Cervical stenotic myelopathy (CSM), which is caused by cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament, is a critical cause of neurological deterioration. Conventional anterior approaches used to treat this condition include anterior cervical discectomy and fusion and anterior cervical corpectomy and fusion, whereas posterior approaches include laminectomy with or without fusion and laminoplasty. Conventional laminectomy has the drawbacks of axial pain, loss of cervical spinal angle, and reduced range of motion due to extensive injury to the posterior extensor muscles and spinous processes, which serve as insertion points for stabilizing muscles. When fusion is performed, the mobility of the surgical level is lost, and postoperative complications, such as non-fusion, device failure or dislodgment, and adjacent segment disease, may occur [1]. Laminoplasty was introduced to overcome these limitations, allowing the preservation of the fulcrum of the spinous process. However, extensive damage to the posterior extensor muscles remained unavoidable, ultimately affecting the posterior tension band and failing to prevent axial pain. With advances in spinal endoscopy, various treatments for CSM have emerged. Owing to the thin and shallow lamina of the cervical spine, unilateral laminotomy and bilateral decompression (ULBD), as in the lumbar and thoracic spines, can exert pressure on the cord. Freeing of the spinous process is necessary to ensure safe bilateral decompression, and this led to the development of spinous process-preserving laminectomy. By preserving the spinous process, which serves as the insertion point for stabilizing muscles, the posterior tension band can be maintained. However, despite favorable outcomes, the fulcrum of the spinous process may be damaged during the procedure. Laminoplasty using a unilateral biportal endoscopy (UBE) system was recently introduced. To secure bilateral visualization and facilitate the insertion of fixation plates, this technique involves resection of the base of the spinous process (similar to spinous process-preserving laminectomy), thereby allowing bilateral mobilization of the posterior elements. After securing sufficient exposure, a gutter is created on one side, and a hinge is created on the contralateral side to perform laminoplasty. However, this method results in a structural compromise identical to that of the spinous process-preserving laminectomy, thereby damaging the fulcrum of the spinous process, and presenting the disadvantage of requiring instrumentation. Therefore, in this study, we introduced a novel cervical multilevel laminoplasty technique utilizing the UBE system, specifically designed to preserve both the posterior tension band and the fulcrum of the spinous process.

All surgeries were performed using the UBE approach under general anesthesia, with the patient in the prone position. A 0° rigid endoscope (Model RUSC4-00A, Endovision, Korea) with a 4.0-mm outer diameter and 170-mm working length was used. A titanium laminoplasty plate (GS Medical, Korea) was used for fixation. The patient’s neck was slightly flexed and fixed on a Wilson frame. A right-sided approach was used, and 2 incisions were made in the midline to allow for bilateral decompression. At the C5 level, a 0.7-cm incision was made for the endoscopic viewing portal, and at the C2 level, a 2-cm incision was made for instrumentation and plate insertion. To facilitate angular manipulation of the instruments during creation of the opening and hinge, a subcutaneous dissection of approximately 1.5 cm was performed around each incision to allow for a slight axis shift of the instruments. If the tip of the spinous process is not prominent, minimal axial shifting of the instruments may suffice. Accordingly, the decision to perform a subcutaneous dissection depends on the size of the spinous process tip. A gutter was created at the junction between the lateral mass and lamina at the opening site (Figures 1A and 2A). After forming the gutter, all instruments were withdrawn, and the skin was retracted to the contralateral side to create a hinge at the junction of the lateral mass and lamina in the same manner (Figures 1B and 2B). To create a greenstick fracture, drilling was performed using a 2-mm burr through the outer cortex and cancellous bone, while leaving the inner cortex intact. Returning to the opening side, the lamina was gradually elevated in a dorso-contralateral direction using a hook and a right-angled probe while carefully checking for any adhesions between the ventral lamina and spinal cord (Figures 1C and 2C). The mouth of the plate was inserted into the lamina using an original plate holder, which is commonly used for this procedure (Figure 2D). At this time, the kickstand rested slightly on the lateral mass (Figure 2E). Subsequently, the kickstand portion of the plate was securely seated on the lateral mass (Figures 1D and 2F). As the insertion of the tapper and screw through the original incision was likely to interfere with the instrument holding the plate, a third auxiliary incision was made approximately 3-cm lateral to the midline and aligned parallel to the plate to allow easier access. A 1-mL syringe barrel with the tip removed (Figure 3A) was inserted into the auxiliary port to facilitate the delivery of the tapper and screw (Figures 1E and 2G). Tapping and screw insertion into the lateral mass were performed under direct visualization (Figures 1F, 2H–K, and 3B), as for their insertion into the lamina (Figures 1G, 1H, 2L, 2M, and 3C). Proper placement of the instrument was confirmed (Figures 1I and 2N). A drain was placed (Figure 2O) and exteriorized through a third auxiliary incision using subcutaneous tunneling. The skin in both the visualization and instrumentation channels was closed using subcutaneous sutures and reinforced with skin glue.

