Simulating A Subcondylar Mandibular Fracture With Intraoral Open Reduction and Internal Fixation: A Novel Education Tool for Residents

Abstract

Study Design: Face and content validation of a surgical simulation model. Objective: Open reduction and internal fixation in displaced subcondylar mandibular fractures is standard care. This requires an extraoral (eg: retromandibular, transparotideal) or intraoral approach. An intraoral approach requires further training since specialized instrumentation such as the 90° screwdriver system and endoscopes might be needed. Currently, no simulation models are available for training residents in intraoral reduction and fixation of subcondylar mandibular fractures. Therefore, we present a validated simulation model for intraoral treatment of subcondylar mandibular fractures. Methods: Based on a computer tomography data set, we designed and printed a 3D model of a mandible with a unilateral subcondylar fracture. To simulate intraoral work depth, it was positioned inside a dental phantom. We tested the model by a group of experts (n = 8), simulating intraoral reduction and fixation of a unilateral subcondylar fracture, using a 90° screwdriver system, a 1.0 subcondylar plate (lambda), and 5-6 mm screws. We assessed Face and Content validity by survey. Results: We provided an open-source printable fracture model. Printing costs were approximately US $10. Experts “Agreed” the model resembling the real scenario and its use for training intraoral reduction and fixation of subcondylar mandibular fractures. Conclusions: We developed a low cost, reproducible, open-source simulator for subcondylar mandibular fractures. Face and Content validity was achieved through evaluation by a group of experts.

Introduction

Proper management of subcondylar mandibular fractures has been a subject of debate for many years. Open reduction might be challenging, with risks including sialocele, facial nerve palsy, bleeding, hematomas, insufficient reduction, and malunion of bone fragments. There is no consensus on the gold standard treatment on various patterns of condylar and subcondylar mandibular fractures. Recently, the indication for surgery has undergone a paradigm shift. [1,2,3,4] Advances in 3D modeling, anatomical plates, endoscopy, and 90° screwdriver systems made surgery more predictable by giving surgeons tools to achieve better outcomes. [5,6,7]

The COVID-19 pandemic brought challenges to surgery residency programs because of low exposure to their specialty’s daily duties. But this scenario gave more attention to simulation tools. Patient care needs a resident with experience and proper exposure to various treatments, resulting in better surgical outcomes, less hospitalization time, and complications. Despite existing considerable literature describing the use of simulation in surgical specialties and anesthesiology residents, there is insufficient information in oral and maxillofacial surgery (OMS) programs. [5,6,7,8,9] Programs on OMS need to evaluate the reality of clinical work with the importance of better outcomes, low risk, and proficiency-based training that simulation can provide. Simulation gives the occasion to evaluate specific educational objectives consistent with a program’s strengths and ensure that residents gain experience in non-frequent and high complexity procedures making learning conducive to all levels. Current residency programs with plans of executing simulation education might need a change in ideology, where the learner is the educational focus, ensuring that errors are used as teaching points, with the benefit of previous exposure and experience before real treatments. Further, it promotes competency based on validated measurements. [5,6,9,10]

The OMS residency program at Pontificia Universidad Católica de Chile is developing and implementing simulation with the institution’s Medicine School and Simulation Training Center into the curriculum of residency training.

The aim of our study was to develop and validate a low cost, reproducible simulator for an intraoral approach for open reduction and internal fixation of subcondylar man-dibular fractures.

Materials and Methods

Model Design

After signing informed consent, a head and neck computer tomography scan of a random patient was modified using a 3D software (Meshmixer 3.5). A subcondylar fracture was designed using a linear osteotomy from the sigmoid notch to the subcondylar area of the right side of the mandible. Figure 1 and Figure 2 shows the printed 3D model of the mandible fracture with filaments of Polylactic acid (PLA). Figure 3 shows the model inside a dental phantom to simulate intraoral work depth.

Osteosynthesis Systems

Plates and screws of the “Matrix Mandible subcondylar plates system” (DePuy Synthes) were used. We performed open reduction and internal fixation with the 90° screwdriver system, 1.0 subcondylar plates (lambda), and 5–6 mm screws (DePuy Synthes). Traditional maxillofacial surgery instruments were used.

Evaluation: Face and Content Validity

A group of 8 expert maxillofacial surgeons tested the simulation model for subcondylar fractures performing reduction and fixation in the simulator, followed by answering a face and content validity questionnaire to evaluate the realism of the model and its utility in surgical training for maxillofacial residents.

Face validity evaluates if the surgical simulator has a high degree of reality. Content validity describes the extent to which a simulator teaches the skills required for a successful surgical procedure.

All experts considered eligible were trained oral and maxillofacial surgeons in Chile and have experience in treating maxillofacial trauma. After testing the subcondylar fracture simulation model, performing reduction and fixation of the fractures, all participants completed a Likert face and content validity questionnaire. The survey was conducted among the experts using Google Forms (Google Inc, California, US). Survey Form is enclosed in

Table 1. Likert Survey of Face and Content Validity.

, and results were analyzed in Microsoft Excel v.18 (Microsoft Corporation, Washington, US). Descriptive statistics were used.

