Hybrid Endoscopic Thoracic Discectomy Using Robotic Arm and Navigation for Highly Migrated Calcified Disc Herniation

Yi-Hao Liang; Rohit Akshay Kavishwar; Maria Pedraza; Dimas Rahman Setiawan; Jae-Hwan Kim; Jin-Sung Kim

doi:10.14245/ns.2449024.512

Abstract

This video provides a step-by-step guide for performing the hybrid endoscopic thoracic discectomy using navigation and robotic arm for addressing high migrated calcified disc herniation. With the development of techniques, endoscopic spine surgery has emerged as a reliable treatment for thoracic myelopathy. This approach offers high-resolution, off-axis visualization of the surgical field. The field is poised to advance further as endoscopic instruments are refined, becoming less invasive and more precise through the integration of navigation and robot-assisted systems. A 62-year-old woman presented to us with chief complaints of both legs weakness. She had difficulty standing and walking after squatted due to weakness in her legs and her Oswestry Disability Index score was 66. On examination her both side knee extension and ankle dorsiflexion were grade 4 without dysesthesia. The imaging examination confirmed the diagnosis of thoracic myelopathy caused by a highly migrated calcified disc herniation at T5–6 level. The patient underwent an endoscopic thoracic discectomy using robotic arm and navigation for addressing highly migrated calcified disc herniation, resulting in an excellent outcome. The continuous development of navigation and robotic systems in endoscopic thoracic surgery enhanced accuracy in surgical incisions and instrument placement, as well as improved efficiency in locating pathology and achieving precise decompression. Endoscopic thoracic discectomy combines full-endoscopy and unilateral biportal endoscopic (UBE) techniques to leverage the benefits of both approaches, including the cross-viewing of full-endoscopy cannula and the use of larger Kerrison rongeurs under UBE.

Keywords: Spinal surgery, Endoscopy, Herniated disk, Thoracic, Surgical navigation systems, Robotics

INTRODUCTION

The advancement of endoscopic spine surgery (ESS) has revolutionized the treatment of thoracic myelopathy, particularly in cases involving high migrated calcified disc herniation.

This innovative approach combines high-resolution visualization with minimally invasive techniques, enhancing surgical precision and patient outcomes. The integration of navigation and robotic systems further refines the procedure, allowing for accurate instrument placement and improved efficiency in addressing complex spinal pathologies.

This article details a case study of a 62-year-old woman who underwent hybrid endoscopic thoracic discectomy using navigation and robotic arm, showcasing the effectiveness of this method in alleviating symptoms associated with thoracic disc herniation.

WRITTEN TRANSCRIPT

• 00:00 In this video, we discuss a case of T5–6 highly migrated calcified disc herniation on the right side that was successfully treated by hybrid endoscopic thoracic discectomy robotic arm and navigation.

• 00:12 Introduction1

Surgical intervention is the preferred approach for patients with thoracic disc herniation with refractory symptoms and progressive myelopathy [1]. ESS, a reliable method for treating thoracic myelopathy, provides high-resolution visualization and lower complication rates compared to minimally invasive or traditional techniques [2,3].

Navigation systems enhance precision by determining optimal trajectories and incision points, while also confirming instrument placement during surgery [4]. Robotic assistance has been validated as a safe and effective alternative to conventional fluoroscopic endoscopic procedures [5].

• 00:49 Introduction2

This video provides a step-by-step guide for performing the hybrid endoscopic thoracic discectomy using navigation and robotic arm for addressing highly migrated calcified disc herniation.

• 01:01 Case description

A 62-year-old female patient presented with a body mass index (BMI) of 22.2 kg/m². Her main complaint was bilateral leg weakness, with difficulty in standing and walking, reflected by an Oswestry Disability Index (ODI) score of 66. On physical examination, both knee extension and ankle dorsiflexion were graded at 4 out of 5 on the Medical Research Council (MRC) scale, with no evidence of dysesthesia. The patient underwent a C5–6 anterior cervical discectomy and fusion 8 years ago and had a Charlson Comorbidity Index (CCI) score of 3. Her symptoms began 6 months ago and worsened in recent days. After ruling out neurological conditions, she was transferred to the Department of Neurosurgery for further management.

