Evaluation of training models for intraventricular neuroendoscopy

doi:10.21203/rs.3.rs-4809603/v1

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Evaluation of training models for intraventricular neuroendoscopy

https://doi.org/10.21203/rs.3.rs-4809603/v1

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Introduction: Structured surgical education has become increasingly important in recent years. Intraventricular neuroendoscopic procedures have been widely established. However, training surgical skills with these techniques is crucial for young residents due to the potential harm to adjacent tissue. Therefore, we evaluated two different training models.

Methods: Participants in two different international workshops were trained on a prefixed cadaver model and on a living murine intraabdominal model. Crucial neuroendoscopic techniques such as membrane perforation and tissue biopsy were performed. A blinded questionnaire evaluated both models.

Results: Sixty-three participants were trained on the animal model. Forty of these were trained on the cadaver model. The training effect was evaluated almost equally, with 8.5/10 for the animal model and 8.9/10 for the cadaver model. The tissue properties were rated higher regarding realism in the animal model, whereas the anatomic realism was rated higher in the cadaver model.

Conclusion: The animal model is a valid alternative to cadaver models for teaching endoscopic neurosurgical skills. This model benefits from the simulation of real surgical tissue properties, including bleeding. The low costs and availability of this technique make it more ubiquitous and can help train further generations of neurosurgeons.

neuroendoscopy

surgical education

murine model

cadaver model

endoscopy

The first neuroendoscopic procedures were performed more than 100 years ago but soon stopped due to technical and medical limitations [6]. Neuroendoscopy was revolutionized after the collaboration of Harold Hopkins and Karl Storz in the 1970s [20]. Endoscopic techniques were restricted to a few specialized centers until the end of the 1980s when well-known neurosurgeons began to take this technique seriously into account [9].

Endoscopic treatment options include the restoration of the physiological pathway, e.g., with foraminoplasty, or the opening of alternative pathways through fenestrations, e.g., ETV, fenestration of the lamina terminalis or septostomy. In the case of mass lesions, the removal of the lesion must be considered [4, 10, 13, 14]

The goal of international societies is to promote these minimally invasive techniques and teach their application in low-income countries, for instance. However, neuroendoscopy differs slightly from other endoscopic procedures in other surgical fields. General surgeons, orthopedics or urologists, for example, have implemented endoscopic procedures in their daily practice, including different levels of difficulty. Arthroscopic or laparoscopic procedures are well established, and physicians start practicing these procedures early during residency. Courses and training models are available in large numbers. Moreover, the indications for an intraventricular neuroendoscopic procedure are rather rare or are only frequently performed in specialized centers, for instance, for pediatric neurosurgery, or in larger departments with a high number of cases per year. Therefore, compared with other young surgeons, residents might not have the chance to see and practice endoscopic procedures. Although intraventricular procedures are mostly straightforward short procedures and can be performed by unexperienced surgeons under the instruction of an experienced neuroendoscopist, some limitations must be mentioned. First, the knowledge and handling of the endoscope and the instruments must be understood. As mentioned, it might be unfamiliar to young neurosurgeons to look at the screen and not through the microscope. Second, the space in the ventricle system might be limited, and maneuvers can be challenging. Third, the structures adjacent to the ventricle system are very eloquent. Accidental injuries to these structures might cause permanent deficits such as short-term memory deficits (due to Fornix lesions), eye muscle palsy (due to oculomotor nerve lesions) or even hemiparesis (due to thalamic lesions). Injuries to vessels such as the thalamostriate vein or even the basilar artery can result in severe bleeding and even death, as previously reported [1, 5, 12, 18] These injuries can occur not only by false instrument handling but also, for example, by incorrect coagulation and thermal damage. This emphasizes how important the teaching of these techniques is to avoid complications for the patient. The logical alternatives to train neuroendoscopic procedures on patients are models and simulations.