Results

Model Development

The segmented mandible in Figure 1 is accessible as a Standard Tessellation Language-File (stl-file) for 3D printing at the National Institutes of Health 3D print exchange website (https://3dprint.nih.gov). The 3D subcondylar mandibular fracture model was printed in polylactid acid (PLA) and inserted in a dental phantom. Cost for printing the 3D model using PLA was approximately US $10.

Face and Content Validation

Table 2. Likert Survey Assessing Face and Content Validity Results.

shows the results of the Likert survey assessing face and content validity describing the realistic degree of this model and to which extent it can teach the skills required for the surgical intervention.

Face Validation Results

A total of 6 (75%) experts strongly agreed and 2 (25%) agreed that the visual appearance of the simulator looked realistic, 4 (50%) experts strongly agreed that the dental phantom simulated deepness and shape of a human mouth, 3 (37.5%) agreed and 1 (12.5%) experts remained neutral, 4 (50%) experts strongly agreed that the 3D mandible felt realistic when drilling, 3 (37.5%) agreed and 1 (12.5%) experts remain neutral. Regarding if bone marrow and cortical bone feels realistic when drilling and screwing, 4 (50%) experts strongly agreed, 3 (37.5%) experts agreed and 1 (12.5%) expert disagreed, 2 (25%) experts strongly agreed that the soft tissue felt realistic on the dental phantom, 4 (50%) experts agreed and 2 (25%) disagreed, 5 (62.5%) experts strongly agreed and 2 (25%) agreed on practicing with this subcondylar simulation model before a real surgery.

Content Validation Results

Half of the experts 4 (50%) strongly agreed and 3 (37.5%) experts agreed the simulator achieving overall realism for practicing subcondylar fracture reduction and fixation, whereas 1 (12.5%) expert disagrees, 7 (87.5%) experts strongly agreed, and 1 (12.5%) expert agreed the simulator being a useful tool for training residents and teaching them how to perform reduction and fixation of subcondylar fractures. After testing the simulator, 4 (50%) experts strongly agreed and 4 (50%) agreed the simulator being useful for training surgeons with previous maxillofacial trauma experience. Seven (87.5%) experts strongly agreed on implementing the simulator as a training model for maxillofacial surgery residents, meanwhile 1 (12.5%) expert remained neutral on the matter. Also, seven (87.5%) experts strongly agreed the simulator being usable to learn how to reduce and fixate subcondylar fractures via intraoral approach.

This simulator was found adequate for learning how to use the 90° screwdriver system and the subcondylar plates system, with 6 (75%) experts strongly agreeing and 2 (25%) of them agreeing.

Discussion

Oral and maxillofacial surgery programs have increased their interest in simulation as a part of their learning curve for residents. New simulation models have been designed and validated in several surgical specialties, where new learning programs based in simulation training have shown to improve abilities, shorten the learning curve, and reduce complications, giving the residents more confidence in surgical practice. This requires transferring what has been learned from the simulation model to the operating room, through a validated educational tool. [11,12]

Literature supports results and reduction of clinical costs when a procedure is performed by surgeons with this method of learning, in comparison to professionals with little experience, which in some cases could be applied to the reality during the pandemic. [5,6,9,12]

The acquisition of surgical and therapeutic experience is not an easy task; however, the use of simulators could contribute to the transfer of knowledge and skills from the theory to the patient. However, this requires an adequate validation process. [12,13,14,15,16,17,18,19,20,21,22]

Surgical simulation courses have become crucial for resident training and board certification with an exponential increase in development of new simulation models. As they showed improvement in technical skills, confidence and transferability of the acquired skills to the operating room. [10,13] In total, 79% of trainees report that simulation training would be beneficial in surgery providing them better technical preparation and confidence towards the trained procedure. [18] This study designed and examined the realism and usefulness of a novel subcondylar fracture simulating model. The expert testing group agreed the simulation model being highly realistic and usable in training maxillofacial surgery residents.

On this model, 28%% of the experts agreed and 62.5% strongly agreed with the validation process. The present model would be a good tool for training residents in the future but needs experienced surgeons teaching proper techniques and surgical steps. Regarding the material used for bone simulation, PLA showed good performances in other maxillofacial simulation models because of its low cost, biodegradability, non-toxicity, and with more similarity to bone than other materials while drilling at low temperature with continuous cooling. A disadvantage is lack of simulation of the difference in drilling sensation between cortical and cancellous bone and it may melt at higher temperatures. [13] In our study, experts reported the bone drilling sensation feeling realistic overall. From all experts, 87.5% strongly agreed that this simulator is a useful tool for training residents and teaching them how to perform reduction and fixation of subcondylar fractures, and also strongly agreed on implementing this simulator as a training model for maxillofacial surgery residents.

However, additional soft tissues and cortical perforation sensation may be further developed with other materials. Further research must aim at assessing construct validity and clinical skill transferability as some simulation models lacked transferability to the operating room. [18,19,20,21,22]

Conclusions

In the context of COVID-19 pandemic, surgical simulation courses have become crucial for training residents. This study describes the design and validation of a subcondylar fracture simulation model, its usefulness on training maxillofacial surgery residents and how realistic it is when comparing with real patients. We present a low cost, reproducible, realistic subcondylar fracture simulation model, adequate for training maxillofacial surgery residents in subcondylar fractures. Evaluated scores correspond to a high evaluation level, and all participants characterized the simulation model as realistic and with high teaching potential for maxillofacial surgery residents.