Endoscopic Lumbar Discectomy

Summary of Key Points

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The endoscope provides unique capabilities for visualization in spine surgery.
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Numerous applications of the endoscope are available in spine surgery; the least invasive of these is working channel endoscopy, which uses a 7-mm port and allows for discectomy to be performed.
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There is a robust literature demonstrating the effectiveness of this approach, but the effective treatment of central stenosis treatment remains challenging.
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Future applications of endoscopy will include the ability to perform interbody fusion and treat spondylolisthesis.

Background

When patients fail all conservative treatments, surgery remains an option for relieving symptomatic neural compression. However, most patients are reluctant to undergo spine surgery given the putative risks, pain, and recovery associated with traditional spine surgery. Thus, surgeons have been in search of potential treatments that may reduce these untoward surgical sequelae. This pursuit has led to the growth in the early 2000s of minimally invasive surgery (MIS) techniques. Various new MIS techniques have thus emerged, all with the goals of reduced soft tissue destruction and retraction, less blood loss, and smaller incisions.

Endoscopy has thus grown as a technical advancement in surgery in general and spine surgery in particular. A wide variety of spine surgical methods have utilized the endoscope to advance the goals of MIS. These interventions include the following:

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Thoracoscopic discectomy
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Endoscope-assisted anterior thoracolumbar fusion
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Endoscope-assisted tubular discectomy
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Endoscope-assisted lumbar interbody fusion
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Endoscope-assisted cervical foraminotomy
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Balloon-assisted endoscopic retroperitoneal gasless interbody fusion
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Working channel lumbar discectomy

Of these procedures, working channel endoscopic discectomy has been the only procedure to gain widespread acceptance. Thus, the bulk of this chapter focuses on this procedure.

Advantages of Endoscopy

Visualization is critical to the safety and success of most surgical procedures. Options for enhancing visualization in spine surgery include loupe magnification, the operating microscope, and the surgical endoscope. The endoscope offers some unique advantages over other methods. These include use of an especially small access site, delivery of light close to the point of intervention, visualization close to the site of intervention, and the ability to visualize at various angles ( Fig. 170-1 ) other than directly forward (0 degrees). In spine surgery the target organ is deep within the body, making soft tissue damage particularly problematic. These elements make endoscopic surgery more amenable in the high-risk patient population. For example, in the morbidly obese patient population, the use of the endoscope allows patients to be treated with less tissue destruction and presents fewer problems with target organ visualization and manipulation due to depth ( Fig. 170-2 ).

Disadvantages include a substantial learning curve, as the procedures are so different than conventional surgery. The surgeon must learn how to percutaneously access the spinal canal in a safe manner. After port placement, orientation may easily be lost, leading to a failure to recognize critical anatomic landmarks. Finally, the tissues seen under the endoscope often have a different color and texture than when seen through loupes or the microscope.

Nevertheless, the advantages of reduced soft tissue damage allow endoscopic surgeries to be performed with less pain and morbidity, and many of these procedures can be done without general anesthesia and in the lateral position. Because the incision through the skin, subcutaneous tissues, and musculature is less than 8 mm in diameter, reduced damage to the soft tissue envelope compared to open surgery is obvious. This was exemplified in a study by Pan and colleagues. The investigators found that the serum C-reactive protein levels of endoscopic discectomy were 21% of open discectomy at 24 hours ; interleukin-6 (IL-6) levels were 73 times greater at 24 hours with open surgery. Hospital stays are also typically much shorter, with a high proportion of these actions being performed as outpatient procedures.

Working Channel Endoscopic Discectomy

Indications

True endoscopic lumbar discectomy is typically performed through one of two access routes. The majority of procedures are done through an oblique transforaminal approach, entering through the Kambin triangle from lateral to the facet ( ). Paracentral discs at L4-5 and L5-S1 can also be advanced through an interlaminar approach that involves puncturing the ligamentum flavum and accessing the disc just lateral to the thecal sac but medial to the facet joint. This approach can be more difficult to perform, and thus this report will focus on the transforaminal approach.

The transforaminal method offers a complementary approach to traditional microdiscectomy. It allows for a better access to far lateral and foraminal pathology and can also be used for revision cases where paracentral scar tissue may prove problematic. However, this lateral approach also makes removal of more central pathology more challenging. Hence, the interlaminar approach was developed ( Fig. 170-3 ).