Robotic-Assisted Trans-Superior Articular Process Endoscopic Decompression: A Case Illustration and Technical Overview
Article information
Abstract
The growth of minimally invasive techniques in spine surgery has accelerated in recent years, leading to development of new techniques and technology such as robotic-assisted spine surgery and full-endoscopic surgery. While robotic spine surgery offers the potential of increased precision and accuracy in instrumentation, endoscopic techniques are beneficial in reducing collateral tissue damage and allowing patients a faster return to function. We describe a case where we combine a robotic guidance system with a full-endoscopic technique, the trans-superior articular process decompression. We aim to share our experience as well as an overview of the surgical technique.
INTRODUCTION
Over the years, advances in techniques and technology in spine surgery have resulted in a new era for minimally invasive spine surgery, especially in ultraminimally invasive surgery such as full-endoscopic surgery. One such technique is the trans-superior articular process (SAP) endoscopic approach [1], which is a modification of the traditional transforaminal approach. This allows excellent decompression of the intervertebral foramen and the lateral recess, while safely negotiating the exiting nerve root. Apart from novel techniques that increase the safety of minimally invasive procedures, advances in technology such as robotic-assisted technology have also allowed for increased precision and accuracy in spinal instrumentation techniques. We aim to describe a case where we combine the accuracy of robotic-assisted technology with an ultraminimally invasive endoscopic technique, the trans-SAP endoscopic decompression.
CASE DESCRIPTION
A 42-year-old lady who had a prior tubular left L4–5 microdiscectomy 6 months prior presented with recurrence of her left lower limb radicular pain for the past 2 months. She reported pain in her left lower extremity that was aggravated by walking and standing. Physical examination revealed reduced sensation to pinprick and light touch in the left L5 dermatome, and motor power of 3/5 of the left extensor hallucis longus (EHL) indicating L5 weakness. Neurological function across the other myotomes and dermatomes were preserved.
Radiographs of her lumbar spine showed disc degeneration at the L4–5 and L5–S1 levels (Fig. 1), with no dynamic instability demonstrated on flexion and extension radiographs. Magnetic resonance imaging of her lumbar spine showed severe left lateral recess stenosis, as well as severe left foraminal stenosis at the L4–5 level (Fig. 2). In view of her significant pain and lower extremity weakness, surgical intervention was offered.
Radiographs of the patient’s lumbar spine. Anteriorposterior (A) and lateral (B) images demonstrating mild disc space degeneration at L4–5 and L5–S1.
Magnetic resonance imaging of the patient’s lumbar spine. (A) T1-weighted left parasagittal image demonstrating severe foraminal stenosis at L4–5 (red arrow). (B, C) T2-weighted midsagittal and axial images demonstrating severe left lateral recess stenosis at L4–5 (red arrow).
Written informed consent for publication was obtained from the patient prior.
1. Preoperative Planning
A robotic-assisted trans-SAP endoscopic decompression of the left L4–5 neural foramen and lateral recess was planned. The procedure utilized the Mazor X Stealth Edition (Medtronic, Minneapolis, MN, USA) for robotic assistance and the patient’s preoperative computed tomography scan was used for preoperative planning. Using the Mazor X software, the trajectory and final docking position for the robotic arm was planned (Fig. 3). The aim was for the robotic arm to dock at the lateral aspect of the SAP to create a trans-SAP working corridor with bone reamers. The anterior-posterior (AP) view shows the planned trajectory of the approach, ensuring it was not medial to the medial pedicular line, while the lateral view shows the planned trajectory which ensures the reamers are dorsal to the posterior vertebral line. The surgical aim was to perform a decompression of the left L4–5 neural foramen, and the left L4–5 lateral recess.
Preoperative planning of the robotic arm’s final trajectory. The ideal axial, lateral, and coronal trajectories are planned using the Mazor X Stealth Edition (Medtronic, Minneapolis, MN, USA) software.
