Keywords teaching materials - anatomical models - otological surgical procedures - otolaryngology
Palavras-chave materiais de ensino - modelos anatômicos - procedimentos cirúrgicos otológicos - otolaringologia
Introduction
With the creation of the first american residency program in surgery, by William S.
Halsted, in the John Hopkins Hospital, in the beginning of the 20th century, was created
the teaching method of “learn by doing it”, which the resident assumes increasing
levels of independence and responsibility[1 ]. This progressive gain of knowledge involves numerous medical-legal issues, but
many studies show a reduction of this kind of problem like previous training in animal
models, corpses and simulators.
It is important to remember that this process is, according to the theory of FITSS
and POSNER, three distinct phases: cognitive, associative and autonomous, where the
student goes through a increasing curve of learning for the acquisition of knowledge[2 ].
In recent years, simulators have emerged to improve the cognitive phase, for the student
to get to the training phase in humans, more prepared and aware of the arsenal of
instruments and techniques available, through extensive previous training. Before,
the training was made only in animal models and corpses, but this is limited due to
increasing difficulty for obtaining[3 ], the simulators are responsible by the progressive filling of this gap.
So, this present work has as goal to describe and compare the many available simulators
to the learning of the otological surgery found in the literature.
Synthesis of Data
The otorhinolaryngology is a surgical specialty well covered with simulators for technical
improvement. In otology we have simulators that allows from the training in myringotomy
to dissection complex three-dimensional of structures of temporal bone.
Volski e col.[4 ] described a model developed to the training of myringotomy and insertion of ventilation
tubes. Constituted by three units: channel, coupler and head. The simulator promises
to present the same texture, color, opacity and elasticity of the human ear. Has the
financial advantage, the possibility of exchanging only the coupler who contains the
tympanic membrane to be reused. This model proved to be useful to resident training
in the beginning of the surgical learning, with improvement of the time and execution
technique of the procedure, although they have not proved to be so useful to improvement
of experienced surgeons.
Seeking similar interactivity and realism of the dissection of a cadaver in laboratory,
Wiet e col.[5 ] developed a virtual model to dissection of the temporal bone. Developed by a computer
program, the Simulator allows to visualize in three dimensions through a special binocular
system, that stimulate a microscope, with good image resolution, also promotes a good
tactile sensitivity through a device of haptic reality, similar to a joystick ([Image 1 ]), simulating the milling and irrigation, besides allowing the hearing of the sound
emitted by the engine in different harmonic scales, depending on the type of drill,
as well as the sound of the vacuum suction, giving a good feedback to the user. The model was fully developed from tomographic images of temporal bones
of corpses reconstructed by computer, to faithful reproduction of dissection. The
system also has the identification mode of anatomical structures, where is possible
to individual study: the system prompts the user to point a specific structure, as
well as show the structure and asks to the user to name it. Has the demonstration
mode, that rescues the complete dissection already made and taped.
Image 1. Model of Wiet[5 ].
The german group of Zirlke
[6 ] also developed a model of simulation of the temporal bone which includes special
glasses to three dimensional vision, plus pedal to virtual control of the engine,
that have the sensitive control of the milling. Is also possible to adjust the magnification
of the image. It is a simulator composed by a special structure ([Image 2 ]) that simulates a drill with a joystick that mimics the actual sensitivity. This model can evaluate the user, through numerous
performed movements, speed of the movements, total time of execution of the procedure
and effectiveness of the movement. This assessment can serve as to compare the beginner
user and the experienced one, how to evaluate the evolution of them. However, the
model doesn't use the real color of the structures that are found while dissecting
temporal bones of corpses.
Image 2. Model of Zirkle[6 ].
O'Leary e col.[7 ], has a model that is different from the ZIRLKE e col.[6 ] by the absence of pedal, but count with a probe for the monitorization of the facial
nerve, plus if there is bleeding milling from the sigmoid sinus. Have the shape of
a bench, with special glasses and a pen that simulates a drill, with hearing and sensitive
feedback. The zest of bones accumulates until being aspirated. The simulator present
the structures with the real colors in vivo. Also was developed from tomographic images.
Allows the identification of the structures as they are found during the dissection,
although do not contain a system of evaluation.
The virtual German simulator of Sorensen e col.[8 ] can be obtained by internet as a freeware allowing the training at home ([Image 3 ]). Is a type of model that allows the evaluation of the user, through the obtainment
of a score from zero to ten, depending from the success of preservation from the structure.
However, needs a graphic card of high resolution for a good performance of the program
and do not contain mechanisms that allow the haptic feedback for free as the program.
It contain a joystick acquired separately, although can be used just by the mouse.
Image 3. Model of Sorensen[8 ].
More recently, Bakhos e col.[9 ] published their work showing a real simulator for the dissection of the temporal
bone. Based in tomographic cuts and using the technology of fast prototyping already
reproduced in other works[10 ]
[11 ], the author developed a prototype for the temporal bone, that, after performed all
the measures and concluded all microdissections, was noticed that the models were
very similar to the temporal bone of a cadaver ([image 4 ]), that was made a tomography for the obtainment of a prototype. This model allow
the use of their own materials that are used during the surgery and use a material
similar to the bone, reproducing a very close to real dissection in what concerns
the haptic reality.
