Full-Endoscopic Transforaminal Approach for Lumbar Discectomy

Summary

The present protocol describes the full-endoscopic transforaminal approach for lumbar discectomy, which is a safe technique that does not require muscle retraction or bone removal.

Abstract

With technical advancements, the full-endoscopic transforaminal approach for lumbar discectomy (ETALD) is gaining popularity. This technique utilizes various tools and instruments, including a dilator, a beveled working sleeve, and an endoscope with a 20-degree angle and 177 mm length, equipped with a 9.3-diameter oval shaft and a 5.6 mm diameter working channel. Additionally, the procedure involves using a Kerrison punch (5.5 mm), rongeur (3-4 mm), punch (5.4 mm), tip control radioablator applying a radiofrequency current of 4 MHz, fluid control irrigation and suction pump device, 5.5 mm oval burr with lateral protection, burr round, and the diamond round. During the surgery, it is essential to identify significant landmarks, including the caudal pedicle, ascending facet, annulus fibrosis, posterior longitudinal ligament, and the exiting nerve root. The steps of the technique are relatively easy to follow, especially when utilizing the appropriate instruments and having a good understanding of the anatomy. Research studies have demonstrated comparable outcomes to open microdiscectomy techniques. ETALD presents itself as a safe option for lumbar discectomy, as it minimizes tissue disruption, results in low postoperative surgical site pain, and allows for early mobilization.

Introduction

The full-endoscopic transforaminal approach for lumbar discectomy (ETALD) is gaining popularity as a minimally invasive technique in various medical centers. It offers the advantage of requiring less muscular retraction and bone removal compared to conventional techniques^1,2. Over time, the technique has undergone advancements since its initial description. Conventional surgeries have shown good results; however, epidural fibrosis occurs in around 10% of cases, leading to symptoms^3,4.

The transforaminal approach provides lateral access, eliminating the risk of disrupting spinal canal structures, making it a more physiological route and reducing the risk of operation-induced destabilization. It also facilitates easier revision surgery if needed^5,6,7,8. ETALD is effective in removing both intra- and extraforaminal disc herniations, and it allows for the removal of disc material from the spinal canal by approaching the disc space^9,10.

Despite its advantages, ETALD does have limitations, such as limited access due to abdominal and pelvic structures, and obstruction by a high iliac crest^8,11,12,13. Initially, disc space evacuation was required for adequate decompression, but with advancements in surgical tools and optics, direct visualization enables the removal of the disc fragment from its location^14,15,16.

The primary goal of this new procedure is to minimize tissue damage and reduce negative long-term outcomes. This study aims to describe the current technique for ETALD in detail.

Protocol

This study protocol has been approved by the Institutional Review Board of Istanbul University, Faculty of Medicine, ensuring adherence to ethical guidelines and patient safety. Additionally, prior to their participation in the study, informed consent was obtained from all patients.

1. Preoperative procedures

1. Perform the surgery under general anesthesia, adhering to the institutionally approved protocol for anesthetization. Set the endoscope, optic instruments, and C-arm devices in the operating room (see Table of Materials).
2. Check the tools before starting the procedure.
   ​NOTE: The necessary tools are: the dilator, beveled working sleeve, an endoscope with 20 degrees angle and 177 mm length with a 9.3 diameter oval shaft with a 5.6 mm diameter working channel, rongeur 3-4 mm, Kerrison punch 5.5 mm, punch 5.4 mm, burr round, fluid control irrigation and suction pump device, tip control radioablator applying a radiofrequency current of 4 MHz, 5.5 mm oval burr with lateral protection, and the diamond round (see Table of Materials).

