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Surgical Simulation
This chapter includes an accompanying lecture presentation that has been prepared by the authors: 
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Key Concepts
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Simulation often refers to a virtual three-dimensional (3D) visual model created with CT and MRI data.
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The role of simulation in neurosurgery is still being developed as a training tool, but it is used in everyday workflows through presurgical rehearsal and for understanding complex anatomic relationships.
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Advantages of a physical model include the ability to practice tactile skills with haptic feedback. The limitations of this feedback relate to difficulties with simulating tissue and heterogeneous brain structures realistically, both virtually and in 3D printed scenarios.
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Three-dimensional printing can be a useful tool for proof-of-concept surgical options or for planning approach solutions preoperatively.
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The use of mixed solutions combines both virtual and physical models, which allows integration of technologies for specific skills assessment and training.
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Further development of both simulators and assessment criteria is necessary in order to enhance the field of surgical training without the use of cadaveric or animal models.
Imagine a concert pianist performing a concerto in front of an audience after having only sight-read the piece, or a professional basketball team playing together for the first time in a championship game. These ideas seem absurd, but why? Expert performance is more than the product of generalized practice and past success but also depends on performance-specific preparation. We understand intuitively that the closer the circumstances of practice are to the circumstances of performance, the better the performer will be. There is an association between experience and proficiency that can be enhanced with practice and preparation. This is important because proficiency in the technical performance of surgery has been shown to affect complication rates between individual surgeons, and proficiency in surgical care has been shown to affect outcomes between surgical teams. We are constantly in search of better ways to practice and prepare. Simulation is a method of practice wherein one or more elements of a performance are isolated and studied to refine the cognitive and physical skills involved in successful execution. In this chapter we discuss a framework for understanding the stages of procedural learning, tools for successful practice in surgery, and how simulation can enhance practice for clinicians at any stage of experience.
Surgery involves both cognitive and physical skill mastery and in this way shares many similarities with skill acquisition in sports and music. Unlike with a complicated musical solo, technical practice of the critical portions of an operation is difficult to remove from the patient encounter. Practice can be made more successful if we understand how to use it to attain proficiency. In studies of attributes and skill sets that distinguish expert performers from high-average performers, the type and degree of practice have been identified as possible factors that promote high-level success. Deliberate practice, or mentor-guided learning oriented toward improved performance in specific skills, is a highly effective form of practice. Medicine and surgery are full of examples of deliberate practice, and thoughtfully applied simulation may offer advantages in acquiring deliberate practice over traditional methods.
Like other motor skills, development of the surgical skillset requires both cognitive and motor development. Simulation has been used in both areas. Although deliberate practice of the motor skills required for surgery occupies a specific part of the pathway of motor skills development, as described by Fitts and Posner ( Table 27.1 ), we use deliberate practice of surgical decision making dialectically to facilitate learning of cognitive domains of surgery as well. That cognitive development precedes mechanical development speaks to the importance of context in motor skill development. In our practice we have been able to use simulation through virtual reality to create a common mental model of specific surgical cases so that advanced learners can develop ways to enhance their own adaptability while more junior individuals can more fully understand the tasks required to accomplish the operative goals.
