CASE REPORTS
1. Case 1
A 63-year-old woman presented with a 2-year history of left leg pain. Magnetic resonance imaging (MRI) demonstrated left L5–S1 foraminal stenosis. On plain radiographs, the anteroposterior view revealed a high iliac crest and large transverse process (TP), suggesting that initial working sheath placement for the transforaminal approach at the left L5–S1 level would be challenging. Therefore, we planned a full-endoscopic paraspinal foraminotomy at L5–S1, which could be performed regardless of such anatomical barriers.
Under epidural anesthesia, a vertical line was drawn approximately 1 cm lateral to the lateral margin of the left L5 pedicle along with 2 horizontal lines at the lower margin of the L5 pedicle and the superior margin of the S1 pedicle. A 1-cm skin incision was made between these lines. After serial dilation, the working sheath was advanced not through Kambin triangle but to the outer surface of the bone at the junction of the laminar isthmus, TP, and superior articular process (SAP). A large-caliber endoscope was then introduced (Figure 1).
Before bone removal, the field was prepared, and anatomical landmarks were identified using the working sheath, pituitary forceps, and a high-power 90° bipolar radiofrequency (RF) coagulator. The laminar isthmus, TP, sacral ala, and SAP were confirmed. Bone work was performed with large endoscopic burrs on the TP, the lower pedicle of L5, lateral isthmus, and SAP, with careful removal of adjacent soft tissues along the expected course of the exiting nerve root (ENR). The facet joint and foraminal ligament were subsequently exposed. When extraforaminal decompression was required, bone work was extended to the sacral ala. Bone resection continued until the superior and medial edges of the foraminal ligament were visualized.
The foraminal ligament was detached with a curved dissector while minimizing ENR irritation and then excised with pituitary forceps and a Kerrison punch. The large endoscopic system permitted the use of a wider range of dissectors, forceps, punches, and curettes, thereby facilitating a faster and technically easier procedure than the small-caliber transforaminal endoscopic system. Because the working sheath was positioned outside Kambin triangle, the risk of ENR injury from sheath placement was also reduced.
Residual ligament and surrounding fibrous or fatty tissues were removed using Kerrison punches and dissectors, and the bony structures around the SAP, TP, pedicle, and isthmus were contoured. If bone removal was insufficient, endoscopic burrs of different sizes were reapplied. After confirming adequate dorsal decompression of the ENR, ventral decompression was performed as required. In this patient, preoperative MRI revealed no significant disc herniation or osteophytes requiring extensive resection. Therefore, after slight retraction of the ENR using the inner sleeve of the large endoscope, a small endoscopic RF probe was inserted through the sleeve to perform limited annuloplasty. If disc or osteophyte removal had been necessary, instruments such as pituitary forceps or Kerrison punches could have been inserted through the inner sleeve while protecting the ENR, or alternatively, the system could have been switched to a small working sheath with a small endoscope. (the channel-in-channel technique) [1].
After confirming sufficient dorsal decompression of the ENR, the ventral aspect was inspected with an RF probe. Bleeding was controlled, and no drain was placed. Postoperative MRI demonstrated adequate decompression of the left L5 root at L5–S1, and the patient experienced significant improvement in radicular leg pain.
2. Case 2
A 67-year-old man presented with a 1-year history of bilateral leg pain, more severe on the left side. MRI revealed left L4–5 and L5–S1 foraminal stenosis with associated disc pathology, as well as central stenosis at L4–5. On anteroposterior plain radiographs, a high iliac crest and large TP were observed, indicating that a transforaminal approach to the left L5–S1 level would be difficult, whereas the left L4–5 level was anticipated to present no major limitations. Accordingly, unilateral laminotomy for bilateral decompression was planned for the L4–5 central stenosis, transforaminal endoscopic lumbar foraminotomy (TELF) for the left L4–5 foraminal stenosis, and full-endoscopic paraspinal foraminotomy for the left L5–S1 foraminal stenosis.
The left L5–S1 full-endoscopic paraspinal foraminotomy was performed in a manner similar to that described in case 1. However, to further relieve compression of the ventral portion of the left L5–S1 ENR caused by the protruding disc and osteophyte identified on preoperative MRI, annuloplasty was performed more extensively and for a longer duration. This was achieved either by using the inner sleeve in combination with a radiofrequency probe or by applying a high-power 90° bipolar RF coagulator alone while gently retracting the ENR. Bleeding was controlled, and no drain was placed. Postoperative MRI demonstrated sufficient central decompression of the L4–5 thecal sac and adequate foraminal decompression of the left L4–5 and L5–S1. The patient’s bilateral leg symptoms improved significantly postoperatively.
