Over the past decade, robotic surgery has gained wide popularity, making a significant impact on multiple surgical specialties. In the head and neck arena, transoral robotic surgery has proven to be safe and associated with acceptable oncological and superior functional outcomes for surgery of the oropharynx, hypopharynx, supraglottis, and glottis; thus, changing the paradigm for the management of tumors in these anatomic locations. Robotic surgery of the ventral skull base is at an early stage of development. In this article reviews the literature discussing the role of robotic surgery in managing sinonasal and ventral skull base malignant lesions.
Key points
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Multiple extended approaches have been described to optimize access and surgery through the confines of the sinonasal cavities and skull base.
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Robotic surgery offers several advantages over conventional, endoscopic, or endoscopic-assisted surgery including 3-dimensional visualization, tremor-free surgery, fine precise dissection, and bimanual surgery.
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Robotic surgery also presents disadvantages, such as the lack of haptic feedback, absence of drills, bone cutting or any other power instrumentation, and relatively large size of the instruments.
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Despite very active research in this regard, the current indication for robotic sinonasal and ventral skull base surgery is the resection of recurrent nasopharyngeal carcinoma or the primary resection of malignancies of salivary origin.
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Transoral robotic surgery (TORS) can be combined with an expanded endonasal approach to resect large malignant lesions extending inferiorly below the level of the hard palate. These 2 techniques are complementary in their anatomic reach and available instrumentation.
Video content accompanies this article at http://www.oto.theclinics.com .
Introduction
Over the past decade, robotic surgery has gained wide popularity, making a significant impact on multiple surgical specialties, such as gynecology, urology, abdominal surgery, and cardiac surgery. In the head and neck arena, transoral robotic surgery (TORS) has proven to be safe and associated with acceptable oncological and superior functional outcomes for surgery of the oropharynx, hypopharynx, supraglottis, and glottis; thus, changing the paradigm for the management of tumors in these anatomic locations. Robotic surgery of the ventral skull base is still at an early stage of development; however, some case series have been published over the past few years. In this article, we review the literature discussing the role of robotic surgery in managing sinonasal and ventral skull base malignant lesions.
Introduction
Over the past decade, robotic surgery has gained wide popularity, making a significant impact on multiple surgical specialties, such as gynecology, urology, abdominal surgery, and cardiac surgery. In the head and neck arena, transoral robotic surgery (TORS) has proven to be safe and associated with acceptable oncological and superior functional outcomes for surgery of the oropharynx, hypopharynx, supraglottis, and glottis; thus, changing the paradigm for the management of tumors in these anatomic locations. Robotic surgery of the ventral skull base is still at an early stage of development; however, some case series have been published over the past few years. In this article, we review the literature discussing the role of robotic surgery in managing sinonasal and ventral skull base malignant lesions.
Available robots and instrumentation
Currently, there are only 2 surgical robotic systems approved by the Food and Drug Administration that have been used to perform endoscopic ventral skull base surgical procedures: the da Vinci Surgical System (Intuitive Surgical, Inc, Sunnyvale, CA) and the Medrobotics Flex Robotic System (Medrobotics Corp, Raynham, MA). We will describe each in the following section.
The da Vinci Surgical System is the most widely used robotic surgical system in the United States and its applications have been well documented in the otolaryngology literature. It consists of a console that serves as the surgeon control center, a patient-side surgical robot with a 3-dimensional (3D) rigid endoscope, and a video display cart. The endoscopes for use in the newest version of the system is 8.5 mm in diameter and has 0° and 30° viewing angles available. The entire endoscope arm can pivot, rotate, and translate to change the operator’s view; however, it is rigid and cannot change its trajectory within the surgical field. The endoscope, which is fit with a dual-lens, 3-charge-coupled device camera, gives the operating surgeon a high-definition, stereoscopic view of the surgical field. Various instrument attachments, as small as 5 mm in diameter, are designed to operate with 7° of freedom, based on the “wristed” movements of the operating surgeon.
The da Vinci system has been used in head and neck surgery since 2005 and has gone through several product cycles since its initial launch. This affords a level of relative maturity for the da Vinci product line when compared with the only other surgical robot system cleared for use in the United States. The newest version of the da Vinci Surgical System is the da Vinci Xi, which offers several improvements over its predecessors. One of these is the automatic configuration of its boom arms based on endoscopic and laser guidance, a feature that reduces the set-up time, which has been a common source of criticism. Nonetheless, even this current iteration does not provide the surgeon with haptic feedback or stereotactic navigation features.
