Minimally Invasive Biportal Endoscopic Spinal Cord Stimulation : Technical Report and Case Series

Equipment used in UBE-SCS

During the procedure, a zero-degree endoscope with a 4 mm diameter and 18 cm length (Karl Storz SE & Co., Tuttlingen, Germany) was used. Standard spinal surgical instruments, including 2 mm and 3 mm Kerrison punches, pituitary forceps, and curettes, were utilized. For bone removal, a 3–4 mm diamond and cutting burr (NSK Co., Inc., Tokyo, Japan) and a 5 mm shaver (Stryker Corp., Kalamazoo, MI, USA) were employed. Intraoperative bleeding control was achieved using a 90-degree radiofrequency (RF) probe and a hook-type RF probe (C&S MEDICAL Co., LTD., Pocheon, Korea). All patients underwent implantation of a surgical paddle lead with BurstDR™ technology (Abbott, Plano, TX, USA).

Surgical procedure and SCS trial

All patients underwent routine radiographic evaluation including magnetic resonance imaging (MRI) and computed tomography to identify any bony abnormalities and assess spinal cord compression at the surgical level of the lower thoracic region. The T9-10 level was the standard site for paddle lead placement. Surgeries were performed under general anesthesia, with intraoperative neurophysiological monitoring to evaluate motor-evoked potentials (MEPs) and somatosensory-evoked potentials (SSEPs). Patients were positioned in the prone position on a radiolucent table with proper padding to ensure stability and minimize the risk of pressure-related injuries.

A waterproof surgical drape was used to ensure a sterile environment. Fluoroscopic guidance was used to identify and mark the midline intervertebral space and the pedicles. UBE-SCS was performed through two incisions, which were designated the scope portal and the working portal, allowing the introduction of an arthroscope and surgical instruments. At our center, all UBE-SCS procedures were conducted using a left-sided approach. The scope portal was created through a 1.0 cm incision at the lower margin of the upper pedicle (typically at the T9 level). The working portal was established with a 2.5–3 cm incision at the upper third of the lower pedicle (typically at the T10 level), positioned 2.5–3 cm away from the scope portal (Fig. 1).

Fig. 1.

Surgical incision for UBE-SCS. A : For the scope portal, a 1.0 cm incision is made at the lower margin level of the pedicle of the upper-level spine usually T9. For the working portal, a 2.5–3.0 cm incision is made approximately one-third above the pedicle of the lower level of the thoracic spine, usually T10. The medial pedicular line should be located midline of two portal incision. Also, two portals should be 2.5–3 cm apart to avoid fighting with the scope and instruments. B : Clinical photo of skin incision for UBE-SCS. UBE : unilateral biportal endoscopy, SCS : spinal cord stimulation.

For all UBE procedures, the creation of the docking point is important. The docking point is where the scope and surgical instruments meet, and soft tissue dissection and bone work begin. If proper docking is not performed, additional time and effort are needed for anatomical orientation. The spino-laminar junction is typically used as the docking point for laminectomy procedures, and the T9 spino-laminar junction is the usual docking site for UBE-SCS procedures (Fig. 2A). After the incision was made, docking was facilitated using a serial dilator to expand the potential space between the fascicle of multifidus muscle and to perform soft tissue dissection around the spinolaminar junction and the interlaminar space. After successful docking, potential space for triangulation is created with dilators through scope and working portals (Fig. 2B). Triangulation, where the endoscope and surgical instruments meet at the docking site, is done as it is essential for understanding the spatial relationship between the endoscope and instruments (Fig. 2C). Normal saline was subsequently infused to expand the potential surgical space, ensuring clear visualization and maneuverability. Excessive hydrostatic pressure during the procedure can result in complications such as increased intracranial pressure or potential spinal cord compression. To mitigate these risks, maintaining a slight reverse Trendelenburg position should be considered. Conversely, insufficient pressure can lead to a less clear operative field due to bleeding. Therefore, positioning the normal saline reservoir approximately 70–100 cm above the patient is recommended to ensure adequate inflow. Once the potential working space was established through saline infusion, the spino-laminar junction was readily identifiable after soft tissue dissection (Fig. 3A). At this stage, bone work for UBE-SCS begins. Soft tissue bleeding during the procedure was controlled using an RF wand, whereas bone bleeding at the laminectomy site was managed with either an RF probe or bone wax.