DISCUSSION
As a full-endoscopic surgical technique for lumbar foraminal stenosis, TELF was conceptually developed and technically advanced with the aim of decompressing the ENR through Kambin triangle while preserving as much of the facet joint as possible. Accordingly, this approach favors partial rather than complete resection of the SAP. To achieve this, the surgical trajectory toward the lumbar foraminal area must be set at a more oblique angle than that used in previous fusion surgery or microscopic foraminotomy via the Wiltse approach, and the skin incision must be placed more laterally. Because the procedure is performed within a narrow foraminal space without injuring the ENR, the endoscope and instruments must be of sufficiently small caliber. Moreover, the relatively long distance between the lateral skin incision and lumbar foraminal target requires instruments of sufficient length. These factors pose disadvantages in terms of surgical convenience and maneuverability, rendering the procedure technically demanding and contributing to the steep learning curve associated with full-endoscopic spine surgery.
Nevertheless, numerous reports have demonstrated favorable clinical outcomes and safety of TELF, and the technique is now widely applied [2,3]. Early TELF involved placing the working sheath across Kambin triangle onto the SAP base and performing minimal partial resection of the SAP along the course of the ENR. During this process, the foraminal ligament visualized in the surgical field was partially removed, and the disc material and osteophytes compressing the ventral aspect of the ENR were resected, thereby achieving decompression. However, this method may provide insufficient decompression in patients with severe lumbar foraminal stenosis. Furthermore, when anatomical barriers, such as a high iliac crest, sacral ala, or enlarged TP, are present, advancing the working sheath to the intended landing point may be technically challenging.
With advancements in endoscopic instruments and surgical techniques, several strategies have been developed to overcome these anatomical limitations. Currently, various enhanced TELF techniques have been introduced, including the bone reamer technique [4], floating technique [5], mobile out-in technique [6], and the outside-in-outside technique [7]. Additionally, for severe lumbar foraminal stenosis or foraminal stenosis associated with grade I spondylolisthesis, complete ENR decompression has been reported using full-scale TELF [8] and extended TELF [9].
Although numerous advanced techniques and modifications of TELF have been introduced, its fundamental characteristics remain unchanged. The approach still relies on a relatively lateral trajectory with a shallow angle, and the use of long, small-caliber endoscopes and instruments is required. Therefore, in cases of severe lumbar foraminal stenosis or lower lumbar foraminal stenosis with anatomical barriers, achieving sufficient decompression of the ENR using this method may increase surgical difficulty and prolong operative time. Additionally, because TELF involves introducing the working sheath directly into Kambin triangle at the beginning of the procedure and continuing surgery within this narrow space, the risk of postoperative dysesthesia due to ENR irritation has been reported to be relatively high [10].
In the present study, we describe 2 patient cases who underwent full-endoscopic paraspinal foraminotomy. In our institution, TELF is generally performed using a long and narrow endoscope (TESSYS HD Foraminoscope, Ocular [Joimax GmbH, Germany]; working length [WL], 171 mm; outer diameter [OD], 6.3 mm; working channel diameter [WChD], 3.7 mm; optic angle, 30°) together with small-sized instruments compatible with this system. In contrast, for full-endoscopic paraspinal foraminotomy, as in the present case, we employed a shorter and wider endoscope (iLESSYS Delta HD Laminoscope, Ocular [Joimax GmbH]; WL, 125 mm; OD, 10.0 mm; WChD, 6.0 mm; optic angle, 15°), along with larger and more diverse instruments suitable for this system. In this technique, the tip of the SAP forming the facet joint is almost completely resected from lateral to medial and from outside to inside. Because the working sheath is placed on the outer surface of the SAP, isthmus, and TP without passing through Kambin triangle, the skin incision is located more medially than in TELF, and the surgical trajectory is correspondingly steeper. The skin-to-foramen distance is also shorter than that in TELF, which allows for the use of larger-caliber and shorter endoscopes and instruments. Surgeons could freely select from various instruments with superior handling characteristics and different shapes and sizes. Bony structures responsible for foraminal or extraforaminal stenosis can be removed more efficiently using larger endoscopic burrs, whereas subsequent removal of the foraminal ligament and soft tissues can be easily accomplished with pituitary forceps, Kerrison punches, and dissectors of various sizes and configurations. When additional work on protruding discs or osteophytes at the ventral aspect of the ENR is required, an inner sleeve can be inserted, and small-caliber endoscopic instruments can be introduced through the sleeve to safely perform the procedure. For more extensive removal of protruding discs or osteophytes, the large working sheath and endoscope can be withdrawn and replaced with a small endoscopic system introduced through the same skin entry point.
