Full-Endoscopic Midline Foraminoplasty: An Alternative Method for Treating Lumbar Foraminal Stenosis
Article information
Abstract
Objective
To describe the full-endoscopic lumbar foraminoplasty with midline skin incision (FEFM) and lateral recess decompression procedure and to report its clinical outcomes at the 1-year follow-up.
Methods
Consecutive patients with lumbar foraminal and/or lateral recess stenosis who underwent FEFM procedures were retrospectively reviewed. Clinical outcomes were evaluated with a visual analogue scale (VAS) of back and leg pain and Oswestry Disability Index (ODI) up to 1 year postoperatively. The complications and recurrence rate were also recorded.
Results
A total of 30 cases (51 levels) were included (L3–4, 6 cases [11.8%]; L4–5, 23 [45.1%]; L5–S1, 22 cases [43.1%]). VAS scores collected at preoperative, postoperative day 1, 3 months, 6 months, and 1 year were 9.16, 1.7, 1.36, 1.3, and 1.43, respectively. The ODI scores collected at preoperative, postoperative 3 months, 6 months, and 1 year were 46.63, 11.5, 10.66, and 10.46, respectively (p<0.05). The mean operation time was 88.7 minutes (range, 45–152 minutes). The length of hospital stay was 1.21 days (range, 1–3 days). No immediate complications were identified, and no patients experienced a recurrence of symptoms requiring revision surgery.
Conclusion
FEFM is an effective procedure for treating foraminal and/or lateral recess stenosis. It demonstrates the capability to decompress both bilateral foraminal and lateral recess stenosis through a single-entry point.
INTRODUCTION
Lumbar foraminal stenosis (LFS) is a condition in which a spinal nerve becomes entrapped in a narrow lumbar foramen due to degenerative lumbar spinal disorders. It presents challenges in both clinical approach and management [1,2]. The incidence of LFS is reported to be about 8%–11% [1,2]. This condition is sometimes overlooked, leading to failed back surgery [1-3]. Various operative techniques have been described to address this issue, including foraminotomy, facetectomy, partial pediculectomy, fusion, and distraction instrumentation. However, each surgical procedure has its own advantages and disadvantages. Nowadays, full-endoscopic lumbar spine surgery is capable of decompressing the lumbar foramen, thus preventing the need for more aggressive procedures.
We introduced a modified approach to manage foraminal stenosis, which simultaneously addresses central and/or lateral recess stenosis through full-endoscopic lumbar foraminoplasty with midline skin incision (FEFM) decompression. The advantage of this approach lies in its accessibility to both bilateral foramens and the bilateral subarticular (lateral recess) zones, as well as the central zone, all from a single-entry point. The purpose of this study was to describe the surgical technique of this procedure and assess the clinical outcomes and complications associated with this proposed surgery.
MATERIALS AND METHODS
The consecutive patients with lumbar foraminal and/or lateral recess stenosis who underwent FEFM procedure were retrospectively reviewed. Thirty cases between August 2021 and August 2022 underwent FEFM performed by 2 experienced endoscopic spine surgeons (SP, CR). The inclusion criteria were unilateral or bilateral foraminal stenosis with or without central and/or lateral recess stenosis patients who showed no improvement after 3 to 6 months of conservative treatment protocol. Exclusion criteria included trauma, history of previous operation, infection, tumor, and significant spinal instability.
Our research was under the ethical standards of the institutional and national research committee and its later amendments or comparable ethical standards. It was performed according to the Helsinki Declaration and approved by the Institutional Review Board (IRB) of Queen Savang Vadhana Memorial Hospital (IRB No. 014/2567).
1. Surgical Techniques
1) Preparation
After routine general anesthesia, the patient was positioned prone with both hips and knees flexed on a radiolucent operating table. The desired level was identified and marked under C-arm fluoroscopic guidance, with both anterior-posterior and lateral views obtained (BV Pulsera mobile C-arm, Philips, Denmark).
2) Instrumentation
All aforementioned procedures were performed using a uniportal endoscopic instrument system and radiofrequency ablator (RIWOSPINE, Vertebris Stenosis, RIWOspine GmbH, Germany).
3) Entry point
The entry point was made at the midline and slightly below the level of the index disc. The surgeon made an 8-mm incision just between the 2 cranial and caudal spinous processes (the incision size and location may vary depending on the size and location of spinous processes) (Fig. 1). Next, the blunt dilator was introduced until the ligamentum flavum in the interlaminar space between the cranial and caudal laminae was reached.
