Full-Endoscopic Lumbar Interbody Fusion Using the Modified Transfacet Approach: A Novel Technique to Reduce the Risk of Inadvertent Neurovascular Injury

Article information

J Minim Invasive Spine Surg Tech. 2025;10(Suppl 1):S67-S74

Publication date (electronic) : 2025 January 31

doi : https://doi.org/10.21182/jmisst.2024.01697

Akarawit Asawasaksakul¹, Abhirat Suebsing², Warayos Trathitephun³, Jin-Sung Kim⁴, Siravich Suvithayasiri^,3,5

¹Spine Clinic, Department of Orthopedics, Ramkhamhaeng Hospital, Bangkok, Thailand

²Department of Orthopedics, Warinchamrab Hospital, Ubon Ratchathani, Thailand

³Department of Orthopedics, Chulabhorn Hospital, Chulabhorn Royal Academy, Bangkok, Thailand

⁴Department of Neurosurgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea

⁵Bone and Joint Excellence Center, Thonburi Hospital, Bangkok, Thailand

Corresponding Author: Siravich Suvithayasiri Department of Orthopedics, Chulabhorn Hospital, Chulabhorn Royal Academy, 906 Kamphaeng Phet 6 Road. Talat Bangkhen, Lak Si, Bangkok 10210, Thailand Email: brightkeng3@gmail.com

Received 2024 August 6; Revised 2024 September 21; Accepted 2024 November 27.

Abstract

INTRODUCTION

Since the introduction of Kambin triangle in 1986 [1], there have been many significant advancements in minimally invasive spine surgery. Endoscopic procedures have become mainstream, ranging from discectomy to interventions for varied spinal pathologies, including spinal stenosis, infection, or tumor diseases [2]. These procedures, applicable to both the lumbar and thoracic regions, have proven their effectiveness clinically [3,4]. Yet, achieving spinal fusion through endoscopic surgery remains a significant challenge that has stimulated extensive research [5]. Recently, the potential of full-endoscopic lumbar interbody fusion (FE-LIF) has been illustrated via the evolution of surgical instruments and techniques. This study introduces a secure and efficient "transfacet" technique for 1- or 22-level endoscopic spinal fusion using standard full-endoscopic equipment.

MATERIALS AND METHODS

This technical-note-type article elucidates the case study of a patient who suffered from the progression of degenerative spinal disease, specifically instability and spinal canal stenosis. After the approval from Ubon Ratchathani Provincial Office of Institutional Review Board (No. SXJ.UB2566-001.1), a retrospective review of our demonstrating patient from our hospital’s database was performed. Written inform consent was obtained from all the patients for publications. A step-by-step overview of the surgical process, supplemented with a comprehensive surgical video, is provided (Supplementary video clip 1).

RESULTS

1. Case Information

A 61-year-old male presented with low back pain for 5 months. He reported having an associated right leg radiating pain with numbness but without any motor weakness. The pain visual analogue score (VAS) of her back and leg pain varied between 5–8 points out of 10. He denies any alcohol or tobacco use. A plain radiograph study revealed spondylosis with spondylolisthesis grade I at the L4–5 level. His Magnetic resonance imaging (MRI) showed moderate to severe spinal canal stenosis at the central and both sides of the lateral recess. She decided to receive surgery after failed conservative treatment with medication and physical therapy. After discussing several options available, the FE-LIF operation at the L4–5 level, approaching from the right side of the patient and using our proposed novel technique of modified transfacet technique, was planned. (Figure 1).

Figure 1.

Imaging studies of the 61-year-old patient who underwent our modified transfacet approach for full-endoscopic lumbar interbody fusion. (A) T2-weighted sagittal and axial magnetic resonance imaging. (B and C) Comparisons between the preoperative and 3-month postoperative plain radiographs.

3. Surgical Technique

1) Operating room setup

During this stage, the proper positioning and visualization of the patient are vital. When under general anesthesia, the patient lays prone on a radiolucent operating table. A slight flexion of the hips and knees creates more room for the surgery, allowing for the opening of facet joints and the expansion of the posterior part of the disc space. The table should be able to move the C-arm thoroughly for continuous imaging. It is crucial for the endoscope and C-arm monitors to be clearly visible. The assisting surgeon starts by standing across from the operating surgeon during the guide wire placement for the later percutaneous screw application, then moves to the same side during the endoscopic interbody fusion procedure (Figure 2).

