- Email: [email protected]
Development of a high fidelity subglottic stenosis simulator for laryngotracheal reconstruction rehearsal using 3D printing
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Development of a high fidelity subglottic stenosis simulator for laryngotracheal reconstruction rehearsal using 3D printing
T
Chelsea L. Reigharda, Kevin Greena, Allison R. Powella, Deborah M. Rooneyb, David A. Zopfa,c,∗ a
Otolaryngology—Head and Neck Surgery, Pediatric Division, University of Michigan Health Systems, CS Mott Children's Hospital, Ann Arbor, MI, USA Department of Learning Health Sciences, University of Michigan, Ann Arbor, MI, USA c Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA b
ARTICLE INFO
ABSTRACT
American Society of Pediatric Otolaryngology (ASPO) Meeting 2017 in Austin, Texas; Title: Development of a Novel, High Fidelity Laryngotracheal Reconstruction Simulator using Computer Aided Design and Three Dimensional Printing Technology.
Introduction: Laryngotracheal reconstruction (LTR) with cartilage graft augmentation is an effective treatment for subglottic stenosis and a critical advanced procedure for Pediatric Otolaryngologists. Trainees almost exclusively learn this procedure intraoperatively on children due to the lack of adequate pediatric training models. An enhanced and accelerated educational experience may be possible if trainees can rehearse the key portions of the procedure on a simulation model. Objective: To design and manufacture a low-cost, high fidelity surgical simulation model of subglottic stenosis for LTR. Methods: This simulator is composed of two component models: rib cartilage and trachea. Additive manufacturing techniques, including Computer Aided Design and Three Dimensional (3D) printing, were utilized to create the simulator. Three expert Pediatric Otolaryngologists rated the functionality and realism of the simulator using Likert scale survey data. Results: The use of CAD and 3D printing techniques allowed for realistic, reproducible surgical simulation of key aspects of LTR. The validation evidence indicated good to excellent means across the five domains relevant to the simulator's fidelity and usability (M = 3.47 to 4.00) out of a maximum of 4 points. Lowest rated items were consistent with expert comments suggesting minor simulator improvements. Time of production is approximately 20 h from print to post-processing, and consumable material costs per model are $2.60 USD. Conclusions: This subglottic stenosis airway simulator facilitated Laryngotracheal Reconstruction rehearsal and is a promising training tool for pediatric otolaryngologists. Our methods allow patient-specific, pre-surgical rehearsal for complex airway scenarios that could benefit the experienced airway surgeon and trainees alike. Future research aims to validate this device's utility for accelerating attainment of proficiency and improving surgical outcomes.
Keywords: Surgical simulation 3D printing Computer aided design Laryngotracheal reconstruction simulation Laryngotracheal reconstruction simulator Laryngotracheal reconstruction
1. Introduction Pediatric subglottic stenosis is a luminal narrowing in the area above the trachea and below the vocal cords. This condition often requires airway reconstruction, advanced surgical procedures demanding meticulous surgical technique and robust training. Congenital subglottic stenosis may be caused by incomplete recanalization during embryogenesis. Acquired subglottic stenosis is often secondary to trauma from long-term intubation [1]. Subglottic stenosis is the most common location of laryngotracheal stenosis in children, and Laryngotracheal Reconstruction (LTR) is the predominant procedure for its correction in patients who do not respond to more conservative measures [2,3] or those with high grade stenosis requiring cricotracheal ∗
resection. Surgical simulators, such as animal, cadaveric, computer-based, and physical models, have the potential to provide safe, standardized, competency-based surgical education for trainees [4]; however, adult cadaveric simulations fail to convey the experience of pediatric LTR. Animal lab simulations using porcine and ovine specimens are performed, though the downsides include costs, both financial and sacrifice of animal life, and the lack of ability to maintain/archive work or preserve progress. Presently, resident and attending physicians almost exclusively learn and perfect their LTR surgical technique in the operating room. To our knowledge, we are describing the first high fidelity pediatric subglottic stenosis or airway reconstruction model in the literature [5].
Corresponding author. Department of Otolaryngology, University of Michigan, 1540 E. Hospital Dr, CW 5-702, SPC 4241, Ann Arbor, MI, 48109, USA. E-mail address: [email protected] (D.A. Zopf).
https://doi.org/10.1016/j.ijporl.2019.05.027 Received 5 February 2019; Received in revised form 23 May 2019; Accepted 23 May 2019 Available online 01 June 2019 0165-5876/ © 2019 Elsevier B.V. All rights reserved.
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
C.L. Reighard, et al.
Fig. 1. Segmentation of laryngotracheal airway from high resolution CT scan.
