14.7. Endoscopic stage
@ProfFishchenkoWe then use the electrode in coblation mode to expose the cranial and caudal laminae and the inferior articular process. After identifying the bony landmarks, we remove excess soft tissue over the ligamentum flavum with a shaver (Tomcat, Aggressive Plus) or the electrode in coblation mode under continuous endoscopic visualization. We clearly visualize the base of the spinous process, lamina, and inferior articular process of the cranial vertebra, as well as the lamina and base of the spinous process of the caudal vertebra.
We achieve hemostasis outside the spinal canal with a 5 mm RF electrode. After removal of the ligamentum flavum, we use only a 1.5 mm RF electrode.
At this stage, we clearly visualize the V-point — the anatomical zone formed by the cranial and caudal laminae and the medial edge of the articular process.
After clearly visualizing the bony landmarks, we obtain a fluoroscopic check to confirm the level. The C-arm can then be moved away; it must remain available if repeat imaging is needed.
Bone resection
In cervical foraminal stenosis, we determine the extent of bone resection from the location and extent of nerve root compression. It is not limited to the attachments of the ligamentum flavum to the cranial and caudal laminae and includes the partial resection of the medial portions of the articular processes needed for foraminal decompression.
We perform bone resection with a 3 mm cutting burr. We begin with the lamina and inferior articular process of the cranial vertebra. We remove the outer cortical and cancellous layers of the lamina; at this stage, we preserve the inner cortical layer adjacent to the ligamentum flavum and spinal canal structures. We resect 5–6 mm of the medial portion of the inferior articular process. We clearly visualize the medial edge of the superior articular process of the caudal vertebra. We resect the outer cortical and cancellous layers of the cranial and caudal laminae over a length of 4–5 mm.
We perform further bone resection to the cranial and caudal attachments of the ligamentum flavum using 2 mm Kerrison punches. After identifying the cranial and caudal edges of the ligamentum flavum, we resect the medial portion of the superior articular process of the caudal vertebra. For nerve root decompression in foraminal stenosis, lateral resection of 5–7 mm is usually sufficient.
We begin removal of the ligamentum flavum at its caudal or cranial edge. Under endoscopic visualization, we carefully place the Kerrison punches beneath the ligament and remove it in stages.
Work within the spinal canal
In the cervical spine, beneath the ligamentum flavum is a membrane containing vessels and covering the dura mater. We create an opening in the membrane with a Caspar vascular hook, then remove it with 2 mm Kerrison punches.
After removal of the ligamentum flavum and hemostasis, the medial pedicle border is identified. This bony landmark is used to clarify the relative positions of the dural sac and the exiting nerve root before root mobilization [4].
We manipulate the nerve root with particular care in the cervical spine.
⚠️ WARNING: Forceful nerve root retraction may cause persistent neuropathy.
We mobilize the nerve root by gently separating it from the pedicle with an elevator. After mobilization, we assess completeness of decompression: under endoscopic visualization, we inspect the nerve root from all sides using a Caspar vascular hook. We inspect the operative cavity and achieve final hemostasis.
We do not place a drain in the cervical spine.
We place one interrupted Vicryl 2-0 suture in each skin incision.
References
1. Song KS, Lee CW. The biportal endoscopic posterior cervical inclinatory foraminotomy for cervical radiculopathy: technical report and preliminary results. Neurospine. 2020;17(Suppl 1):S145–S153.
2. Kim JY, et al. Comparative analysis of 3 types of minimally invasive posterior cervical foraminotomy for foraminal stenosis, uniportal-, biportal endoscopy, and microsurgery: radiologic and midterm clinical outcomes. Neurospine. 2022;19(1):212–223.
3. Kim JY, et al. Anatomical importance between neural structure and bony landmark: clinical importance for posterior endoscopic cervical foraminotomy. Neurospine. 2021;18(1):139–146.
4. Song K.-S.D., Sun S.D., Kim D.H. Cervical Posterior: Foraminotomy and Discectomy. In: Unilateral Biportal Endoscopic Spine Surgery: Basic and Advanced Technique. Springer; 2022. P. 187–200; relevant passage: p. 192.
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