Figure 2.

(A) The diagram shows the usual operative setup for modified transfacet full-endoscopic lumbar interbody fusion. (B) The outline of the intraoperative fluoroscopy of the vertebral body reveals the initial incision site at the lateral pedicle line for the Jamshidi and guidewire insertion. (C) Intraoperative fluoroscopic images demonstrating the position of Jamshidi placement and the initial docking point of the endoscopic working sleeve.

2) Level marking and skin incision

The parallel alignment of the operating level's endplate in the anteroposterior (AP) view and the pedicle alignment in the lateral view is ensured through level marking, guided by the C-arm. The optimal incision points are determined using the lateral pedicular line at the respective pedicle level. For percutaneous pedicular screw insertion, 2-cm skin incisions are usually adequate. To better facilitate endoscopic interbody fusion, we divide the skin incision into 3 parts, with two-thirds of the incision made caudal to the center of the corresponding pedicle (Figure 2).

3) Guidewire placement

The procedure involves guiding a Jamshidi needle with the assistance of the C-arm, inserting it through the incision, and gently hammering it until the needle tip reaches the medial wall of the pedicle in AP view. In lateral view, if the needle goes beyond the posterior vertebral line at this point, it is hammered until it reaches the midpoint of the vertebra. A guide wire is then inserted into the vertebral body through a Jamshidi needle. These steps are then repeated until guide wires are placed in all corresponding pedicles (Figure 2).

4) The dilator and working sleeve placement

The same cranial incision used for percutaneous pedicular screw insertion is also used to palpate the most dorsal part of the facet joint, serving as the starting point for the bone drilling procedure (Figure 3). Following C-arm guidance in the AP and lateral views, serial dilators are placed over the facets, followed by a working sleeve. We suggest using a circular opening sleeve for better soft tissue protection and effortless drilling.

Figure 3.

(A) The starting point for the bone drilling procedure is pointed at the sawbones. (B) Intraoperative visualization revealed the anatomical landmark as the most dorsal tip of the facet joint. (C) After the removal of the dorsal part of the facet joint, the joint line below could be used as a local navigator to lead the way through the facet joint into the posterior annulus. (D and E) A switching rod was used to facilitate the insertion of the customized cage glider. (F) An optimized Harrison Cage Glider. (G) A serial intervertebral disc space shaver and customized cage glider were used. (H) The cage insertion step is shown on lateral views of the intraoperative fluoroscopic images.

5) Transfacet approach

Once the peak of the facet joint is reached, the facet capsule is cleared using a cutting punch and radiofrequency (RF)-bipolar before drilling. The facet joint line serves as a guide for initiating a keyhole facetectomy in a posterolateral to anteromedial direction, utilizing a diamond burr or initially an endoscopic osteotome for better collecting autogenous bone graft. This approach, known as the transfacet approach, helps minimize the risk of traversing root injury, exiting root injury, and bleeding. When drilling, it is important to keep the medial and lateral walls of the facet joint intact by drilling lateral to the facet joint line. If there is insufficient foraminal space, the lateral walls of the facets can be removed to facilitate cage trajectory. We recommend resecting the medial facet wall of both the inferior articular process dorsally and superior articular process ventrally until a 1.2-cm sleeve can be passed through the facet, allowing partial visualization of the lateral extension of the ligamentum flavum to ensure the safety of the traversing nerve root. During cage insertion, a breach or fracture of the facet's medial wall may occur; however, with this approach, the intact ligamentum flavum remains attached to the facet fragments, preventing these bony fragments from becoming dislodged. These fragments can then be removed later in the procedure to achieve adequate decompression. The posterolateral aspect of the disc is exposed by removing a small portion of the lateral extension of the ligamentum flavum and foraminal ligaments adjacent to the caudal pedicle (Figure 3).