• 01:44 Radiologic findings (x-ray)

Her lumbar spine x-rays showed general degenerative changes, with an overall acceptable coronal and iliac lordosis balance, as indicated by coronal vertical alignment (CVA) and sagittal vertical axis (SVA) measurements. Thoracic kyphosis was 48.78°, and lumbar lordosis was 59.46°.

• 02:01 Radiologic findings (MRI)

Magnetic resonance imaging (MRI) revealed a herniated disc at T5–6, with the disc fragment migrating down to the T6 pedicle level. The cervical spine, previously operated, showed no significant signs of compression. Imaging at the T5–6 level indicated spinal cord compression and displacement to the left posterior side due to the migrated disc fragment.

• 02:21 Radiologic findings (CT)

Computed tomography (CT) scans further clarified the pathology and anatomical location, the disc migration extended from the T5–6 level downward past the T6 pedicle, with significant calcification.

• 02:33 Preoperative gait

This video reveals that she exhibits a slow gait with compromised control, attributed to progressive weakness in her lower extremities. She was prone to falls when changing direction, starting, or stopping.

• 02:48 Diagnosis

By correlating the clinical and radiological findings. The principal pathology is the herniated disc in T5–6, with migration to the T6 level, leading to thoracic myelopathy. The final diagnosis concluded thoracic myelopathy secondary to thoracic disc herniation at the T5–6 level.

• 03:06 Operation title

Our objective is to achieve precise and thorough decompression of the thoracic central canal at the T5–6 level while utilizing the least invasive surgical method.

• 03:17 Patient positioning

After the patient was intubated and placed under general anesthesia, the positioning and operating room setup were completed. The patient was positioned prone on a radiolucent spinal frame and modular table system. Following sterile preparation, the entire posterior back was draped with a waterproof surgical drape.

• 03:35 Reference array placement & O-Arm registration

A small incision was made on the contralateral side of the surgical site, over the posterior side of T1 spinous process, to secure the navigated reference base array. An intraoperative CT scan using an O-arm was conducted to center the reference base array within the imaging.

• 03:52 Planning the skin incision

The navigation system was utilized to identify the optimal surgical incision site, targeting the precise location of the pathological lesion at the convergence of the channels. Two vertical skin incisions, each 1 cm in length, were made in the right paraspinal area, spaced approximately 2 cm apart.

• 04:10 Endoscope insertion

Serial dilators were used to dissect the back muscles and create an operative space along the spinous process and lamina. A caudal incision served as the endoscopic viewing portal, while a cranial incision was for the working portal. The robotic arm was then employed to stabilize the endoscope tube, facilitating stable instrument handling in procedures.

• 04:29 Endoscopic thoracic discectomy

Endoscopic thoracic discectomy alternates between unilateral biportal endoscopic (UBE) and full endoscopic techniques. Endoscope with a 9.3-mm outer diameter working channel, and 20° viewing angle was used. And hydrodissection over the right T5 and T6 lamina was performed with a 1.8-m saline irrigation system to create the working space.

• 04:49 Drilling remove part of the T5 laminae (uniportal)

Once the endoscope was inserted, anatomical landmarks, including the T5–6 right facet joint capsule, were identified and exposed using the curved tip of radiofrequency forceps. A 3.5-mm diamond bur (Primado, NSK, Japan) under full endoscopy was subsequently utilized to excise portions following the T5 inferior articular process to the lamina.

• 05:09 Navigation check (biportal)

With the assistance of the navigation system, the direction of the intervertebral direction of T5–6 was located and confirmed.

