Abstract
Background Adult isthmic spondylolisthesis often remains stable in adulthood, but progressive neural compression can occur due to scar tissue, bony overgrowth, and disc degeneration. Conventional endoscopic techniques such as the interlaminar or transforaminal approaches may be limited by anatomical constraints in adult isthmic spondylolisthesis, making complete decompression difficult.
Methods A 70-year-old man presented with bilateral leg pain and neurogenic claudication. Imaging revealed bilateral L4 to L5 lateral recess narrowing, L5 foraminal stenosis, and a bulging L5 to S1 disc compressing the extraforaminal nerve roots. A novel craniocaudal interlaminar approach via unilateral biportal endoscopic spine surgery was used to decompress the central and contralateral foraminal regions. The residual ipsilateral extraforaminal lesion was accessed through a separate full endoscopic transforaminal approach. Three incisions of 7 mm each were used.
Results The patient experienced immediate and significant relief of radicular symptoms and improved function and was discharged the next day. At 18-month follow-up, he remained pain-free and without new-onset back pain or signs of instability.
Conclusions This is the first reported case combining unilateral biportal endoscopic spine surgery and full endoscopic spine surgery. The approach enabled full decompression from central to extraforaminal zones with minimal invasiveness. This dual-endoscopic strategy may serve as a model for treating complex spine cases not amenable to single-approach techniques.
Level of Evidence 4.
Introduction
Although the slippage associated with adult isthmic spondylolisthesis (AIS) generally stabilizes in adulthood, secondary issues, such as nerve compression, may develop due to scar tissue formation, bone spurs, and intervertebral disc degeneration.1–3 Symptoms such as buttock pain, radiculopathy, and, in more severe cases, neurogenic claudication may develop, significantly impairing the patient’s quality of life. Decompression alone, rather than addressing the slippage, can be a less invasive treatment for patients without significant mechanical back pain or those unable to tolerate fusion surgery.
Endoscopic spine surgery, including the interlaminar and transforaminal (TFA) approaches, has become an increasingly favored option for treating AIS patients with radiculopathy due to its precision and minimal tissue disruption.4–9 However, due to the location of the pathology, thorough decompression is considered difficult using conventional approaches to endoscopic surgery. In our previous work, we developed the craniocaudal interlaminar approach (CIA), which utilizes the proximal adjacent interlaminar space to achieve a better trajectory for complete decompression of the AIS pathoanatomic lesions, demonstrating favorable outcomes.10
However, another subset of patients with AIS may also present with extraforaminal stenosis due to disc herniation, a condition that falls outside the treatment range of CIA. In such cases, an additional approach can be a favorable option to ensure adequate decompression and minimize soft tissue damage. This report presents a case where CIA, via unilateral biportal endoscopic spine surgery (UBESS), was combined with TFA via full endoscopic spine surgery (FESS), allowing for effective decompression from the spinal canal to the extraforaminal regions.
Case Presentation
History and Physical Examination
A 70-year-old man, previously active and healthy, presented with buttock pain radiating to both legs, especially the left side, for several months. The pain worsened with back extension and was relieved by a stooping posture. He also reported intermittent claudication and was unable to walk for more than 15 minutes. The visual analog scale score for the buttock was 3/10, for the right leg was 3/10, and for the left leg was 4/10. The straight leg raise test was negative bilaterally. Dynamic flexion-extension radiographs of the lumbar spine demonstrated Meyerding grade 1 L5 to S1 spondylolisthesis (Figure 1). Magnetic resonance imaging and computed tomography revealed a bilateral isthmic defect at L5, disseminated ragged spurs extending from the bilateral L4 to L5 lateral recesses to the L5 foramen (Figure 2A), and an L5 to S1 degenerated bulging disc compressing the bilateral exiting roots from the neuroforaminal to the extraforaminal region (Figure 2B).
Dynamic flexion-extension radiographs demonstrated Meyerding grade 1 L5 to S1 spondylolisthesis.
(A) The green arrows indicate the wide-based bulging disc causing foraminal and extraforaminal stenosis of the L5 root on magnetic resonance imaging. (B) The red arrows highlight the ragged spur responsible for L5 root stenosis at the L4 to L5 lateral recess and L5 to S1 foramen on computed tomography.
