Capítulo 20. Impact of Virtual Reality Technologies on Maxillofacial Surgery Education

Capítulo 20. Impact of Virtual Reality Technologies
on Maxillofacial Surgery Education

*Hugo Medellín Castillo, **Jorge Zaragoza Siqueiros, ***Eder Govea Valladares

Universidad Autónoma de San Luis Potosí

The development and use of computer and virtual reality (vr) technologies have increased enormously in the last decades. A wide range of vr applications are proposed at engineering, medicine, architecture, archaeology, entertainment and education. At medical education, the aim is to develop computer and vr systems that can be used for teaching and training students and young practitioners. However, although modern engineering technologies have conducted to the development or computer-aided surgical procedures and systems, education and training in maxillofacial surgery still relies mainly on the classic physical hands-on approach, which requires years of hand-on training in the operating room (or) or in laboratory-based surgical practices over cadavers or models. In this chapter is analyzed and discussed the potential impact of the use of virtual reality technologies on maxillofacial surgery education.

Introduction

The use of modern computer technologies in the area of medicine —such as Computer-Aided Design (cad), image processing and 3D reconstruction, robotics and computer vision, vr and augmented reality (ar)— has significantly increased in the last three decades. The Engineering Assisted Surgery (eas) is defined as the application of engineering and manufacturing technologies in the delivery of healthcare (Lohfeld et al., 2007). The aim is to improve the overall healthcare process taking advantage of the digitalization of medical data and procedures. Some applications of engineering technologies on the medical area include the visualization and reconstruction of human anatomy; organ and tissue modelling; surgical simulators for planning and training; robotic surgery; locomotion and gait analysis; and the design and manufacture of medical devices such as prosthesis, orthesis and implants.

vr technologies can enhance traditional medical procedures by providing an equivalent digital-based procedure at an immersive environment where students, medical practitioners or specialists can plan and practice. For this reason, the development of computer assisted surgery and simulation systems has been one of the main applications of vr technologies in medicine (Girod et al., 1995; Palter & Grantcharov, 2010). vr based surgery simulators allow the interaction with human anatomy, reducing the risk and cost of surgical procedures, and enhancing the surgical skills of students and practitioners. In addition, the integration of haptic technologies in surgical simulators enables the sense of touch in the computer user interface, increasing the level of realism and immersion.

According to the United Nations Educational, Scientific and Cultural Organization (unesco), Information and Communication Technologies (ict) can contribute to universal access to education, equity in education, and delivery of quality learning and teaching (unesco, 2017). In the case of medical education, particularly at surgical education, the traditional educational and skill transfer process depends on the accessibility to physical hands-on training sessions in the operating room or in the laboratory using cadavers or models. However, such training is usually limited, affecting the accessibility and quality of the teaching and learning process. To overcome some of these limitations, several vr based surgical simulators have been proposed and evaluated in the literature.

Virtual Reality

Virtual Reality is defined as a synthetic environment generated by computer and other external devices, that allows the user to interact with a 3D virtual world in which objects behave and look like they were real. vr systems allow people to interact with a virtual environment beyond reality (Berg & Vance, 2016), and have become very popular due to their high level of realism and immersion, although they require advanced computing systems to process large amounts of data and graphics. The level of realism depends on the amount of data being processed, whereas the level of immersion refers to the level of visual and touch interaction (Coles et al., 2011). It also refers to the level of how deeply the user is sensorially involved inside the virtual environment, i.e. how much the user can see, hear, feel and even smell or taste the virtual objects. There are different immersion levels; for instance, at the highest immersion level, the user would be fully isolated from the real world and would be using his/her five senses to interact with the virtual environment. Nowadays, there is no such a fulfill immersion. Table 20.1 presents a classification of vr systems and their characteristics, including input and output devices, resolution, level of immersion and interaction, and cost (Mujber et al., 2004).

