WO2011044048A2

WO2011044048A2 - Endo-rhinal endoscopic-technique trainer

Info

Publication number: WO2011044048A2
Application number: PCT/US2010/051335
Authority: WO
Inventors: Scott Burge; Kevin Chris Mcmains; Leonid Bunegin
Original assignee: Board Of Regents, The University Of Texas System
Priority date: 2009-10-05
Filing date: 2010-10-04
Publication date: 2011-04-14
Also published as: WO2011044048A3

Abstract

A modular endoscopic-technique training model provides feedback that can be use to quantify the skills of the practitioner. The training model may be customized for training for specific surgeries.

Description

TITLE: ENDO-RHINAL ENDOSCOPIC-TECHNIQUE TRAINER

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to medical training devices. More particularly, the invention relates to anatomical model of the nasal cavity and associated sinuses which may be used for medical training purposes.

2. Description of the Relevant Art

Since the mid-1980s, fiber optic endoscopes have been used to treat various sinus pathologies that were otherwise treatable by open techniques. Endoscopic sinus surgery has resulted in decreased morbidity, but it has also introduced a need for new skills requiring training to master. Historically, this training has been "on the job", with surgeons and surgical trainees learning on live patients in the operating theater. In recent years, questions have arisen about the ethical foundation of this arrangement. These concerns have been backed by data which suggests that complication rates for trainees were greater than that of nontrainees (16.6% vs. 10.5%). Ideally, each trainee would have maximum exposure and training prior to engaging in a real surgical interaction with a patient. For endoscopic sinus surgery training, sinus labs with cadaver models have been used for almost 10 years. Cadaver material, however, is in limited supply. Furthermore, when embalmed, cadaver material generally does not exhibit the same tissue characteristics of live tissue. Recently, virtual endoscopic simulators have been developed and validated. However, the cost of virtual simulators limits application of these methods. Models have been proposed as a useful alternative to these types of trainers.

SUMMARY OF THE INVENTION An anatomical model of the nasal cavity and associated sinuses was developed having two sets of components for assessing dexterity by measuring accuracy and speed of instrument positioning. The training model and its corresponding training tasks may be used for developing baseline endoscopic sinus surgery skills in medical residents while simulating the operation- room environment. It is a medium-fidelity alternative to "real-life" surgical experiences as well as to the more expensive and less accessible training simulations.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description of embodiments and upon reference to the accompanying drawings in which:

FIG. 1 depicts a top view of a training model;

FIG. 2 depicts a side view of the training model of FIG. 1;

FIG. 3 depicts an anterior view of mucosal lining of the nasal/paranasal cavities prior to plastering;

FIG. 4 depicts a lateral view of the mucosal lining of the nasal/paranasal cavities;

FIG. 5 depicts a superior view of mucosal lining of the nasal/paranasal cavities;

FIG. 6 depicts a training model prior to covering with an external "skin";

FIG. 7 depicts the training model of FIG. 6 with the support removed from the base;

FIG. 8 depicts an anterior view of a support having mucosal lining disposed in the support;

FIG. 9 depicts an posterior view of a support having mucosal lining disposed in the support;

FIG. 10 depicts mounting of the support into the base;

FIG. 11 depicts the view upon entrance into the "manipulations side" w/ uncinate process protruding from superior wall; FIG. 12 depicts the view of the posterior wall of the "manipulations side" w/ forceps approaching pegs for adjacent displacement; FIG. 13 depicts another anterior view of the entrance into the "manipulations side" of the main nasal cavity;

FIG. 14 depicts another view of "manipulations side" posterior wall w/ pegs in place and holder for "superior turbinate" bone removal at top center of picture;

FIG. 15 depicts a view upon entrance into the "electrical side" w/ "target" and surrounding "error" areas located on the inferior turbinate;

FIG. 16 depicts a view of the posterior wall of the "electrical side" w/ probe approaching "target" area during a testing task;

FIG. 17 depicts another view of entrance into the "electrical side" w/ probe approaching target; FIG. 18 depicts a stress-strain loading/unloading curve for skin over vastas medialis muscle and for alginate simulating skin;

FIG. 19A depicts simple task completion times during use of the training model; FIG. 19B depicts complex task completion times during use of the training model; and

FIG. 20 depicts the number of errors occurring during repetitive completion of a simple task. While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In an embodiment, a plaster mold of a human head may be made using standard molding techniques. After forming the plastic mold, the interior of the mold may be coated with a release compound, and used to cast an external skin. A cassette blank may then be positioned within the formed external skin, filled with an expanding polymeric foam, and allowed to cure.

