INTRODUCTION
The evolution of spinal endoscopy has broadened the application of minimally invasive techniques for cervical degenerative disease. Endoscopic posterior cervical procedures—including foraminotomy, discectomy, and laminotomy—offer effective alternatives to open surgery for treating radiculopathy and myelopathy [1-3]. Unilateral biportal endoscopy (UBE), initially developed for lumbar surgery, has since been adapted to the thoracic and cervical spine, providing superior visualization, instrument maneuverability, and ergonomics compared with uniportal endoscopy.
Recurrence remains a concern in posterior cervical surgery, often resulting from progressive degeneration or incomplete decompression [4-6]. Revision surgery is technically demanding because fibrotic adhesions, distorted anatomy, and the risk of instability limit safe re-exploration through the posterior route. Consequently, many revision cases are managed with anterior cervical discectomy and fusion (ACDF) or posterior instrumented fusion, procedures that sacrifice motion and carry risks such as graft-related complications, dysphagia, and adjacent segment degeneration [7,8].
With the growing emphasis on motion preservation and minimally invasive approaches, UBE has emerged as a promising alternative for posterior cervical revision [9]. However, its use in revision cases remains poorly characterized.
In this technical note, we describe the application of UBE for revision posterior cervical decompression in patients with recurrent radiculopathy or myelopathy. We outline the techniques of inclinatory foraminotomy and unilateral laminotomy with bilateral decompression, and illustrate their feasibility, safety, and effectiveness through representative clinical cases.
MATERIALS AND METHODS
1. Study Design and Patient Selection
This study was conducted following approval from the Institutional Review Board, which designated the research as exempt from formal review (CHOSUN 2025-05-003). Given its retrospective design based on medical record reviews, the requirement for informed consent was waived. Patients were enrolled between August 2022 and November 2024. Those presenting with recurrent cervical radiculopathy or myelopathy after prior posterior decompression were considered for biportal endoscopic posterior cervical revision surgery. The inclusion criteria were:
• Recurrence of symptoms (motor/sensory deficit or pain) after initial posterior cervical decompression
• Imaging-confirmed recurrent disc herniation, foraminal stenosis, or central canal stenosis at previously operated levels
• Absence of cervical instability
• Minimum follow-up of 1 year
The exclusion criteria included radiographic segmental instability, progressive kyphosis, infection, neoplasm, or ossification of the posterior longitudinal ligament. All patients underwent UBE-assisted revision via the posterior approach, using either an inclinatory foraminotomy or unilateral laminotomy with bilateral decompression, depending on the predominant pathology.
2. Operative Setup and Positioning
All procedures were performed under general anesthesia with patients in the prone position. A gel facial pad and H-shaped chest pillow were used to minimize ocular, facial, and abdominal pressure. The neck was positioned in mild flexion to flatten the posterior cervical contour, and the operating table was placed in slight reverse Trendelenburg. The head and shoulders were secured with tape to prevent drift. Continuous gravity-driven saline irrigation, positioned approximately 2 m above the surgical field, was employed to maintain visualization and hemostasis. Figure 1 illustrates the operative setup.
3. Surgical Techniques
1) Operative procedure for recurrent radiculopathy
The surgeon was positioned contralateral to the lesion, with the assistant standing on the opposite side. Under C-arm fluoroscopy, the affected level was identified and marked on the skin, along with the spinous processes immediately above and below the target level. Two vertical skin incisions (~0.5 cm each) were made approximately 2 cm apart, adjacent to the spinous tip on the side of the lesion. For a right-handed surgeon, the left incision functioned as the viewing portal and the right incision as the working portal. The left hand controlled a 0° endoscope, while the right hand manipulated the surgical instruments (Figure 2).
Serial dilators were advanced under fluoroscopic guidance to triangulate on the cervical lamina and establish a working corridor. After placement of the endoscopic cannula, adequate saline outflow between the portals was confirmed. A radiofrequency (RF) probe was then used to remove residual muscle and granulation tissue, exposing the laminar bone. Adhesions between the prior laminectomy margins and fibrotic tissue were carefully dissected with a curette.
A 4-mm spherical diamond burr was used to drill the inferior margin of the upper lamina until normal bone was exposed. The superior margin of the lower lamina was drilled in a similar manner. Adherent granulation tissue over the dura served as a protective barrier during drilling; if it impaired visualization, it was removed using 1-mm Kerrison punches or low-power RF.
Next, lateral bony decompression was performed using a 3-mm diamond burr to expose the medial facet joint and decompress the nerve root. The superior articular process was undercut at an inclined angle, preserving facet integrity while creating a tunnel along the nerve root silhouette. As the working space narrowed distal to the root, the superior articular process was thinned to an eggshell thickness with a 1.8-mm diamond burr, and the fragile bone was removed with a curette. When additional space was needed for root mobilization, the superior articular process tip was further resected or a pediculotomy was performed. Adhesiolysis and hemostasis in these confined areas were achieved with a ball-tip RF probe.
