The Effect and Feasibility Study of Transforaminal Percutaneous Endoscopic Lumbar Discectomy Via Superior Border of Inferior Pedicle Approach for Down-Migrated Intracanal Disc Herniations

Transforaminal percutaneous endoscopic lumbar discectomy (PELD) is gradually regarded as an effective alternative to posterior open surgery. However, migrated herniations bring a great technical challenge even for experienced surgeons due to the absence of the appropriate approaching guideline. We aimed to describe a safe and effective approaching technique for the removal of down-migrations on the basis of the clinical outcomes and complications compared with the conventional approaching method. A total of 45 patients recommended to single-level PELD with foraminoplasty were randomly divided into 2 groups, group A received foraminoplasty via upper border of inferior pedicle, group B was approached through the common transforaminal route. The clinical outcomes were evaluated by Visual Analog Scale (VAS) for leg pain and Oswestry Disability Index (ODI) scores. Then participants were classified into 2 types of migrations (high-grade and low-grade) based on the extent of migration presented on preoperative magnetic resonance imaging (MRI). The various comparisons between the 2 surgical techniques were analyzed. The postoperative VAS and ODI scores significantly decreased in both of the 2 groups after surgery (P < 0.001). The follow-up continued 1 year. With increasing length of follow-up, the disparities in clinical outcomes between the 2 groups were gradually narrowing and there was no significant difference at the end of follow-up (P = 0.32; P = 0.46). There were no differences in the operation time and duration of hospital stay (P = 0.36; P = 0.08). The highly migration group in group B showed a significant longer operation time (P = 0.02), but the extent of migration did not have a significant influence on the operation time in group A with the modified approach (P = 0.19). There were no apparent approach-related complications in group A during the procedure and follow-up period. Foraminoplastic-PELD via upper border of inferior pedicle can serve as a safe and effective minimally invasive technique for removal of down-migrated herniations. Furthermore, it is essential to identify the radiologic characteristics so as to choose the most appropriate approaching technique.