2. Operative Technique
The patient was placed under general anaesthesia for the procedure and positioned prone on a radiolucent modular table frame system with chest and pelvic supports. After the patient was positioned, the robotic arm was then secured to the caudal end of the table frame using a bed rail adapter. The patient’s posterior back and left lateral aspect was then prepped in a standard sterile fashion. A Shanz pin was inserted over the right posterior superior iliac spine for attachment of the bone mount bridge, thus connecting the robotic arm to the patient. After performing registration of the Mazor X, the robotic arm then moved into position based on the predefined trajectory that was planned. The setup time for the Mazor X was 10 minutes, while the registration of the Mazor X, which involves taking an AP and lateral fluoroscopy shot, took an additional 10 minutes.
After the robotic arm moved into its final position, a stab incision was made in the skin and a navigated Midas drill was inserted through the outer cannula until bone was felt (Fig. 4). The navigated drill has a 3-mm drill bit with a stop at 30 mm to prevent over drilling. After drilling, a guide wire was inserted through a centering device, and intraoperative C-arm fluoroscopy images were taken to confirm the correct position of the wire on the AP and lateral view (Fig. 5). Sequential dilators and reamers were then inserted to partially ream the SAP and create the trans-SAP working corridor. During reaming, fluoroscopy is used to ensure that the reamers do not pass the medial pedicular line on the AP view to avoid damage to the traversing nerve root. After the final reaming, the working tube for the endoscope (TESSYS, joimax GmbH, Karlsruhe, Germany) is then inserted, and a navigated dilator is inserted through the working tube to check its position on the Mazor X navigation system (Figs. 6, 7). A 30° endoscope (joimax GmbH, Karlsruhe, Germany) is then inserted into the working port for uniportal endoscopic decompression. Soft tissue is debrided with the aid of radiofrequency ablation to expose the bony anatomy. Once the bony landmarks such as the ventral surface of the SAP and the caudal L5 pedicle have been identified, a diamond burr is used to drill the ventral surface of the SAP for foraminoplasty till the arch of the SAP leading to the caudal pedicle is well visualized. A Kerrison rongeur or the radiofrequency ablation instrument is placed at the caudal L5 pedicle, and the location checked on fluoroscopy to confirm the accurate location at the “principal anatomical landmark” as described by Hasan et al. [1] (Fig. 8). The yellow ligament is identified and resected, and the epidural space with its epineural fat is then exposed. The annular defect was identified, and herniated disc material removed. The traversing L5 nerve root in the lateral recess, as well as the exiting L4 nerve root in the intervertebral foramen was well visualized to ensure adequate decompression (Fig. 9). After haemostasis, the wound was closed with a single layer of nonabsorbable suture without insertion of a drain. The total operative time for the procedure was 150 minutes.
Navigated drill insertion. (A) Intraoperative picture of the navigated drill inserted through the robotic arm working cannula. (B) Checking the drill trajectory on navigation. (C) Clinical photograph of the navigated drill used.
Guide wire insertion. (A) Intraoperative image of the guidewire placement. (B) Placing the guidewire through a centering device. (C, D) Fluoroscopy images demonstrating accurate placement of the guidewire.
(A) Insertion of the endoscopic working tube and confirmation of position with the navigated dilator. (B) Clinical photograph of the navigated dilator with endoscopic working tube.
Navigated dilator insertion. (A) Intraoperative fluoroscopy image of the working tube placement with dilator. (B) Confirmation of location of the working tube using navigation.
Confirmation of location at the principal anatomical landmark of the caudal L5 pedicle. (A) Endoscopic picture. (B) Fluoroscopy image corresponding to the location at the L5 pedicle.
Endoscopic views after foraminoplasty. (A) Traversing L5 nerve root seen (red arrow). (B) Exiting nerve root well decompressed. SAP, superior articular process.
A detailed surgical video (Supplementary video clip 1) is accompanied with this article.
RESULTS
The patient was transferred to the general ward and mobilized the next day. There was complete resolution of her left lower limb radicular pain, with recovery of power in the left EHL. The patient was discharged uneventfully on postoperative day 2. At the 3-month follow-up, there was no recurrence of pain, and she had returned back to work.
DISCUSSION
The emergence of technology such as robotics and full-endoscopic techniques have led to a paradigm shift in minimally invasive spine surgery techniques. By marrying the 2 techniques, the accuracy and precision of robotic technology can be combined with the ultraminimally invasive full-endoscopic techniques to reduce collateral soft-tissue damage, targeted removal and decompression of pathology, to ensure the best possible outcome for patients while reducing recovery time.