CT scans of the sinus anatomy of a human may be converted to a CAD/CAM 3 dimensional model ("3D model"). The 3D model may be horizontally sectioned at 0.5 mm levels to generate 2D plots of the horizontal sections. The 2D plots are directed into a 3D lithography device for fabrication of the sinus cavity bone structure trimmed to the appropriate cassette size for insertion into the head model. The material used to simulate the boney structures of the sinus cavities, in one embodiment, is chosen based on the similarity of the material's properties to the properties of sinus bone material.

In one embodiment, the model is configured to be used for training and testing of electrosurgical techniques. In one embodiment, the model is formed using materials that are electrically conductive to allow the electrosurgical techniques to be functional. Additionally, the material used to form the model may have additional features such as: the material may be moldable; the material may be modified to mimic various tissue textures; and the material may have sufficient shear strength to allow suturing with minimal tear-out. The material used to form the model, in an embodiment, is capable of withstanding tensile and retraction forces; the material may be distensible, and may be able to hold liquid media. Additionally, the material used in some embodiments, is inexpensive. Electrically conductive polymers and rubbers, alginates, and hydrogels all represent materials that could potentially fulfill the required characteristics.

While several polymers and rubbers that conduct electricity are available, they contain little or no molecular water within their matrices and as a result, their response to electrosurgical manipulation may be minimal. Hydrogels are networks of hydrophilic polymers that swell with the addition of water. Various techniques are used to form these matrices. The most common approach to their synthesis is polymerization of vinyl monomers by free radicals in the presence of a crosslinking agent that also induces swelling. The resulting hydrogel polymer has properties that categorize it as both liquid and solid like. The liquid like properties arise from the large water content of the hydrogel polymer, which may be as much as 80% by volume. The crosslinked matrix that is formed during the polymerization reaction adds shear strength to the material thereby conferring solid-like properties to the hydrogel. A range of textures and distensability may be achieved by controlling the extent of crosslinking and water content in the hydrogel.

Alginate is a protein derived from kelp that forms a hydrogel with the addition of water. Alginate forms a strong structured material that can be prepared with a range of textures by varying the calcium ion concentration. Alginate also exhibits excellent electrical conductivity when prepared with physiologic solutions (e.g., polyonic, sodium chloride or ringers lactate). Additionally alginate is easily moldable and inexpensive. Alginate test blocks prepared with physiologic solutions are easy to cut and cauterize with electrosurgical instruments. When prepared with mixtures of cotton fibers, tearout strength of the resulting alginate material was sufficient to hold fine sutures. In an embodiment, a model of the human nasal mucosa is formed from a material having the characteristics and material properties of human nasal mucosa. A variety of hydro- colloids may be used that exhibit properties that mimic many of the desired qualities of simulated soft tissue. Alginates, in particular have physical properties that can be easily manipulated into a form that can imitate human tissue. Alginates are a complex of 6 member rings composed of mannuronic and guluronic acid which form a complex when hydrated in water with either sodium or calcium ion. They are a linear unbranched polymer of beta (1-4) linked D-mannuronic acid and alpha (1-4) L-guluronic acid. The nature of the complex when hydrated in water depends on the mannuronic/guluronic ratio, the cation, and the amount of water used for hydration. In addition, cotton fibers can be added to supplement shear strength. Color can be manipulated through the use of dyes.

Following identification of the appropriate alginate formulation, the bone structure will be coated with the alginate material and allowed to cure. An anatomical model of the nasal cavity and associated sinuses (maxillary and frontal sinuses) is lined by a silicone "mucosa" allowing for adequate haptic feedback to aid in the training of medical residents learning how to use tools necessary for endoscopic sinus surgery. The anatomical left nasal cavity is equipped with two separate sets of electrical circuits. Each set of circuits includes four circuits in parallel to one another. The first set of circuits, named the "target", includes four circuits that begin at a copper disc. The copper discs are located throughout the nasal cavity and sinuses at each of the following locations: one copper disk is located at the entrance to the nose just anterior to the base of the inferior turbinate, one copper disk is located on the posterior wall of the nasal cavity inferior to the superior turbinate, one copper disk is located on the lateral wall inside the maxillary sinus, and one copper disk is located on the posterior wall inside the frontal sinus. To each copper disc is soldered a copper wire that runs through the scaffolding of the model and out the neck of the mannequin, in which the model resides. The four wires are then connected together and in series with the positive end of a green LED light. The negative end of this light is connected to a wire that attaches to the non-endoscope instrument which will be responsible for completing the circuit should its surgeon make appropriate contact between the metal instrument and the copper disc of the "target" area.