Stab skin incision at midline and slightly caudal area of interlaminar space (A) and a picture of spinal model shows trajectory of endoscope to ipsilateral and contralateral foraminal area (B–D).
4) Portal placement
To navigate past the intervening spinous processes, the trajectory of the working portal should be aligned in a caudo-cephalad direction (Fig. 2). The working sleeve was inserted along the dilator and docked on the ipsilateral lamina and medial facet joint.
Fluoroscopic lateral (A) and anteroposterior (B) views of trajectory of working portal and endoscope during full-endoscopic lumbar foraminoplasty with midline skin incision.
5) Bone working
Once all structures were identified and oriented, similar to interlaminar decompression, the ipsilateral inferior articular process (IAP) was removed using a high-speed drill from the lowest tip up to the caudal edge of the superior lamina to expose the underlying superior articular process (SAP). The IAP and cephalad lamina/pars were removed to a certain extent (approximately 4–5 mm). However, caution must be exercised to avoid overremoving the pars, as it could lead to iatrogenic pars fracture. Next, the tip of the SAP was identified directly beneath the IAP. The Kerrison Rongeur was then utilized to remove the SAP tip and ligamentum flavum at the central, subarticular, and foraminal zones until the exiting root in the foramen and the traversing root were fully decompressed (Fig. 3A).
Endoscopic views after complete decompression. (A) Ipsilateral traversing and exiting roots. (B) Contralateral traversing and exiting roots. (C) Bilateral exiting and traversing roots (4 roots decompression).
In cases of concomitant contralateral subarticular or foraminal stenosis, the endoscope can be tilted to the contralateral side, and the aforementioned steps can be repeated to decompress the contralateral subarticular recess and foraminal area. For bilateral decompression, all 4 roots (bilateral exiting roots and bilateral traversing roots) can be simultaneously decompressed (Fig. 3C).
6) Finishing the procedure
At the endpoint of the procedure, free mobilization of the nerve roots and pulsation of the dural sac were confirmed. A tube drain was placed, and 2% Marcaine was simultaneously applied subcutaneously for local pain control. Routine postoperative care protocol was administered. All complications, including dural injury, postoperative nerve palsy, cauda equina syndrome, and infection, were recorded. Patients could be discharged soon after the tube drain was removed.
2. Statistical Analysis
Data were described using frequency and mean (standard deviation) for categorical and continuous data, respectively. Baseline characteristics of the patients and cointerventions were compared between the 3 intervention groups using the chi-square test (or exact test) for categorical data and repeated measures 1-way analysis of variance (or Kruskal-Wallis test) for continuous data. A p-value <0.05 was considered statistically significant.
RESULTS
Thirty patients consisted of 15 females and 15 males, with an average age of 66.13 years (range, 50–77). Mean body mass index was 24.88 ± 1.51 kg/m2. There were 11 cases for 1 level, 17 cases for 2 levels and 2 cases for 3 levels surgery. The operative levels at L3–4, L4–5, and L5–S1 were 6 (11.8%), 23 (45.1%), and 22 (43.1%), respectively. The mean operative time was 88.7 minutes, ranging from 45 to 152 minutes. The length of hospital stay ranged from 1 to 3 days, with a mean of 1.21 days.
The VAS scores were collected at preoperative, postoperative day 1, 3 months, 6 months, and 1 year, with results of 9.16, 1.7, 1.36, 1.3, and 1.43, respectively. The Oswestry Disability Index (ODI) scores were collected at preoperative, postoperative 3 months, 6 months, and 1 year, with scores of 46.63, 11.5, 10.66, and 10.46, respectively. These results are shown in Figs. 4 and 5. For complication and recurrent cases, there were 2 cases (6.6%) of postoperative transient neuralgia, which resolved within 2 weeks. There was no superficial or deep infection, dural injury and recurrence at 1-year follow-up period.
Visual analogue scale (VAS) at preoperative, postoperative day 1, 3 months, 6 months, and 1 year (mean±standard deviation).
Oswestry Disability Index (ODI) at preoperative, postoperative at 3 months, 6 months, and 1 year (mean±standard deviation).
DISCUSSION
The demographic shift towards aging populations has led to a significant increase in the prevalence of lumbar degenerative disorders. Fortunately, advancements in technology and the quality of full-endoscopic surgical systems have progressed rapidly, enabling surgeons to effectively manage a wide range of lumbar pathologies. The evolution of newer spinal endoscopy versions allows surgeons to access the “McNab Hidden zone” without causing significant muscle, bone, or joint damage, thereby providing a high-quality magnified visual field. It is conceivable that spinal endoscopy may become the standard treatment for lumbar disc herniation and stenosis in the near future [4,5].
