Conical working tube: a special device for endoscopic surgery of herniated lumbar discs

The instrumentation for endoscopic discectomy continues to evolve to allow for acceptable clinical outcomes and expanding applications. The authors describe their experience in using a conical working tube equipped with a guide for angular entry of the telescope to perform endoscopic discectomy in patients with lumbar disc herniation.

Fifty-one patients (38 men and 13 women) with herniated lumbar discs underwent endoscopic lumbar surgery during the past 2.5 years at the authors' institutions. A conical working tube was inserted over sequential coaxial dilators via a muscle-splitting approach. Conventional neurosurgical instruments were used in conjunction with an angled insertion telescope. Endoscopic discectomy was performed at the L1-2 (one case), L3-4 (two cases), L4-5 (32 cases), and L5-S1 (18 cases) levels. The surgical approach was bilateral in two patients: bilateral L4-5 in one, and right L4-5 and left L5-S1 in the other. The remaining patient suffered adjacent two-level (right-sided L4-5 and L5-S1) herniations. Outcome was assessed at a mean of 11 months after surgery by using modified Macnab criteria. Outcomes were excellent in 46 (90%), fair in three (6%), and poor in two patients (4%). Complications occurred in four patients and included a dural tear in one case, postoperative neurological deterioration in two, and discitis in two; in two of these patients open surgical exploration was required.

A separate angled entry of the telescope shortens the effective length of the working sheath and creates a better working space, thereby allowing greater instrument maneuverability and ability to use conventional neurosurgical instruments. In addition, use of this telescope in other endoscopic procedures reduces overall cost of instrumentation and treatment, and results are comparable to those reported in association with microscopic lumbar discectomy.