The authors have established annual workshops for neuroendoscopy training over the last 15 and 12 years in two neurosurgical departments. These workshops include lectures, live surgeries and practical hands-on sessions. One model is based on a murine model for the simulation of intraventricular procedures. It was introduced by the authors from the very first edition of their workshop more than 15 years ago, who recalled the experience of Professor Jacques Camaert, who first introduced this model to train in neuroendoscopic procedures in his workshops held for almost 15 years in Ghent, Belgium, until the last edition in 2012. To the best of our knowledge, he has never described or reported his model in the literature. Since then, it has been adopted and described in the literature [8, 11].

Given the potential risk of an intraventricular procedure, models simulating this environment might not cover all aspects, such as bleeding or tissue properties. With a live animal model, these aspects should be simulated as intended.

The use of animal models is under constant debate, and animal protection laws in many countries encourage scientists and physicians to refine, reduce and/or replace animal experiments. Therefore, the aim of the present study was to evaluate this model in comparison to other models on the learning effect of trainees.

Animal model

The procedures were performed under approval by the local governmental animal care committee (registration number TVA 11-2023) and were in accordance with the UKCCCR Guidelines for the Welfare of Animals in Experimental Neoplasia (Br J Cancer 1998; 77:1–10) and the Interdisciplinary Principles and Guidelines for the Use of Animals in Research (New York Academy of Sciences Ad Hoc Committee on Animal Research, NY). Sprague–Dawley rats with a minimum weight of 250 grams were obtained from Charles Rivers Laboratories, Sulzfeld, Germany. The animals were housed in cages at a room temperature of 22–24°C and a relative humidity of 60–65% with a 12-h light/dark cycle. The rats were allowed free access to drinking water and standard laboratory chow (Altromin®, Lage, Germany). The animals were anesthetized by initial inhalation of isoflurane. Anesthesia was induced by intraperitoneal injection of 90 mg/kg bodyweight ketamine (Ketavet®, Parke Davis; Freiburg, Germany) and 8 mg/kg bodyweight xylazine (Rompun®, Bayer; Leverkusen, Germany). All animals received 5 mg/kg body weight carprofen (Vetranal™, Sigma‒Aldrich; St. Louis, USA) subcutaneously in addition to pain relief.

The animals were fixed in the supine position, and the limbs were fixed with tape. The anesthesia was constantly evaluated, and additional ketamine was applied if necessary. A median skin incision was made to access the peritoneal space. An endoscope was inserted, and the skin was closed with a circular suture. There are two options: the model can be applied under water and constant irrigation with Ringer’s solution or under air conditions. The authors suggest the use of antifogging fluids to avoid forging of the lenses if the second method is used. The surgical steps were demonstrated to the trainees by the tutor on videos or pictures before the surgery. The following surgical steps were performed by the trainee.

First, the endoscope is introduced, and an inspection of the abdominal space is performed. Second, the liver lobes are identified, and coagulation at the rim of the liver lobe is performed. Then, the coagulated tissue was removed with biopsy forceps. Possible bleeding from the parenchyma can be stopped with a bipolar probe.

After this step, the endoscope can be rotated 180 degrees to expose the bladder. This procedure simulates tumor removal. The attaching ligaments can be cut with scissors, and the bladder can be removed with grasping forceps.

Then, the endoscope is turned again and moves up to the upper part of the liver and the diaphragm. As a next step, the ligamentum falciforme is exposed and can be cut.

The last step is fenestration of the diaphragm. Here, coagulation is performed, the diaphragm is perforated with blunt perforating forceps, and the stoma is enlarged with balloon catheters. This simulates an ETV. The animal was then euthanized with a lethal dose of pentobarbital as it otherwise died due to collapse of the lung.

