Extending the application of virtual reality simulation in temporal bone anatomy and advanced surgical training

Abstract

Cochlear implant surgery has a strong foundation in the treatment of profound hearing loss. In the last decade, there have been marked developments in technology which have enabled the expansion of eligibility criteria. Cochlear implantation is now offered to patients with residual low-frequency hearing or those with unilateral or asymmetrical hearing loss. It is evidenced that to optimise hearing outcomes for patients with residual hearing, it is necessary to reduce the trauma during the insertion of the cochlear implant, in particular by precise surgical technique.

Current temporal bone surgery training, including cochlear implant surgery, is based on an apprenticeship model, where registrars observe and practice with consultant supervision. Prior to performing surgery on a patient, it is common practice to perform cadaveric temporal bone dissections. In addition to concern regarding decreasing availability of cadaveric temporal bones are financial constraints and regulations that reduce teaching time available in surgery. The generally low caseload, specifically relevant to cochlear implant surgery, minimises the opportunities for apprenticeship training. As such, this traditional model of training is not maintainable.

Similar pressures face the training of anatomy of the temporal bone to medical students and junior doctors. While otologic presentations make a sizable proportion of presentations to emergency departments and general practice, due to the reduction in medical school training time, education in otology is in decline.

Virtual reality (VR) surgical training is an attractive adjunct to the current training pathway as it provides a cost effective platform where risk-free, repetitive practice is readily available. VR also has several unique benefits. By presenting automated feedback, VR training allows for self-directed learning. In addition, automated assessment tools have been validated to objectively measure performance. While the effectiveness of VR simulation for mastoidectomy training has previously been well established, to the author’s knowledge there have been no VR simulators adapted to teach more complex temporal bone surgery such as cochlear implant surgery, or clinically oriented temporal bone anatomy.

The aims of this thesis were: 1) to determine the viability of expanding the role of VR simulation in otology, including anatomy education and advanced temporal bone surgery and 2) to explore patient factors that relate to surgical technique in cochlear implant surgery. To these ends, several investigations were performed. Firstly, a randomised control trial was conducted to determine whether a clinically oriented VR temporal bone simulator module improved anatomy knowledge of medical students and junior doctors. Participants were randomly allocated to three groups of differing display modality: stereoscopic 3D, monoscopic 3D and 2D presentations. The participants completed a pre-tutorial questionnaire before working through the self-guided tutorial. The module was followed by a post-tutorial questionnaire and a retention questionnaire at 6 weeks. The questionnaires assessed factual anatomic knowledge, spatial relationships and clinically oriented knowledge as well as student’s perception of the display modality. It was observed that the module was effective in imparting factual knowledge in all modalities. The students exposed to the 3D technologies performed better in the spatial relationship and clinically oriented questions. The Stereoscopic 3D modality showed particular benefit for ease of use.

Secondly, a training module specifically designed for the surgical approach to cochlear implant surgery was assessed with a prospective pre- and post-study of ENT registrars. All participants were exposed to the same training module that included concurrent and terminal feedback on temporal bones with a range of common anatomical variations. The participants’ performances were compared before and after the training. The assessment temporal bones used at the end of training consisted of a mirror image of the one used prior to training and one novel temporal bone. It was found that there was a significant improvement with a large effect size after training for both the previously encountered temporal bone and the novel temporal bone.

Thirdly, a conceptual anatomical study was performed using the University of Melbourne temporal bone simulator data. The study explored patient factors that affect the surgical technique used in approaching cochlear implantation. In particular, the relationship of surgical preparation of the facial recess to the acceptable electrode trajectories into the cochlea. It was found that acceptable trajectories through a round window membrane approach most likely originated superiorly in the facial recess, adjacent to the facial nerve. Conversely, acceptable trajectories through a cochleostomy approach most likely originated inferiorly in the facial recess, adjacent to the junction of the facial nerve and chorda tympani. Furthermore, the skeletonisation of the facial recess was found to be critical in the preparation of the temporal bone for a cochleostomy approach. The results presented throughout the thesis will help guide medical educators in the areas of otology and cochlear implant surgery. These results suggest the viability of an expanded application of virtual reality temporal bone simulations to use in anatomy education and advanced temporal bone surgery training.