforaminal, interlaminar