TABLE 27.1
Definitions in Simulated Neurosurgery
| Simulation | A technique that creates a situation or environment to allow persons to experience a representation of a real event for the purpose of practice, learning, evaluation, or testing, or to gain understanding of systems or human actions. The user is in a central role through the exercising of decision making, motor control, and communication skills with a physics-based model. |
| Virtual reality simulation | Recreation of reality depicted on a computer screen; it involves real people operating patient-specific rendering of anatomy on a computerized system. The user can interact with visualized data in a number of ways; however, the anatomy does not change. |
| Computerized neurosurgical simulation device | A computer device that provides a surgery-like environment, including a three-dimensional visualization of various surgical scenarios such as cerebral aneurysm clipping, or tumor resection. A user is provided two instruments with adjustable forces, such as suction and cauterization. Simulators can accurately calculate and display in real time the deformation of the brain tissues in accordance with the force applied from the suction and cauterization as applied by the operator of the machine. At the end of the “operation,” simulators can also provide feedback about the case, including metrics such as the amount of blood loss, amount of tumor resected, and amount of excessive force used. |
| Haptic technology | Technology that provides tactile feedback to a user by re-creating a sense of touch. For example, haptic devices can provide users with a sense of objects that are “hard” or “soft” when force is applied in the simulated setting. Haptics are typically used in tandem with computerized neurosurgical simulation devices to provide the user with combined visual and sensory feedback during a simulated surgical task. |
| Navigation | A coordinate system created using volumetric Digital Imaging and Communications in Medicine (DICOM) images, which can be correlated to the patient’s anatomy in real time. |
| Augmented reality/heads-up display | Enhances the user experience by applying known information to a real-world situation; digital information is superimposed over the surgical field, and both are immediately available for interpretation while the surgeon is operating. |
Mental rehearsal or mental practice is a technique of preparation whereby the performer creates internal visual stimuli to rehearse motor movements without engaging in actual movement. It has been associated with improved performance in both expert and novice performers in sports, music, and other disciplines. Mental rehearsal may function as a primer for complex motor activities, strengthening existing pathways before they are to be activated. Performance is then more efficient and precise. Mental rehearsal has been suggested in other species and may be a potential candidate target for brain-computer interface research. Perhaps because of the nature of surgical practice, mental rehearsal has been used for teaching and personal preparation by generations of surgeons. The vividness of a mental image and the degree of detail with which a mental image can be described have both been linked with improved performance, suggesting that efforts targeted toward improving mental rehearsal will also lead to improved performance.
Mental practice alone is not enough to attain expert or “automation” level performance. Some physical practice of the motor skills involved must also occur. Historically, surgical simulation has been limited to cadaveric and animal courses wherein the fundamentals of surgery can be practiced. Within the past decade, computerized surgical simulation has progressively increased in sophistication, playing a growing role in the education and training of surgeons. As radiologic and digital technology have improved, it is increasingly possible to recreate more complex information so that deliberate practice can be applied to other steps in surgical preparation in which cognitive and communicative tasks dominate. Computerized surgical simulation with haptic feedback has been shown to distinguish experienced practitioners from learners, suggesting that these tools may be useful in motor skill practice and development.
Simulation
Through simulation, surgery’s complex environment can be pared down to focus only on specific tasks or conditions so that deliberate practice of these components can be performed. Benefits of virtual simulation devices in the hands-on training of surgical residents have been reported. Although simulators now play a critical role in laparoscopic surgery training, they have not yet been as widely adopted in neurosurgical training—but enthusiasm is growing. In comparison to laparoscopic surgery, the techniques of neurosurgical approaches and the array of different pathologies are broad. Experience from laparoscopic surgery teaches us that many elements of surgical training can be successfully removed from the patient encounter, and with increasing focus on efficient training in surgery, it is very likely that neurosurgery will continue to integrate simulation into routine practice.
Virtual reality simulation is a type of simulation designed to specifically improve mental rehearsal by recreating anatomic relationships from CT and MRI data. Although the up-front cost is high, these models are easily adjusted to fit specific interests or patient parameters and become cost-effective with increasing use. , This type of simulation is most commonly used for presurgical rehearsal and education relating to cognitive understanding of complex anatomy. Applied in this way, the virtual model can be used to improve basic understanding of the case but also to guide experts in ways that might improve their own adaptability.
For the purposes of this chapter, four currently available neurosurgery-specific simulation devices are discussed:
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NeuroVR simulator with Touch X
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Simbionix ARTHRO Mentor
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Surgical Theater Planner and Surgical Navigation Advanced Platform
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Immersive Touch Simulation System
Although there are overlaps between the graphical user interface and device haptics of these simulators, each offers a unique user experience. These devices use a pair of handheld instruments to re-create various neurosurgery-specific scenarios ranging from bipolar cautery to aneurysm clipping. They also provide performance feedback to a user that can be tracked over time to monitor variables such as progress, learning, and speed.