Treatment
Since the spondylolisthesis was considered stable, the treatment decision was made to perform endoscopic decompression alone. The surgery was planned to start with the CIA via UBESS for bilateral decompression of the main pathoanatomic lesions, including the bilateral ragged spurs primarily located from the L4 to L5 lateral recess to the L5 foramen. The contralateral bulging disc can also be addressed due to the ideal instrument trajectory from ipsilateral to contralateral. Subsequently, an L5 TFA via FESS was used for ipsilateral bulging disc decompression. This research received a waiver from approval by the Institutional Review Board of Chi Mei Medical Center. Informed consent was obtained from the patient.
The patient was positioned prone on a radiolucent table with soft cushions after general anesthesia was administered. Level confirmation and marking were performed under fluoroscopic guidance before the incision (Figure 3). The first incision for the CIA scope portal was made at the upper border of the L4 to L5 interlaminar space, 5 mm lateral to the spinous process, while the second incision for the instrument was placed approximately 2 cm distal to the first. Shavers and radiofrequency wands were used to create the initial working space. Once the instrument workflow was optimized, the superficial ligamentum flavum was removed to expose the upper border of the index lamina (Gill fragment). The bilateral laminotomy of the Gill fragment was incrementally extended laterally until the pars defect was exposed. Fibrocartilage, adhesions, and isthmic ragged spurs from both the Gill fragment and the proximal lamina remnant at the lateral recess were removed bilaterally. After adequate adhesiolysis, the Gill fragment was pushed distally and posteriorly with the endoscope or instruments, further exposing the bilateral neuroforamina. Due to the aligned trajectory of the contralateral pars defect and the instrument, the contralateral lesion, including the bulging disc, was completely addressed in the extraforaminal area (Figure 4). The contralateral disc could mostly be accessed and removed from the axilla of the L5 root. However, from the perspective of the CIA, the ipsilateral disc is usually hidden directly beneath the ipsilateral L5 root, making it more difficult to reach (Figure 5). The ipsilateral extraforaminal disc was unreachable.
Incisions used in the combined approach.
(A) The contralateral lesion, including the ragged isthmic spur and fibrocartilage adhesion. Asterisk: ragged spur on Gill’s fragment. Red arrow: ragged spur on the proximal laminar remnant. (B) Well decompression of the contralateral lesion, including undermining the bulging disc under the exiting root. Triangle: contralateral bulging disc excised from the axillary portion of the root. Green arrow: decompressed root.
(A) The ipsilateral ragged spur and compressed exiting root. Asterisk: ragged spur on the proximal laminar remnant. Red arrow: squeezed and cyanotic root. (B) The ipsilateral lesion can mostly be addressed by this approach; however, accessing the ipsilateral disc from this trajectory is challenging. Triangle: inferior border of the pedicle. Green arrow: decompressed and relief root.
For the bulging disc on the ipsilateral side, another 7-mm incision for FESS TFA was made approximately 8 cm lateral to the L4 spinous process. Under fluoroscopic guidance, a spinal needle was used to inject methylene blue dye into the intervertebral disc via the left L5 to S1 Kambin’s triangle. The needle was then replaced with a guide wire to facilitate the insertion of the pencil dilator. The endoscope was introduced through the dilator, and after establishing the initial working field, bony landmarks—including the S1 pedicle and the superior articular process—were identified and confirmed fluoroscopically. The bulging L5 disc was visualized adjacent to the S1 pedicle, with the methylene blue dye serving as double confirmation (Figure 6). Partial discectomy of the ipsilateral disc was performed to achieve complete decompression (Figure 7). The endoscopic video clips with animation and annotations can be seen in Supplemental Video 1.
Bulging disc in the extraforaminal area.
Partial discectomy of the extraforaminal disc using full endoscopic spine surgery.
