2.7. Creating the Working Space
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I begin creating the working space for a left-sided interlaminar BESS/UBE approach by reestablishing bony landmarks and stable triangulation.
Initial orientation and triangulation
After introducing the endoscope through the viewing portal, I locate the RF electrode with a 5 mm working tip introduced through the working portal. For the left-sided approach described here, the meeting point of the endoscope and instrument is the lamina of the cranial vertebra. I use the bone surface as the main landmark at this stage.
First, I feel and see the bone!
If the bony landmark has not been identified, I do not advance the instrument deeper blindly: I first restore orientation and visibility of its tip. I do not consider the ligamentum flavum a mechanical stop that permits forceful advancement. In revision procedures, I take altered anatomy and scar adhesions into account.
Exposing bony landmarks
I then use the RF electrode in ablation mode to expose the laminae of the cranial and caudal vertebrae and the inferior articular process of the cranial vertebra. After exposing the bony landmarks, I remove excess soft tissue over the ligamentum flavum with a shaver fitted with a Tomcat or Aggressive Plus blade, or continue using the RF electrode in ablation mode.
At this stage, I clearly visualize the following landmarks:
- the lamina and base of the spinous process of the cranial vertebra;
- the inferior articular process of the cranial vertebra;
- the lamina and base of the spinous process of the caudal vertebra;
- the boundaries of the interlaminar space and the ligamentum flavum.
I remove soft tissue under endoscopic visualization. When using the RF electrode and shaver, I keep the working part of the instrument continuously in view; at this stage, I preserve the deep layer of the ligamentum flavum as a protective barrier. I limit the extent of exposure to what is needed for the planned approach.
Criteria for an established working space
I consider the working space established when the necessary anatomical landmarks have been identified, the endoscope and instrument move without obstructing each other, and clear visibility, controlled hemostasis, and free irrigation fluid outflow are maintained. I do not compensate for impaired outflow by increasing irrigation pressure.
References
1. Park DK, Weng C, Zakko P, Choi DJ. Unilateral Biportal Endoscopy for Lumbar Spinal Stenosis and Lumbar Disc Herniation. JBJS Essent Surg Tech. 2023;13(2):e22.00020. DOI: 10.2106/JBJS.ST.22.00020.
2. Choi CM, Chung JT, Lee SJ, Choi DJ. How I do it? Biportal endoscopic spinal surgery (BESS) for treatment of lumbar spinal stenosis. Acta Neurochir (Wien). 2016;158(3):459–463. DOI: 10.1007/s00701-015-2670-7.
3. Zhang Q, Wei Y, Wen L, Tan C, Li X, Li B. An overview of lumbar anatomy with an emphasis on unilateral biportal endoscopic techniques: A review. Medicine (Baltimore). 2022;101(48):e31809. DOI: 10.1097/MD.0000000000031809.
4. Park J, Ahn DK, Choi DJ. Treatment Concept and Technical Considerations of Biportal Endoscopic Spine Surgery for Lumbar Spinal Stenosis. Asian Spine J. 2024;18(2):301–323. DOI: 10.31616/asj.2023.0409.
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