Fig. 2.

Intraoperative fluoroscopic images for UBE-SCS. A : For UBE-SCS, the docking points is the spino-laminar junction at the T9 level. After incision, serial dilators can be used for soft tissue dissection. The first dilator is docked at the spino-laminar junction of T9. B : Potential space for triangulation is created with dilators through scope and working portals. C : Triangulation is performed, when the endoscope and surgical instruments meet at docking site. D : Dummy lead is inserted to create potential epidural space for surgical paddle lead placement. E and F : Surgical paddle lead is inserted and placed in the midline. UBE : unilateral biportal endoscopy, SCS : spinal cord stimulation.

Fig. 3.

Intraoperative endoscopic images for UBE-SCS. A : The spino-laminar junction was easily identifiable after soft tissue dissection. B : After bone work, the ligamentum flavum (LF) can be identified. Cranial margin of bone work is until midline cleft of LF is exposed. C : Lateral margin of bone work can be done until medial aspect of the superior articular process and lateral attachment of LF are exposed. D : A 13 mm wide of laminotomy and LF removal was sufficient to facilitate the placement of the surgical paddle lead. E : Securing potential epidural space with dummy lead placement. F : Advancement of surgical paddle lead toward epidural space. UBE : unilateral biportal endoscopy, SCS : spinal cord stimulation.

A high-speed diamond burr or shaver with a protective guard was utilized for bone work. The base of the T9 spinous process was drilled out to expose the T9 lamina evenly, ensuring balanced laminotomy (Fig. 3B). This step was critical for facilitating midline insertion of the surgical paddle lead, as the dorsal column was the primary target for UBE-SCS. The size of the laminotomy was carefully tailored to match the width of the surgical paddle lead; the creation of an excessively wide laminectomy was avoided, as it may result in off-midline placement of the paddle lead and an increased risk of excessive epidural bleeding. After the bone work, the ligamentum flavum (LF) is exposed. The cranial margin of the bone work is until the midline cleft of LF is exposed (Fig. 3C). Lateral margin of bone work can be done until medial aspect of the superior articular process and lateral attachment of LF is exposed (Fig. 3D). Caudal margin of bone work can be done until caudal laminal and caudal attachment of LF is exposed (Fig. 3E). It was not necessary to remove the entire LF, as excessive exposure of the epidural space may increase the risk of epidural bleeding and postoperative epidural fibrosis.

A 13 mm width of laminotomy and LF removal was sufficient to facilitate the placement of the surgical paddle lead (Fig. 3F). Once the potential insertion space was prepared by using dummy lead placement (Figs. 2D and 3E), the surgical paddle lead was inserted smoothly without resistance (Figs. 2E, 2F, and 3F). For surgical paddle lead placement, the insertion angle is critical for preventing spinal cord damage. Given that a stiff surgical paddle lead insertion angle could damage the spinal cord, an obtuse insertion angle should be considered. Resistance during lead insertion may indicate the presence of adhesion at the epidural space, in which case extending the laminotomy and releasing the adhesion at the epidural space should be considered to ensure safe and effective placement. The endoscopic view is often be obscured due to epidural bleeding from the midline of the laminectomy site. Since surgical paddle lead insertion without a clear endoscopic view can endanger the spinal cord, it is better to extend laminectomy cranially and control epidural bleeding before lead insertion. To evaluate potential spinal cord damage, intraoperative monitoring of MEPs and SSEPs is recommended, particularly during the early phases of UBE-SCS, both before and after surgical paddle lead insertion. After the paddle lead is placed, intraoperative fluoroscopic imaging can verify the position of the lead at the midline. If the lead is off midline, the primary cause is often uneven laminectomy or epidural adhesion, which can be corrected by extending the laminectomy on the contralateral side of the lead deviation or releasing the adhesion after additional laminectomy. In conventional surgical paddle lead insertion, anchoring is required to prevent lead mobilization. However, UBE-SCS typically involves minimal bone work and leaves negligible dead space, making anchoring unnecessary in most cases. Hemostasis during the procedure was meticulously performed using a small hook-type RF probe for epidural bleeding and bone wax for hemostasis at the laminotomy site. Prior to permanent SCS implantation, a trial period is essential to determine the effectiveness of the SCS in reducing neuropathic leg pain by at least 50%. During the trial period, externalization of the surgical paddle lead is needed (Fig. 4A). The surgical paddle lead is connected to an extension lead, which exits the body at the left lower back and connects to the external generator (Fig. 4A). A strain relief loop at the surgical paddle lead incision site should be considered to reduce the risk of lead fracture or migration (Fig. 4B). After the surgical paddle lead is placed, a Jackson-Pratt surgical drain (100 mL) is usually placed through the working portal to prevent postoperative hematoma.