When treating LFS, avoiding the creation of significant spinal instability is crucial. In the literature, full-endoscopic lumbar foraminotomy can be performed via 3 routes: transforaminal, contralateral, and paramedian/Wiltse approaches. According to Giordan et al. [6], transforaminal approaches, such as endoscopic transforaminal lumbar foraminotomy, have been reported to be safe, economical, and suitable for elderly patients who are not eligible for major surgery, although some cases of nerve root injury and neurapraxia have been reported [6-8].
The contralateral approach, where the working portal and endoscope are inserted from the opposite side of the lesion, emerged in the late 2010s. Kim et al. conducted a systematic review of 8 retrospective cohort studies involving 194 patients who underwent uniportal interlaminar contralateral endoscopic lumbar foraminotomy. The study demonstrated good to excellent results with a low rate of complications [9-11].
The paramedian approach was proposed in 2019 [12], introducing a pars-docking technique that claimed the benefit of limited facet and bony removal, thereby minimizing bleeding and preserving stability. Nam et al. [12] conducted a study involving 106 patients who underwent the paramedian stenoscopic approach for LFS.
We proposed FEFM as our modified procedure of choice for patients with foraminal stenosis with or without centro-lateral recess stenosis. With our technique, simultaneous decompression of the ipsilateral lateral recess and central area stenosis is conceivable. Additionally, in complex cases with a combination of bilateral stenosis, decompression of up to 4 roots—bilateral exiting and traversing roots—can be accomplished in a single approach, which is cumbersome for other approaches.
The approach technique and entry point of FEFM closely resemble the interlaminar approach for lumbar stenosis, albeit with a more medial and caudal placement. This similarity enhances the feasibility and familiarity of the anatomy for surgeons. To access the foramen, a certain amount of pars and inferior facets must be removed to expose the dorsal root ganglion.
Postoperative dysesthesia is a relatively common occurrence in full-endoscopic decompression procedures, particularly with the transforaminal approach, with reported incidence rates ranging from 5% to 15% [13]. However, in our study, we observed only 2 cases of transient neuralgia, which were mild and resolved within 2 weeks postoperatively. This suggests a potential benefit of our technique in reducing the occurrence of postoperative dysesthesia. Further studies may be necessary to confirm and validate this observed benefit of our technique.
Theoretically, our midline foraminotomy technique has several limitations. Firstly, it may not be suitable for addressing extraforaminal and far lateral lesions, which are better managed with transforaminal or paramedian/Wiltse approaches. Second-ly, there is a risk of severing radicular vessels due to their proximity within the lumbar foramen. Careful attention is needed when decompressing the dorsal root ganglion to avoid encountering massive bleeding that could obscure visualization. Thirdly, there is a concern regarding over-resection of the pars interarticularis and facet joint, which could potentially lead to increased postoperative instability. Finally, it is essential to acknowledge that our approach may not be suitable for addressing upper lumbar foraminal lesions. The morphology of facet joints and the narrow interlaminar space in this region may render our technique less appropriate, with transforaminal or paramedian techniques potentially being more suitable. In our study, the uppermost index level was L3–4, which still remained compatible with the FEMF technique in properly selected cases.
Limitations of our study include, firstly, its retrospective design, which may introduce bias and limit the strength of our conclusions. Additionally, the number of patients included in the study was small, and the follow-up duration was relatively short. Furthermore, we did not compare the outcomes of our proposed technique with those of previously described approaches. Therefore, further prospective and comparative studies may be necessary to better understand and reveal the benefits of this modified midline foraminotomy technique.
CONCLUSION
FEFM emerged as an acceptable option for managing foraminal and/or centro-lateral recess stenosis. Its feasibility and surgeon-friendly techniques make it a versatile approach suitable for ipsilateral or bilateral decompression, with the potential to decompress up to 4 roots from a single incision. However, further prospective and comparative studies are necessary to expand its indications and underscore its usefulness in clinical practice.
Notes
Conflict of Interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Author Contribution
Conceptualization: GK, SP, KJ, CR; Formal Analysis: SP, CR; Investigation: SP, KJ, CR; Methodology: SP, KJ, CR; Project Administration: GK, JK; Writing – original draft: GK, SP, KJ, CR; Writing – review & editing: GK, SP; Supervision: GK, JK.