Additive manufacturing, or the use of Computer Aided Design (CAD) and 3D printing, allows for rapid prototyping of complex designs, including surgical simulators. Our group has extensive experience with these technologies and utilizes these processes to develop a number of models and high fidelity surgical simulators for medical and surgical education [6–8]. This study aims to evaluate preliminary validity evidence from a low cost, high fidelity LTR simulator for trainee education and for the refinement of surgical technique.
and the optional mold to seal the base of the model [Fig. 3]. The negative trachea mold was printed in polylactic acid (PLA). Silicone dyed with intrinsic coloring was poured into the trachea mold. Once cured, the subglottic stenosis model was ready for evaluation [Fig. 4A, C]. A piece of a silicone-starch costal cartilage model, using techniques previously published by the senior author, was provided to each expert airway surgeon [7].
2. Methods
2.2. Study design
2.1. Simulator development
Following exempt determination by our institution's Internal Review Board, three expert pediatric airway surgeons from three different institutions independently performed the LTR, utilizing their preferred technique and standard surgical equipment. Surgeons were instructed to carve an anterior airway graft from the rib cartilage simulator, perform an anterior airway incision focused at the level of the stenosis, and suture the graft into the airway model allowing for physical airway expansion [Fig. 4B, D, E]. They evaluated the LTR model using a Likert based survey.
The subglottic stenosis/LTR simulator consists of two models representing different anatomic structures: pediatric laryngotracheal complex with subglottic stenosis and rib. A de-identified computed tomography (CT) scan was obtained from the University of Michigan. The laryngotracheal complex was isolated and segmented utilizing Mimics/3-matic CAD software [Materialise, Plymouth MI, US; Fig. 1]. The trachea was modified to contain a grade III subglottic stenosis and to reflect pediatric tracheal dimensions [Fig. 2]. A Boolean subtraction technique was implemented to create the negative mold for the trachea
Fig. 2. 3D representation of laryngotracheal model with subglottic stenosis. Left to right: right lateral view, frontal view, and coronal section through mid airway. 135
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
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Fig. 3. Laryngotracheal model in manufacturing system with green insert and gray PLA molding system, all designed and manufactured within our research group. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)
Fig. 4. [A] LTR model; [B] Final repaired LTR model; [C] endoscopic view of pre-repair stenosis in LTR model; [D] Process of repairing LTR model; and [E] endoscopic view after repair to LTR model.
2.3. Survey and rating procedures
22-item survey was used to rate the simulator across five domains—physical attributes, realism of experience, value, relevance to practice, and ability to perform tasks—and one overall/global impression. Four-point rating scales were utilized for all domains [Table 1].
The novel survey was developed via cognitive task analysis, with items independently reviewed by four pediatric otolaryngologists for language clarity and the items’ alignment of critical anatomical functions and features with curricular learning objectives [9,10]. The final 136
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
ItemNo.
Domain/Characteristic
Fidelity: Physical Attributes (Domain M = 3.47) 1 External appearance of laryngeal complex 2 Endoscopic appearance of laryngeal complex 3 External appearance of cricotracheal complex 4 Endoscopic appearance of cricotracheal complex 5 Subglottic stenosis Fidelity: Realism of Experience (Domain M = 3.50) 6 Optional: endoscopic diagnosis and assessmenta 7 Optional: pre-repair assessment with anesthetic circuit (presence of airway leak)* 8 Amount of pressure needed to make anterior airway incision 9 Texture of rib graft material 10 Carving of rib graft material 11 Suturing of rib graft material 12 Integration of cartilage graft – airway interface 13 Optional: post-repair assessment with anesthetic circuita Fidelity: Value (Domain M = 3.67) 19 Value of the simulator as training tool 20 Value of the simulator as an evaluation tool 21 Fidelity: Relevance of Simulator to Practice Ability (Domain M = 3.53) 14 Optional: pre-repair endoscopic diagnosisa 15 Anterior airway incision 16 Fashioning anterior graft 17 Integration of graft into airway 18 Optional: post-repair assessmenta 22 Global Rating a
M (SD) (n = 3)
95% CI
3.67 (0.58) 3.50 (0.71)
3.09–4.00 2.79–4.00
3.33 (0.58)
2.75–3.91
3.50 (0.71)
2.79–4.00
3.33 (0.58)
2.75–3.91
3.00
NA
4.00
NA
3.67 (0.58)
3.09–4.00
3.67 (0.58) 3.33 (0.58) 4.00 3.33 (0.58)
3.09–4.00 2.75–3.91 NA 2.75–3.91
3.00
NA
3.67 (0.58) 3.67 (0.58) 4.00
3.09–4.00 3.09–4.00 NA
4.00 3.33 (1.15) 3.00 3.33 (0.58) 4.00 3.67 (0.58)
NA 2.18–4.00 NA 2.75–3.91 NA 3.09–4.00
Optional steps performed by only one rater.
