New minimally invasive discectomy technique through the interlaminar space using a percutaneous endoscope.

INTRODUCTION: The serial dilating technique used to access herniated discs at the L5-S1 space using percutaneous endoscopic discectomy (PED) via an 8 mm skin incision can possibly injure the S1 nerve root. In this paper, we describe in detail a new surgical procedure to safely access the disc and to avoid the nerve root damage. This small-incision endoscopic technique, small-incision microendoscopic discectomy (sMED), mimics microendoscopic discectomy and applies PED. MATERIALS AND SURGICAL TECHNIQUE: The sMED approach is similar to the well-established microendoscopic discectomy technique. To secure the surgical field, a duckbill-type PED cannula is used. Following laminotomy of L5 using a high-speed drill, the ligamentum flavum is partially removed using the Kerrison rongeur. Using the curved nerve root retractor, the S1 nerve root is gradually and gently moved caudally. Following the compete retraction of the S1 nerve root to the caudal side of the herniated nucleus pulposus (HNP), the nerve root is retracted safely medially and caudally using the bill side of the duckbill PED cannula. Next, using the HNP rongeur for PED, the HNP is removed piece by piece until the nerve root is decompressed. A total of 30 patients with HNP at the L5-S1 level underwent sMED. In all cases, HNP was successfully removed and patients showed improvement following surgery. Only one patient complained of moderate radiculopathy at the final visit. No complications were encountered. DISCUSSION: We introduced a minimally invasive technique to safely remove HNP at the L5-S1 level. sMED is possibly the least invasive technique for HNP removal at the L5-S1 level.