NeuroVR Simulator
The NeuroVR, previously NeuroTouch simulator, was developed and released in 2012 by the National Research Council Canada (Ottawa, Ontario) in collaboration with neurosurgeons from numerous Canadian teaching hospitals. NeuroVR is a virtual reality training simulator that uses task-specific, predeveloped scenarios offering a relatively wide spectrum of user practice tasks, including brain tumor resection, establishment of hemostasis, and ultrasonic aspiration ( Fig. 27.1A ) . Depending on the specific training module a user selects, there are several different performance variables that will generate data based on a specific task. Examples of performance variables include time to completion, blood loss, and excess force applied to tissue. The variable of “force” is measured through the use of haptic feedback, driven by the integrated Touch X haptic device (Geomagic) (see Fig. 27.1B ). These performance variables have been shown to vary based on the user’s level of training and experience. For example, Azarnoush and colleagues demonstrated a significant difference in performance of a neurosurgery resident and an attending physician during a simulated brain tumor resection on the NeuroVR platform. Similarly, Gelinas-Phaneuf and associates used the NeuroVR platform to examine performance differences in medical students compared with neurosurgery residents during a simulated brain tumor resection. Interesting to note, the study was able to demonstrate a significant difference between the performance of medical students compared with neurosurgery residents, but not between junior and senior neurosurgery residents. Alexander Winkler-Schwartz et al. have collaborated with interdisciplinary groups to develop a Machine Learning to Assess Surgical Expertise (MLASE) checklist composed of 20 essential key elements when reporting studies using machine learning algorithms to assess technical skills in virtual reality surgical simulators. Taken together, the results of these studies suggest that virtual reality simulators such as NeuroVR in their current state can be used to detect differences in user training and experience among relatively inexperienced practitioners but not those with more experience. Research is ongoing to test the efficacy of NeuroVR in enhancing hands-on resident training in the operating room.
Simbionix Arthro Mentor
Outside of intracranial surgery, simulations of angiographic techniques have been developed for surgical rehearsal of aneurysm repair and carotid stenting, including by Simbionix (3D Systems). Clinicians found that by practicing femoral endovascular access prior to entering the angiography suite, they could reduce fluoroscopy time. With use of the ANGIO Mentor endovascular simulator (Simbionix) three-dimensional (3D) model simulation with novice proceduralists and experienced clinicians to rehearse surgery, it was found that overall procedure time was reduced by 33.8% ( P < .0001). Another study involving aneurysm repair found that the patient-specific model helped in rehearsal and allowed for optimized preoperative preparation. However, there were some limitations in the biologic nature of simulated versus real anatomy.
Surgical Theater Planner and Surgical Navigation Advanced Platform
Patient-specific surgical simulation has been a topic of renewed interest, as MRI and CT have increasingly advanced in sophistication over the past decade. The 3D Surgical Planner (SRP) and Surgical Navigation Advanced Platform (SNAP) are two neurosurgical simulation devices recently developed by Surgical Theater ( Fig. 27.2 ). Unlike the NeuroVR system, which uses task-specific, predeveloped training scenarios, the SRP allows a user to upload a patient’s CT/MRI sequences (using the Digital Imaging and Communications in Medicine [DICOM] protocol) for patient-specific practice. This enables a user to plan and rehearse complex patient-specific surgical procedures such as cerebral aneurysm clipping or skull base approaches in a virtual, risk-free environment. The patient-specific data are imported into the SRP, which generates a 360VR model that can be used on the SRP and SNAP with the Vive to simulate surgery.
The SNAP allows surgeons to take the preoperative surgical plan from the SRP into the operating room and use it in conjunction with a traditional frameless navigation system during surgery. When connected to navigation, the SNAP can extract and display intraoperative navigation data inside an interactive 3D scene from multiple points of views. Both the SRP and the SNAP have been cleared by the US Food and Drug Administration (FDA) for planning and simulating surgery strategies. The software has the ability to adjust the opacity of structures, allowing the surgeon to selectively visualize what is critical to the case. In many scenarios the preoperative plan will include transparent bone so that the physician can clearly view the anatomy inside. As reported by Surgical Theater, this technology has been used in over 5000 cranial tumor and vascular cases in the United States, including increased use across other specialties.
