Generating Operative Workflows for Vestibular Schwannoma Resection: A Two-Stage Delphi's Consensus in Collaboration with the British Skull Base Society. Part 2: The Translabyrinthine Approach

Objective  An operative workflow systematically compartmentalizes operations into hierarchal components of phases, steps, instrument, technique errors, and event errors. Operative workflow provides a foundation for education, training, and understanding of surgical variation. In this Part 2, we present a codified operative workflow for the translabyrinthine approach to vestibular schwannoma resection. Methods  A mixed-method consensus process of literature review, small-group Delphi's consensus, followed by a national Delphi's consensus was performed in collaboration with British Skull Base Society (BSBS). Each Delphi's round was repeated until data saturation and over 90% consensus was reached. Results  Seventeen consultant skull base surgeons (nine neurosurgeons and eight ENT [ear, nose, and throat]) with median of 13.9 years of experience (interquartile range: 18.1 years) of independent practice participated. There was a 100% response rate across both the Delphi rounds. The translabyrinthine approach had the following five phases and 57 unique steps: Phase 1, approach and exposure; Phase 2, mastoidectomy; Phase 3, internal auditory canal and dural opening; Phase 4, tumor debulking and excision; and Phase 5, closure. Conclusion  We present Part 2 of a national, multicenter, consensus-derived, codified operative workflow for the translabyrinthine approach to vestibular schwannomas. The five phases contain the operative, steps, instruments, technique errors, and event errors. The codified translabyrinthine approach presented in this manuscript can serve as foundational research for future work, such as the application of artificial intelligence to vestibular schwannoma resection and comparative surgical research.


Introduction
In Part 1 of this series we generated, through expert Delphi's consensus, a codified operative workflow for the retrosigmoid approach to vestibular schwannoma 1 .An operative workflow systematically deconstruct complex procedures into defined tasks and errors. 2,3The surgical procedure is broken down into phases which contain a series of steps, generating the operative workflow. 35][6][7] Practical benefits of consensus-driven operative workflows include: (1) workflow analysis; (2) training; (3) creation of high-fidelity simulation models; (4) objective assessment of procedure-specific surgical skills; (5) evaluation of novel technologies or techniques; (6) operating room efficiency improvements. 3,5,8,9][12] In Part 2, we herein present an operative workflow for translabyrinthine approach for vestibular schwannoma, through an expert consensus process in collaboration with the British Skull Base Society (BSBS).This operative workflow aimed to digitize the approaches and provide foundational research in which to build, for example, the application of artificial intelligence to vestibular schwannoma resection.

Methods Overview
The methodology was drawn from previous work from our group and was completed in parallel to the retrosigmoid operative workflow generation 1,6 .This process aimed to generate a comprehensive workflow framework which captured how each approach could reasonably be performed.We did not aim to dictate how an operation should be done.The beginning of the operation was taken as the first incision, adhering to the American College of Surgeon's definition of surgery, "structurally altering the human body by the incision or destruction of tissues." 13Therefore, variation relating to position of the patient and incision analysis was not within the scope of this work, although the authors recognize that positioning plays a critical role for any given procedure.The components for workflow analysis and associated definitions are listed in ►Table 1. Expert input will be derived through an iterative, mixed-methods consensus process (►Fig.1).

Delphi's Round 1
The initial literature-based operative workflow was reviewed by a group of five consultant skull base surgeons including neurosurgery and ear nose and throat (ENT), based at the National Hospital for Neurology and Neurosurgery, London, United Kingdom.Each consultant surgeon reviewed the operative workflow individually, via computerized document with the definitions of phases, steps, instruments, technical errors, and adverse events as above (►Table 1).Each expert was asked a series of questions via e-mail, seeking to assess the completeness and accuracy of the workflow (►Supplementary Material A, available in the online version). 7Any additional suggestions were reviewed and added to the workflow matrix if in scope and not duplicate.According to the Delphi technique, circulation and iterative revision of the workflow was repeated until data saturation was achieved, that is, all experts were satisfied that the operative workflow was complete and accurate. 7sults Seventeen consultant skull base surgeons (nine neurosurgeons and eight ENT [ear, nose, and throat]) with median of 13.9 years of experience (interquartile range: 18.1 years) of independent practice participated.There was a 100% response rate across both the Delphi rounds.The translabyrinthine approach had the following five phases and 57 unique steps: Phase 1, approach and exposure; Phase 2, mastoidectomy; Phase 3, internal auditory canal and dural opening; Phase 4, tumor debulking and excision; and Phase 5, closure.Conclusion We present Part 2 of a national, multicenter, consensus-derived, codified operative workflow for the translabyrinthine approach to vestibular schwannomas.The five phases contain the operative, steps, instruments, technique errors, and event errors.The codified translabyrinthine approach presented in this manuscript can serve as foundational research for future work, such as the application of artificial intelligence to vestibular schwannoma resection and comparative surgical research.

