10.4. Decompression
@ProfFishchenkoEndoscopic Portal
We always hold the endoscope in the left hand and instruments in the right. For a left-sided approach, the cranial portal is endoscopic and the caudal portal is the working portal; their roles are reversed for a right-sided approach.
We use longitudinal skin incisions. We anticipate the possibility of conversion to open surgery before the procedure, particularly during training: longitudinal incisions are easier to join.
We first create the endoscopic portal. Using a pointed scalpel, we incise the skin and subcutaneous tissue; we incise the fascia in a cruciate pattern. We direct the trajectory at an angle of 20–40° toward the base of the transverse process. We sequentially insert the first and second dilators until they contact the junction of the lamina and the base of the transverse process. We separate the muscles using dilators or muscle dissectors. We palpate the bony landmarks: the dorsal part of the base of the L5 transverse process, the isthmus, and the dorsolateral part of the bases of the L5 inferior articular process and the S1 superior articular process. We avoid uncontrolled advancement into the paravertebral space. We replace the dilators with a trocar, again identify the bony surface and the slope between the base of the transverse process and the lateral part of the base of the superior articular process.
Working Portal
Using a scalpel, we incise the skin and subcutaneous tissue at approximately 20° toward the base of the transverse process. We incise the outer layer of the thoracolumbar fascia (fascia thoracolumbalis) in a cruciate pattern, rotating the scalpel 90° for the second incision. This promotes free outflow of irrigation fluid. We sequentially introduce three dilators, palpating the dorsal part of the base of the transverse process and the lateral parts of the bases of the S1 superior articular process and the L5 inferior articular process. We bring the dilator together with the trocar in the endoscopic portal until metal-to-metal contact is felt. The convergence point is the L5 isthmus.
At this stage, we obtain lateral fluoroscopy if necessary.
We replace the trocar stylet with the scope and camera, and the dilators with an RF electrode with a 5 mm working tip. The electrode must be visible in the endoscopic field near the L5 isthmus. We not only palpate the bone but also clearly visualize it: it is the principal landmark. If orientation is lost, we stop manipulating until it is restored.
If instrument position is uncertain, we perform an additional radiographic check in two views.
Using the RF electrode in ablation mode, we expose the distal border of the L5 transverse process, the isthmus, the articular processes, and the S1 lateral mass. After clearly identifying the bony landmarks, we remove excess soft tissue lateral to them with a 5 mm shaver or an RF electrode under continuous visual guidance. We carefully advance deeper along the S1 superior articular process. In marked degeneration, hypertrophied bony structures limit the approach. Lateral to the articular processes, we identify the junction of the L5 transverse process and the S1 lateral mass.
In far-out syndrome, the radicular artery usually courses above the superior sacral notch. During soft-tissue dissection in this area, the course of the vessel is identified and the tissues are carefully separated under endoscopic guidance. Injury to the artery may cause profuse bleeding [6, 7].
After meticulous hemostasis, we begin bone resection.
We begin by resecting the S1 lateral mass with a 5 mm burr, alternating it with an osteotome. We move from the base of the S1 superior articular process toward its junction with the L5 transverse process. A distal resection of 5–10 mm is usually sufficient; the bone may be more than 1 cm thick. We identify the L5 nerve, which passes deeper beneath the S1 lateral mass. We carefully remove the surrounding soft tissues with Kerrison rongeurs under visual guidance. We selectively coagulate bleeding vessels with a 5 or 1.5 mm electrode, with continuous irrigation and free outflow. Near the nerve, we use COAG 2 on the BONSS ARS600 generator — this is a setting level, not power in watts. During coagulation, we use a separate nonactivated instrument to retract the nerve; the active surface of the RF electrode must not contact the nerve.
We then resect the distal border of the L5 transverse process. We prepare a surface with the burr and remove 3–5 mm of bone with the osteotome. We consider that the anteroposterior dimension of the transverse process may be 10–15 mm.
After sufficient resection, we visualize the released L5 nerve from its emergence beneath the S1 superior articular process and L5 isthmus to its passage deeper beneath the S1 lateral mass. If necessary, we partially resect the connection between the lateral portion of the L5 transverse process and the S1 lateral mass.
We avoid complete resection of this connection, considering its contribution to load distribution.
In far-out syndrome, L5 nerve compression may be sustained by a thickened lumbosacral ligament between the L5 transverse process and the sacral ala, as well as by the deeper and more distal extraforaminal ligament—the far-out band. These structures may tether the nerve within the narrowed space. After bony resection, the extraforaminal course of the nerve is assessed for persistent ligamentous compression [6].
In isolated extraforaminal compression, additional foraminal decompression is unnecessary; before completion, we ensure there is no residual L5 nerve compression. If CT and MRI show compression both inside and outside the foramen, we decompress both regions.