The use of the trans-SAP technique, in this case, instead of the traditional transforaminal approach, was utilized as the robot can better localize bony anatomical landmarks instead of soft-tissue landmarks. With the traditional transforaminal approach, there is a risk of injury to the exiting nerve root, hence the trans-SAP approach aims to dock on the lateral aspect of the SAP, so that there is a bony anchoring landmark, and thereby reducing the risk of nerve root injuries. However, there is still a risk of injury to the nerve root in the event of accidental slippage of the bone reamers. During the positioning of the working channel, the initial reamer should be positioned on the lateral aspect of the SAP as this maximizes the distance to the exiting nerve root. As described by Hasan et al. [1], if the initial reamers are too dorsal on the SAP, the facet joint will be entered, and conversely reaming will be insufficient if the reamer is positioned too ventral.
Additionally, avoiding an interlaminar approach allowed us to avoid dissecting through an area previously operated on, which may be challenging to safely identify a plane between the scar tissue and dura.
Our early experience with the use of the robot as a guidance system is positive, especially with providing a relatively more shallower learning curve in localization. This is particularly helpful as the steep learning curve for endoscopic techniques such as the transforaminal techniques is well recognized, with a learning curve of 72 cases on average in order to reach a good or excellent clinical outcome [2]. With such steep learning curves, this may hamper the development and take-up of endoscopic spine surgery as a technique, and robotic assistance may help early adopters to the technique in this regard. Using robotic assistance in localization also allows the trajectory to be preplanned, and executed accordingly, with greater precision and accuracy. The use of navigation instruments allows for another layer of safety in intraoperative localization, with less fluoroscopy required.
However, the pitfalls of such a technique include involving an extra incision for the Shanz pin, and requiring additional time for setup and registration of the robot. Additionally, whilst the robot may help in initial localization, the surgeon still needs to be familiar with the endoscopic approach, and be sufficiently proficient at handling endoscopic instruments and bone reamers. While the robotic-guided navigation may give early adopters added confidence in performing the technique, it does not completely flatten the significant learning curve involved. As this was a novel case illustration, we simultaneously utilized the robot navigation system as well as fluoroscopy in order to ensure accuracy, and acknowledge that the routine use of both may be costly and time consuming. For future cases, the use of fluoroscopy may be limited to just a single AP and lateral shot at the beginning for registration of the robot.
In recent years, while there has been increasing use of navigation and robotic guidance systems in spine surgery, there has also been reservations about its cost-effectiveness and long-term differences in clinical outcomes. The cost of the Mazor X, for example, is approximately USD 1.5 million, and together with the maintenance expenses, certainly proves as a high barrier to entry for most healthcare systems, especially those that are not-for-profit. This additional cost and resource availability is likely to limit the broader application of this technique in various healthcare settings, especially for surgeons practicing in settings with limited resources.
Additionally, a limitation of the trans-SAP approach is the amount of bone work that is required. For cases that involve predominantly foraminal or extra-foraminal pathology, the transSAP approach may not be ideal as minimal bone work is typically required to access such pathology using a transforaminal approach.
CONCLUSION
Our case highlights the possibility of combining the MIS benefits of the trans-SAP approach, with the accuracy and precision of robotic spine surgery. This novel technique allows for targeted localization based on a preplanned trajectory, optimizing the approach for subsequent endoscopic decompression. In selected cases such as when there is distortion of bony anatomy, this may be helpful, particularly for early adopters. As the field of endoscopic surgery and technology such as robotic guidance systems in spine surgery continues to evolve, new innovations and techniques will likely continue to gain traction in the future.
Supplementary Materials
upplementary video clip 1 is available at https://doi.org/10.14245/ns.2449082.541.
Notes
Conflict of Interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Author Contribution
Conceptualisation: TLTS, JYLO; Formal analysis: TLTS, ZC, JYLO; Investigation: TLTS, JYLO; Methodology: TLTS, ZC, JYLO; Project administration: TLTS, ZC, JYLO; Writing – original draft: TLTS, JYLO, CPH; Writing – review & editing: TLTS, ZC, JYLO, CPH.