• 05:14 Drilling remove part of the T6 laminae (uniportal)

Additional bony decompression was achieved using a burr to extend toward the T6 lamina caudally, further enlarging the interlaminar space.

• 05:26 Kerrison remove parts of T6 laminae, spinous process and ligament flavum (biportal)

Under the biportal approach, Kerrison rongeurs and other large-caliber tools were employed to further excise portions of the T6 lamina and base part of T5 spinous process. Following the removal of these structures and ensuring clear anatomical delineation, the ligament flavum was also resected.

• 05:49 Rotate the working cannula and incise the annulus (uniportal)

After identifying the annulus of the right T5–6 intervertebral disc and exposing the calcification, rotating the endoscopic cannula to safely incise and secure the working channel over the calcified disc and annulus under full endoscopic visualization.

• 06:04 Careful exploration to T6 pedicle level (uniportal) and navigation assist locate herniated disc (biportal)

After removing parts of disc fragments, the exploration hook was used to carefully explore to the T6 pedicle level, and the pathology is located with the help of the navigation system.

• 06:17 Separate and take out herniated disc fragments (uniportal)

By utilizing the cannula to expand and expose the surrounding tissues and the ventral aspect of the dura mater, tools such as specialized semi-flexible forceps were employed to gradually separate and remove disc fragments from the spinal canal at the T6 level. It is crucial to maintain clear visibility of the neural structures and ensure their protection throughout the exploration and clamping of herniated disc fragments.

• 06:49 Confirm decompression (uniportal)

The ventral dura mater was fully extended once the pathology are addressed. This allows for a thorough examination and verification of decompression and hemostasis to be completed swiftly.

• 07:01 Closure

Subcutaneous suturing was done for the surgical incision after placement of a drainage tube. The navigated reference array was removed. Estimated blood loss was around 15 mL. The surgical duration was 85 minutes and there were no intraoperative complications.

• 07:18 Postoperative gait

The patient was able to walk safely on the first postoperative day and reported an 85% improvement in weakness. This video taken on the fourth postoperative day demonstrates significant improvements in gait speed and stability with no pain.

• 07:34 Postoperative MRI image

Comparison with preoperative MRI images confirms that the migrated T5–6 disc fragment was precisely removed. Although slight edema remains in the decompression area. Adequate decompression was achieved, and the spinal canal space and position were effectively restored.

• 07:52 Postoperative CT image

Pre- and postoperative CT scans demonstrate that bony decompression of the spinal canal at the T6 pedicle level was successfully achieved. Endoscopic surgery allowed for effective decompression while fully preserving the facet joint structure.

• 08:19 Discussion1

The development and integration of robotic systems in spine surgery offer significant benefits, such as enhanced accuracy in surgical incisions and instrument placement, reduced operative time, and lower radiation exposure [5].

Endoscopic thoracic discectomy combines full-endoscopy and UBE techniques to leverage the benefits of both approaches, including the cross-viewing of full-endoscopy cannula and the use of tools with larger diameter such as Kerrison rongeurs and dissectors under UBE, which can effectively accomplish more efficient anatomical separation and decompression [6].

• 08:43 Discussion2

Navigation-guided spinal surgery enhances orientation in complex or rare spine procedures and improves the learning curve for these techniques [7].

Further refinement of robotic instruments tailored specifically for endoscopic techniques, as well as the incorporation of augmented reality (AR) technologies, could significantly enhance the precision and safety of these procedures [8].

CASE REPORT

1. Medical History

A 62-year-old female patient had a BMI of 22.2 kg/m². Her main symptom was bilateral leg weakness, having difficulty in standing and walking, indicated by an ODI score of 66. On physical examination, both knee extension and ankle dorsiflexion were 4 on the MRC scale of 5, with no dysesthesia. The patient had undergone a C5–6 anterior cervical discectomy and fusion 8 years ago and had a CCI score of 3. Her symptoms started 6 months ago and got worse recently.

