INTRODUCTION
Cervical foraminotomy is a surgical procedure aimed at decompressing nerve roots affected by foraminal stenosis. The location and extent of the pathological changes within the foraminal canal intricately guide the planning of this intervention. In cases where stenosis occurs in the middle and exit zones or involves the entire transcanal segment, traditional foraminotomy techniques may not suffice to alleviate symptoms effectively.
Conventional foraminotomy typically focuses on pathologies arising from the posterolateral corner of the cervical disc usually involving the disc or disc osteophytic complex and involves accessing the medial facet and excising the medial half of the facet joint, including the inferior articular process (IAP) and superior articular processes (SAPs), also known as the superior and inferior lateral masses. However, in instances where stenosis affects the entire transforaminal canal or involves pathology in the outer part of the canal, a standard foraminotomy necessitates the sacrifice of a complete facet joint. This sacrifice can iatrogenically destabilize the facet joint, requiring subsequent lateral mass fixation to restore stability. Advancements in imaging techniques, such as 2D sagittal-oblique multiplanar reconstruction (2D SOMPR) computed tomography (CT) scans, have enhanced the ability to identify and analyze the stenotic zones within the foramen, providing a detailed end-on view of the pathology [1,2]. This detailed visualization facilitates the planning of a modified approach that combines standard and inclinatory foraminotomy techniques [3-5]. The inclinatory approach allows for undercutting the overgrown SAP, which may result from collapse or other pathological changes, ensuring complete decompression of the exiting nerve root while preserving the integrity and function of the facet joint. Unilateral biportal endoscopy (UBE) has emerged as a minimally invasive surgical technique that aligns with the principle of motion preservation [6] and yet prevents instability. UBE facilitates the simultaneous decompression of one or more severely stenotic nerve roots while maintaining the natural biomechanics of the cervical spine.
This study investigates a combined approach, utilizing UBE with 2D sagittal-oblique multiplanar reconstruction (2D SOMPR) CT scan-aided imaging and evaluates the clinical outcomes of unilateral biportal endoscopic cervical foraminotomy in patients with severe complex and transcanal foraminal stenosis, focusing on the efficacy of the combined approach for comprehensive decompression.
MATERIALS AND METHODS
We retrospectively reviewed hospital records for patients who underwent cervical UBE foraminal decompression between January 2023 and January 2024. All patients were operated on by a single surgeon (MDP), and hospital records were evaluated by 2 spine consultants (MDP and SRG). Institutional Review Board of the Golden Park Hospital, approval was obtained prior to conducting this study (approval number: IEC/2024/11/02). All patients were included after clinical correlation of symptoms with standard x-rays and magnetic resonance imaging (MRI). Patients were additionally subjected to CT scans, and 2D-SOMPR images in the plane of the foramen were obtained. After reviewing the records, the following patients were included: (1) Patients with symptomatic single or multilevel cervical foraminal stenosis confirmed on MRI and CT evaluation. (2) Patients who failed to have relief of symptoms following a trial of conservative treatment for 6 weeks. The authors excluded the following patients: (1) Patients who underwent surgical treatment options other than the UBE approach. (2) Patients having segmental spinal instability as confirmed by dynamic x-rays. (3) Patients who followed up for less than 12 months.
1. Postoperative Assessment
Clinical outcomes were assessed preoperatively, immediately postoperatively, at 1 month, 6 months, and 1 year. To measure neck and arm pain, the visual analogue scale (VAS) and functional capacity were evaluated using the Neck Disability Index (NDI) preoperatively and at 1 month, 6 months, and 1 year postoperatively. Patient satisfaction was evaluated using the modified NDI criteria. Data on operating times, intraoperative and perioperative complications, duration of hospital stay, and recurrences were recorded. NDI [7,8]. The authors have relied on this index to assess pre- and postoperative pain improvement, numbness, and the ability to return to work in patients with cervical radiculitis.
2. Key Considerations in Surgical Approach
1) Preservation of joint integrity and function
In cases where the pathology affects the entire foraminal canal or the exit zone of the facet joint, standard cervical foraminotomy may lead to incomplete decompression of the nerve root. Moreover, excessive bone resection or undercutting risks destabilizing the facet joint, potentially necessitating lateral mass fixation [9]. By integrating both standard and inclinatory foraminotomy techniques, the surgeon can accurately identify and target the pathological components of the SAP. Preoperative sagittal-oblique CT imaging in the foramen plane facilitates precise localization of the stenotic segment, allowing for selective resection of the impinging SAP portion while preserving overall joint stability and function.
2) Enhanced safety and visualization for complete decompression
Standard foraminotomy is necessary for all pathology arising from disc herniation and disc-osteophyte complex, particularly in severe stenotic cases where the nerve root is tightly entrapped in the entry and middle zone of the foraminal canal [10]. Utilizing the inclinatory approach after initial decompression offers improved visualization of the dorsal transcanal compressive elements. Utilizing a combination of specialized tools—including high-obtuse angle Kerrison punches (120°, 1 mm), micro-osteotomes (1–1.5 mm), and angled chisels—facilitates precise resection through a controlled corridor between the SAP tip and its contact point with the superior pedicle, significantly reducing the risk of iatrogenic damage.
