Ovine ear model for fully endoscopic stapedectomy training

Training in Endoscopic Ear Surgery: A Scoping Review

OBJECTIVE

Despite the increasing popularity of Endoscopic Ear Surgery (EES), there is a lack of evidence to guide trainees as they introduce EES into practice. This review aims to evaluate training in EES including the optimal introductory procedures, methods of training, the learning curve, and the determination of competency in EES. In addition, this review seeks to identify any areas falling within these themes requiring further clarification.

DATA SOURCES

A database search of Pubmed, Embase and the Cochrane Library was conducted in June 2022. Original articles, systematic reviews, and meta-analyses reporting on training in EES, introduction into practice, learning curves, and competency assessment were included.

REVIEW METHODS

A scoping review was carried out in accordance with the Joanna Briggs Institute guidelines and reported according to PRISMA guidelines for scoping reviews. A qualitative assessment of results grouped thematically was performed.

RESULTS

Twenty-eight studies met the inclusion criteria, with 24 rating as "fair" or "good" on quality assessment. Surgical simulation was the most frequently described method of training as utilized in 11 studies. The most suggested introductory procedure was tympanoplasty which was advocated for in five studies. Heterogeneity existed in the outcomes and methodologies used to measure EES learning curves, with an overreliance on surgical times. No robust definition of competency in EES procedures exists at present.

CONCLUSIONS

Surgical simulation appears to be a beneficial training methodology for EES. However, there is a marked lack of objective data to describe the optimal introductory procedures or assessment of competency in EES. Laryngoscope, 133:3269-3278, 2023.

Sheep as a Large-Animal Model for Otology Research: Temporal Bone Extraction and Transmastoid Facial Recess Surgical Approach

PURPOSE

Sheep are used as a large-animal model for otology research and can be used to study implantable hearing devices. However, a method for temporal bone extraction in sheep, which enables various experiments, has not been described, and literature on middle ear access is limited. We describe a method for temporal bone extraction and an extended facial recess surgical approach to the middle ear in sheep.

METHODS

Ten temporal bones from five Hampshire sheep head cadavers were extracted using an oscillating saw. After craniotomy and removal of the brain, a coronal cut was made at the posterior aspect of the orbit followed by a midsagittal cut of the occipital bone and disarticulation of the atlanto-occipital joint. Temporal bones were surgically prepared with an extended facial recess approach. Micro-CT scans of each temporal bone were obtained, and anatomic dimensions were measured.

RESULTS

Temporal bone extraction was successful in 10/10 temporal bones. Extended facial recess approach exposed the malleus, incus, stapes, and round window while preserving the facial nerve, with the following surgical considerations: minimally pneumatized mastoid; tegmen (superior limit of mastoid cavity) is low-lying and sits below temporal artery; chorda tympani sacrificed to optimize middle ear exposure; incus buttress does not obscure view of middle ear. Distance between the superior aspect of external auditory canal and tegmen was 2.7 (SD 0.9) mm.

CONCLUSION

We identified anatomic landmarks for temporal bone extraction and describe an extended facial recess approach in sheep that exposes the ossicles and round window. This approach is feasible for studying implantable hearing devices.

Endoscopic vs. microscopic stapes surgery: An anatomical feasibility study

Objectives

To investigate the feasibility of the endoscopic approach vs. microscopic approach during stapes surgery, focusing on the visualization of the important anatomical structures of the middle ear, the volume of the resected scutum and chorda tympani (CT) injury.

Methods

Fresh frozen human cadaveric heads underwent two stapes surgeries using an operating microscope on one ear and an endoscope on the other ear. The surgeon documented the visualization of critical landmarks, as well as exposure and injury of the CT. The volume of resected scutum was evaluated using cone beam computed tomography scanning and three-dimensional imaging.

Results

We performed endoscopic stapes surgery in 10 ears and microscopic stapes surgery in 11 ears. A stapes prosthesis was placed in all ears. The volume of bony scutum resection was significantly lower in the endoscopic group (median = 2.20 mm³, IQR = 4.17) than in the microscopic group (median 13.25 mm³, IQR = 8.71). No scutum was removed in two endoscopic ears, while scutum was removed in all microscopic ears. The endoscopic and microscopic group had similar CT injury.

Conclusions

This study showed that the endoscopic stapes surgery procedure is feasible and might be less invasive than microscopic stapes surgery. Future clinical prospective and functional studies will be needed to support our findings.