Delphi's Round 2
The refined workflow was circulated nationally with skull base surgeons (neurosurgeons and ENT) who were members of the BSBS, 19 the United Kingdom and Ireland's society primarily focused on skull base pathology.The entirety of the BSBS was invited to participate via e-mail.All contributing authors are specialist lateral skull base surgeons with an independent surgical practice in vestibular schwannoma surgery who are members of the BSBS (either neurosurgery or ENT).Consultant surgeon members from the BSBS were asked to assess the workflow and suggest any amendments to encompass possible variation in practice and technique.
Additional suggestions were reviewed and added to the workflow if (1) in scope and (2) not duplicate. 7Round 2 was completed until all surgeons agreed that the workflow captured the operative practice and that there were no additional suggestions for the workflow from the participant group.Both the retrosigmoid and translabyrinthine approaches were completed in parallel: surgeons within the BSBS were given the opportunity to contribute to either approach depending on their personal clinical practice and expertise.Experience for all authors was calculated from the date they were added to the General Medical Council's Specialist Register, a list of doctors who have completed their postgraduate training and eligible to work as a consultant. 20

Administration
Invitations to participate in the Delphi process were sent via direct e-mail only.Workflow documents were presented using Microsoft Word (Version 16.4,Microsoft, United States) in both rounds and supported by Google Forms in Round 2 (Google LLC, United States).

Data Collection and Analysis
Participant demographics collected included surgical specialty and unit.The collected data regarding the surgical workflow were quantitative (whether participants agree that it is complete and accurate) and qualitative (additional suggestions or comments). 7Summary statistics (frequencies) were generated for participants demographics.Content analysis was used to analyze free-text responses: to remove out-of-scope suggestions, group similar suggestions together, and compare them to existing data points in the workflow.Data analysis and workflow updates were performed in duplicate by two independent analyzers (H.L.H. and P.G.).

Ethics
This study is independent of national health services and does not require ethical approval interrogated via online Health Research Authority decision tool (►Supplementary Material B, available in the online version). 7,21ble 1 Definition of operative workflow terminology per domain

Domain Definition Example
Phase A major event occurring during a surgical procedure, composed of several steps 7 Approach and exposure, encompassing the beginning of surgery until tumor debulking Step A sequence of activities used to achieve a surgical objective 24 Seal mastoid air cells Instrument A tool or device for performing specific actions (such as cutting, dissecting, grasping, holding, retracting, or suturing) during a surgical step

Bone wax
Technical error Lapses in operative technique while performing a surgical step 25 Failure to seal mastoid air cells

Adverse event
An intraoperative event which is a result of a technical error and has the potential to lead to a postoperative adverse outcome/complication 25 Cerebrospinal fluid rhinorrhea

Participants
The Delphi Round 1 was completed by a group of five consultant skull base surgeons.Two neurosurgeons at the National Hospital for Neurology and Neurosurgery, London, United Kingdom, and three ENT surgeons at the Royal National Throat, Nose and Ear Hospital, London, United Kingdom.Cumulatively, they had a median of 12.3 years and interquartile range (IQR) of 16.0 years of experience (IQR: 1 9.6 years; IQR: 25.5 years).The Delphi Round 1 was repeated four times during a 4-month period (October 2020-February 2021) until saturation.The Delphi Round 2 was completed by nine neurosurgeons and eight ENT surgeons based at 10 centers across the United Kingdom.All contributing authors are specialist lateral skull base surgeons with an independent surgical practice in vestibular schwannoma surgery who are members of the BSBS (either neurosurgery or ENT).Cumulatively, they had a median of 13.9 years and IQR of 18.1 years of experience (IQR: 1 7.5 years; IQR: 3 25.5 years).Round 2 was repeated twice during a 3-month period (May-July 2021) until saturation.There was a 100% response rate and no attrition across both the Delphi Rounds.

Translabyrinthine Approach
Five distinct phases were delineated as follows: (1) approach and exposure, (2) mastoidectomy, (3) internal auditory canal and dural opening, (4) tumor debulking and excision, and ( 5) closure.As with the retrosigmoid approach, the preoperative set-up and postoperative protocols were recognized as important, but not within the scope of this study.

Phase 1: Approach and Exposure
This phase consisted of four steps, beginning with the postaural curvilinear incision to expose the mastoid bone (►Table 2).

Phase 2: Mastoidectomy
This phase consisted of 13 steps, starting with an extended cortical mastoidectomy to give lateral petrous dissection, systematic three canal osseous labyrinthectomy, and completion of the labyrinthectomy (►Table 3).

Phase 3: Internal Auditory Canal and Dural Opening
This phase consisted of 13 steps, from developing the inferior dissection by drilling out the retrofacial air cells to completion of dural dissection superiorly and inferiorly (►Table 4).The petrosal vein may be encountered superiorly.Consensus dictated that the petrosal vein may be coagulated and divided only if absolutely necessary to reduce the risk of venous infarct.

Phase 4: Tumor Debulking and Excision
This phase consisted of 18 steps and begins with attempted identification of the facial nerve (►Table 5).Similar to the retrosigmoid approach, this phase describes the stepwise debulking of the tumor at the superior and inferior poles, with lateral-medial and medial-lateral dissection, and culminating in stepwise rolling and debulking of the tumor.Surgeon preference, intraoperative findings, and tumor characteristics define the exact order of the constituent steps within this phase.Further, depending on the patient's clinical history and presentation, a cochlear implant may be considered.