A potential concern of this technique is the biomechanical effect of complete resection of the SAP tip. Although the remaining inferior portion of the SAP and the contralateral facet joint are expected to preserve overall facet stability, the degree to which this partial facetectomy affects segmental motion has not been fully elucidated. Previous studies on endoscopic foraminotomy have suggested that limited SAP removal does not significantly compromise stability [11]; however, complete tip resection may theoretically increase localized motion or loading. Therefore, long-term radiological follow-up and future biomechanical or prospective cohort studies are needed to clarify whether this technique influences facet joint integrity or segmental stability over time.
1. Limitations of the Technique
Because a larger endoscopic system was used compared with TELF, the skin incision was slightly longer, and epidural anesthesia was required to prevent intraoperative pain associated with the use of a high-power 90° bipolar RF coagulator. This video case presentation is based on retrospective medical records and operative videos.
2. Complications and Follow-up
No major complications—including infection, hematoma, dural tear, or postoperative dysesthesia—were observed. Over more than one year of follow-up, both visual analog scale and Oswestry Disability Index scores showed significant improvement, demonstrating favorable outcomes (Table 1). Furthermore, no recurrence of foraminal stenosis or instability-related complications following complete resection of the SAP was observed during this period.
3. Educational Value of the Video
In cases of severe lumbar foraminal stenosis or when anatomical barriers, such as a high iliac crest, sacral ala, or large TP, are present, the full-endoscopic paraspinal lumbar foraminotomy demonstrated in this video can be effectively employed to achieve safer and more adequate decompression of the ENR. Additionally, for extraforaminal stenosis at the L5–S1 level, this technique may allow for a more efficient and faster procedure when working around the sacral ala and TP of the L5 vertebra.
CONCLUSION
The full-endoscopic paraspinal foraminotomy technique provides the advantage of operating with greater ease in a wider surgical field using a variety of instruments. This approach facilitates more complete decompression of the ENR by minimizing irritation while effectively addressing compressive bony structures, soft tissues, and disc or osteophyte pathologies. However, given the limited number of cases presented, further large-scale and prospective studies are required to validate the long-term clinical efficacy and safety of this technique.
WRITTEN TRANSCRIPT
00:00 Full Endoscopic Paraspinal Foraminotomy for Lumbar Foraminal Stenosis
In this video article, we present 2 cases of full-endoscopic paraspinal foraminotomy performed in patients with lumbar foraminal stenosis at lower lumbar segments complicated by anatomical barriers.
00:13 Case #1: Presentation
Case #1: A 63-year-old female presented with left leg pain that had persisted for two years. MRI demonstrated left L5–S1 foraminal stenosis. On AP radiographs, a high iliac crest, large TP, and sacral ala indicated that a standard transforaminal approach would be difficult. The skin entry point for a transforaminal approach is usually located far lateral to the midline, and the target landing point of the working sheath is near the base of the SAP via Kambin triangle. Therefore, the initial sheath insertion was expected to be challenging. Although several advanced TELF techniques have been introduced to overcome such difficulties, these often increase operative time and surgical complexity. For this patient, we planned a full-endoscopic paraspinal foraminotomy at L5–S1 left side using a large endoscopic system, which is less affected by anatomical barriers. This technique utilizes a short and large-caliber endoscope together with a wider variety of surgical instruments. The initial working sheath landing point is placed on the outer surface of the bone at the junction of the laminar isthmus, TP, and SAP. Thus, the procedure begins outside the foramen rather than inside it. Under epidural anesthesia, a vertical line was drawn approximately 1 cm lateral to the lateral margin of the left L5 pedicle, along with two horizontal lines at the lower margin of the L5 pedicle and the superior margin of the S1 pedicle. A 1-cm skin incision was made between these lines. Following serial dilation, the working sheath was advanced not through Kambin’s triangle but to the bony surface at the junction of the laminar isthmus, TP, and SAP. A large-caliber endoscope was then introduced.
01:12 Case #1: Initial Landmark
This technique utilizes a short and large-caliber endoscope together with a wider variety of surgical instruments. The initial working sheath landing point is placed on the outer surface of the bone at the junction of the laminar isthmus, TP, and SAP. Thus, the procedure begins outside the foramen rather than inside it.
Under epidural anesthesia, a vertical line was drawn approximately 1 cm lateral to the lateral margin of the left L5 pedicle, along with two horizontal lines at the lower margin of the L5 pedicle and the superior margin of the S1 pedicle. A 1-cm skin incision was made between these lines. Following serial dilation, the working sheath was advanced not through Kambin’s triangle but to the bony surface at the junction of the laminar isthmus, TP, and SAP. A large-caliber endoscope was then introduced.