Perspectives and early experience on endoscopic stapedotomy from a group of "traditional school" otologists

Background: This paper evaluates endoscopic stapedotomy from the perspectives of a group of 3 surgeons, each of whose experience in endoscopic and microscopic stapedotomy is 3 years and more than 12 years, respectively.Methods: Thirty-four patients clinically diagnosed with stapedial otosclerosis were alternately assigned for unilateral, microscope- and endoscope-assisted stapedotomy following the selection criteria given. Results were evaluated with predetermined epidemiologic, preoperative, perioperative, and postoperative outcome parameters.Results: The microscope group had 12 ears with otosclerosis and the endoscope-assisted group 14. Ears found to have conditions other than otosclerosis at surgery, and patients lost to follow-up were excluded. Apart from the operative time, the difference in the results of none of the parameters was statistically significant in the two groups. The average operative times for microscope- and endoscope-assisted stapedotomy were 63 minutes and 86.5 minutes, respectively, the difference being statistically significant (P < .001).Conclusions: From the perspectives of otologists in differential positions in the learning curve for microscope- and endoscope-assisted stapedotomy, there were no statistically significant differences between the two procedures in the execution of the steps to achieve "adequate surgical exposure" and in postoperative outcomes, except for operative time.

Exclusive Endoscopic Laser-Stapedotomy: Feasibility of an Ovine Training Model

OBJECTIVE

Stapedotomy is an effective treatment for conductive hearing loss associated with otosclerosis. However, the procedure, especially using the endoscopic technique requires extensive training and experience for optimal results. Due to limited training options in endoscopic stapes surgery, we aim to develop an ovine stapedotomy model and assess its feasibility for surgeons at different training levels.

METHODS

A fully endoscopic ovine laser-stapedotomy model was developed and described. During repetitive dissections, surgical time required for the different steps to assess the training curve and associated intraoperative complications were recorded in three surgeons of different training level. Additionally, subjective feedback was assessed.

RESULTS

Successful endoscopic laser-stapedotomy was performed in 25 cases in the ovine model. Assessment of surgical time revealed a stable curve for the experienced surgeon (mean 15:01 min) for the whole training with no intraoperative complications. The fellow showed a gradual reduction of surgical time from 27:21 (first five cases) to 24:10 minutes (last five cases) and the resident a reduction from 42:38 to 21:08 minutes respectively. The assessed learning curve for the trainees revealed a significant association between the operative time and observed intraoperative complications.

DISCUSSION

In this study, an ex-vivo model for exclusively endoscopic laser-stapedotomy was developed and tested for feasibility. We suggest the ovine model as a cost-effective, easily available, and realistic training model for future otologic surgeons. The surgeons were able to improve their performance with satisfactory results despite the small number of cases.

Investigating the learning curve in endoscopic compared to microscopic myringotomy and ventilation tube insertion

OBJECTIVE

Rate of learning is often cited as a deterrent in the use of endoscopic ear surgery. This study investigated the learning curves of novice surgeons performing simulated ear surgery using either an endoscope or a microscope.

METHODS

A prospective multi-site clinical research study was conducted. Seventy-two medical students were randomly allocated to the endoscope or microscope group, and performed 10 myringotomy and ventilation tube insertions. Trial times were used to produce learning curves. From these, slope (learning rate) and asymptote (optimal proficiency) were ascertained.

RESULTS

There was no significant difference between the learning curves (p = 0.41). The learning rate value was 68.62 for the microscope group and 78.71 for the endoscope group. The optimal proficiency (seconds) was 32.83 for the microscope group and 27.87 for the endoscope group.

CONCLUSION

The absence of a significant difference shows that the learning rates of each technique are statistically indistinguishable. This suggests that surgeons are not justified when citing 'steep learning curve' in arguments against the use of endoscopes in middle-ear surgery.

Training model for salvage procedures in endoscopic stapes surgery

PURPOSE

The learning curve in endoscopic stapes surgery, is flat and long. There is limited space during training for advanced and salvage procedures, which could be necessary in unexpected intraoperative scenarios. The aim of the present study is to develop an ex-vivo animal model for training in salvage and advanced procedures in endoscopic stapes surgery METHODS: After defining the difficult intraoperative scenarios requiring a salvage procedure during stapes surgery, we used the ovine model to create those intraoperative situations. After assessing the suitability of the model for that purpose, it was validated by subjective feedback rating (scale from 1 to 10) and by comparing the relevant anatomical structures for stapes surgery with the human. Finally, an optimal sequence of surgical steps was defined.

RESULTS

8 Fresh frozen lamb heads (16 ears) were studied. The selected intraoperative scenarios were: floating footplate, footplate fracture, luxation of the incus or necrosis of the long process, overhanging facial nerve, obliterative otosclerosis. The simulation resulted feasible and close to real. The mean overall rating for surgical scenarios ranged from 7.5 to 8.8 for residents and was consistent with the rating of senior surgeons, ranging from 7.67 and 9.0. Anatomical measures of the oval window area resulted similar between the ovine and the human.