The potential implications of patient-specific rehearsal in improving patient safety and outcomes are of interest. Over the years Surgical Theater has implemented many tools for surgical planning and rehearsal. Two of the most common uses of the SRP and SNAP have been to plan cerebral aneurysm clipping and skull base tumor approaches. The best cases for simulation are those in which the pathology avidly enhances with intravenous contrast, allowing for vivid segmentation of patient-specific anatomy. A user can upload a patient’s CT/MRI sequences to the device to plan head positioning and different approaches, including minimally invasive and “keyhole” approaches. In the planning phase of an aneurysm operation, virtual surgical tools can be manipulated during the approach. For example, bone drilling and placement of an aneurysm clip can be simulated and rehearsed. In virtual reality the users can physically choose which type, style, and size of clip to place across the aneurysm and practice clipping on the patient-specific model. There are limitations to the response of the virtual model, as they are primarily based on patient scans and do not react to manipulations at this time. In addition, they do not provide simulations of complications, and so on. This has the potential to reduce intraoperative decision-making time during a critical phase of the procedure. Planning can be performed in two-dimensional (2D) or 3D graphical interface modes; however, the device does not fully incorporate haptic feedback during simulation.
The HTC Vive and other virtual reality hardware platforms that use hand controllers can easily integrate with both the SRP and the SNAP. On either platform, in virtual reality the surgeon or resident can now plan the approach and practice bone drilling ahead of time ( Fig. 27.3 ). The hand grips of the Vive provide a vibration-like sense that provide some haptic feedback to simulate bone drilling. This surgical rehearsal feature has the potential to decrease operative time and increase situational awareness and anatomic relationships before the surgeon even enters the operating room.
Research is still ongoing as to the integration of the SRP into the education curriculum of neurosurgery residents. This is of particular interest in the resident training of microsurgery techniques used to treat cerebral aneurysms. With a growing proportion of patients being treated with endovascular techniques, there is concern that decreased resident participation in and exposure to aneurysm clipping will lead to a generation of inexperienced vascular neurosurgeons. Therefore the SRP is positioning itself to become an integrated part of a patient’s neurosurgical treatment plan, in addition to improving a surgeon’s confidence and familiarity in the operating room.
The SNAP is an FDA-approved neurosurgical device that imports a 3D plan from the SRP and allows surgeons to visualize and manipulate 3D rendering or virtual simulations to establish multiple views with zoom, rotation, and cropping to permit interaction with the navigation image to see behind pathologic features and vital structures. Tumors, vessels, and tissues can be rendered partially transparent to improve visualization. During surgery the 3D plan is linked to a frameless navigation system, permitting the user to freely manipulate a patient’s preoperative images in numerous 3D points of view. The technology is limed in the ability to create physics-based interactions that are lifelike outside of approach, craniotomy, and aneurysm clipping.
Immersive Touch Simulation System
The Immersive Touch Simulation System ( Fig. 27.4 ), developed at the University of Illinois at Chicago, combines elements of both the NeuroTouch and Surgical Planner systems. The Immersive Touch platform provides several neurosurgical rehearsal scenarios such as ventriculostomy placement, bipolar electrocautery, and spine pedicle screw placement. A user is provided a set of 3D glasses for visualization, a PHANTOM Omni handheld device (Sensable), and an iPad (Apple) for instrument utilization, and a foot pedal for instrument activation. In addition to predeveloped rehearsal scenarios, the Immersive Touch Mission Rehearsal simulator provides for patient-specific rehearsal by allowing a surgeon to upload CT/MRI data to the device. However, the Immersive Touch only allows the surgeon to practice the same rehearsal scenarios noted previously with the patient’s imaging data. In terms of Immersive Touch’s applications to neurosurgical resident training, Yudkowsky and coworkers demonstrated improved resident accuracy and confidence in placing a ventricular catheter after practice with several different ventriculostomy scenarios. Another study by Gasco and colleagues demonstrated improved accuracy and decreased rate of errors in the placement of lumbar pedicle screws in medical students who were allowed to practice on the Immersive Touch prior to screw placement. Although further studies are required, there is evidence to suggest that the Immersive Touch simulator has promise in positively affecting resident training and education.
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