TO THE EDITOR
Re: Nie H, Zeng J, Song Y, et al. Percutaneous Endoscopic Lumbar Discectomy for L5-S1 Disc Herniation Via an Interlaminar Approach Versus a Transforaminal Approach: A Prospective Randomized Controlled Study With 2-Year Follow Up. Spine (Phila Pa 1976). 2016 Oct;41 Suppl 19:B30-B37
We read with great interest the prospective, randomized, controlled study by Nie H et al1 that compared the results between percutaneous endoscopic lumbar discectomy for L5–S1 disc herniation through an interlaminar approach (PEID) and that through a transforaminal approach (PETD). This study attempted to compare the two approaches for their surgical effects and advantages, and emphasized the PEID approach as more suitable for intracanal L5–S1 disc herniation because the PETD approach required higher punctuation techniques and conferred greater radiation exposure. However, several flaws in the study design need consideration. First, it is not a rigorously single-blind randomized controlled trial, as the patients were aware of the surgical procedure. Moreover, power calculation was not performed to justify the sample size in each group that may result in selection bias. Second, the impact of different types of disc herniations on clinical outcomes should be analyzed respectively. PETD in prolapsus and sequestered disc herniations had high rates of operative failure.2 Nevertheless, PETD still has the following advantages over PEID in the remaining intracanal disc herniations: (A) enables approach to the central extruded disc and removal of the disc fragment without neural retraction, thereby minimizing iatrogenic neural injury; (B) requires conscious sedation rather than general anesthesia as a “patient reporting” safeguard against nerve root injury intraoperatively, which could contribute to rapid rehabilitation and reduced hospital stay; and (C) involves the transforaminal access and thus can reduce traumatization of the ligamentum flavum and diminish epidural scarring postoperatively. Third, spine surgeon's experience and updated instruments have been developed recently. The limitations in surgical access, such as a narrow neural foramen and/or a high iliac crest, are no longer contraindications of PETD, which could be solved well using a foraminoplasty technique or patient lateral positioning by using a “broken” operating table.3 Although PETD confers greater radiation exposure, the radiation doses for PETD were well within the safe ranges. From our own perspective, the PEID and PETD approaches offer therapeutic supplementation or alternative, and the optimal choice for lumbar discectomy should depend on the location of the herniated disc fragment, not the surgeon's preference or anatomic relation between iliac bone and disc space.