The second set of circuits, named the "error", includes four circuits that begin at an "error" area which surrounds the perimeter of the copper disc "target" area. The "error" areas are made of electrically conductive paste that is applied on top of the silicone "mucosa". The conduction system for this set of circuits is set up in much the same way as the "target" set except that this set has attachment to a red LED light. In alternate embodiments, this "error" area may be expended to include the entire surface of the left nasal/paranasal cavity as opposed to being confined to the area adjacent to the "target" areas. The LED lights are, in some embodiments, contained in a mobile, hand-held box to allow the researchers/faculty to conceal the results of each attempt at a given task.

In an alternate embodiment, the LED lights may be substituted with a computer system, that includes software that automatically registers and records a time to completion of the "electrical side" tasks as well as the number of errors made during each trial run. This allows the trainee to use the model and get feedback on his/her performance without the need for supervision by an attending surgeon. This also allows the trainee's improvement to be objectively measured, recorded, and even printed out for multiple purposes like meeting accreditation requirements and comparing one's improvement to a pre-determined standard. Additionally, a computer based model may allow for the measurement of "accuracy" (via a count of the number of errors made within the time of completion) which, over a number of trials, can be correlated with the results of the tasks in the "manipulations" side of the model to ensure that tasks done in the "manipulations" side are completed without recklessness.

The "manipulations" side of the model is in the anatomical right nasal cavity and sinuses. It is equipped with 3 sets of pegs or "bones" (e.g., pieces of plastic cut out to resemble removable bone pieces) and their respective holders. The first set includes two "bones" and two pegs. One of the "bones" is situated on the anterior roof of the nasal cavity as it extends across the opening to the frontal sinus. The other "bone" protrudes downward from the inferior portion of the superior turbinate in the posterior area of the nasal cavity. The two pegs are arranged vertical to one another on the posterior wall of the nasal cavity. These pegs will be moved from their current positions to the peg holders directly adjacent to them. The "bones" are to be removed from the "patient". The second set includes two pegs situated on the posterior wall inside of the maxillary sinus. These pegs will also be moved from their current positions to the peg holders directly adjacent to them. The third and final set includes three "bones" situated at 120 angles to one another along the posterior wall of the frontal sinus. Each of these bones is to be removed with the appropriate instrument. For the bones and pegs on this side of the model, the "manipulations" side, a plastic material may be used. In alternate embodiments, each of these pieces and their holders may be formed from an electrically conductive material so that circuits, similar to those on the "electrical" side, can be used to measure time in a computerized, more precise fashion. Assuming that the skills used to complete each side of the model are identical, the rates of improvement on each side can be compared so that even though "errors" are not directly being recorded on the "manipulations side", the "recklessness/care fulness" can still be objectively and accurately measured on the manipulations side. By comparing the rates of improvement for the electrical side and the manipulations side, an assessment may be made on the recklessness of the trainee while he/she is performing the "real-life/manipulations" tasks.

The described trainer is unlike typical training modules since most training modules require that a faculty member spend long hours either directly monitoring the trainee for carefulness or doing so by viewing a trainee's recorded performance. With the disclosed model, the faculty member will not be required to view the performance since the faculty member will still receive a printout that validates the trainee's 1) carefulness and 2) improvement to a certain pre-determined standard in terms of their skill level. For the sets of tasks, it is intended that either a 0 , 30 , or 70 endoscope is used, as assigned by the researcher/faculty. This will allow a broader use of the model to not only aid in the mastery of instrument coordination, but also that of visual-spatial skills.

At the end of each task, it is required that the pegs and "bones" on the "manipulations" side be returned to their original positions. This is possible with this model by removing the styrofoam scaffolding from the mannequin's head. Once the model is free from the scaffolding, it is possible, using forceps, to return each peg or "bone" to its original holder via pre-formed channels attached to the posterior side of the model. In this manner the model may be restored to its original configuration and be reused.

An embodiment of an anatomical model of the nasal cavity and associated sinuses having two sets of components for assessing dexterity by measuring accuracy and speed of instrument positioning is depicted in FIGS 1-17. FIG. 1 depicts a top view of model (10) in an intact form. In an embodiment, the model is formed to be have the appearance of human head. A side view of the model is shown in FIG. 2.

FIG. 3 depicts an anterior view of mucosal lining (20) of the nasal/paranasal cavities prior to plastering. The mucosal lining is made in a form that is anatomically the same as a normal mucosal lining of a human. As shown in FIG. 3, wires (22) extend from sensors embedded in the model to the exterior of the model to allow coupling of the sensors to LED lights or a computer system. FIG. 4 depicts a lateral view of the mucosal lining of the nasal/paranasal cavities. Access ports (24), depicted in the form of tubes extending from the model, may be used to allow access to the interior of the mucosal lining to allow manipulation of the interior of the mucosal lining. FIG. 5 depicts a superior view of mucosal lining of the nasal/paranasal cavities.

