12.3. Surgical Approach
@ProfFishchenkoWe position the patient prone on a Wilson frame, creating lumbar flexion to enlarge the interspinous space. We coordinate head and trunk positioning with the anesthesiologist to maintain ventilation and venous outflow. We keep the neck neutral and avoid pressure on the eyes and abdomen. We place soft supports beneath the knees and lower legs.
The anesthesiologist determines the target blood pressure individually, considering perfusion and bleeding risk. In our practice, a systolic pressure of approximately 100 mmHg may be acceptable under appropriate clinical conditions.
We confirm the operative level under C-arm guidance before making the incision, correlating vertebral numbering with the preoperative images. We use a lateral view whenever there is doubt about the level or instrument depth, particularly in lumbarization, sacralization, or hyperlordosis. We perform an additional lateral check while placing the trocar and dilators if necessary. We check the interbody cage position radiographically during insertion.
Left-Sided Approach
For BELIF/UBE-LIF, we place the portals more laterally than for disc herniation removal or stenosis decompression, at the lateral pedicle line. We plan the cranial incision for the endoscopic portal over the lateral border of the cranial vertebral pedicle. We position the caudal working incision 2–3 cm below it, over the intervertebral disc. More cranial portal positioning facilitates endplate preparation and cage insertion.
Right-Sided Approach
If the clinical situation allows a choice of approach side, in my practice I prefer the right-sided approach: it makes endplate preparation and interbody cage insertion more convenient. I position the caudal endoscopic portal incision over the superolateral border of the caudal vertebral pedicle, and the cranial working incision 2–3 cm above it.
I prefer longitudinal incisions: they can be joined if conversion to a microsurgical approach is required. We anticipate the possibility of conversion before surgery, particularly while learning the technique.
Persistent deterioration of endoscopic visibility due to diffuse bleeding may necessitate conversion during BELIF/UBE-LIF. If a clear view of the operative field cannot be restored, conversion to a microsurgical approach is considered [5].
Endoscopic Portal
Using a pointed scalpel, we incise the skin and subcutaneous tissue. We incise the outer layer of the thoracolumbar fascia in a cruciate pattern. We sequentially insert the first and second dilators until they contact the lamina of the caudal vertebra. We separate the muscles from the bone with dilators or muscle dissectors.
We identify the bony landmarks and transition toward the interlaminar space by palpation, without advancing an instrument blindly into it. We remove the dilators and insert a trocar into the created portal tract while maintaining control of contact with bone.
Working Portal
We incise the skin and subcutaneous tissue. We incise the thoracolumbar fascia (fascia thoracolumbalis) in a cruciate pattern: after the longitudinal incision, we rotate the scalpel 90° and make a transverse incision. This facilitates free outflow of irrigation fluid.
We sequentially insert three dilators until they contact bone and bring them together with the endoscopic portal trocar at the bony landmark. We feel metal-to-metal contact by palpation.
If necessary, we perform a lateral radiographic check. We replace the trocar stylet with the scope and camera, and the working portal dilators with an RF electrode with a 5 mm working tip. The electrode must be visible on the screen; the meeting point is the lamina of the caudal vertebra.
We continuously see and feel the bony landmark. If the bone or tissue boundaries are not clearly visible, we stop manipulating and restore the view. We do not advance instruments blindly or use force to enter beneath the ligamentum flavum.
Under endoscopic video guidance, we use the RF electrode in ablation mode to expose the laminae of the cranial and caudal vertebrae and the inferior articular process. After identifying the bony landmarks, we remove excess soft tissue over the ligamentum flavum with a 5 mm shaver or continue working with the RF electrode. We do not activate the electrode in contact with neural structures; we maintain free outflow of irrigation fluid.
At the end of this stage, we clearly visualize the base of the spinous process and lamina of the cranial vertebra, the inferior articular process, and the lamina and base of the spinous process of the caudal vertebra.
References
1. Heo DH, Hong YH, Lee DC, Chung HJ, Park CK. Technique of biportal endoscopic transforaminal lumbar interbody fusion. Neurospine. 2020;17(Suppl 1):S129–S137. DOI: 10.14245/ns.2040178.089.
2. Park HJ, Shin JI, You KH, Yang JI, Kim N, Kim YH, et al. Biportal endoscopic transforaminal lumbar interbody fusion: how to improve fusion rate? Int J Spine Surg. 2024;18(5):582–588. DOI: 10.14444/8648.
3. Saugel B, Fletcher N, Gan TJ, et al; POQI XI Workgroup. PeriOperative Quality Initiative (POQI) international consensus statement on perioperative arterial pressure management. Br J Anaesth. 2024;133(2):264–276. DOI: 10.1016/j.bja.2024.04.046.
4. American Society of Anesthesiologists Task Force on Perioperative Visual Loss, North American Neuro-Ophthalmology Society, Society for Neuroscience in Anesthesiology and Critical Care. Practice advisory for perioperative visual loss associated with spine surgery 2019. Anesthesiology. 2019;130(1):12–30. DOI: 10.1097/ALN.0000000000002503.
5. Heo D.H., Park M.K., Eum J.H. Biportal Endoscopic Transforaminal Lumbar Interbody Fusion. In: Advanced Techniques of Endoscopic Lumbar Spine Surgery. Springer; 2020. P. 163–172; relevant passage: pp. 166–167. Link to the book chapter.
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