Percutaneous endoscopic lumbar discectomy for L5-S1 disc herniation: transforaminal versus 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.