2.4. Analyses
No value No relevance Requires number of improvements before used in training
Some value Some relevance Can be used as is, but could be improved slightly
A great deal of value Has a great deal of relevance Can be used as is with no improvements made
Table 2 Means for domains and individual items from LTR simulator rating survey.
Preliminary validity evidence relevant to test content was evaluated using previously established methods that applied the current Standards framework to simulator validation processes [10–12]. Traditionally known as “face validity,” evidence relevant to test content was evaluated by calculating raters’ means for each of the 22 survey items. Higher means suggest participants had a higher perceived value for that particular feature or characteristic of the simulator. 3. Results Faculty self-reported a mean (SD) of 10.67 (6.03) years in practice and have completed between 25 and 150 LTR procedures to date (M = 91.67, SD = 62.92). Averaged ratings and specific feedback were collected. Preliminary evaluation indicated good to excellent means (3.47–4.00) across the four Fidelity domains (Physical Attributes, Realism of Experience, Value, and Relevance) [Table 2]. These findings were consistent with surgeon comments indicating the experience is highly realistic, requiring minor to no improvements, and has a great deal of value and relevance in the current training environment. The mean rating for the Ability domain was 3.53, indicating that raters were able to perform the necessary LTR steps of anterior airway incision, anterior graft fashioning, and graft integration into the airway with reasonable, expected ease. The mean Global rating was 3.67, or raters felt the simulator could be used for training as is with slight to no improvements. Only one rater performed the optional steps of pre-repair and post-repair endoscopic diagnosis and assessment [Supplemental Videos 1 and 2]. The overall material costs are low: $6.16 USD for the reusable
Value Relevance Global
Too difficult to perform Don't Know Don't Know (not used) Ability to Perform Tasks
Very difficult to perform
Don't Know Realism of Experience
Not at all realistic
Little value Little relevance Requires small tweaks before used in training
Very easy to perform
Highly realistic, no changes needed
Highly realistic, no changes needed
Adequate realism as is, but could be improved Adequate realism as is, but could be improved Somewhat easy to perform Lacks too many key features to be useful Lacks too many key features to be useful Difficult to perform Don't Know Physical Attributes
Not at all realistic
(3) (2) (1) (.)
Scale Rating Domains
Table 1 Rating domains and associated 4-point scales used in LTR simulator rating survey.
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role of this airway reconstruction simulator as a tool for training and assessment of proficiency and competency in resident physicians and fellows. The long-term evaluation of a curriculum that uses this simulator in “just in time” training/rehearsal will include tracking its effect on surgical outcomes.
molding system and $2.60 USD for the consumable components. Time of production is approximately 20 h from print to post-processing. Supplementary video related to this article can be found at https:// doi.org/10.1016/j.ijporl.2019.05.027. 4. Discussion
Financial disclosure statement
We present the first high fidelity subglottic stenosis airway simulator, using CAD and 3D printing technologies to emulate the key portions of the procedure for pediatric laryngotracheal reconstruction. The evidence from this study suggests that this low cost, high fidelity laryngotracheal reconstruction simulator can be used, and holds immense promise, as an educational tool for trainees. This model facilitates increased hands-on exposure for this advanced surgical procedure. The use of readily available materials and compatibility with standard surgical equipment decrease the overall cost, making the model accessible to many domestic training environments, such as residency and fellowship training. Of great importance, the low cost and portability of the simulator make it easy to use in global outreach and international surgical education. The current iteration contains a short length stenosis to simplify principles of laryngotracheal reconstruction for educational clarity. This model adds versatility by facilitating the ability to rehearse certain endoscopic procedures such as balloon dilation. Our team has future plans for stenosis variations, such as a longer segment stenosis and varying grades of stenosis. Furthermore, the additive manufacturing process allows for rapid prototyping of patient-specific scenarios for pre-surgical planning in challenging revision or atypical subglottic stenosis cases. Finally, the model could be utilized easily as a patient or caregiver educational tool. Minor modifications to the LTR simulator may enhance its use in a training environment; however, as indicated by the global rating scale and rater comments, are not essential. Suggestions from expert raters centered on a few improvements to the physical attributes of the laryngotracheal simulation model. These included making the vocal cords more obvious, adjusting the configuration of the cricoid cartilage relative to the thyroid cartilage, and designing a thin, inner mucosal layer to allow for improved suturing practice. These first two improvements have been easily addressed in our research laboratory, and the third feature requires additional research to determine its feasibility, labor requirements, and cost-effectiveness. This report has limitations to consider. The study targeted responses from a relatively small group of highly experienced surgeons. Furthermore, the validity evidence was limited to test content as a training tool. It did not include the breadth of validity evidence required to infer the model's value as a testing tool with the capability to discriminate between novice and experienced physician performances. Lastly, this model conveys a short segment stenosis and does not supplant the experience obtained from managing the wide range of airway pathology encountered during a complex Pediatric Otolaryngology Fellowship.