The Medrobotics Flex Robotic System was approved for use in the United States in July 2015 and was specifically designed for use in the oropharynx, hypopharynx, and larynx. The primary advantage of the Flex system lies in the maneuverability of its endoscope and accompanying instrumentation, offering a flexible system capable of steering around obstructing anatomy ( Fig. 1 ). In spite of its flexible, steerable configuration, the large diameter of the endoscope and instrumentation preclude a purely endonasal approach to the ventral skull base. Schuler and colleagues demonstrated a successful endoscopic visualization of the anterior ventral skull base using the Flex system; however, a midfacial degloving was required to accommodate the robotic arms. In their study, the Flex endoscope was used for visualization, whereas the actual surgical maneuvers were performed using standard, conventional instrumentation. The robotic arms were able to reach pertinent anatomic features; however, they did not perform any actual procedural tasks. Like the da Vinci system, the Flex does not provide haptic feedback or stereotactic navigation features.
Neither robotic system is able to access the sinonasal cavity or ventral skull base using a purely endonasal approach, instead requiring additional morbidity through traditional open approaches. A common limiting factor of both systems is the size of their endoscopes and instrumentation. A typical endonasal endoscope is only 4 mm in diameter, and the size of endonasal instruments is only on the order of millimeters. Further limitations of both systems are the lack of a high-speed drill, which is required to remove the hard bone of the sinonasal cavity and ventral skull base and the lack of adequate suctions to handle the typical bleeding arising from the sinonasal corridor and surgical field. In addition, the lack of tactile feedback is a significant barrier to the practical use of either robotic system in sinonasal and ventral skull base surgery. Alternatives to overcome these hurdles are being actively investigated by teams across the world. Haptics is of utmost importance in dissection within anatomically critical areas, such as the ventral skull base, and its study is a subject of high interest within robotics. A feasibility study to investigate haptic feedback in TORS was recently performed by the University of Pennsylvania, and this concept may transfer to endonasal surgery in the near future.
To create steerable robotic instrumentation capable of navigating the sinonasal cavity, a team at Vanderbilt has developed a prototype system using concentric tube robotic arms, allowing tentaclelike motion and manipulation. These advances, when combined, will help to expand the indications and relevance of robotic-assisted ventral skull base surgery.
In addition to the systems discussed, there are several automated endoscope holders and positioning systems that allow for hands-free visualization, but do not have instrumented arms to enable a truly robotic-assisted solution. The neurosurgical literature describes the use of several other robotic systems, including the stereotactic navigation-enabled NeuroMate (NeuroMate PLC, Gloucestershire, UK), which can be used for functional neurosurgical procedures and the BrightMatter Drive by Synaptive Medical Inc (Synaptive Medical, Toronto, Canada). These robots, however, have designs that are physically incompatible with an endonasal ventral skull base approach and are outside the scope of this article.
Surgical routes to the sinonasal cavities and ventral skull base
Given that the size of the instruments used for the da Vinci robot are not designed to fit the sinonasal cavities, additional augmented surgical routes have been developed on cadaveric models to optimize access and reach the ventral skull base.
Purely Transoral Approach
Transoral robotic skull base surgery was among the initial approaches to the ventral skull base and was developed by the University of Pennsylvania group in 2007. This approach was aimed at dissecting the parapharyngeal and infratemporal space and was initially tested on cadaveric specimens and on a live mongrel dog model. It was then applied on a patient with a benign cystic lesion of the parapharyngeal and infratemporal space.
Technique: The da Vinci robot is docked at the head of the bed. A Crowe-Davis mouth gag retractor (Storz, Heidelberg, Germany) is used to open the oral cavity and expose the oropharynx. The camera and both robotic arms are introduced transorally. The procedure starts with incisions lateral to the anterior tonsillar pillar, followed by dissection of the branches of the external carotid; the jugular vein; internal carotid; and cranial nerves IX, X, XI, and XII. The styloid and pterygoid musculatures are released to gain lateral access within the infratemporal fossa.