Image 4. Model of Bakhos[9 ].
Okada e col.[12 ], in Brazil, developed a model of real temporal bone, by the use of the temporal
bone from a cadaver donator and, using a molding of a thermoplastic resin, obtained
a prototype from the temporal bone that was analyzed by experienced ear surgeons,
that pointed as a good complementary element for the surgical training. As seen in
the [Image 5 ], is similar to the model of BAKHOS e co.[9 ], but without the need of using the prototyping equipment, reducing the costs of
confection of the model.
Image 5. Model of Okada[12 ].
Discussion
The learning for the execution of the surgical procedure, by many authors, used to
be divided in three phases: 1) didactic phase, when is acquired knowledge about the
instrumental and techniques to be used, including the training in artificial models,
in animals and cadavers; 2) the phase of human training under supervision; and 3)
the practice phase, when there is a progressive increase of independence from the
new surgeon, with the concomitant acquisition of competence[13 ]. In the theory from FITTS and POSNER, these phases are categorized as cognitive
stages, associative and autonomous, having gain of automation and a decrease in the
mistakes along the process of acquisition of knowledge[3 ].
The simulators are a learning technique, and not a technology, used to reproduce real
situations in a environment closest to the real one[14 ]. They can be used for training and evaluation. The evaluation from simulators can
be formative (gives a feedback to the user so that he can improve himself) or a summation
(the user need to reach a determined level of ability to pass to the next level).
The evaluation can be intern (made by the simulator itself) or extern (made by someone
more experienced that accompanies the examined one)[6 ].
The simulators already showed their efficiency in the training of pilots and astronauts
in military operations[15 ], gaining a increasing space in many areas of medicine, mainly the surgical ones.
Jackson e col.[16 ], in his review from the art of development of a simulator, describe the characteristics
that must have in a good model, including the bases from virtual reality and ergonomic
considerations in the drawing of the systems. He still highlights the ways of obtainment
from the anatomic reconstruction, including tomographic cuts and histological. Dexterity,
knowledge and experience are the most appreciated characteristics by the author for
the performance of the procedures as in the mastoidectomy, cochlear implant and surgery
in the cerebellopontine angle and simulators that have their own importance for the
acquisition of those surgical abilities. In the [Table 1 ] we can visualize and compare the many types of simulators described in this work.
Table 1.
Models of Simulators.
Author
Type
Instruments
Cost
Observations
Wiet, 2002
Virtual
Joystick, binocular microscope and hearing recurrence
+ +
Allows self evaluation
Zirlke, 2007
Virtual
Special stand with joystick, pedal and vison 3D,
+ + +
Do not use real colors evaluate the user
O'Leary, 2008
Virtual
Special stand, with joystick and 3d glasses
Allows hearing recurrence. Aspiration is essential during the milling
+ + +
Probe for monitoring from the facial nerve
Volski, 2009
Real
Instrumental Surgical
+
Only to myringotomy with placement of a ventilation tube
Sorensen, 2009
Virtual
Mouse
–
Free Download
High resolution video card
Bakhos, 2010
Real
Instrumental Surgical
+ +
Fast prototyping from Tomographic Cuts
Okada, 2010
Real
Instrumental Surgical
+
Model in resin from the cadaver donator
The virtual simulators have an elevated cost when compared to a real simulator, but
allows to be used many times through the initiation from the program, besides giving
opportunities to the user to be evaluated. However, there are programs in the computer
that can be acquired from the internet, freely, but that reproduces only the visual
stimulation of a dissection, not allowing the development from the surgical dexterity.
Besides, for as simple as it can be the simulator, he needs a video card of high resolution
for a good performance of the program, which already brings costs for the dissection.
The real simulators allow the user to have sensations very closely from the dissection
of corpses, because use models with texture and similar material to the human bone,
besides the user can use materials similar to the used in the surgeries. Besides,
the use of a fast prototyping, by means of stereolithography, makes us so that, through
a tomography of a real patient, develop a model to dissect previously the surgery,
for example, allowing predicting the real difficulties that it can be found in a real
surgery.
Final Comments
And so, we can conclude that the simulators are seen as a tool to complement the training
and improvement of ear surgeons, because of the increasing difficulty and many times
the prohibition of the temporal bones in cadavers.
Is important to highlight that the evaluation of the student, in a process of acquisition
of knowledge, must be in a constant process of evaluation from a more graduated observer,
so that is obtained a maximum use from the associative phase and acquisition of abilities.
The upgrading from the development of simulators, focused in the improvement of the
sensitive feedback from the models, mostly in what concerns to the hearing recurrence,
visual and tactile, will make them every time more useful and faithful to the reality,
for a good training from the user. However, simulators hardly will substitute the
dissection of the human temporal bone in his integrity, because of the intriguing
complexity from its anatomy and consequently the difficulty into reproducing it.