The nerve root was then gently retracted with a blunt hook, taking care to avoid excessive force and minimize neural injury. Retraction toward the disc floor allowed identification of the protruding disc. Annulotomy and discectomy were carried out using a ball-tip RF probe and ring forceps to remove residual disc fragments. A surgical drain was placed and left in situ for 24 hours to control bleeding. Wound closure was performed with subcutaneous sutures and skin staples. Postoperatively, patients were fitted with a cervical collar for 1–2 weeks.
2) Operative procedure for recurrent myelopathy
Under C-arm fluoroscopic guidance, the target surgical level and adjacent pedicles were identified and marked on the skin. Two vertical skin incisions (~0.5 cm each) were then made on the side of the surgeon, approximately 2 cm apart, to establish a viewing portal (left) and a working portal (right). For a right-handed surgeon, the left hand controlled the 0° endoscope, while the right hand manipulated the surgical instruments (Figure 3).
Serial dilators were advanced over the lamina requiring further decompression to create a working corridor, with care taken to avoid the prior laminectomy defect. After insertion of the endoscopic cannula, adequate saline outflow between the portals was confirmed. Residual muscle and granulation tissue surrounding the lamina were removed with an RF probe to expose the underlying bone. Once the boundary between the laminar bone and fibrotic tissue was delineated, adhesions were carefully dissected from the bone margin using a curette.
A 4-mm spherical diamond burr was used to drill the ipsilateral lamina along the boundary between bone and fibrotic tissue. Tissue adherent to the dura was preserved during drilling to serve as a protective cushion. Once intact laminar bone was identified, decompression was continued until dural pulsation was observed. To extend decompression to the contralateral side, the spinous base was drilled out with a 3-mm spherical diamond burr. During this step, adhesions between fibrotic and neural tissues were carefully dissected with a curette.
Any floating bone fragments embedded in granulation tissue were thinned with the burr and removed using a hook and 1-mm Kerrison punches. To avoid dural compression, drilling pressure was minimized and sufficient space was maintained around the floating bone. Contralateral decompression was performed using an inclined trajectory to reach the lateral dural margin; a 1.8-mm spherical diamond burr was employed to thin the bone, and a curette was used to remove the thinned lamina. Kerrison punches were not used on the contralateral side to reduce the risk of kinking.
After completion of bony decompression, the boundary between newly exposed dura and dura adherent from the prior surgery was identified. Adhesion tissue along this interface was gently dissected with a curette, hook, or small pituitary forceps. Dural pulsation was confirmed, and the lateral dural border was carefully separated to complete decompression without dural injury. A ball-tip RF probe was used to coagulate oozing from vascularized tissue. A surgical drain was placed for 24 hours to control postoperative bleeding. Wound closure was performed with subcutaneous sutures and skin staples. After surgery, patients wore a cervical collar for 1–2 weeks.
4. Outcome Measures and Data Collection
Preoperative and postoperative clinical evaluations encompassed the following assessments:
• Visual analogue scale (VAS) scores for both neck and arm pain
• Measurement of motor strength
Radiological evaluation was performed to:
• Confirm that full neural decompression has been achieved immediately after surgery.
• Detect increases exceeding 2° in dynamic segmental angle—defined as the difference between the angle formed by an extended line along the upper endplate of the superior vertebra and the lower endplate of the inferior vertebra, measured during flexion and extension postures on lateral radiographs—throughout the follow-up period.
Follow-up clinical assessments were conducted at 2 weeks, 3 months, and 1 year postoperatively.
RESULTS
1. Demographics of Enrolled Patients
Five patients (4 males and 1 female) underwent biportal endoscopic posterior cervical revision for recurrent degenerative pathology. Demographic details are presented in Table 1. The mean age was 61.6±8.8 (range, 52–76) years. Index procedures consisted of posterior cervical foraminotomy (PCF; n=2), ACDF with unilateral laminotomy with bilateral decompression (n=1), and biportal endoscopic procedures (posterior cervical inclinatory foraminotomy or posterior cervical interlaminar decompression; n=2). The mean interval to revision was 13.0±11.6 (range, 3–31) months. Revision procedures included biportal endoscopic posterior cervical interlaminar decompression (n=3), biportal endoscopic unilateral laminotomy with bilateral decompression (n=1), and biportal endoscopic posterior cervical inclinatory foraminotomy (n=1). The mean follow-up period was 17.8±3.4 (range, 14–22) months. Clinical presentations included radicular pain (n=4) and gait disturbance (n=1). Diagnoses were recurrent herniated nucleus pulposus (C7–T1, C6–7), incomplete decompression (C5–6), foraminal herniated nucleus pulposus (C6–7), and recurrent foraminal stenosis (C5–6).