Although this proved the feasibility of robotic surgery of the parapharyngeal space and infratemporal fossa, there were major limitations noted and reproduced throughout other experimental studies, including the lack of drills and rongeurs to remove the ventral skull base bone and the inability to complete a wide resection, thus precluding its use for malignant lesions. The transoral approach was also described to access the craniocervical junction; however, drilling of the odontoid and arch of C1 was done by an assistant using a conventional technique.
Combined Transnasal and Transantral Approach
In 2007, Hanna and colleagues, using a cadaveric model, described a surgical approach to the cranial fossa using the da Vinci robot via combined transnasal-transantral approach.
Technique: Access to the sinonasal cavities is gained through bilateral, superior, vestibular/sublabial incisions followed by wide anterior and middle maxillary antrostomies (Caldwell-Luc–like). A posterior septectomy is done joining both sinonasal cavities into one surgical field. Then the da Vinci robot is docked at the head of the bed, the camera arm port is introduced through the nostril and the right and left robotic arm ports through the respective anterior and middle antrostomies into the nasal cavity. Then a total ethmoidectomy, wide common sphenoidotomy, resection of the middle and superior turbinates are performed, providing access to the anterior and middle cranial fossa. The cribriform plate is resected and the dural incision is then repaired, suturing a graft in a watertight fashion. This approach provides excellent access to the anterior and central skull base. The investigators emphasized the ability to perform 2-handed tremor-free suturing of dural defects. Cho and colleagues described a similar combined endonasal-transantral approach for robotic nasopharyngectomy.
Combined Transcervical and Transoral Approach
O’Malley and Weinstein described the cervical-TORS (C-TORS) approach of the skull base on a cadaveric model.
Technique: The approach entails placement of a 30-degree angled lens endoscope transorally and the effector robotic arms transcervically. The da Vinci robotic arms are introduced via bilateral incisions along the posterior margin of the submandibular glands, followed by the blind blunt placement of trocars that are directed supero-medially into the oral cavity; thus, accessing the ventral skull base and nasopharynx through the oropharynx. This technique enables surgical dissection in the sphenoid sinus, clivus, sella, and suprasellar fossa with improved instrument angulation and access.
Combined Transoral and Midline Suprahyoid Approach
McCool and colleagues described a cadaveric dissection using a midline suprahyoid approach to the infratemporal fossa with the da Vinci robot.
Technique: The approach entails a midline 15-mm incision at the level of the hyoid bone with blunt dissection to gain access into the vallecula. The midline port is placed through the suprahyoid incision, a 30-degree camera is placed transorally in the midline, and the second robotic arm is placed transorally contralateral to the site of dissection. An incision is made in the posterior tonsillar pillar and carried superiorly along the salpingopharyngeal fold. The superior pharyngeal constrictor and the medial pterygoid muscle are divided, identifying the lingual and inferior alveolar nerve. The internal and external carotid arteries are identified posterior and medial to cranial nerve V3 and the middle meningeal artery is dissected up to the foramen spinosum. The dissection is extended posteriorly to the jugular foramen, identifying the internal jugular vein and cranial nerves IX to XII. The da Vinci robot was used to place surgical clips using an 8-mm clip applier. The combined transoral-suprahyoid approach provides a central port with low risk of damaging neurovascular structures; thus, allowing dissection of the central and lateral skull base.
Combined Transnasal and Transoral Approach
Combined transnasal and transoral approaches were described by Dallan and colleagues in 2012 and Ozer and colleagues in 2013. Ozer and colleagues gained further anterior access using a mucoperiosteal flap to allow an approach through the hard palate.
Technique: The setting includes docking the da Vinci robot cranially at the head of the cadaver with a transnasal 30° lens endoscope facing upward. For dissection, a Maryland dissector (Intuitive Surgical, Inc) and a cauterization device with a spatula tip are placed transorally. The dissection starts with a midline incision in the posterior nasopharyngeal wall followed by bilateral medial to lateral hemi-nasopharyngectomy, including resection of the Eustachian tube. This technique provides an optimal approach to the nasopharynx and posterior skull base, especially in patients who are edentulous, given the transoral access without the need to split the palate. Furthermore, the dissection work is done under typical endonasal endoscopic vision, thus providing the surgeon a more familiar anatomy compared with the purely transoral technique, in which dissection occurs in inferior to superior fashion. As described by Ozer and colleagues, this approach can be augmented by removing the bony hard palate (transpalatal approach) after elevation of a posteriorly based U-shaped palatal flap ( Fig. 2 ).