FIG. 6 depicts model (10) prior to covering with an external "skin". The mucosal lining (20) is set inside of a support (30) which is mounted to a base (40) of model (10), as depicted in FIG. 6. Support (30) may be formed from a hardened material (e.g., a plaster or high density polymer). Base (40) may be formed from a low density polymeric material (e.g., a polymeric foam). The model with support (30) removed from base (40) is depicted in FIG. 7. A conduit (42) runs through base and is configured to receive wires (22) from the muscosal lining allowing the wires to exit the base to be coupled to an LED or computer system.

FIGS 8 and 9 depict anterior and posterior views, respectively, of support (30) having mucosal lining (20) disposed therein. Various openings (32) may be formed in support (30) to allow access to the interior portions of the mucosal lining to allow replacement of task pieces. FIG. 10 depicts mounting of support (30) into base (40). Wires (22) are passed into conduit (42) as support (30) is mounted into base (40).

FIGS. 11-17 depict various interior views of the mucosal lining as seen through an endoscope. FIG. 11 depicts the view upon entrance into the "manipulations side" (patient's right side) w/ uncinate process protruding from superior wall. FIG. 12 depicts the view of the posterior wall of the "manipulations side" w/ forceps approaching pegs for adjacent displacement. FIG. 13 depicts another anterior view of the entrance into the "manipulations side" of the main nasal cavity. FIG. 14 depicts another view of "manipulations side" posterior wall w/ pegs in place and holder for "superior turbinate" bone removal at top center of picture. FIG. 15 depicts a view upon entrance into the "electrical side" (patient's left side) w/ "target" and surrounding "error" areas located on the inferior turbinate. FIG. 16 depicts a view of the posterior wall of the "electrical side" w/ probe approaching "target" area during a testing task. FIG. 17 depicts another view of entrance into the "electrical side" w/ probe approaching target. As shown in FIG. 17, there are two openings at the center which are used to complete various tasks associated with sinus cavity surgeries.

Testing of Alginate Materials

Using a pipette aspiration method, a family of stress-strain curves is generated as a function of the M/G ratio and the concentration of the polyvalent cation Ca⁺⁺ in the alginate to test the suitability of the material. Triplicate alginate samples with 1 :10, 1 :5, 1 : 1, 5: 1, 10: 1 M/G ratios and Ca⁺⁺ concentrations (in the form of calcium benzoate) of 0, 5, 10, 25, 50, 75, 100 mEq at each M/G ratio are tested one hour after preparation. Time related changes in the each samples stress-strain relationship, texture and appearance are evaluated at 2 hour intervals for 6 hours followed by one day intervals for 5 days. Color and texture are evaluated using reflectometry. Shifts in absorbance bands provide data relative to color change as well as surface chemistries. Changes in reflectance and absorbance band broadening provide an indication of texture changes. For example, decreased reflectance and absorption band broadening is an indication of increased incident beam scattering from which changes in surface roughness can be inferred. Samples are stored in non-sterile plastic bags during testing in order to prevent dehydration.

The effect of the addition of calcium benzoate an antifungal and antibacterial agent on bacterial and fungal growth is evaluated by microscopic inspection at each testing interval. These data are used to guide the selection of the alginate based hydrocolloid so as to achieve optimal mimicry of the human material (e.g., the nasal mucosa, vascular, and duct elements). Microspheres that encapsulate a red dye are formed by known techniques. Following incorporation of the microspheres, vascular, and duct elements into the hydrocolloid matrix, the stress-strain curves of the complex are generated and compared to the curves generated in the in- vivo studies. An exemplary stress-strain curve comparison is shown in FIG. 18. Final adjustments to the alginate formulation are made so as to optimally mimic the specific tissues to be simulated.

Method of Using a Model for Training of Students

Four otolaryngology residents (2 PGY2, 2 PGY3) and 7 medical students performed endoscopic tasks on the herein described simulators. Part A of the 1st task was completed using a 0-degree scope and a probe to make appropriate contact with targets in a pre-determined order on the "electrical" side. Part B of the 1st task used a 0-degree scope, graspers, and a similar skill set as in Part A to complete similar but more "real-life" tasks including "bone" removal and peg displacement. Part B takes place on the "manipulations" side. The tasks were repeated 5 times in the same day for each participant. Overall time in seconds for completion of task and number of errors performed during the task were recorded. An error was defined as inappropriate contact between the probe and the area adjacent to the target area. The task was then repeated for each participant after two-weeks. Errors were not recorded for Task 2, but "recklessness" was indirectly measured.

