Endoscopic endonasal surgery is commonly performed in the field of otorhinolaryngology, but has been a major cause of medical disputes. Satisfactory training in endoscopic endonasal surgery, especially for junior residents, is therefore of great importance. Cadaver dissection is the gold standard for such education1; however, this can be difficult to manage, and there are limited opportunities to attend cadaver-dissection courses. Recently, alternative methods for resident training have been reported, including virtual reality simulation,2, 3 although this requires considerable set-up costs. Various physical sinus models based on synthetic materials are also available4, 5; however, these are single use and are comparatively expensive for repeated practices, although they are beneficial for training in basic techniques. To overcome these difficulties and cost issues, we have developed a training model using quail eggs that is both low cost and reusable. Our model is aimed at training residents to handle surgical instruments under an angled endoscopic view, which is a common weak point in surgical beginners.
MATERIALS AND METHODS
Establishing Training Models
We used a commercially available sinus surgery trainer (Sinus Model Otorhino Neuro Trainer; Pro Delphus, Recife, Brazil)4 and carried out complete sinus dissection. The medial wall of the orbit was then resected, and a slow-boiled quail egg was embedded in the orbit or adhered to the lateral wall of the maxillary sinus (Fig. 1A–C). A slow-boiled egg, or hot-spa egg, was boiled in water at 70°C for 15 minutes to achieve a soft egg white and half-boiled yolk. The stiffness of the eggshell membrane acted as the periorbit.
Surgical procedures were performed under visualization with a 30° angled endoscope. In the orbital setting, the egg shell at the medial wall of the orbit was resected using a diamond bur (Curved Diamond DCR Bur, 2.5 mm; Medtronic, Inc., Minneapolis, MN) (Fig. 2A), curettes, and forceps, without damaging the eggshell membrane (Fig. 2B). In the maxillary setting, the eggshell was opened using curved curettes and forceps, followed by removal of the egg contents using a 60° curved shaver (RAD60 curved blade, 4 mm; Medtronic) (Fig. 2C). Before the procedures were performed by the residents, they were tested by three of the authors (E.O-N., T.N., T.S.).
To examine the efficacy of our model for training, we recruited five junior residents at the Department of Otolaryngology–Head and Neck Surgery of Kyoto University Hospital (Kyoto, Japan), who had no previous experience in endoscopic sinus surgery or cadaver dissection.
Training effects were examined using surgical procedures under the orbital setting. The residents performed the procedures five times, and the operating times for the first and last sessions were recorded. The time periods from the start to the first touch of the egg shell, and from the start to completion of the surgical procedure, were statistically analyzed. Differences in the length of time between the first and last session were compared using the paired t test, and statistical significance was determined at P < .05. Self-assessment of surgical skills was carried out by questionnaire (Table I) using a five-point scale (1 = unable, 2 = difficult, 3 = possible with a supervisor, 4 = possible, and 5 = easy). The median scores for each questionnaire before and after the training were calculated.
Table I. Self-Assessment Questionnaires
Stable visualization of surgical fields
Knowledge of surgical instruments
Handling of instruments
Avoiding excessive resection of nasal mucosa
Shortening operation time
Observation of the maxillary sinus by angled endoscopes
Dissection of nasal septum mucosa
Resection of uncinate process
Removal of polyps in the maxillary sinus
Surgical-procedure testing determined that eggshell resection involving inaccurate drilling or peeling with curettes could rupture the eggshell membrane. Accurate removal of the egg shell required the delicate handling of surgical instruments with stable visualization through an angled endoscope. Rupture of the eggshell membrane led to protrusion of the egg white, which mimicked extrusion of the orbital fat caused by injury to the periorbit (Fig. 2D). In the maxillary setting after resection of the egg shell using curved curettes and forceps, the egg contents were removed with the curved blade of a debrider system, which required appropriate visualization of the maxillary sinus through an angled endoscope. Suction of eggshell pieces caused the debrider to become blocked, which hampered the smooth removal of the egg contents. We established that the orbital setting was most useful to evaluate training effects in junior residents, because it required more precise and stable procedures than the maxillary setting.
In junior resident training, we observed a trend that the time required for surgical procedure completion in the orbit setting was reduced after five sessions (Fig. 3A); however, the time difference between the first and last session was not statistically significant (P = 0.078). The mean ± standard deviation (SD) duration for the first session was 840 ± 397 seconds, whereas that for the last session was reduced to 525 ± 64 seconds. Individual differences in duration were reduced after five sessions, which might reflect training effects. The mean ± SD time period until the first touch of the egg shell for the first session was 33 ± 15 seconds, whereas that for the last session was significantly reduced to 13 ± 3 seconds (P = 0.015; Fig. 3B), indicating that residents improved their skills in visualizing surgical fields using an angled endoscope through training.
Self-assessments of surgical skills by questionnaire were performed to examine the training effects on junior residents. Questionnaire scores were found to increase with regard to stable visualization of surgical fields, handling of instruments, avoiding excessive resection of nasal mucosa, shortening of operation time, observation of the maxillary sinus by angled endoscopes, and removal of polyps in the maxillary sinus. By contrast, no improvement in scores was observed for knowledge of surgical instruments, dissection of nasal septum mucosa, resection of the uncinate process, or orbital decompression (Fig. 4).
It is important for junior residents to acquire basic techniques for endoscopic endonasal surgery using appropriate training systems. In the field of neurosurgery, a training model for pituitary surgery using a plastic skull model and chicken eggs was previously reported,6 which allowed residents to practice hypophysectomy at a low cost. This prompted us to investigate whether eggs could be utilized in training for endoscopic sinus surgery.
The present findings indicate that a training model based on quail eggs could be beneficial for the improvement of endoscopic endonasal surgical skills in junior residents. Self-assessment suggested that junior residents had slightly increased confidence in their own surgical skills after five sessions. However, there was no improvement in the self-assessed score for orbital decompression after training, despite the procedures being designed for such techniques. This might have been because the difficulty of orbital decompression was just one of several skills mentioned in the questionnaire; rewording the questions could potentially overcome this discrepancy.
Considering practice of surgical procedures under angled endoscopic view, quail eggs are placed in the orbit or maxillary sinus. The orbital decompression, which is not frequently performed, requires delicate drilling and curetting. We therefore considered that a training model for the orbital decompression might contribute to improvement of surgical skills in endoscopic endonasal surgery. The complete removal of lesions at the lateral or frontal wall of the maxillary sinus is included in difficult procedures in endoscopic sinus surgery for residents, which requires adequate use of angled endoscopes and curved instruments. The removal of egg contents that are set in the maxillary sinus could be a practice for such surgical skills. Actually, the removal of egg contents was previously used for evaluation of the function of several debrider systems.7 Finally, additional programs are necessary for learning the surgical anatomy, although our model might help residents improve their surgical skills.
We have established a surgical training model for endoscopic endonasal surgery using quail eggs, which can provide low-cost training to institutes worldwide.