Table 20.1. Classification and features of vr systems
Features	VR Systems
	Non-immersive	Semi-immersive	Fully-immersive
Input devices	Mice, keyboard, joysticks and track balls	Joysticks, space balls, and data gloves	Gloves and voice commands
Output devices	Standard high-resolution monitor	Large monitor, large screen projector system, and multiple television projection systems	Head Mounted Displays (HMD), and visualization room-size systems (CAVE)
Resolution	High	High	Low-Medium
Sense of immersion	Non-low	Medium-high	High
Interaction	Low	Medium	High
Cost	Lowest	Expensive	Very expensive
Source: Mujber et al. (2004).

More recently, haptic technologies have been integrated in vr systems to increase contextual connections with virtual entities. “Haptic rendering” is the name given to the general process of feeling or touching virtual objects. This comprises tactile feedback to feel properties such as the superficial texture, as long as the kinesthetic feedback to feel shapes, size and weight of virtual objects. Haptic interfaces are commonly used to enable the user to sense touch and kinesthesia during the manipulation of virtual objects. They can also be used for remote manipulation of real objects; for example, to control a robotic arm that manipulates hazardous materials or performs rehabilitation therapies. Computer haptic devices behave as a small robot that exchanges mechanical energy with the user.

In medicine, vr systems have focused on the following areas: surgical planning, simulation and training, medical education, virtual and augmented reality surgery, patient evaluation and diagnosis, rehabilitation, disability solutions, human and organ modelling, and virtual design and manufacture of medical devices. One of the main applications of vr in medicine is the development of vr surgical simulators (Girod et al., 1995; Palter & Grantcharov, 2010).

vr Surgical Simulators

Virtual reality based surgical simulators provide the users (students, young practitioners and specialists) the capability to plan, simulate and train several surgical procedures to enhance their knowledge, experience and manual abilities (Agus et al., 2003; Vázquez-Mata, 2008). Moreover, when the sense of touch is enabled in surgical simulators, the level of realism, interaction and intuitiveness raises (Panait et al., 2009). The sense of touch is enabled for the user as a powerful feedback generated by means of a haptic device (Coles et al., 2011). It’s proven that vr and haptic technologies enrich surgical simulators in areas such as otolaryngology, gastroenterology, urology and pneumology (Owens & Taekman, 2013).

Several surgical simulators have been reported in the literature that help improving the learning and outcomes of different medical procedures and the surgical planning performance. Some of these systems include: surgical simulator for angiology and vascular surgery, surgical training for vascular surgery, surgical training for dental procedures, surgical simulator for paranasal surgery, surgical training for orthopedics, simulator for neurosurgery, surgical planning for spine surgery, surgical training for endoscopy, etcétera.

vr based surgical simulators can be used as an objective approach to evaluate technical surgical skills such as dexterity and tool handling, to enhance the trainee’s learning time, and to reduce the morbidity and operating time for patients (Ahmed et al., 2019). vr simulators contribute to the development of visuospatial awareness of the anatomy and the feeling of medical procedures by allowing practice prior to in-vivo procedures. This improves the patient safety and creates a safe and controlled environment to practice the procedure (Vaughana et al., 2016). Van Hove et al. (2010) identified twenty-six studies on the assessment of surgical skills using vr. The results revealed that only five different simulators were capable to provide surgical tasks to train basic skills for general surgery, gynecology or laparoscopy. Most of the simulators used motion parameters, such as path length or economy of motion, and task completion time to assess the surgical skills. Recently, Gas et al. (2016) proposed an assessment methodology that combines simulation, online learning and self-assessment options. The results demonstrated that the proposed multifaceted remediation methodology allowed clinical residents to achieve good or stellar performances on each station after some practice.

Education on Maxillofacial Surgery

An oral and maxillofacial surgery requires precise pre-surgical planning to generate the surgical information needed in the or and achieve the desired surgical outcomes. The preoperative planning process to obtain the desired skeletal harmony is a complex and extensive process, and represents a significant challenge for surgeons, particularly when correcting complex malformations. Moreover, the final surgical outcomes will depend on the accuracy of the planning process and the technical and manual skills of the specialist in the or. Therefore, the training, acquisition and evaluation of surgical experience and skills is essential to ensure the patient’s safety and the accomplishment of the desired surgical results.