3. Pathoanatomy of Cervical Foraminal Stenosis: Implications for Surgical Decompression
In cases where pathology is confined to the lateral aspect of the uncovertebral joint—such as a disc-osteophyte complex, posterolateral disc herniation, or facet joint cyst—standard foraminotomy techniques are generally adequate. These conditions typically involve localized encroachment within a 5–6 mm zone lateral to the uncovertebral joint. A partial resection of the medial facet joint, approximately 5–6 mm, facilitates adequate decompression, allowing visualization of the inner canal and the outer pedicular corner using a 0° endoscope. In such scenarios, standard foraminotomy effectively alleviates nerve root compression.
However, when disc height collapse occurs simultaneously with pathologies like osteophyte formation or facet cysts, the SAP will about the inferior edge of the cranial pedicle, obstructing the entire length of the foramen.
1) Greek column concept (Figure 1)
If the IAP constitutes the roof of the foramen, then the SAP is the column that supports the IAP. When the cervical disc collapses, the SAP hypertrophies, which compresses the nerve root exiting through that foramen (Figure 2). Partial inclination and undercutting will not free that root and can result in iatrogenic damage to root or facet. Standard medial foraminotomy does not adequately address the compression of the nerve root in the exit zones of the foraminal canal, the use of a 30° scope and assuming an inclined position by crossing over to the opposite side of the patient and turning the scope around to view the foramen end-on allows visualization of the concealed part of the SAP exerting pressure on the exiting nerve root.
3) Nature of anatomy of the collapse
There will always be some space between the tip of the SAP (marked in green in Figure 2B) and the inferior wall of the pedicle of the cranial lateral mass. This allows the surgeon to exploit this corridor after cauterizing the veins that accompany the root in this corridor at the shoulder of the root, gradually creating space and then, using small osteotomes and 2-mm burrs, opening up the rest of the foraminal canal.
4) KIM’s classification and its fallacy
The universal classification for cervical root foraminal stenosis is the Kim classification [13]. Its grading is straightforward, but it does not reveal or emphasize the length of stenosis in the medial region, the central area, or the entire foraminal canal. It classifies stenosis based solely on the percentage of compression of the ipsilateral nerve root. Its uniqueness stems from comparing the same root's entry, exit, and middle zone without comparing it to the contralateral side. This is important because the neck is a highly flexible structure, and rotation will be inherent in every CT scan; therefore, the standard of comparison is the same root at its origin, transition, and exit.
5) Proposed modification classification
Since the Kim’s classification does not specify which part of the canal contributes to stenosis—whether anterior, posterior, or a combination of both or the length of the segment involved- it is proposed to refine the Kim classification further by introducing 3 standard subsets.
6) Modified Kim’s classification
Medial foraminal stenosis: Anterior causes include disc and disc-osteophyte complex formation. Posterior causes consist of focal osteophyte, flaval thickening, and facetal cyst.
Middle foraminal stenosis: Anterior causes are typically foraminal disc herniation, zygo-apophyseal joint osteophyte. Posterior cause is focal osteophyte.
Transcanal stenosis: This type is characterized by disc collapse accompanied by SAP upriding. In most cases, both anterior and posterior contributing factors coexist.
7) Surgical procedure (Supplementary Video Clip 1)
Portals for combined standard and inclinatory foraminotomy are positioned more medially compared to the standard foraminotomy approaches for single, double, or triple foraminal decompression using only 2 portals (Figure 5). This is possible because we use a 30° scope, which provides an appropriate foraminal tunnel view in the inclined position and allows approach adjustments using only 2 ports. Surgery is initiated at the V Junction. Upon addressing all postlateral pathology, an inclinatory view into the foramen is taken to decompress the SAP, thereby relieving the compression on the nerve root until it exits through the foramen.
RESULTS
This study evaluated 23 patients (17 males, 6 females) with a mean follow-up of 13 months, all diagnosed with degenerative spondylosis and extensive transcanal stenosis, confirmed via CT, MRI, and x-rays. All patients underwent unilateral biportal endoscopic cervical combination foraminotomy, with or without hemilaminectomy for associated myelopathy.
The average surgical duration was 42 (range, 40–50) minutes for a single level, and the mean hospital stay was 2 days. Preoperative VAS scores for radicular pain averaged 7.78, which decreased to 1.43 postoperatively (p<0.05). The average NDI score improved from 91.30 preoperatively to 2.87 at final follow-up (p<0.05). According to NDI criteria, 22 patients achieved excellent outcomes, while 1 patient had a poor outcome due to preexisting nerve damage.
Eight patients experienced minor transient irritation of the exiting nerve root, which resolved within 8 weeks with medication. One patient with preoperative C5–6–7 root palsy and severe radiculitis did not recover muscle strength but achieved complete relief of radicular pain at 12.5 months. One patient had bilateral C5 nerve root palsy, which recovered completely at 12 weeks. One patient had transient weakness of the C4 nerve root, which also recovered within 8 weeks.