6) Discectomy and endplate preparation

Annulotomy is carried out using a probe or RF-bipolar, followed by widening of the annulus and subsequent discectomy. The use of a diamond burr and endoscopic curette helps improve the effectiveness of the discectomy and endplate preparation. In cases where the disc space is extremely narrowed, the initial step involves drilling into the disc to create space for guidewire placement and serial dilation, which is crucial for achieving success. Once the disc space is open, the switching rod is inserted through the endoscope's working channel. The optimized Harrison Cage Glider (Harrison Spinartus Hospital, Chungdam) (Figure 3) is then compressed around the switching rod and gently driven into the disc space with the guidance of a C-arm. In 2021, Kim et al. [6] described the use of the Harrison Cage Glider in their uniportal facet-sacrificing posterolateral transforaminal lumbar interbody fusion (TLIF) technique, employing it to protect the traversing nerve root following complete decompression achieved by total removal of the facet joint. In contrast, our endoscopic transfacet approach achieves decompression after cage insertion while preserving the medial border of the facet joint. In this approach, the Harrison Cage Glider serves as a protector for the exiting nerve root and a distractor for the disc space, with the lips of the glider positioned in the disc space parallel to the endplates. It is important to ensure that the lips of the cage glider system are aligned in a craniocaudal direction to protect the exiting nerve root. Further endplate preparation can then be carried out under C-arm guidance at this stage (Figure 3).

7) Cage placement

We gauge the size of the cage using an endplate preparation device. A DBM-packed (autogenous bone graft as an optional) single PEEK cage is inserted obliquely through a cage guiding system with the guidance of a C-arm. Once the cage is optimally positioned, the dilator and the endoscope's working sleeve are inserted, and the cage placement is reevaluated using direct endoscopic visualization (Figure 3).

8) Additional decompression

If necessary, direct decompression of the lateral recess can be accomplished by removing the medial wall of the facet joint and opening the ligamentum flavum to expose the traversing root. Endoscopic laminotomy can also be achieved to decompress either the central canal or the contralateral side by using an over-the-top technique (Figure 4).

Figure 4.

(A and B) Intraoperative endoscopic view after cage insertion. If needed, medial facet wall removal and over-the-top decompression can be continued. (C and D) Final intraoperative fluoroscopic images after the screw-rod system insertion. (E) Axial computed tomography showed the cage position. (F) Postoperative axial-cut T2-weighted magnetic resonance imaging showed adequate lateral recess decompression.

9) Percutaneous screws fixation and skin closure

The procedure then proceeds with percutaneous screw fixation and rod placement (Figure 4). A surgical drain is optional but can be placed through the endoscope at the interbody fusion site and can be removed within 24 hours after the surgery in case of a patient who suspects coagulopathy. Skin closure is completed in a standard routine manner.

DISCUSSION

The transfacet FE-LIF technique is a relevant fusion operation for conditions similar to those requiring lumbar spine fusions, such as low to moderate-grade spondylolisthesis or general degenerative spinal disorders. These conditions often show signs of spinal instability and are potential sources of pain. Recent advancements in full-endoscopic procedures, including smaller incisions, less tissue disruption, and faster recovery, have made them an attractive option. These procedures can provide outcomes that are as good as, if not better than, traditional tubular-assisted minimally invasive TLIF (MI-TLIF) methods [7,8]. However, it's worth noting that certain aspects of fusion procedures using these techniques are still under investigation, particularly the choice of approach and the protection of neural structures. Previous studies on FE-LIF have predominantly described 2 approaches: the trans-Kambin (facet-sparing) technique and the interlaminar (facet-sacrificing) technique. Each approach presents unique advantages and limitations, particularly concerning the risk of injury to neural structures, including the exiting or traversing nerve roots. To address these limitations, we propose a transfacet approach for cage insertion utilizing a full-endoscopic technique under C-arm guidance. This approach was initially described in 2020 by Khalifeh et al. [9] in their work on MI-TLIF. The transfacet approach aims to simplify the drilling process while enhancing the safety of critical anatomical structures. The facet joint line guides safe drilling, and the Harrison Cage Glider is used to provide a safe passage for insertion.