An 82-year-old male patient presented with gait disturbance due to bilateral lower-extremity weakness and had been suffering from repeated falls. Manual muscle testing revealed grade 3 muscle strength in both legs. Cervical magnetic resonance imaging (MRI) showed central canal stenosis at the C3–4–5 levels, with signal changes within the spinal cord (Figure 4A). Plain radiography revealed degenerative changes consistent with cervical spondylosis (Figure 4B). Electromyography and nerve conduction velocity studies confirmed cervical myelopathy. We performed a maintenance anatomy (MA) cervical laminoplasty using the UBE system. Unlike other existing techniques, including microscopic and endoscopic approaches, we preserved the posterior tension band by avoiding detachment of the stabilizing muscles from the spinous process and maintained the fulcrum function of the spinous process by not resecting it. All posterior components were preserved. Postoperative sagittal MRI revealed complete spinal cord decompression from C2 to C5. Axial MRI revealed complete bilateral decompression at each level (Figure 5A). Postoperative radiographs showed well-positioned plates (Figure 5B), and computed tomography (CT) confirmed appropriate placement of the implant, with intact spinous processes (Figure 5C). Neurologically, the modified Japanese Orthopaedic Association score improved from 11 to 16. The Numeric Rating Scale score for neck pain was 1, and postoperative laboratory findings indicated no inflammatory response. Additionally, muscle strength in both lower limbs improved to grade 4. The patient recovered uneventfully and was discharged on postoperative day 4. Postoperative photographs showed a 0.7-cm incision for the visualization channel, a 2-cm incision for the instrumentation channel, and a 0.3-cm incision for screw insertion and drainage (Figure 5D).

The cervical spine has thin and shallow laminae, which present limitations in applying the unilateral approach with over-the-top bilateral decompression that is commonly used in the lumbar or thoracic spine. In some exceptional cases, such as when the base of the spinous process is wide or the lamina is as thick as the lumbar or thoracic spine, ULBD may be safely performed; however, the risk remains significant in patients with typical cervical anatomy. Inserting instruments beneath the contralateral lamina to preserve it may compress the spinal cord, even with extremely thin instruments. Therefore, special caution is required when performing bilateral decompression of the cervical spine [2]. Total laminectomy via the posterior approach was the standard technique to achieve safe bilateral cervical decompression until the 1960s. However, this procedure involves dissection of the deep extensor muscles, which leads to weakening of the posterior tension band. In addition, removal of the spinous process, which serves as a biomechanical fulcrum for muscle reattachment, further compromises posterior structural support. These factors contribute to postoperative kyphotic progression, instability, and neurological deterioration [3-9]. Laminoplasty was developed to avoid these complications. Laminoplasty is widely performed to treat multilevel CSM [10]. If the spinous process is preserved, the fulcrum function of the spinous process can be maintained. However, similar to laminectomy, muscle dissection is necessary in laminoplasty, which inevitably weakens the posterior tension band. Even if muscle reattachment occurs postoperatively, the stability of an intact tension band cannot be fully replicated. Consequently, postoperative neck pain and reduced range of motion may still occur [11,12]. Modified laminoplasty techniques have been developed to reinforce the importance of fulcrum and posterior tension bands. These involve cutting the base of the spinous process and flipping it to the opposite side while maintaining the attachment of the deep extensor muscles at the spinous process tip to preserve at least one side of the posterior tension band. After laminoplasty, the resected spinous process is reattached to the lamina to restore fulcrum function [13,14]. As spinal endoscopic surgery has evolved, minimally invasive techniques, including techniques for myelopathy treatment, have been increasingly applied. However, the anatomical characteristics of the cervical lamina, which is thin and shallow, remain critical in endoscopic procedures. Spinous process-preserving bilateral laminectomy using endoscopy, in which the spinous process is incised and flipped contralaterally, has been introduced to ensure safe bilateral decompression. This technique preserves the posterior tension band almost completely and has shown favorable results owing to the resulting mechanical stability. Nevertheless, it still has the disadvantage of damaging the fulcrum function of the spinous process.

Similar techniques have been attempted using a microscope for muscle-preserving laminectomy, and the outcomes have been comparable to those of laminoplasty [15,16]. With recent advances in endoscopic spine surgery, procedures using the UBE system have been explored. However, in the techniques reported to date, sufficient resection of the spinous process base is performed to allow full mobilization of the spinous process so that the surgeon can freely alternate between the ipsilateral and contralateral lamina under bilateral visualization. This facilitates easier creation of the opening and hinge and makes plate insertion more convenient. However, this approach compromises the fulcrum of the spinous process, which is one of the main biomechanical advantages of laminoplasty, and results in a surgical outcome that biomechanically resembles spinous process-preserving laminectomy, with the additional disadvantage of requiring instrumentation. Although the detached tip of the spinous process may passively reattach to the lamina postoperatively, this reattachment is not intentional and cannot be expected to occur reliably in every case [17]. In contrast, the technique discussed in this study uses the UBE system to take full advantage of muscle preservation, thereby maintaining the posterior tension band. Simultaneously, it allows complete preservation of the spinous process and fulcrum function, ultimately preserving the entire posterior anatomical structure and maintaining normal cervical biomechanics even after surgery.

The UBE system allows the use of standard spinal instruments, making the approach relatively accessible. Nevertheless, the surgical technique itself is technically demanding. This is an advanced endoscopic technique and should be attempted only after gaining sufficient experience, not only in endoscopic procedures but also after performing a good number of open cases. Moreover, as endoscopic laminoplasty is still under development, further research is necessary to evaluate its safety, reproducibility, and long-term outcomes. This endoscopic MA cervical laminoplasty technique highlights the importance of anatomical preservation in cervical spine surgery and offers a novel direction for future endoscopic laminoplasty.