2. Clinical and Radiological Outcomes and Complications
Outcomes are summarized in Table 2. Preoperative VAS scores ranged from 4–8 for neck pain and 7–9 for arm pain. At 2 weeks, scores improved to 0–3 (neck) and 0–2 (arm), with similar results maintained at 3 months. At 1 year, neck pain scores were 0–1 and arm pain scores were 0–2. Four patients presented with motor weakness (grades 2–4); 3 improved to grade 5, and one improved to grade 3. By 1 year, 4 patients achieved “excellent” outcomes and one achieved a “good” outcome according to the MacNab criteria. No significant postoperative instability was noted throughout the follow-up period. No intraoperative or postoperative complications were observed.
3. Illustrative Cases
1) Case 1: revision foraminotomy for recurrent herniated nucleus pulposus at left C7–T1
(1) Patient presentation
A 64-year-old male presented with severe left shoulder and arm pain that worsened with neck flexion. Neurological examination demonstrated paralysis of the left fourth and fifth fingers (motor grade 2) and hypoesthesia in the C8 dermatome. Spurling test was positive, with no evidence of upper motor neuron signs. The neck VAS score was 4, and the arm VAS score was 7. Three months earlier, the patient had undergone endoscopic posterior cervical discectomy for left-sided foraminal stenosis and disc herniation at C6–7–T1.
(3) Surgical procedure
A biportal endoscopic posterior cervical revision was performed at the left C7–T1 level using the UBE technique. Dense epidural adhesions were carefully dissected under endoscopic magnification with RF probes and curettes. The herniated disc fragment was excised without intraoperative complications, and restoration of nerve root pulsation was confirmed (Figure 4D). A video clip illustrating the procedure is provided as Supplementary Video Clip 1.
(4) Outcome and follow-up
Immediately after surgery, the patient experienced significant improvement in neck pain, although mild arm pain persisted. Motor strength improved from grade 2 to grade 3. Postoperative magnetic resonance imaging and computed tomography confirmed complete removal of the C7–T1 disc herniation (Figure 4E–G). The patient was discharged on postoperative day 5. At 1-year follow-up, the neck VAS score had resolved to 0, and the arm VAS score had decreased to 2. Dynamic lateral radiographs at 1 year demonstrated no evidence of segmental instability.
2) Case 2: revision laminectomy for recurrent central stenosis at C5–6 with myelopathy
(1) Patient presentation
A 63-year-old male presented with 3 months of neck and bilateral scapular pain, along with progressive gait imbalance following a motor vehicle accident that caused cervical sprain. Despite conservative management, his walking difficulties worsened over the preceding month. Neurological examination revealed bilateral hand clumsiness (++/++), a positive Babinski sign (++/+), and hyperreflexia (+++/++) in all extremities. His surgical history included ACDF at C5–6 in 2012 and endoscopic posterior cervical unilateral laminectomy with bilateral decompression at C4–5–6 in 2021.
(3) Surgical procedure
A right-sided biportal endoscopic revision was performed at C5–6. Through this approach, an additional C6 laminectomy was carried out to achieve further dorsal decompression. Dense adhesions from the prior unilateral laminectomy with bilateral decompression were carefully dissected under endoscopic visualization using RF probes and curettes (Figure 5E). After removal of residual bone and fibrotic tissue, restoration of dural pulsation confirmed adequate decompression. The procedure was completed without complications. A video clip illustrating the technique is provided as Supplementary Video Clip 2.
(4) Outcome and follow-up
Immediately after surgery, the patient experienced improvement in gait and balance. Postoperative magnetic resonance imaging and computed tomography confirmed sufficient additional decompression at C5–6 (Figure 5F–H). The patient was discharged on postoperative day 7. At 1-year follow-up, a dynamic cervical radiograph demonstrated no evidence of segmental instability.
DISCUSSION
1. Clinical Considerations of the Posterior Cervical Approach
The posterior cervical approach, first described by Spurling and Scoville in 1944, has historically been used less frequently than ACDF, introduced by Smith and Robinson in 1958. Nevertheless, it remains an effective option for radiculopathy caused by posterolateral soft disc herniations or facet osteophytes and continues to have appropriate clinical applications today [10,11]. Advances in endoscopic methods have further enhanced its utility, enabling multiple modifications of the technique [9,12-14].
Although motion preservation is a key advantage, the posterior cervical approach carries a risk of recurrence owing to ongoing degeneration or incomplete decompression [15]. Recurrence rates after traditional posterior surgery range from 4.7% to 9.9%, but are lower with endoscopic techniques, approximately 3.4%–4% [5,16]. Ruetten et al. reported a 3.4% recurrence rate (3 of 87 patients) within 2 years after full-endoscopic posterior foraminotomy, with 2 patients ultimately requiring ACDF for persistent pain [6].