This study was funded by grant NIH T32 DC005356 from the National Institutes of Health. Acknowledgments We would like to acknowledge the following physicians for their expert evaluation of the simulator: Glenn Green, MD (Department of Otolaryngology – Head and Neck Surgery, University of Michigan); Dr. Deepak Mehta (Otolaryngology Division, Texas Children's Hospital); and Dr. Jeremy Meier (Division of Otolaryngology – Head and Neck Surgery, University of Utah). They were not compensated for their contribution. References [1] N.D. Jefferson, A.P. Cohen, M.J. Rutter, Subglottic stenosis, Semin. Pediatr. Surg. 25 (2016) 138–143, https://doi.org/10.1053/j.sempedsurg.2016.02.006. [2] R.T. Cotton, Prevention and management of laryngeal stenosis in infants and children, J. Pediatr. Surg. 20 (1985) 845–851, https://doi.org/10.1016/S00223468(85)80053-1. [3] L.M. Gustafson, B.E.J. Hartley, J.H. Liu, D.T. Link, J. Chadwell, C. Koebbe, C.M. Myer, R.T. Cotton, Single-stage laryngotracheal reconstruction in children: a Review of 200 cases, Otolaryngology-Head Neck Surg. (Tokyo) 123 (2000) 430–434, https://doi.org/10.1067/mhn.2000.109007. [4] J.M. Rosen, S.A. Long, D.M. McGrath, S.E. Greer, Simulation in plastic Surgery training and education: the path forward: Plast. Reconstr. Surg. 123 (2009) 729–738, https://doi.org/10.1097/PRS.0b013e3181958ec4. [5] E.J. Propst, Airway reconstruction surgical dissection manual, http://public.eblib. com/choice/publicfullrecord.aspx?p=1887952, (2014) , Accessed date: 2 January 2019. [6] D.A. Zopf, S.J. Hollister, M.E. Nelson, R.G. Ohye, G.E. Green, Bioresorbable airway splint created with a three-dimensional printer, N. Engl. J. Med. 368 (2013) 2043–2045, https://doi.org/10.1056/nejmc1206319. [7] A.M. Berens, S. Newman, A.D. Bhrany, C. Murakami, K.C.Y. Sie, D.A. Zopf, Computer-aided design and 3D printing to produce a costal cartilage model for simulation of auricular reconstruction, Otolaryngology-Head Neck Surg. (Tokyo) 155 (2016) 356–359, https://doi.org/10.1177/0194599816639586. [8] C.L. Reighard, K. Green, D.M. Rooney, D.A. Zopf, Development of a novel, low-cost, high-fidelity cleft lip repair surgical simulator using computer-aided design and 3dimensional printing, JAMA Facial Plastic Surgery (2018), https://doi.org/10. 1001/jamafacial.2018.1237. [9] K.A. Barsness, D.M. Rooney, L.M. Davis, Collaboration in simulation: the development and initial validation of a novel thoracoscopic neonatal simulator, J. Pediatr. Surg. 48 (2013) 1232–1238, https://doi.org/10.1016/j.jpedsurg.2013.03.015. [10] American Educational Research Association, American Psychological Association, National Council on Measurement in Education, Joint Committee on Standards for Educational and Psychological Testing (U.S.) (Eds.), Standards for Educational and Psychological Testing, American Educational Research Association, Washington, DC, 2014. [11] G.E. Hsiung, B. Schwab, E.K. O'Brien, C.D. Gause, F. Hebal, K.A. Barsness, D.M. Rooney, Preliminary evaluation of a novel rigid bronchoscopy simulator, J. Laparoendosc. Adv. Surg. Tech. 27 (2017) 737–743, https://doi.org/10.1089/lap. 2016.0250. [12] D.M. Rooney, B.L. Tai, O. Sagher, A.J. Shih, D.A. Wilkinson, L.E. Savastano, Simulator and 2 tools: validation of performance measures from a novel neurosurgery simulation model using the current Standards framework, Surgery 160 (2016) 571–579, https://doi.org/10.1016/j.surg.2016.03.035.