If foraminal decompression is needed, we again identify the lateral surface and tip of the superior articular process. Excessive resection may impair segmental stability. In the described technique, we limit tip resection to 5 mm, using the chisel width as a reference. We position it at 45° to the coronal and sagittal planes. Under endoscopic guidance, we separate the tip; if controlled removal as a single fragment is not possible, we divide it into smaller pieces. We consider the triangular shape of the tip base in the axial plane.
We remove the separated fragment with upturned rongeurs. If ligaments retain it, we release only clearly visible attachments while protecting the nerve; we fragment the bone if necessary. We do not push the fragment medially into the intervertebral foramen.
After removing the tip, we visualize the exiting portion of the nerve. We carefully remove residual ligament covering it laterally with 3 mm Kerrison rongeurs under direct guidance.
We trace the course of the nerve and check for additional sources of compression: residual bony overgrowth of the distal transverse process, subpedicular osteophytes, a disc component, and bony spurs of the endplates.
Subpedicular Osteophytes
When the nerve is compressed beneath the pedicle, we partially resect the corresponding bony region. We use a spherical burr to prepare a surface for an upward-curved 30° chisel. We remove bone gradually in fragments 1–2 mm wide. We retrieve the fragments with upturned rongeurs; if necessary, we mobilize them toward ourselves with a curette in a controlled manner.
⚠️ The dorsal root ganglion near the nerve's exit from the intervertebral foramen is particularly sensitive to mechanical and thermal injury. Even minor trauma may cause prolonged neuropathic pain.
Bony Spurs of the Vertebral Endplates
Caudal to the nerve, we identify the disc. We expose osteophytes from the disc side: using an endoscopic annulotomy knife (Indian knife), we incise the annulus fibrosus and enlarge the opening with Kerrison rongeurs. In ablation mode, under visual guidance, we expose bony spurs of the cranial vertebral endplate, avoiding contact between the active electrode and the nerve. In my technique, I simultaneously use a straight chisel as a retractor: I gently displace the nerve cranially with it and hold the nerve with the same chisel while resecting the osteophyte. I position the chisel as perpendicular to the osteophyte as possible. The scrub nurse operates the mallet. We remove the fragments with rongeurs under endoscopic guidance.
After decompression, we check hemostasis: we selectively coagulate bleeding vessels without allowing the active electrode to contact the nerve, with continuous irrigation and free outflow; we control bone bleeding with bone wax.
Under endoscopic guidance, we introduce a 15 Fr drain into the working cavity through the working portal, away from the exposed nerve, and secure it to the skin. We remove it the next day, or immediately if neural structures are irritated. Irritation may result either from drain contact or from negative pressure. We do not place a drain after an intraoperative durotomy or during BELIF/UBE-LIF.
We close each portal incision with a single interrupted Vicryl 2-0 suture.
References
1. Heo DH, Sharma S, Park CK. Endoscopic treatment of extraforaminal entrapment of L5 nerve root (far out syndrome) by unilateral biportal endoscopic approach: technical report and preliminary clinical results. Neurospine. 2019;16(1):130-137. doi:10.14245/ns.1938026.013.
2. Park MK, Son SK, Park WW, Choi SH, Jung DY, Kim DH. Unilateral biportal endoscopy for decompression of extraforaminal stenosis at the lumbosacral junction: surgical techniques and clinical outcomes. Neurospine. 2021;18(4):871-879. doi:10.14245/ns.2142146.073.
3. Nathan H, Weizenbluth M, Halperin N. The lumbosacral ligament (LSL), with special emphasis on the “lumbosacral tunnel” and the entrapment of the 5th lumbar nerve. Int Orthop. 1982;6(3):197-202. doi:10.1007/BF00267730.
4. Tubbs RS, Iwanaga J, Aly I, Moisi MD, Hanscom DR, Chapman JR, et al. Extraforaminal compression of the L5 nerve: an anatomical study with application to failed posterior decompressive procedures. J Clin Neurosci. 2017;41:139-143. doi:10.1016/j.jocn.2017.03.051.
5. Heo DH, Park DY, Hong YH, Kim D, Kim JS. Temperature change of epidural space by radiofrequency use in biportal endoscopic lumbar surgery: safety evaluation of radiofrequency. Eur Spine J. 2023;32(8):2769-2775. doi:10.1007/s00586-023-07719-z.
6. Quillo-Olvera J., Quillo-Olvera D., Quillo-Reséndiz J., Barrera-Arreola M. Challenging Cases Treated with UBE: The Far-Out Syndrome. In: Unilateral Biportal Endoscopy of the Spine: An Atlas of Surgical Techniques. Springer; 2022. P. 301–325; relevant passages: pp. 312, 314.
7. Lee N., Park S.H., An J.W. Far-out Syndrome Decompression Using Unilateral Biportal Endoscopy. In: Unilateral Biportal Endoscopic Spine Surgery: Basic and Advanced Technique. Springer; 2022. P. 121–135; relevant passage: pp. 130–131.
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