02:09 Case #1 Video: Initial Landing and Bone Work
Case #1 Video: To secure a clear surgical view and identify anatomical landmarks, the working sheath, pituitary forceps, and bipolar coagulator were used to palpate the bone and clear surrounding soft tissues. Using endoscopic burrs, bone work was performed on the TP, lower pedicle of the upper vertebra, lateral isthmus, and SAP tip. As the decompression proceeded, the facet joint and dural sac came into view. In this segment, the sacral ala was also identified, and additional bone work could be performed in cases of severe extraforaminal stenosis. The foraminal ligament was exposed between the resected TP, pedicle, lateral isthmus, and SAP. The facet joint surface between SAP and IAP was also confirmed. Bone work was continued until the superior and medial endpoints of the foraminal ligament were clearly visualized.
03:06 Case #1 Video: Resection of Ligamentum Flavum in the Foraminal Area
With a curved dissector, the foraminal ligament was detached while minimizing irritation to the ENR. It was then removed using pituitary forceps and kerrison punches. The use of larger and more varied instruments such as dissectors, pituitaries, kerrison punches, and curettes allowed the procedure to be performed more easily and quickly than with a small TELF system.
03:35 Case #1 Video: Decompression of the Exiting Nerve Root
To achieve complete decompression of the ENR superiorly, inferiorly, medially, and laterally, additional work was performed with kerrison punches. If bone removal was insufficient, the endoscopic burr could be reused. The sacral ala was undercut with kerrison punches to confirm decompression of the lateral portion of the ENR. The SAP, TP, and pedicle margins were also refined. Fibrous bands and fat tissue surrounding the ENR were meticulously removed.
04:08 Case #1 Video: Retraction of the Exiting Nerve Root and Annuloplasty
After confirming adequate dorsal decompression of the ENR, ventral decompression was selectively performed. Preoperative MRI suggested that aggressive resection of disc or osteophytes would not be necessary in this case. Therefore, an inner sleeve was inserted into the large endoscope, and the ENR was gently retracted. A small endoscopic radiofrequency probe was introduced through the inner sleeve to perform limited annuloplasty. If more aggressive disc or osteophyte removal had been required, small endoscopic instruments such as pituitary forceps, cutting pituitaries, and kerrison punches could have been used within the inner sleeve to protect and mobilize the ENR during resection. Alternatively, the procedure could be converted to a small working sheath and endoscope (channel-in-channel technique).
05:02 Case #1 Video: Termination of Surgery
Once adequate decompression of the ENR was confirmed in all directions and the ventral aspect was inspected, hemostasis was achieved and the procedure was terminated.
05:14 Case #1: Postoperative MRI
Pre- and postoperative MRI images are shown. The postoperative MRI demonstrated sufficient decompression of the left L5 root at the L5–S1 segment, correlating with symptomatic relief of the patient’s left leg pain.
05:31 Case #2: Presentation
Case #2: A 67-year-old male presented with bilateral leg pain, more severe on the left side, that had persisted for one year. MRI demonstrated left L4–5 and L5–S1 foraminal stenosis with disc involvement, as well as L4–5 central stenosis. On AP radiographs, a high iliac crest and large transverse process suggested that a transforaminal approach at left L5–S1 would be difficult, while a transforaminal approach at L4–5 appeared more feasible. Therefore, we planned ULBD for L4–5 central stenosis, TELF for L4–5 left foraminal stenosis, and a paraspinal endoscopic lumbar foraminotomy for L5–S1 left foraminal stenosis.
06:22 Case 2 Video: Initial Landing and Bone Work
The skin entry point and target landing point were set in the same manner as in Case 1. The left TP and SAP are identified, and bone work is being performed using endoscopic burrs. As bone work is sufficiently carried out on the tip of the SAP, TP, lateral isthmus, the SAP tip embedded on the ventral side of the TP comes into view, allowing its removal with a kerrison punch. After removal of the SAP tip, we further resect the TP with a kerrison punch to achieve complete decompression of the ENR. The foraminal ligament dorsal to the ENR was meticulously removed. Since the preoperative MRI suggested some degree of far-lateral stenosis caused by the sacral ala, additional bone work was thoroughly performed on the sacral ala using an endoscopic burr or kerrison punch.
07:52 Case 2 Video: Ventral Decompression With Annuloplasty
Once sufficient decompression of the dorsal part of the ENR had been achieved, annuloplasty was performed for the disc and osteophyte located at the ventral part of the ENR using an inner sleeve and a RF probe. This maneuver also facilitated mobilization of the ENR. As seen on the preoperative MRI, disc-related compression of the ENR was more prominent than in Case 1. Therefore, more extensive annuloplasty was carried out using a high-power 90° bipolar RF probe.
08:24 Case 2 Video: Optional Conversion to TELF Endoscopic System
If necessary, this step can be further extended by removing the large working sheath and endoscope, and inserting a TELF small working sheath and small-caliber endoscope through the same entry point, thereby protecting and retracting the ENR while removing the disc and osteophytes. However, in this case such an extensive procedure was not required, and the surgery was completed without changing the endoscope system.
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