5. Conclusions Overall, this study highlights an exciting surgical training tool for laryngotracheal reconstruction. The laryngotracheal subglottic stenosis model simulates key portions of this procedure and requires few to no revisions before use with trainees. Future studies will investigate the
138
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Development of a high fidelity subglottic stenosis simulator for laryngotracheal reconstruction rehearsal using 3D printing
T
Chelsea L. Reigharda, Kevin Greena, Allison R. Powella, Deborah M. Rooneyb, David A. Zopfa,c,∗ a
Otolaryngology—Head and Neck Surgery, Pediatric Division, University of Michigan Health Systems, CS Mott Children's Hospital, Ann Arbor, MI, USA Department of Learning Health Sciences, University of Michigan, Ann Arbor, MI, USA c Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA b
ARTICLE INFO
ABSTRACT
American Society of Pediatric Otolaryngology (ASPO) Meeting 2017 in Austin, Texas; Title: Development of a Novel, High Fidelity Laryngotracheal Reconstruction Simulator using Computer Aided Design and Three Dimensional Printing Technology.
Introduction: Laryngotracheal reconstruction (LTR) with cartilage graft augmentation is an effective treatment for subglottic stenosis and a critical advanced procedure for Pediatric Otolaryngologists. Trainees almost exclusively learn this procedure intraoperatively on children due to the lack of adequate pediatric training models. An enhanced and accelerated educational experience may be possible if trainees can rehearse the key portions of the procedure on a simulation model. Objective: To design and manufacture a low-cost, high fidelity surgical simulation model of subglottic stenosis for LTR. Methods: This simulator is composed of two component models: rib cartilage and trachea. Additive manufacturing techniques, including Computer Aided Design and Three Dimensional (3D) printing, were utilized to create the simulator. Three expert Pediatric Otolaryngologists rated the functionality and realism of the simulator using Likert scale survey data. Results: The use of CAD and 3D printing techniques allowed for realistic, reproducible surgical simulation of key aspects of LTR. The validation evidence indicated good to excellent means across the five domains relevant to the simulator's fidelity and usability (M = 3.47 to 4.00) out of a maximum of 4 points. Lowest rated items were consistent with expert comments suggesting minor simulator improvements. Time of production is approximately 20 h from print to post-processing, and consumable material costs per model are $2.60 USD. Conclusions: This subglottic stenosis airway simulator facilitated Laryngotracheal Reconstruction rehearsal and is a promising training tool for pediatric otolaryngologists. Our methods allow patient-specific, pre-surgical rehearsal for complex airway scenarios that could benefit the experienced airway surgeon and trainees alike. Future research aims to validate this device's utility for accelerating attainment of proficiency and improving surgical outcomes.
Keywords: Surgical simulation 3D printing Computer aided design Laryngotracheal reconstruction simulation Laryngotracheal reconstruction simulator Laryngotracheal reconstruction
1. Introduction Pediatric subglottic stenosis is a luminal narrowing in the area above the trachea and below the vocal cords. This condition often requires airway reconstruction, advanced surgical procedures demanding meticulous surgical technique and robust training. Congenital subglottic stenosis may be caused by incomplete recanalization during embryogenesis. Acquired subglottic stenosis is often secondary to trauma from long-term intubation [1]. Subglottic stenosis is the most common location of laryngotracheal stenosis in children, and Laryngotracheal Reconstruction (LTR) is the predominant procedure for its correction in patients who do not respond to more conservative measures [2,3] or those with high grade stenosis requiring cricotracheal ∗
resection. Surgical simulators, such as animal, cadaveric, computer-based, and physical models, have the potential to provide safe, standardized, competency-based surgical education for trainees [4]; however, adult cadaveric simulations fail to convey the experience of pediatric LTR. Animal lab simulations using porcine and ovine specimens are performed, though the downsides include costs, both financial and sacrifice of animal life, and the lack of ability to maintain/archive work or preserve progress. Presently, resident and attending physicians almost exclusively learn and perfect their LTR surgical technique in the operating room. To our knowledge, we are describing the first high fidelity pediatric subglottic stenosis or airway reconstruction model in the literature [5].
Corresponding author. Department of Otolaryngology, University of Michigan, 1540 E. Hospital Dr, CW 5-702, SPC 4241, Ann Arbor, MI, 48109, USA. E-mail address: [email protected] (D.A. Zopf).
https://doi.org/10.1016/j.ijporl.2019.05.027 Received 5 February 2019; Received in revised form 23 May 2019; Accepted 23 May 2019 Available online 01 June 2019 0165-5876/ © 2019 Elsevier B.V. All rights reserved.
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
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Fig. 1. Segmentation of laryngotracheal airway from high resolution CT scan.