Cadaver model

The endoscopic procedures can also be trained on cadaver models. The Institute of Anatomy and Cell Biology of the Saarland University provides the human cadavers. The education of physicians was performed under approval by the local governmental ethic committee (registration number 245/22). In general, these fresh frozen or prefixed cadavers allow surgical procedures, including borehole trepanation, endoscopic puncture of the ventricle and inspection and perforating steps. The trainees were instructed to perform a ventricle puncture 2.5 cm parasagittal and before the coroner suture by themselves under instructions. Then, the ventricles were inspected with different angled optics. They then perform ETV. As a next step, a more lateral base hole was cut 4–5 cm parasagittally, and a septostomy was performed.

Evaluation form

A questionnaire, as added to the supplemental section, was distributed to the participants at the end of the workshop. The questionnaire included general questions regarding age, educational level, and experience in neuroendoscopy. The model was subsequently rated concerning the handling, realism and overall learning effect. The trainees were also asked for their desired qualities of an ideal training model for neuroendoscopy.

Statistical analysis

The questionnaires were transferred to SPSS (IBM, Armonk, USA). The results were analyzed by the chi-square test and likelihood test. A level of statistical significance was assumed at p ≤ 0.05. The data are presented as the mean and standard error of the mean.

Overall, 63 trainees participated in the workshop events. Twenty-six were residents, and 37 were consultants. Years of practice were categorized as follows: 1–5 years (n = 21); 5–10 years (20); 10–15 years (n = 16); and more than 15 years (n = 6). Twenty-eight participants had not previously undergone ETV. The remaining 35 participants had performed 1.8 ± 0.1 ETVs and were almost exclusively consultants. They frequently use neuronavigation (80%) and balloon catheters (94%). Laser techniques are only applied in 11% of cases.

A total of 97% of the participants evaluated the animal model as “very realistic” or “what is realistic” regarding surgical handling, 90% regarding anatomy, 97% regarding tissue properties and 98% in general.

The cadaver model was evaluated by 95% of the participants as “very realistic” or “what is realistic” regarding surgical handling, 100% regarding anatomy, 80% regarding tissue properties and 100% in general. These data are summarized in Table 1.

Table 1

summarizes the evaluation of the realism of the murine training model and the cadaver model in terms of “handling”, “anatomy”, “tissue properties” and “overall impression”.
	Murine Model Handling [n]	Murine Model Anatomic realism [n]	Murine Model Tissue Properties [n]	Murine Model Overall Impression [n]	Cadaver Model Handling [n]	Cadever Anatomic Realism [n]	Cader Tissue Properties [n]	Cader Overall Impression [n]
very realistic	35	27	36	37	24	29	13	23
kind of realistic	24	29	24	25	14	11	19	17
more unrealistic	0	4	2	1	2	0	6	0
unrealistic	1	1	0	0	0	0	2	0
don’t know	4	2	1	0	0	0	0	0

The learning effect was assessed on an asset scale from low = 1 to high = 10. The animal model was evaluated with a mean score of 8.5 ± 0.2, and the cadaver model had a mean score of 9.0 ± 0.2. Residents and consultants evaluated the models nearly identically (8.4 ± 0.3 vs 8.6 ± 0.3 and 8.9 ± 0.3 vs. 9.0 ± 0.3). There was no statistically significant difference between the groups.

The trainees were asked about their confidence in performing an ETV after performing the training model. A total of 74.0% of the participants were confident after the animal model was established, and 87.5% of the participants were confident after the cadaver model was established. After each model, the consultants felt more confident than did the residents (89% vs 58% and 96% vs. 71%, respectively).

In addition, the trainees were asked about the requirements of an ideal training model. The participants “strongly agreed” or “agreed” in 100% with realistic simulation of anatomical structures, 98% with realistic simulation of tissue strength, 80% with realistic simulation of pulsation, 78% with realistic simulation of complications, 76% with realistic simulation of bleeding and 71% with a realistic simulation of an OR setting.