According to the American Association of Oral and Maxillofacial Surgeons (aaoms, 2020), oral and maxillofacial surgeons (oms) are trained to identify and treat a wide range of diseases, injuries and defects in the head, neck, face, jaws and the hard and soft tissues of the oral and maxillofacial region. oms are also trained to administer anesthesia and provide care in an office setting. The total length of education and training of an oms after secondary school ranges from 12 to 14 years (aaoms, 2020).

Surgical trainees commonly acquire technical and manual skills through years of hands-on training in the or, or in an apprenticeship model, complemented with anatomy examinations, tutorials and laboratory-based surgical skill practices using cadavers or models (Ghasemloonia et al., 2017). However, most of the evaluation methods of surgical skills are subjective since they are based on the assessment by an expert surgeon who observes the trainee or resident performing surgical procedures. Moreover, surgical training programs often lack of objective approaches to evaluate surgical skills, in addition to complicated schedules that make it difficult for surgical residents to undergo formal assessment (Gas et al., 2016). The traditional educational and training paradigms for surgical trainees should provide an accurate evaluation of their surgical skills. Consequently, the new surgical training needs are accuracy, quantitative evaluation and improved training efficiency in order to reduce training hours and resources (Reznick & MacRae, 2006).

Virtual Reality in Maxillofacial Surgery Education

An exhaustive review identifying all digital and mannequin maxillofacial simulators for education and training of oms was reported by Maliha et al. (2018). A total of 22 simulators were identified: 10 virtual reality haptic-based simulators, 6 physical model simulators, and 6 web-based simulators. However, only 9 formalized studies with low-level of evidence were identified; the rest of the studies are only descriptive. This reduced amount of scientific and validated studies suggests that simulation in maxillofacial surgery education is underused. Ahmed et al. (2019) revealed that while other surgical disciplines have adopted simulated clinical teaching, maxillofacial surgery has only seen limited formal use; therefore, the potential benefits of simulation-based surgical training in maxillofacial surgery are still to be seen.

To evaluate the effectiveness and impact of haptic-enabled virtual training in maxillofacial surgery, the orthognathic surgery system (OSSys) —shown in Figure 20.1— has been proposed and developed. This system comprises four modules:

1. Facial analysis module. It allows trainees the realization of facial analyses on the patient’s images and provides a preliminary diagnosis of the orthognathic pathology.

2. Cephalometric analysis module. It allows trainees the realization of 2D, 2½D and 3D cephalometric analyses. In the case of 2½D cephalometric analysis, the cephalometric landmarks are defined on the 3D model but are projected on the sagittal plane to compute the cephalometric values.

3. Model surgery module. It allows trainees to perform surgical procedures on the patient 3D model by means of the haptic device.

4. Surgical template module. It provides assistive tools to generate the surgical wafer needed to reposition the maxillary during the real surgical procedure.

Three major experimental tests to evaluate the virtual cephalometry training, the virtual osteotomy training and the virtual surgery planning training were conducted using the proposed OSSys system. The participants on each of these experimental tests included students, young practitioners and specialists in the area of oral and maxillofacial surgery. Figure 20.2 shows some participants during the virtual training. Meanwhile, Figure 20.3 shows the user’s graphic interface of the OSSys system.

The results of the cephalometric training are summarized in Table 20.2, which shows that the group of trainees obtained the largest errors and standard deviations because of their limited experience and skills; however, they were able to train and improve their cephalometric skills.

Table 20.2. Average 2D cephalometric errors and standard deviations
Cephalometric variable	Group of participants
	Trainees	Semi-experts
SNA (°)	7.32±3.86	2.12±1.59
SNB (°)	3.38±2.82	3.36±3.60
ANB (°)	3.80±0.47	0.22±0.11
INA (°)	8.16±6.78	1.42±1.00
INA (mm)	8.80±3.89	1.92±1.01
INB (°)	3.92±3.35	1.76±0.69
INB (mm)	3.40±2.76	2.54±0.49
Sn-GoGn (°)	5.98±2.32	2.92±1.94
FMA (°)	8.92±4.60	9.46±5.85
OC-SN (°)	2.00±1.95	1.20±0.44
IMPA (°)	7.36±4.66	8.44±6.96

On the other hand, the results of the osteotomy training are summarized in Table 20.3. These results show that the group of participants who undertook virtual training performed better than the participants who trained through video. In other words, participants who trained in OSSys completed the real osteotomy procedure faster and more accurately.