Additive manufacturing, or the use of Computer Aided Design (CAD) and 3D printing, allows for rapid prototyping of complex designs, including surgical simulators. Our group has extensive experience with these technologies and utilizes these processes to develop a number of models and high fidelity surgical simulators for medical and surgical education [6–8]. This study aims to evaluate preliminary validity evidence from a low cost, high fidelity LTR simulator for trainee education and for the refinement of surgical technique.
and the optional mold to seal the base of the model [Fig. 3]. The negative trachea mold was printed in polylactic acid (PLA). Silicone dyed with intrinsic coloring was poured into the trachea mold. Once cured, the subglottic stenosis model was ready for evaluation [Fig. 4A, C]. A piece of a silicone-starch costal cartilage model, using techniques previously published by the senior author, was provided to each expert airway surgeon [7].
2. Methods
2.2. Study design
2.1. Simulator development
Following exempt determination by our institution's Internal Review Board, three expert pediatric airway surgeons from three different institutions independently performed the LTR, utilizing their preferred technique and standard surgical equipment. Surgeons were instructed to carve an anterior airway graft from the rib cartilage simulator, perform an anterior airway incision focused at the level of the stenosis, and suture the graft into the airway model allowing for physical airway expansion [Fig. 4B, D, E]. They evaluated the LTR model using a Likert based survey.
The subglottic stenosis/LTR simulator consists of two models representing different anatomic structures: pediatric laryngotracheal complex with subglottic stenosis and rib. A de-identified computed tomography (CT) scan was obtained from the University of Michigan. The laryngotracheal complex was isolated and segmented utilizing Mimics/3-matic CAD software [Materialise, Plymouth MI, US; Fig. 1]. The trachea was modified to contain a grade III subglottic stenosis and to reflect pediatric tracheal dimensions [Fig. 2]. A Boolean subtraction technique was implemented to create the negative mold for the trachea
Fig. 2. 3D representation of laryngotracheal model with subglottic stenosis. Left to right: right lateral view, frontal view, and coronal section through mid airway. 135
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Fig. 3. Laryngotracheal model in manufacturing system with green insert and gray PLA molding system, all designed and manufactured within our research group. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)
Fig. 4. [A] LTR model; [B] Final repaired LTR model; [C] endoscopic view of pre-repair stenosis in LTR model; [D] Process of repairing LTR model; and [E] endoscopic view after repair to LTR model.
2.3. Survey and rating procedures
22-item survey was used to rate the simulator across five domains—physical attributes, realism of experience, value, relevance to practice, and ability to perform tasks—and one overall/global impression. Four-point rating scales were utilized for all domains [Table 1].
The novel survey was developed via cognitive task analysis, with items independently reviewed by four pediatric otolaryngologists for language clarity and the items’ alignment of critical anatomical functions and features with curricular learning objectives [9,10]. The final 136
International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
ItemNo.
Domain/Characteristic
Fidelity: Physical Attributes (Domain M = 3.47) 1 External appearance of laryngeal complex 2 Endoscopic appearance of laryngeal complex 3 External appearance of cricotracheal complex 4 Endoscopic appearance of cricotracheal complex 5 Subglottic stenosis Fidelity: Realism of Experience (Domain M = 3.50) 6 Optional: endoscopic diagnosis and assessmenta 7 Optional: pre-repair assessment with anesthetic circuit (presence of airway leak)* 8 Amount of pressure needed to make anterior airway incision 9 Texture of rib graft material 10 Carving of rib graft material 11 Suturing of rib graft material 12 Integration of cartilage graft – airway interface 13 Optional: post-repair assessment with anesthetic circuita Fidelity: Value (Domain M = 3.67) 19 Value of the simulator as training tool 20 Value of the simulator as an evaluation tool 21 Fidelity: Relevance of Simulator to Practice Ability (Domain M = 3.53) 14 Optional: pre-repair endoscopic diagnosisa 15 Anterior airway incision 16 Fashioning anterior graft 17 Integration of graft into airway 18 Optional: post-repair assessmenta 22 Global Rating a
M (SD) (n = 3)
95% CI
3.67 (0.58) 3.50 (0.71)
3.09–4.00 2.79–4.00
3.33 (0.58)
2.75–3.91
3.50 (0.71)
2.79–4.00
3.33 (0.58)
2.75–3.91
3.00
NA
4.00
NA
3.67 (0.58)
3.09–4.00
3.67 (0.58) 3.33 (0.58) 4.00 3.33 (0.58)
3.09–4.00 2.75–3.91 NA 2.75–3.91
3.00
NA
3.67 (0.58) 3.67 (0.58) 4.00
3.09–4.00 3.09–4.00 NA
4.00 3.33 (1.15) 3.00 3.33 (0.58) 4.00 3.67 (0.58)
NA 2.18–4.00 NA 2.75–3.91 NA 3.09–4.00
Optional steps performed by only one rater.