Outcomes
Following the surgery, no neurological deficits or complications were observed. The patient experienced immediate and significant relief from buttock and leg pain. Postoperative visual analog scale scores improved notably, from 3/10 to 1/10 for the buttock, from 3/10 to 1/10 for the right leg, and from 4/10 to 2/10 for the left leg. The patient was discharged the day after surgery. He expressed satisfaction with his early ambulation, ability to fully extend his back, and the short hospitalization enabled by the minimally invasive, nonfusion procedure. At the latest follow-up, 18 months after the operation, the patient was completely free of pain with no newly developed back pain.
Discussion
The pathogenesis of radiculopathy in lumbar spondylolysis patients is well understood.1,3,11,12 Minimally invasive techniques such as endoscopic spine surgery reduce tissue damage, shorten recovery time, and precisely address AIS pathoanatomic lesions. In our previous work, we described the CIA technique via UBESS for treating AIS. UBESS uses 2 portals for better triangulation and comprehensive lesion access, allowing tools and the camera to operate independently without interference. Compared with FESS, this approach enhances visibility and flexibility when addressing complex conditions like AIS, which often involves multiple lesions.1–3 The CIA technique utilizes the upper-level interlaminar space, providing an ergonomic and safe trajectory for bilateral isthmic region decompression. This technique enables contralateral decompression from the upper-level lateral recess to the extraforaminal region, as well as ipsilateral decompression from the upper-level lateral recess to the index foramen’s exit.9
However, addressing ipsilateral foraminal and extraforaminal disc herniation remains a challenge, even with CIA via UBESS. In fact, foraminal and extraforaminal discs are best treated with FESS TFA.13 FESS requires only a single small incision, with specifically designed instruments operating in the same canal, resulting in minimal tissue trauma. However, this technique demands meticulous preoperative planning to ensure precise targeting, which may limit its utility in complex cases.14 In our case, FESS was used specifically for the foraminal and extraforaminal bulging disc. Although the TFA of UBESS could achieve similar results, it requires an additional portal and more soft tissue dissection. Additionally, the abundance of microvascular structures around the foramen’s exit raises the risk of bleeding during UBESS, potentially resulting in longer operation times compared with the TFA of FESS.15
In patients with grade I or grade II AIS without significant mechanical back pain, endoscopic decompression alone offers substantial benefits for younger patients, where spinal fusion may be premature for purely radicular symptoms and for elderly patients who cannot tolerate the stress of fusion procedures. Our combined approach requires only 3 small incisions, each measuring 7 mm, incorporating CIA via UBESS and TFA via FESS, successfully addressing the limitations of standalone techniques that struggle to tackle disseminated pathological lesions in AIS. UBESS, with its high flexibility, was used to target most lesions within the isthmic region and contralateral foramen, while the residual ipsilateral bulging disc was treated with FESS TFA. This approach effectively targets ipsilateral foraminal and extraforaminal compressive elements with minimal tissue trauma. However, careful patient selection remains critical, as certain factors predict poor outcomes following isolated decompression. Patients with significant dynamic instability (ventral translation >4 mm or angular variation >10 degrees on dynamic imaging) represent poor candidates for decompression alone. Similarly, patients with vacuum disc phenomenon, focal scoliosis with endplate microfractures, and associated bone marrow edema are at elevated risk for progressive collapse following decompression. In these scenarios, solid spinal fusion represents the more appropriate therapeutic intervention to prevent further structural deterioration.
Conclusion
This case report highlights the potential of combining UBESS CIA and FESS TFA to treat AIS lesions thoroughly, from the upper lateral recess to index extraforaminal stenosis. The favorable clinical outcomes in our patient, including significant pain relief and functional recovery, demonstrate the efficacy of this dual-endoscopic approach. As endoscopic techniques advance, the distinctions between FESS and UBESS may diminish. A patient-specific approach that integrates the strengths of each method may yield the best outcomes.
Footnotes
Funding The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests The authors report no conflicts of interest in this work.
Ethics Approval This retrospective case study was approved by the Ethics Committee and Institutional Review Board of Chi Mei Medical Center. The work described has been carried out in accordance with Declaration of Helsinki.
Consent for Publication Informed consent was obtained from the patient. All authors confirm that they have reviewed the manuscript and provided their consent for its publication.
- This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2025 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.
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