2. Diagnostic Evaluation

Her lumbar spine x-rays showed general degenerative changes, with an overall acceptable coronal and iliac lordosis balance, as indicated by CVA and SVA measurements. Thoracic kyphosis was 48.78°, and lumbar lordosis was 59.46°.

MRI revealed a herniated disc at T5–6, with the disc fragment migrating down to the T6 pedicle level. The cervical spine, previously operated, showed no significant signs of compression. Imaging at the T5–6 level indicated spinal cord compression and displacement to the left posterior side due to the migrated disc fragment. CT scans further clarified the pathology and anatomical location, the disc migration extended from the T5–6 level downward past the T6 pedicle, with significant calcification.

3. Diagnosis and Surgical Planning

The principal pathology is a herniated disc at T5–6 with migration to the T6 level, leading to thoracic myelopathy. The final diagnosis is thoracic myelopathy secondary to a thoracic disc herniation at the T5–6 level.

Our objective is to achieve precise and thorough decompression of the thoracic central canal at the T5–6 level using the least invasive surgical method. Hybrid endoscopic thoracic discectomy with navigation and robotic arm assistance based on the interlaminar approach is to achieve distal central and sufficient decompression.

The necessary patient informed consent was obtained in this study.

DISCUSSION

This case demonstrated outstanding outcomes following surgical treatment, highlighting the benefits of both single-channel and dual-channel endoscopic spinal surgery (ESS) techniques.

Although the significant advantages of utilizing navigationassisted technology were evident throughout the procedure. A key challenge of minimally invasive surgeries, including endoscopic procedures, is the restricted surgical view, which can complicate the operation or cause confusion for the surgeon, potentially leading to longer operation times and increased risks. However, when properly registered and used effectively, navigation in conjunction with an endoscope can reduce some of the uncertainties associated with minimally invasive approaches [9].

Over the past 2 decades, ESS has expanded from the lumbar to thoracic and cervical regions, with the choice of approach often based on the lesion’s location or the surgeon’s preference. Although ESS is progressing, including developments in endoscopy-assisted fusion surgery, it remains challenging with a steep learning curve. Technological advancements, such as computerassisted navigation and augmented reality, are improving imaging, making spinal disease treatment more practical, and helping to shorten the learning curve [10].

The integration of robotic systems in spine surgery offers significant benefits, such as enhanced precision in surgical incisions and instrument placement, which reduced operative times, and lower radiation exposure [5,6]. Hybrid endoscopic thoracic discectomy combines full-endoscopy and UBE techniques to leverage the benefits of both approaches, including the crossviewing of full-endoscopy cannula and the use of tools with larger diameter such as Kerrison rongeurs and dissectors under UBE. At the same time, UBE can also offer additional tool operation angles when compared with Uniportal. With these can effectively achieve more efficient anatomical separation and bony decompression [6].

Navigation-guided spinal surgery improves orientation in complex or uncommon spine procedures and helps to ease the learning curve for these techniques [7]. In this case, robotic arm assistance exhibits extremely significant ergonomic advantages. Specifically, in biportal operations, it provides stable and precise visualization, effectively reducing the risk of accidental damage to nerve tissue in the visual field pipeline. At the same time, it provides an opportunity for holding instruments such as drills with both hands. Robot arm assistance technology is predominantly grounded on optical navigation systems that enable 3-dimensional physical grasping. In comparison with traditional navigation systems, it can always maintain the tool position without frequently navigation confirmations. Particularly when dealing with cervical and thoracic spine segments as well as complex and difficult-to-locate lesions, it holds significant application value [10].

However, this surgical study has some areas for improvement. Given the application characteristics of robotic arms, manual operation is needed during the establishment of building up working channel. Additionally, the time required for preoperative preparation of robot and navigation systems is not negligible, and a large number of surgical instruments also pose challenges to the surgical team in actual operations.

Further advancements in robotic instruments designed for endoscopic techniques, along with the integration of AR technologies, could greatly enhance the precision and safety of these surgeries [8].