Paired Student's T-tests were performed on all repetitive measures, comparing one time period to the next. When comparing residents to students as a group, unpaired Student's T-test was used. Graphs and statistics were calculated using Microsoft Excel 12.2.1. Significance was set at 0.05.

Statistically significant improvement in time was noted between the first two repetitions of each task and remained significant for every other repetition compared to the initial attempt. FIG. 19A shows Time (seconds) to completion of Task 1 for each person, FIG. 19B shows Time (Seconds) to completion of Task 2 for each person. Students (solid line with squares) and residents (dotted line with diamonds) show exponential decreases in time over repeated attempts at completing an endoscopic task in one day. Attempt six represents a two-week interval since attempt five. As the task was repeated, the trend for improvement became asymptotic with significant improvement lost on both tasks between the 3rd, 4th, and 5th repetitions. The performance at two-weeks was not statistically different compared to that at the end of five repetitions of the same task in our sample. Errors likewise improved over repetitive testing. FIG. 20 shows the number of errors occurring during repetitive completion of Task 1 by students (solid line with squares) and residents (dotted line with diamonds). Attempt six represents a two-week interval since attempt five. Statistically significant improvement in errors was realized by the 4th repetition relative to the initial attempt and remained significant for the 5th attempt as well. The two-week repeated task performance errors did not achieve significance relative to the initial attempt (0.06) but clearly show a trend. Again, there was no statistical increase in errors at two-weeks relative to that achieved at the end of five repetitions.

Predictably, residents fared better on all tasks vs. students in terms of both time and errors, and residents achieved statistical significance for time to task completion and number of errors. Although the number of students used was small, the results show typical learning curves for tasks. Generally, three attempts at the tasks administered were enough to show significant, sustained improvements in time. However, recording the number of errors makes this task a bit more complex in its overall ramifications. The minimum number of repetitive tasks to note a statistically significant decrease in errors was four. Also, sustained improvement in errors was not as evident as was improvement in time to task completion. Therefore, further study on the ideal length of time between cases and sustained Improvement in both time and errors in task completion may be warranted. Findings like this suggest that resident education should be directed away from concentrated blocks of surgical experience with long periods in between that do not reinforce the same task set.

Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

Claims

WHAT IS CLAIMED IS:

1. An anatomical model of the nasal cavity and associated sinuses comprising components configured to be used for measuring endoscopic sinus surgery skills, the components being coupled to an output device providing an indication of the actions of the user.

2. The anatomical model of claim 1, wherein a portion of the anatomical model is composed of an electrically conductive polymer.

3. The anatomical model of claim 1, wherein the components configured to be used for measuring endoscopic sinus surgery skills comprise one or more electrical circuits in the cavity configured to determine the position of a probe in the anatomical model.

4. The anatomical model of claim 3, wherein the one or more electrical circuits record a time needed to complete a sinus surgery task.

5. The anatomical model of claim 3, wherein the one or more electrical circuits record error made by the user during a sinus surgery task.

6. The anatomical model of claim 3, further comprising one or more visual indicators coupled to one or more electrical circuits, wherein the visual indicators provide a visual indication when a user makes an error during a sinus surgery task.

7. The anatomical model of claim 1, further comprising one or more pegs disposed in the model, wherein the pegs are positioned to represent bones found in a sinus cavity of a human.

8. A method of accessing endoscopic sinus surgery skills comprising: providing an anatomical model of the nasal cavity and associated sinuses, the model comprising components configured to be used for measuring endoscopic sinus surgery skills, the components being coupled to an output device providing an indication of the actions; and monitoring the output device during use.

9. The method of claim 8, wherein a portion of the anatomical model is composed of an electrically conductive polymer.

10. The method of claim 8, wherein the components comprise one or more electrical circuits in the cavity configured to determine the position of a probe in the anatomical model, and wherein one or more of the electrical circuits are coupled to the output device.

11. The method of claim 10, further comprising recording a time needed to complete a sinus surgery task using one or more of the electrical circuits.

12. The method of claim 10, further comprising recording errors made during completion of a sinus surgery task using one or more of the electrical circuits.

13. The method of claim 8, wherein the output device comprises one or more visual indicators, and wherein the method further comprises providing visual indications using one or more of the visual indicators when a user makes an error during a sinus surgery task.

14. The method of claim 8, wherein the model further comprises one or more pegs, wherein the pegs are positioned to represent bones found in a sinus cavity of a human.