2.4. Analyses
No value No relevance Requires number of improvements before used in training
Some value Some relevance Can be used as is, but could be improved slightly
A great deal of value Has a great deal of relevance Can be used as is with no improvements made
Table 2 Means for domains and individual items from LTR simulator rating survey.
Preliminary validity evidence relevant to test content was evaluated using previously established methods that applied the current Standards framework to simulator validation processes [10–12]. Traditionally known as “face validity,” evidence relevant to test content was evaluated by calculating raters’ means for each of the 22 survey items. Higher means suggest participants had a higher perceived value for that particular feature or characteristic of the simulator. 3. Results Faculty self-reported a mean (SD) of 10.67 (6.03) years in practice and have completed between 25 and 150 LTR procedures to date (M = 91.67, SD = 62.92). Averaged ratings and specific feedback were collected. Preliminary evaluation indicated good to excellent means (3.47–4.00) across the four Fidelity domains (Physical Attributes, Realism of Experience, Value, and Relevance) [Table 2]. These findings were consistent with surgeon comments indicating the experience is highly realistic, requiring minor to no improvements, and has a great deal of value and relevance in the current training environment. The mean rating for the Ability domain was 3.53, indicating that raters were able to perform the necessary LTR steps of anterior airway incision, anterior graft fashioning, and graft integration into the airway with reasonable, expected ease. The mean Global rating was 3.67, or raters felt the simulator could be used for training as is with slight to no improvements. Only one rater performed the optional steps of pre-repair and post-repair endoscopic diagnosis and assessment [Supplemental Videos 1 and 2]. The overall material costs are low: $6.16 USD for the reusable
Value Relevance Global
Too difficult to perform Don't Know Don't Know (not used) Ability to Perform Tasks
Very difficult to perform
Don't Know Realism of Experience
Not at all realistic
Little value Little relevance Requires small tweaks before used in training
Very easy to perform
Highly realistic, no changes needed
Highly realistic, no changes needed
Adequate realism as is, but could be improved Adequate realism as is, but could be improved Somewhat easy to perform Lacks too many key features to be useful Lacks too many key features to be useful Difficult to perform Don't Know Physical Attributes
Not at all realistic
(3) (2) (1) (.)
Scale Rating Domains
Table 1 Rating domains and associated 4-point scales used in LTR simulator rating survey.
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International Journal of Pediatric Otorhinolaryngology 124 (2019) 134–138
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role of this airway reconstruction simulator as a tool for training and assessment of proficiency and competency in resident physicians and fellows. The long-term evaluation of a curriculum that uses this simulator in “just in time” training/rehearsal will include tracking its effect on surgical outcomes.
molding system and $2.60 USD for the consumable components. Time of production is approximately 20 h from print to post-processing. Supplementary video related to this article can be found at https:// doi.org/10.1016/j.ijporl.2019.05.027. 4. Discussion
Financial disclosure statement
We present the first high fidelity subglottic stenosis airway simulator, using CAD and 3D printing technologies to emulate the key portions of the procedure for pediatric laryngotracheal reconstruction. The evidence from this study suggests that this low cost, high fidelity laryngotracheal reconstruction simulator can be used, and holds immense promise, as an educational tool for trainees. This model facilitates increased hands-on exposure for this advanced surgical procedure. The use of readily available materials and compatibility with standard surgical equipment decrease the overall cost, making the model accessible to many domestic training environments, such as residency and fellowship training. Of great importance, the low cost and portability of the simulator make it easy to use in global outreach and international surgical education. The current iteration contains a short length stenosis to simplify principles of laryngotracheal reconstruction for educational clarity. This model adds versatility by facilitating the ability to rehearse certain endoscopic procedures such as balloon dilation. Our team has future plans for stenosis variations, such as a longer segment stenosis and varying grades of stenosis. Furthermore, the additive manufacturing process allows for rapid prototyping of patient-specific scenarios for pre-surgical planning in challenging revision or atypical subglottic stenosis cases. Finally, the model could be utilized easily as a patient or caregiver educational tool. Minor modifications to the LTR simulator may enhance its use in a training environment; however, as indicated by the global rating scale and rater comments, are not essential. Suggestions from expert raters centered on a few improvements to the physical attributes of the laryngotracheal simulation model. These included making the vocal cords more obvious, adjusting the configuration of the cricoid cartilage relative to the thyroid cartilage, and designing a thin, inner mucosal layer to allow for improved suturing practice. These first two improvements have been easily addressed in our research laboratory, and the third feature requires additional research to determine its feasibility, labor requirements, and cost-effectiveness. This report has limitations to consider. The study targeted responses from a relatively small group of highly experienced surgeons. Furthermore, the validity evidence was limited to test content as a training tool. It did not include the breadth of validity evidence required to infer the model's value as a testing tool with the capability to discriminate between novice and experienced physician performances. Lastly, this model conveys a short segment stenosis and does not supplant the experience obtained from managing the wide range of airway pathology encountered during a complex Pediatric Otolaryngology Fellowship.