The results the orthognathic surgery planning using the traditional and the virtual approaches are shown in Table 20.4. As we can see, in the case of the expert surgeons the planning outcomes obtained from the virtual and the traditional approaches are in agreement. These results validate the usability and correctness of the virtual approach since it replicates the planning outcomes of the traditional planning method. In the case of the trainees, the planning outcomes using the traditional approach are also in agreement with the outcomes using the virtual approach.

Table 20.3. Osteotomy results
Group of trainees	Mentoplasty				Sagittal
	VO time (s)	RO time (s)	Cutting error (%)	Total time (s)	VO time (s)	RO time (s)	Cutting error (%)	Total time (s)
Video training	NA	432	24.2	432.0	NA	389	27.7	389.0
Haptic disabled VR training	19.4	308	14.6	327.4	56.0	317	21.2	373.0
Haptic-enabled VR training	11.6	120	6.4	131.6	21.5	241	4.9	262.5
Notes: VO: Virtual Osteotomy, RO: Real Osteotomy, NA: Not applicable.

The results of the virtual training experimental tests demonstrated that the use of haptic-enabled virtual training is an effective and objective training tool in oral and maxillofacial surgery. Trainees enhanced their surgical skills and time performance associated to the different procedures in maxillofacial surgery. Virtual training also helped to reduce the errors associated to the traditional surgery planning approach, such as measuring facial and cephalometric values, the creation of dental casts, the mounting of casts on the articulator, the manual segmentation and repositioning of dental casts, and the wafer generation.

Finally, it can be said that the use of haptic-enabled virtual training is a potential technology capable to overcome some of the current problems in maxillofacial education. This means students can practice in a computer surgical simulator and successfully improve their skills. Thus, the problems associated to training efficiency, resources, work, cost and characteristic complicated scheduling of trainees can be reduced by implementing a vr surgical simulator. Another major advantage of the surgery simulator is that it can be installed in any educational or medical facility and executed as many times as needed, reducing the dependency on hands-on physical activities in the operating room or laboratories.

Table 20.4. Orthognathic surgery planning using the traditional and the virtual approaches
Planning stage	Outcome variable	Planning outcomes
		Trainee		Expert surgeons
		Traditional	Virtual	Traditional	Virtual
Facial Analysis	Third facial analysis	Second facial third diminished	Second facial third diminished	Second facial third diminished	Second facial third diminished
	Fifth facial analysis	Third facial fifth diminished	Third facial fifth diminished	Third facial fifth diminished	Third facial fifth diminished
	Powell’s analysis	Surgical and orthodontic treatment	Surgical treatment	Surgical and orthodontic treatment	Surgical treatment
Cephalometric analysis	Facial profile	Concave	Concave	Concave	Concave
	Overbite in mm (SD)	-3 (1)	-3.24 (0.5)	-3 (0.7)	-3.62 (0.4)
	Molar ratio	Class III	Class III	Class III	Class III
	Diagnosis and proposed treatment	Bimaxilar (LeFort I BSSO)	LeFort I BSSO	Bimaxilar (LeFort I BSSO)	LeFort I BSSO
Model surgery	Surgery type	LeFort I BSSO	LeFort I BSSO	LeFort I BSSO	LeFort I BSSO
	Maxillary projection in mm (SD)	9.1 (0.7)	10.3 (0.65)	9.5 (0.4)	10.42 (0.21)
	Mandibular projection in mm (SD)	2.3 (0.6)	3.1 (0.48)	2.7 (0.5)	3.03 (0.35)
Surgical template	Surgical template fabrication	Surgical template	Surgical template	Surgical template	Surgical template
Note: SD: Standard deviation.

Acknowledgment

This research was supported by Conacyt (National Science and Technology Council of Mexico), research grant CB-2010-01-154430. Acknowledgments are also given to the Prodep and fai programs from sep and uaslp, respectively, for the supplementary financial support.

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