Fig. 4.

Surgical photo of the externalization of the surgical paddle lead and radiologic image showing permanent implantation of the surgical paddle lead and implantable pulse generator (IPG). A : The surgical paddle lead is connected to an extension lead, that exits the body at the left lower back and connects to the external generator. B : A strain-relief loop at the surgical paddle lead incision site should be considered to reduce the risk of lead fracture or migration. C : Permanent implantation of the surgical paddle lead with IPG insertion in the right buttock.

Permanent implantation

The patient can usually walk and be stimulated immediately after the operation. During the trial period, if neuropathic back and leg pain improved by more than 50%, permanent implantation can be considered.

Permanent implantation can be easily performed with either general anesthesia or regional anesthesia. After removing the externalized extension lead and connecting a new extension lead to the surgical paddle lead, tunneling and inserting an implantable pulse generator (IPG) on the contralateral side, usually the right side, to externalization by creating a pocket on the right buttock are recommended to prevent infection (Fig. 4C). Another strain relief loop of the extension lead at the IPG insertion should be considered to prevent disruption of electrical system due to lead fracture or migration.

Typical UBE-SCS case for neuropathic leg pain (Fig. 5 and Supplementary Video 1)

Fig. 5.

Typical UBE-SCS case for neuropathic leg pain (case No. 2). A and B : A 60-year-old women suffered from neuropathic leg pain after she had L4-5-S1 fusion surgery due to isthmic spondylolisthesis. There was no neural compression lesion on magnetic resonance imaging. C and D : After a week of the trial phase, there was more than 80% of pain reduction. Under general anesthesia, permanent implantation was done. E and F : Postoperative computed tomography image showed location of surgical paddle lead placement. UBE : unilateral biportal endoscopy, SCS : spinal cord stimulation.

A 60-year-old woman experienced neuropathic leg pain with paresthesia following L4-5-S1 fusion for isthmic spondylolisthesis. MRI revealed no neural compression, and her symptoms persisted despite years of opioid analgesics and epidural injections. She opted for an SCS trial, during which T9 laminectomy and surgical paddle lead insertion were performed at the T9-10 level using the UBE approach. After 1 week, her pain had reduced by more than 80%. Permanent implantation was subsequently performed under general anesthesia. At the 14-month follow-up, the patient reported sustained 80% pain relief, with no lead-related complications such as migration or breakage.

Case of UBE-SCS insertion with a previous spine surgery site (Fig. 6 and Supplementary Video 2)

Fig. 6.

UBE-SCS insertion with previous spine surgery site (case No. 14). A-D : A 48-year-old man with more than 10 years of neuropathic leg pain after traumatic spinal cord injury. With T11 chance fracture, he underwent T10-11 laminectomy and thoracolumbar posterior fixation (T8-L2). E : After docking at T9 lamina, triangulation was done at docking site. F : Once soft tissue dissection was performed, the T9 spino-laminar junction was identified. G : The subsequent procedure proceeded as usual. UBE : unilateral biportal endoscopy, SCS : spinal cord stimulation.

A 48-year-old man with a decade-long history of neuropathic leg pain following a traumatic spinal cord injury underwent an SCS trial. He had previously undergone T10-11 laminectomy and thoracolumbar posterior fixation (T8-L2) due to a T11 Chance fracture. Given the prior surgery at the standard lead insertion site, the T9 spinous process was used as the docking point for endoscopic access. Following soft tissue dissection, the T9 spino-laminar junction was identified, allowing the procedure to proceed as usual. Three days post-trial, his leg pain had improved by more than 90%, leading to permanent implantation. At the 3-month follow-up, he reported high satisfaction with the pain relief, and no implant-related complications were observed.