2. Surgical technique

1. Place the patient in a prone position with thorax and pelvis support pillows. One surgeon can perform the surgery, but an assistant would ease the procedure.
2. Place the C- arm and obtain a lateral X-ray view to mark the posterior line of the facet. Obtain the anteroposterior (AP) view to mark the middle of the intervertebral disc space where the discectomy is intended.
   NOTE: While obtaining the X-rays, ensure the end plates are parallel. The endplates are parallel when there is no double contour in the scan and only a superimposed single line.
3. Perform a 1 cm skin incision by an 11-blade at the intersection of the lines.
4. Place the 10-inch long 18 G spinal needle under the AP X-ray view until the medial border of the pedicle. Check the lateral X-ray view to be in the inferior border of the intervertebral foramen and dorsal and caudal to the dorsal border of the annulus fibrosis.
5. Place the guide wire inside the spinal needle. Remove the spinal needle, and then introduce the dilator over the guide wire. While introducing the dilator, ensure its direction is the same as the guide wire.
6. Obtain AP X-ray views while advancing the dilator for safe entry. Remove the guide wire when the dilator is in the foramen's caudal part and the pedicle's medial border in the AP view. Check the lateral view, so the dilator is dorsal to the annulus and not in the disc space.
7. Introduce the beveled working sleeve over the dilator. Ensure that the handle of the beveled working sleeve is on the same side as the long edge of the instrument's tip.
   1. When introducing the working sleeve, ensure the handle is in the dorsal aspect to protect the exiting nerve root. When the working sleeve is in place, rotate the working sleeve 180 degrees from the caudal side.
      NOTE: Rotation from the caudal side is again to protect the exiting nerve root since the nerve root is superior to the working sleeve. On the inferior side is the caudal pedicle, which is the safer place to rotate the long edge of the beveled working sleeve.
8. Remove the dilator, and introduce the endoscope through the working sleeve.
9. Visualize the annulus fibrosis, posterior longitudinal ligament (PLL), and epidural fat tissue. Do not enter the spinal canal since the pathology is not there.
10. Coagulate bleeding to have clear visualization throughout the procedure. Here, one will see the ascending facet in the dorsal part, and in the inferior part, one will see the caudal pedicle.
11. Rotate the working sleeve and the endoscope to the cranial aspect. This maneuver allows for a clear view of the vessels, fat tissue, and ligaments within the intervertebral foramen. Utilize the bipolar radioablator to coagulate these structures, and subsequently, remove them with the 3 mm rongeur.
12. After removing the soft tissues, ensure that the disc fragment becomes visible, positioned superior to the annulus defect. Above the disc material, the exiting nerve root can be observed, which is being compressed by the disc fragment.
13. Remove the disc fragment with the Kerrison punch and the rongeur. The disc fragment can appear larger during the surgery than it appears in preoperative magnetic resonance imaging (MRI) due to compression in a confined area. However, upon removal of the disc material, the nerve root is effectively decompressed.
    NOTE: If bony stenosis exists in the intervertebral foramen, bone removal can be achieved by a 5.5 mm oval burr with lateral protection, burr round, or diamond round.
14. Evacuate the disc space by using the existent annulus defect by rongeur. Especially for high intervertebral disc space, the evacuation of the disc space is recommended to prevent recurrent disc herniation.
15. Seal the evacuated area and the annulus defect margins by coagulation to prevent recurrence.
16. After hemostasis, complete the procedure by removing the endoscopic system. Use a single 3-0 suture for closure; no drainage is necessary.

3. Postoperative procedures and follow-up

1. Ask the patients to begin oral intake in 6 h postoperatively. Mobilize the patients on the next day of the operation.
   NOTE: Postoperative pain levels are minimal, eliminating the necessity for prolonged painkiller usage. To address any discomfort at the operation site, nonsteroidal anti-inflammatory drugs (NSAIDs) can be administered.
2. Do not recommend physical therapy and rehabilitation or a lumbar corset.
3. If the patient's symptoms have resolved after the surgery, do not perform a postoperative MRI.
4. Remove the suture in the first week of operation.
5. Recommend the patients to be admitted to the outpatient clinic in the first and fourth weeks of operation.

Results

The preoperative Magnetic Resonance Imaging (MRI) scans reveal a left paracentral extruding disc herniation that was causing compression on the left L5 nerve root. However, the postoperative MRI scans demonstrate successful decompression of the left L5 nerve root, as depicted in Figure 1. Throughout the procedure, continuous irrigation was utilized, making it challenging to precisely measure the exact amount of blood loss. Nonetheless, it is noteworthy that none of the patients required sign...

Discussion

In cases of spinal disc herniation, achieving complete decompression is essential and can be optimally accomplished under visual control^17,18,19. Technical advancements have made it possible to achieve such decompression even through a full-endoscopic approach. The development of improved optics, endoscopes, and instruments introduced through the working channel has expanded the safe usage of this technique²⁰

Materials

Name	Company	Catalog Number	Comments
BURR OVAL Ø 5.5 mm	RiwoSpine	899751505	PACK=1 PC, WL 290 mm, with lateral protection
C-ARM	ZIEHM SOLO		C-arm with integrated monitor
DILATOR ID 1.1 mm OD 9.4 mm	RiwoSpine	892209510	For single-stage dilatation, TL 235 mm, reusable
ENDOSCOPE	RiwoSpine	892103253	20 degrees viewing angle and 177 mm length with a 9.3 mm diameter oval shaft with a 5.6 mm diameter working channel
KERRISON PUNCH 5.5 x 4.5 mm WL 380 mm	RiwoSpine	892409445	60°, TL 460 mm, hinged pushrod, reusable
PUNCH Ø 3 mm WL 290 mm	RiwoSpine	89240.3023	TL 388 mm, with irrigation connection, reusable
PUNCH Ø 5.4 mm WL 340 mm	RiwoSpine	892409020	TL 490 mm, with irrigation connection, reusable
RADIOABLATOR RF BNDL	RiwoSpine	23300011
RF INSTRUMENT BIPO Ø 2.5 mm WL 280 mm	RiwoSpine	4993691	for endoscopic spine surgery, flexible insert, integrated connection cable WL 3 m with device plug to Radioblator RF 4 MHz, sterile, for single use
RONGEUR Ø 3 mm WL 290 mm	RiwoSpine	89240.3003	TL 388 mm, with irrigation connection, reusable
WORKING SLEEVE ID 9.5 mm OD 10.5 mm	RiwoSpine	8922095000	TL 120, distal end beveled, graduated, reusable