Table 2

summarizes the expected requirements for an ideal training model by the participants.
	Same Instruments like in the OR [n]	Same Setting like in the OR [n]	Realistic Anatomical Structures [n]	Realistic Tissue Properties Regarding Resistance [n]	Realistic Bleeding Conditions [n]	Realistic Pulsation [n]	Simulation of Complications [n]
strongly agree	49	17	44	41	31	23	24
agree	14	34	19	21	17	23	19
neither nor	0	5	0	1	5	6	6
disagree	0	1	0	0	4	5	6

This study showed that a low-cost murine model can achieve training effects comparable to those of cadaveric models for neuroendoscopic procedures. More experienced surgeons feel comparable confidence in performing an ETV after bypassing such a model in comparison to a cadaver hands-on session. Young colleagues also rated the model as an adequate learning method. A limitation of the murine model is surely that it cannot help to teach the intra- and paraventricular anatomy of the human brain. Simulating the anatomy was one of the most important requirements for an ideal model in our poll. Other training models may overcome this problem, as cadaver models are not ubiquitously available all over the world or are restricted by shortages or low prices. 3D-printed models are helpful for teaching anatomy and might help to encourage medical students to choose neurosurgery at all; however, training manual skills effectively is doubtable [7, 17].

Various computer simulations have been developed and have shown fair results concerning anatomical learning effects. Nonetheless, as this technology was promoted more than 15 years ago, it is still not routinely implemented [2]. A major drawback of virtual reality is the inadequate simulation of force sensing and tissue properties. The importance of this simulation aspect has also been shown in our evaluation. Emerging technologies might overcome this problem in the near future toward establishing low-cost, high-performance MIS force sensors, such as promising piezoelectric sensors. Recent rapid advances in computer vision and machine learning have drawn increasing attention to imaging-based tactile sensing, also known as vision-based sensing [16]. Augmented or virtual reality will continue to result in rapid advancements in operative planning, intraoperative navigation, and neurosurgical training [19].

Interestingly, complication simulation was only important for 76% of all trainees. In our opinion, this aspect is common in neuroendoscopic intraventricular procedures, as complications are major risks for patients [1, 12]. In particular, hemorrhages might be challenging to handle and need immediate proper measures [15].

Models could be improved by testing the effects on the manual skills and knowledge of the participants. However, standardized evaluation methods are lacking and should be developed by surgical societies regardless of the proper model type [3].

To evaluate the current status of neurosurgical models with other surgical fields, we performed a PubMed search for the “Laparoscopic training model”, “Arthroscopic training model” and “neuroendoscopic training model”. This simple keyword search revealed 21537 papers concerning laparoscopic training models, 5656 papers concerning arthroscopic training models and only 194 papers concerning neuroendoscopic training models. These results emphasize how underrepresented this topic is in the neurosurgical community and should be further supported to ensure proper education of future generations of neuroendoscopists.

CSF

cerebral spine fluid

ETV

endoscopic third ventriculostomy

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Competing interests

The authors do not have any financial or non-financial interests that are directly or indirectly related to the work submitted.

Author Contributions

Author contributions to the study and manuscript preparation include the following. Conception and design: Sebastian Senger, Thomas Tschernig, Joachim Oertel, Guiseppe Cinalli

Acquisition of data: Sebastian Senger, Magomed Lepshokov

Analysis and interpretation of data: Sebastian Senger, Thomas, Tschernig,

Joachim Oertel, Guiseppe Cinalli

Drafting the article: Sebastian Senger

Critically revising the article: Joachim Oertel, Guiseppe Cinalli

Reviewed the final version of the manuscript and approved it for submission: Sebastian Senger, Joachim Oertel, Guiseppe Cinalli

Study supervision: Joachim Oertel, Guiseppe Cinalli

Ethics approval

All animal experiments were performed under approval by the local governmental animal care committee (registration number TVA 11-2023). The education of physicians on cadavers were performed under approval by the local governmental ethic committee (registration number 245/22).

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No competing interests reported.

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You are reading this latest preprint version

Evaluation of training models for intraventricular neuroendoscopy

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Version 1

Abstract

Figures

Introduction

Materials and Methods

Animal model

Cadaver model

Evaluation form

Statistical analysis

Results

Discussion

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1