Although our demonstrating case showed no complication up to our last follow-up of 12 months after the surgery, potential complications related to endoscopic fusion could still exist. Incidental durotomy with cerebrospinal fluid leakage is a known complication, with management determined by tear size [10,11]. The management to address the lesion can range from observation, collagen matrix inlays, sealants, or even primary closure via endoscopy or open repair. Nerve injuries, though less frequent, can occur from thermal damage caused by RF probes or direct mechanical trauma during the procedure. Preventative measures include careful RF probe placement away from nerve roots, using coagulation mode at low power for short durations, and meticulous bone work to avoid mechanical trauma [12]. Additionally, cage-related complications, such as migration, subsidence, or pseudarthrosis, can compromise fusion rates. Intraoperative fluoroscopic guidance and contrast during disc preparation help mitigate these risks, and using 2 cages in a convergent alignment may distribute the load more evenly across the endplate, potentially reducing cage subsidence or migration as proposed by some previous studies [13-15].

FE-LIF is a key endoscopic spine surgery (ESS) technique that offers significant advantages over traditional MI-TLIF. FE-LIF provides enhanced visualization, minimal tissue disruption, and promising clinical outcomes, including higher fusion rates and lower subsidence compared to MI-TLIF [8,16,17]. However, challenges remain, particularly the limited operating space and difficulties in achieving proper cage positioning, which may affect its ability to restore lumbar lordosis or correct sagittal imbalance [18]. While unilateral biportal endoscopic TLIF also offers superior visualization, it has been criticized for potentially causing more collateral damage than FE-LIF [6]. Overall, FE-LIF demonstrates promising potential, but further research is needed to fully establish its efficacy, especially in patients with significant lordosis loss or sagittal imbalance.

While the proposed method offers several advantages, it does come with a steep learning curve, mainly due to the restricted operational space and the requirement for advanced surgical skills in performing ESS. Implementing a systematic and strategic training program would be highly beneficial in overcoming these learning curves. The development of supporting technologies, such as navigation-assisted surgery (both optical and electromagnetic-based systems), augmented realities, or even robotic guidance could further enhance the overall process of novice surgeons through their learning curves, as stated in some previous literature [19-22]. There also might be challenges in cage positioning that could limit the cage size that can be used, potentially affecting the overall fusion rate [18]. More high-quality evidence is needed to fully understand the potential and efficacy of full-endoscopic spine surgery, especially when compared to other methods like biportal endoscopy or traditional MI-TLIF. To minimize complications, using the facet joint line as a guide ensures safe drilling and direct access to the disc space while protecting vital structures. Once the joint capsule is opened, facet joint space will have the ability to expand, which makes it easier to insert a retractor into the disc space for cage insertion. This method also ensures the protection of neural structures. The medial wall of the facets and the lateral extension of the flavum protect the traversing root. while the lip of the retractor guards the exiting root. This technique allows for smooth endplate preparation and cage insertion, demonstrating the safety and value of our proposed method.

Finally, it is important to inform the patient that despite the promising outcomes from previous research on the full-endoscopic-assisted fusion procedure, the level of evidence is still catching up to more traditional fusion techniques, such as MI-TLIF [23]. Therefore, the effectiveness of this method remains a subject of ongoing debate. Using an optimized cage guiding system with the transfacet approach streamlines the operation and improves the safety of the neighboring neural structures during the cage insertion process. However, patients should be aware that this method, while promising, does not completely eliminate all associated risks.

CONCLUSION

The advent of minimally invasive spine surgery, especially FE-LIF, brings with it immense promise for transformative changes in spinal fusion as it provides a promising solution for reducing tissue disruption, minimizing incision sizes, and hastening patient recovery. Notably, our proposed transfacet approach holds the potential for both simplicity and safety. Even though the operational space may be limited, this method streamlines the process while ensuring the protection of critical structures. Its efficacy and ease of application underline its appeal for broader adoption. While further research is needed to fully ascertain its effectiveness compared to traditional methods such as MI-TLIF, the safety, simplicity, and potential of this technique render it a compelling field for future exploration by spine surgeons.

Supplementary Material

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