2. Challenges and Considerations in Reoperation After PCF
Several studies have identified factors that contribute to technical difficulty and elevated risks in reoperations following PCF. These include postoperative instability, adhesion formation, and limitations in preserving cervical range of motion [17].
1) Postoperative instability
PCF generally requires partial facetectomy to decompress the nerve roots, which may compromise structural stability. This increases the likelihood of mechanical instability during revision surgery and may necessitate additional procedures, such as fusion, to stabilize the spine.
2) Adhesions and scarring
The posterior cervical approach often leads to significant scar tissue formation around neural structures. This makes reoperations technically demanding and raises the risk of inadvertent injury to nerve roots or dura.
3) Preservation of range of motion
Although PCF is frequently chosen to preserve cervical range of motion, certain preoperative factors—such as marked segmental angulation or advanced degenerative changes—can result in reduced postoperative motion and increased neck pain. These conditions complicate surgical planning in revision cases.
Considering these challenges, anterior approaches such as ACDF are often favored for recurrent cervical radiculopathy to address instability and reduce risks associated with posterior re-exploration. However, reoperation rates for ACDF at adjacent segments within 2 years are comparable to those reported for PCF reoperations at the index level [18]. If endoscopic PCF techniques can overcome these limitations, they may provide additional benefits, including lower economic burden and shorter hospital stays [19].
At present, literature on endoscopic cervical revision surgery remains limited. Nevertheless, studies of reoperative biportal endoscopic lumbar radiculopathy offer valuable insights. The considerations highlighted in these lumbar series, along with the advantages demonstrated by biportal endoscopic approaches, suggest promising potential for their application in cervical revision cases [9,20].
3. Technical Advantages of UBE in Revision Surgery
First, biportal endoscopic surgery provides superior visualization, magnified nearly 30-fold compared with microscopic techniques, with brightness ranging between 2700 and 6700 lux. This enhanced visualization is critical for precise scar dissection and for clearly distinguishing healthy tissue within adhesion-prone and delicate neural regions. The water-based technique further minimizes visual interference from bleeding and debris.
Second, biportal endoscopic surgery reduces the need for neural tissue retraction by enabling lesion access through endoscopic movements combined with versatile surgical instruments. In contrast to single-portal endoscopic methods, the biportal technique facilitates more effective manipulation, allowing safe dissection of the dura and nerve roots, even in revision cases complicated by scar tissue.
Third, preservation of facet integrity—particularly important in reoperations—is a major advantage of biportal endoscopic surgery, especially when performed via the cervical inclinatory approach. The combination of facet undercutting and clear visualization of the distal nerve root, further enhanced by contralateral access, optimizes instrument maneuverability. This ensures adequate decompression around the nerve root while minimizing the risk of facet joint damage.
4. Key Safety Considerations in Revision Surgery
Based on our experience with the presented cases, the following safety measures are recommended for revision biportal endoscopic posterior cervical surgery.
1) Fluoroscopic localization and adhesion boundary dissection
The surgical level should always be reconfirmed after draping. In revision cases, the prior foraminotomy or laminectomy site should not be reused as the entry point. Instead, under meticulous fluoroscopic guidance, the lamina adjacent to the prior defect should be targeted to establish the working corridor, which can then be gradually expanded toward the revision site. During exposure, dissection should proceed along the interface between residual bone and adherent scar tissue, using this boundary as a roadmap to minimize the risk of inadvertent dural or neural injury.
2) Gradual adhesiolysis and dural protection
Initial preservation of fibrotic or granulation tissue covering the dura serves as a protective layer against unintended dural tears during drilling. Low-power RF probes or fine Kerrison punches should be used for early debridement, with more aggressive bony work reserved until the dura is adequately shielded.
3) Controlled bony work with diamond burrs
Initial decompression should be performed with larger burrs (4 mm) to remove bulk bone, followed by smaller burrs (3 mm and 1.8 mm) as the working corridor narrows. Drilling should be performed in short bursts with frequent withdrawal for irrigation, while rotating the endoscope to continuously confirm key anatomical landmarks. Smooth diamond burrs are preferred to minimize soft-tissue injury and to ensure precise bone resection.
4) Avoidance of iatrogenic instability
During facet undercutting for foraminotomy, at least 50% of the facet joint should be preserved. In bilateral decompression, only the minimal amount of laminar bone and spinous base required for adequate decompression should be removed to maintain the integrity of the posterior tension band.
CONCLUSION
UBE-assisted posterior cervical revision appears to be a feasible and effective option for recurrent radiculopathy and myelopathy after prior decompression. This approach allows safe neural decompression and adhesiolysis while preserving stability through minimally invasive access. In this small series, UBE achieved favorable outcomes without the need for fusion or major complications, supporting its potential as a motion-preserving revision strategy.
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