This study was funded by grant NIH T32 DC005356 from the National Institutes of Health. Acknowledgments We would like to acknowledge the following physicians for their expert evaluation of the simulator: Glenn Green, MD (Department of Otolaryngology – Head and Neck Surgery, University of Michigan); Dr. Deepak Mehta (Otolaryngology Division, Texas Children's Hospital); and Dr. Jeremy Meier (Division of Otolaryngology – Head and Neck Surgery, University of Utah). They were not compensated for their contribution. References [1] N.D. Jefferson, A.P. Cohen, M.J. Rutter, Subglottic stenosis, Semin. Pediatr. Surg. 25 (2016) 138–143, https://doi.org/10.1053/j.sempedsurg.2016.02.006. [2] R.T. Cotton, Prevention and management of laryngeal stenosis in infants and children, J. Pediatr. Surg. 20 (1985) 845–851, https://doi.org/10.1016/S00223468(85)80053-1. [3] L.M. Gustafson, B.E.J. Hartley, J.H. Liu, D.T. Link, J. Chadwell, C. Koebbe, C.M. Myer, R.T. Cotton, Single-stage laryngotracheal reconstruction in children: a Review of 200 cases, Otolaryngology-Head Neck Surg. (Tokyo) 123 (2000) 430–434, https://doi.org/10.1067/mhn.2000.109007. [4] J.M. Rosen, S.A. Long, D.M. McGrath, S.E. Greer, Simulation in plastic Surgery training and education: the path forward: Plast. Reconstr. Surg. 123 (2009) 729–738, https://doi.org/10.1097/PRS.0b013e3181958ec4. [5] E.J. Propst, Airway reconstruction surgical dissection manual, http://public.eblib. com/choice/publicfullrecord.aspx?p=1887952, (2014) , Accessed date: 2 January 2019. [6] D.A. Zopf, S.J. Hollister, M.E. Nelson, R.G. Ohye, G.E. Green, Bioresorbable airway splint created with a three-dimensional printer, N. Engl. J. Med. 368 (2013) 2043–2045, https://doi.org/10.1056/nejmc1206319. [7] A.M. Berens, S. Newman, A.D. Bhrany, C. Murakami, K.C.Y. Sie, D.A. Zopf, Computer-aided design and 3D printing to produce a costal cartilage model for simulation of auricular reconstruction, Otolaryngology-Head Neck Surg. (Tokyo) 155 (2016) 356–359, https://doi.org/10.1177/0194599816639586. [8] C.L. Reighard, K. Green, D.M. Rooney, D.A. Zopf, Development of a novel, low-cost, high-fidelity cleft lip repair surgical simulator using computer-aided design and 3dimensional printing, JAMA Facial Plastic Surgery (2018), https://doi.org/10. 1001/jamafacial.2018.1237. [9] K.A. Barsness, D.M. Rooney, L.M. Davis, Collaboration in simulation: the development and initial validation of a novel thoracoscopic neonatal simulator, J. Pediatr. Surg. 48 (2013) 1232–1238, https://doi.org/10.1016/j.jpedsurg.2013.03.015. [10] American Educational Research Association, American Psychological Association, National Council on Measurement in Education, Joint Committee on Standards for Educational and Psychological Testing (U.S.) (Eds.), Standards for Educational and Psychological Testing, American Educational Research Association, Washington, DC, 2014. [11] G.E. Hsiung, B. Schwab, E.K. O'Brien, C.D. Gause, F. Hebal, K.A. Barsness, D.M. Rooney, Preliminary evaluation of a novel rigid bronchoscopy simulator, J. Laparoendosc. Adv. Surg. Tech. 27 (2017) 737–743, https://doi.org/10.1089/lap. 2016.0250. [12] D.M. Rooney, B.L. Tai, O. Sagher, A.J. Shih, D.A. Wilkinson, L.E. Savastano, Simulator and 2 tools: validation of performance measures from a novel neurosurgery simulation model using the current Standards framework, Surgery 160 (2016) 571–579, https://doi.org/10.1016/j.surg.2016.03.035.
5. Conclusions Overall, this study highlights an exciting surgical training tool for laryngotracheal reconstruction. The laryngotracheal subglottic stenosis model simulates key portions of this procedure and requires few to no revisions before use with trainees. Future studies will investigate the
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