Phase 5: Closure
This phase consisted of 11 steps (►Table 6), encompassing hemostasis, packing of the Eustachian tube and middle ear, and multilayer closure of the wound.There was variability in the substance to pack the Eustachian tube with (bone wax, muscle, periosteum, and dural substitute) and the location for harvesting a tissue graft (abdomen, leg, and fascia lata).

Discussion Principal Findings
We present Part 2 of a series that generated a consensusderived codified operative workflow for the translabyrinthine approach to vestibular schwannoma.Each workflow considers the phases, steps, technique errors, and event errors of the operation.The operative workflow was  The translabyrinthine approach operative workflow comprises the following five distinct phases with a total of 59 individual steps: (1) approach and exposure, (2) mastoidectomy, (3) internal auditory canal and dural opening, (4) tumor debulking and excision, and (5) closure.The translabyrinthine approach contains two more phases and 19 more steps than the retrosigmoid approach. 1he codified operative workflow for the translabyrinthine approach provides an illustrative example of how surgical procedures can be deconstructed.The presented workflow is foundational research for future work exploring the application of artificial intelligence to surgery or comparative

Operative Workflows to Facilitate Comparative Surgical Research
There is little high-quality evidence comparing both surgical and nonsurgical factors at reducing morbidity in vestibular schwannoma surgery.5][26] Despite advances in practice and improving mortality rates, the morbidity remains high for these common tumors 27 which can significantly impair a patient's quality of life.For a complex procedure, practiced by experienced surgeons, any small incremental improvement in technique may result in improved outcomes.As such, the workflows in the present study provide an objective consensus in the current variability within practice and a foundation in which to develop further research questions.For example, for each variation in technique outlined within our workflows, we could further explore how many surgeons perform which technique and correlate this with outcomes.This could drive a national or international audit process to provide guidance on how the operation should be performed in the future.The operative workflow could also assist in the generation of performance metrics for each procedure.

Computer Vision and Operative Workflows
The parcellation of operative videos can be achieved through computer vision, an artificial intelligence-driven algorithm that automatically detects the phase and step of an operation. 289][30] The effectiveness of such automation is dependent on the generation of a codified, comprehensive operative workflow to train deep neural networks to recognize the phases, steps, instruments, and errors of an operation. 7Our group has previously demonstrated that a machine learning algorithm can accurately and autonomously identify the various phases and steps of an endoscopic transsphenoidal resection of pituitary adenomas. 7If a machine learning algorithm can identify the correct phase and step of a vestibular schwannoma resection and compare multiple operative videos against outcomes, it might identify subtleties within technique that could improve functional outcomes or reduce surgical complications.It might also permit the ability to separate between essential and nonessential steps or highlight specific steps that are with high risk during an operation.It is unclear presently if machine learning will be able to identify the phases and steps of a vestibular schwannoma resection accurately and autonomously, due to heterogeneity between technique and order of phases.We plan to use this workflow to test this hypothesis in future work.

Strengths and Limitations
This is the first expert, consensus-derived operative workflow for the translabyrinthine approach.Our methodology follows precedence within in the literature.Further, both operative workflows are presented with concordant nomenclature, and share homogenous descriptions of the steps, instruments, and errors if appropriate.This will allow greater transparency and comparison between approaches, and indeed further scope to develop the workflows in the future.However, our methodology did not deconstruct which phase and steps were performed by neurosurgeons and ENTsurgeons, nor did we include the use of endoscopy, for example, endoscopic exploration of the internal acoustic canal to identify potential mastoid cells opening before closure.This is likely different in each center based on local expertise.This will require consideration when trying to evaluate outcomes in future work.

Conclusion
We present Part 2 of a national, multicenter, consensusderived codified operative workflow for the translabyrinthine approach to vestibular schwannomas.The five phases contain the operative steps, instruments, technique errors, and event errors.The codified translabyrinthine approach presented in this manuscript can serve as foundational research for future work, such as the application of artificial intelligence to vestibular schwannoma resection and comparative surgical research.

Previous Presentations
This work has not been presented, either partly or wholly.

Fig. 1
Fig.1Schematic diagram of Delphi's process, highlighting the generation of a surgical workflow through iterative consensus from British Skull Base Society expert members.1 Adapted from Marcus et al.7

Table 2
Translabyrinthine operative workflow phase 1: approach and exposure

Table 4
Translabyrinthine operative workflow phase 3: internal auditory canal and dural opening

Table 5
Translabyrinthine operative workflow phase 4: tumor debulking and excision Journal of Neurological Surgery-Part B Vol. 84 No. B5/2023 © 2022.The Author(s).Vestibular Schwannoma Operative Workflow Horsfall et al. 439 achieved through national collaboration with the BSBS following an open invitation to all members to participate.This comprised 17 independently practicing neurosurgeons and ENT surgeons from 11 centers across the United Kingdom.