CONCLUSION

The ex-vivo ovine model is a suitable model for training in salvage and advanced procedures in exclusively endoscopic stapes surgery. The model can be used both for the training and maintenance of the acquired advanced skills in endoscopic stapes surgery.

Feasibility of ovine and synthetic temporal bone models for simulation training in endoscopic ear surgery

Objective

Comparing the feasibility of ovine and synthetic temporal bones for simulating endoscopic ear surgery against the ‘gold standard’ of human cadaveric tissue.

Methods

A total of 10 candidates (5 trainees and 5 experts) performed endoscopic tympanoplasty on 3 models: Pettigrew temporal bones, ovine temporal bones and cadaveric temporal bones. Candidates completed a questionnaire assessing the face validity, global content validity and task-specific content validity of each model.

Results

Regarding ovine temporal bone validity, the median values were 4 (interquartile range = 4–4) for face validity, 4 (interquartile range = 4–4) for global content validity and 4 (interquartile range = 4–4) for task-specific content validity. For the Pettigrew temporal bone, the median values were 3.5 (interquartile range = 2.25–4) for face validity, 3 (interquartile range = 2.75–3) for global content validity and 3 (interquartile range = 2.5–3) for task-specific content validity. The ovine temporal bone was considered significantly superior to the Pettigrew temporal bone for the majority of validity categories assessed.

Conclusion

Tympanoplasty is feasible in both the ovine temporal bone and the Pettigrew temporal bone. However, the ovine model was a significantly more realistic simulation tool.

Middle ear structure and transcanal approach appropriate for middle ear surgery in rabbits

The current study aimed to investigate the middle ear structure and surgical approach appropriate for middle ear surgery in rabbits. A total of eight healthy New Zealand rabbits (16 ears) were dissected under a surgical microscope. The dimensions of the auditory canal and the middle ear were measured. In the present study, the transcanal surgical approach to the middle ear in rabbits was performed without complications, the anatomical landmarks in the auricle and the external auditory canal were apparent, no large vessels were present in the surgical zone and the bleeding was minor. Furthermore, the surgical procedure did not require removal of large bone sections of the external auditory canal. Additionally, the constitution of the ossicular chain, the leverage ratio of the ossicular chain and the constitution of ligaments and muscles in rabbits were similar to humans. Otherwise, the facial nerve canal in rabbits was more prominent compared with humans and the mobility of pars flaccida in rabbits was more noticeable compared with humans. The results of the current study indicate that the transcanal surgical approach was suitable to study the middle ear in rabbits. Furthermore, the rabbit middle ear may be used as a model for ossicular surgery and facial nerve research.

Improvement of hearing results by bone cement fixation in endoscopic stapedotomy

Objective

This study aimed to compare the hearing results of two different stapedotomy techniques used in the clinic at different time points.

Methods

An endoscopic surgery group (group 1; n = 37) were compared retrospectively with a microscopic surgery group (group 2; n = 57). A small fenestra and Teflon piston technique were used in all patients. Bone cement was used for fixation between the prosthesis and incus in the endoscopic group only. Bone conduction threshold and air–bone gap were used as the comparison parameters.

Results

The pre-operative air–bone gap was 31.26 dB in group 1 and 32.51 dB in group 2. The post-operative air–bone gap was 8.93 dB in group 1 and 14.28 dB in group 2. There was a significant difference between the groups in post-operative air–bone gaps. There was no significant difference between the groups in post-operative bone conduction thresholds.

Conclusion

The endoscopic technique using bone cement fixation was better for closing the air–bone gap.

Evaluation of resident's training for endoscopic sinus surgery using a sheep's head

Training in functional endoscopic sinus surgery (FESS) is an essential part of each ENT resident and it takes place on a very fragile area. This study focus on showing the learning curve of FESS, using an anatomical model such as the sheep's head. Four residents in our centre performed dissections. Each of these residents operated eight sheep's head. They performed an endoscopic septoplasty followed by maxillary antrostomy, total ethmoidectomy and frontal sinusotomy on every head. A staff member guided all procedures and checked for the appropriate dissection and complications occurred. Analysis was made upon the residents' performance of their first four septoplasties and eight nasal sides against their subsequent performance of the same. Final procedures presented better outcomes than the initial ones on every step of them. Results were measured by means of decrease of time (P < 0.0001) and complications, showing no major complications on the latest ones. Sheep's head is a suitable substitute for the cadaveric human head, to obtain the surgical skills needed for FESS procedures. Sheep's nasal cavity allows gaining dexterity and it is an easy model to obtain.