Percutaneous Endoscopic Decompression for Lumbar Central and Lateral Recess Spinal Stenosis: A Combined Uni-Portal and Bi-Portal Approach.

Abstract

Background: Endoscopic decompression of lumbar spinal stenosis has been gaining popularity as the least invasive of several minimally invasive surgical treatment options. This procedure offers similar outcomes to those of conventional open procedures; however, endoscopic procedures are technically demanding and involve a substantial learning curve. The typical endoscopic approach is a "uni-portal" approach that utilizes a special spinal endoscope and endoscopic instruments. However, a "bi-portal" approach has been developed more recently, which utilizes a regular arthroscope and the same type of instruments that are utilized in open spine surgery.

Description: The patient is placed in a prone position under general anesthesia with electromyographic neuromonitoring. The primary portal is made at the interlaminar space with use of an obturator and a working cannula. The side of the approach is chosen according to the side of symptoms and radiographic compression. A 15°-angle, 10-mm external diameter spinal endoscope is introduced through the cannula, and the interlaminar space is exposed with use of a radiofrequency bipolar probe. Cranial and caudal laminectomies are performed with use of a 5-mm endoscopic high-speed burr or endoscopic osteotomes. A 5- to 7-mm accessory portal can be created 2 to 2.5 cm caudally (for the left side) or cranially (for the right side) on the same line as the primary portal in order to enable use of a short-distance dissector, curets, and/or osteotomes. Decompression is performed at the central and ipsilateral lateral recess with use of an endoscopic drill, various sizes of Kerrison rongeurs, and curets. Finally, the contralateral lateral recess is accessed by tilting the working cannula, and decompression is performed until the contralateral traversing nerve root and medial border of the caudal pedicle are exposed.

Alternatives: Alternative surgical treatments include conventional open microscopic laminectomy and decompression and other minimally invasive surgical options involving the use of a tubular retractor or similar minimally invasive retractor systems.

Rationale: The development of endoscopic spine surgery has expanded indications from simple lumbar discectomy to lumbar central, foraminal, and extraforaminal stenosis, as well as revision surgery. However, the endoscopic approach to lumbar spinal stenosis is challenging and has not been widely adopted because of the steep learning curve and technical difficulty. A fully endoscopic, uni-portal approach is the least invasive option for lumbar decompression because all access and decompression procedures are performed within the limited space inside the working cannula. However, this "full-endoscopic" approach may limit the access angle to the surgical field because the working channel is fixed by the trajectory of the endoscope. Also, spinal endoscope-specific, long, small-diameter instruments are needed for use in the long, narrow endoscopic working channel. In contrast, an arthroscopic bi-portal approach enables the use of a regular arthroscope and surgical instruments. This approach offers variable working angles and the versatility of various shorter- and larger-diameter instruments, which can make the procedure more efficient, similar to open surgeries. However, a bi-portal approach requires the creation of a separate working portal because the arthroscopic portal does not have a working channel in it. Also, more soft-tissue dissection is needed to create a submuscular working space. Uni-portal and bi-portal approaches can be combined as needed to take advantage of both options.

Expected outcomes: Compared with open surgery or other minimally invasive surgical approaches to lumbar spinal stenosis, the mid- and long-term clinical outcomes and complication rates are similar or identical. Endoscopic decompression provides superior short-term outcomes in terms of back pain (as measured on a visual analog scale), duration of hospital stay, and return to work. The main disadvantage is the technical difficulty of the approach.

Important tips: For a left-side approach, the main portal is made on the lower border of the cranial lamina on a fluoroscopic anteroposterior view. An accessory portal can be made on the vertical line over the primary portal, approximately 2 to 2.5 cm caudal. For a right-side approach, the main portal is on the upper border of the caudal lamina, and the accessory portal is approximately 1 inch cranial (if the surgeon is right-handed). The accessory portal enables the use of various short, strong instruments and expedites the procedure compared with the fully endoscopic uni-portal approach.Irrigation hydrostatic pressure provides natural dura retraction and some bleeding control in muscles, the bone surface, and the epidural space. In general, the pressure is set to 45 mmHg.Bleeding control is one of the time-limiting factors. Before creating the portal(s), injection of 20 to 30 mL of 0.25% bupivacaine with epinephrine 1:100,000 around the facet joint and cranial and caudal laminae can minimize muscle bleeding. Bone surface bleeding from drilling can be controlled through the use of radiofrequency bipolar cautery, bone wax, and low-speed reverse-direction drilling over the cancellous bleeding foci.

Acronyms and abbreviations: BMI = body mass indexCT = computed tomographyEQ5D = EuroQol-5 DimensionMRI = magnetic resonance imagingODI = Oswestry Disability IndexVAS = visual analog scaleOR = operating roomAP = anteroposteriorPO = postoperative.