No infections or permanent iatrogenic damage occurred. Functional mobility was restored in all patients. Details regarding individual cases are summarized in Tables 1–3. Some of the case illustrations have been demonstrated in images 6 to 11. Comparison of preoperative and postoperative CT scans is shown in Figure 6. Figures 7–11 show images of of some of the cases in this cohort.
DISCUSSION
Cervical radiculopathy is one of the most frequently encountered spinal symptom that leads to significant disability. Posterior cervical foraminotomy gained popularity as an alternative to fusion surgery. Conventional foraminotomy typically focuses on pathologies arising from the posterolateral corner of the cervical disc usually involving the disc or disc osteophytic complex. In cases presenting with transcanal stenosis, the standard foraminotomy fails to address the pathology in the exit zone. Thus, the authors have described their technique of combination foraminotomy aided with 2D-SOMPR CT scan imaging to adequately address such pathology using biportal endoscopic technique. To the authors best knowledge, this is the primary description of combination foraminotomy using biportal endoscopic technique. The combined (standard and inclinatory) foraminotomy approach via UBE offers a distinct advantage in the surgical management of cervical foraminal stenosis by addressing both posterolateral and transcanal pathology simultaneously, facilitating safe visualization and decompression of the exiting nerve root while preserving the integrity of the cervical facet joint. Combined with preoperative 2D-SOMPR CT images in the plane of the foramen, our technique has demonstrated safety profiles and complication rates comparable to traditional foraminotomy and stand-alone inclinatory foraminotomy [3,4]. Our paper has described a novel technique of combination foraminotomy i.e., standard as well as inclinatory foraminotomy based on evaluation using specialized sagittal CT scan images in the plane of the foramen. Our technique differs from that of Song and Lee [3] with respect to certain key points: (1) In our technique, a standard foraminotomy is performed first and then the surgeon switches to the side opposite to the pathology to complete the inclinatory foraminotomy. (2) Our technique does not use extreme medial portals, but uses medialized standard portals which help us achieve a standard as well as inclinatory foraminotomy with the same incisions.
A combination foraminotomy can be used to decompress multiple foramina simultaneously in a single sitting. Majority of our patients had excellent outcomes with significant relief from preoperative symptoms as evident from VAS scores and NDI scores (Tables 2 and 3). Eight patients in our cohort did experience transient pain for 8 weeks which subsided with over-the-counter analgesics. We demonstrate favorable outcomes of combined foraminotomy for primary as well as revision surgery with a minimum follow-up of 12 months. No dural tear occurred, and the procedure had an excellent success rate of 95%. Combination foraminotomy is a strong and versatile option for complex long-segment transcanal stenosis in the cervical spine.
Inclinatory component: allows long-segment decompression for transcanal stenosis, prevents potential exiting nerve root damage.
Standard foraminotomy part: allows for safe and effective decompression of disc and disk osteophytes when associated with transcanal stenosis and prevents cord injury.
Versatility in surgical context: This approach can be applied to primary cases and challenging revision surgeries, with single- and multiple-level involvements [15].
Preservation of the facet joint: long-segment stenosis decompression through standard foraminotomy can lead to excessive destruction of the facet joint, resulting in instability and chronic neck pain [16].
CT scan: A sagittal-oblique CT scan image obtained at the angle of the foramen shows an end-on view of the foramen and can help identify long-segment stenosis in all 3 zones of the cervical foraminal canal.
Outcome data: The inclusion of preoperative and postoperative outcomes (e.g., VAS and NDI scores) significantly strengthens the efficacy of this technique. The reported reduction in complications, including the zero incidence of dural injury, further supports the argument for its safety and effectiveness.
Furthermore, literature states that patients could expect a shorter hospital stay and more rapid rehabilitation than after fusion surgeries [17]. Additionally, endoscopic techniques like ours have advantages of excellent high-quality magnification that allows precise imaging of this delicate anatomy of the cervical foramen that allows the local pathology to be addressed accurately.
This study has some limitations. Our sample size consisted of a relatively small cohort of 23 patients. However, we aimed to introduce this novel technique. Our results have been significantly superior to other conventional approaches, and we have achieved satisfactory outcomes. Comparative studies evaluating the outcomes of conventional techniques alongside our own will better clarify the results in the future.
CONCLUSION
In conclusion, this study demonstrates that the minimally invasive cervical combination foraminotomy is a safe, effective, and technically innovative approach for treating various forms of foraminal stenosis. By preserving key spinal structures and utilizing advanced imaging techniques, this method offers significant advantages in both primary and revision surgeries, leading to improved patient outcomes. The introduction of a new classification system and the application of 2D-SOMPR imaging further enhance diagnostic accuracy and surgical planning. These findings support the continued adoption and development of endoscopic minimally invasive techniques in spine surgery, promising a safer and more efficient future for complex spinal interventions.
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