3D Exoscopic Surgery (3Des) for Transoral Oropharyngectomy

Transoral laser exoscopic surgery of the larynx: state of the art and comparison with traditional transoral laser microsurgery

Objective

To evaluate the efficacy of transoral laser exoscopic surgery (TOLES) in a unicentric series of patients affected by benign and malignant glottic and supraglottic lesions, and compare outcomes with those of transoral laser microsurgery (TOLMS).

Methods

To demonstrate the non-inferiority of TOLES in terms of operative time, margin status and complication rates, we compared outcomes of 93 patients treated by TOLES between July 2021 and July 2023 with those of a match-paired group of 107 historical patients treated by TOLMS. To perform a multiparametric ergonomic evaluation of TOLES vs TOLMS, we used observational methods for biomechanical overload risk assessment and wearable technologies comparing 15 procedures with TOLES vs a paired match of 13 surgeries performed with TOLMS by the same surgeon.

Results

No significant differences were found in terms of surgical duration, positive margins, or complications between TOLES and TOLMS. Ergonomics assessment by inertial measurement units and electromyographic surface electrodes demonstrated a reduced biomechanical overload with TOLES compared to TOLMS.

Conclusions

The many advantages of TOLES, such as its superior didactic value, better digital control of light even through small-bored laryngoscopes, improved binocular vision, and increase in surgical performance by 3 or 4-hand techniques, are difficult to be quantified. In contrast, its non-inferiority in terms of oncological results and better ergonomics compared to TOLMS are demonstrated herein.

Craniovertebral Junction Surgical Approaches: State of Art

Surgical approaches directed toward craniovertebral junction (CVJ) can be addressed to the ventral, dorsal, and lateral aspects through a variety of 360° surgical corridors Herein, we report features, advantages, and limits of the updated technical support in CVJ surgery in clinical setting and dissection laboratories enriched by our preliminary surgical results of the simultaneous application of O-arm intraoperative neuronavigation and imaging system along with the 3D-4K EX in TOA for the treatment of CVJ pathologies.In the past 4 years, eight patients harboring CVJ compressive pathologies underwent one-step combined anterior neurosurgical decompression and posterior instrumentation and fusion technique with the aid of exoscope and O-arm. In our equipped Cranio-Vertebral Junction Laboratory, we use fresh cadavers (and injected "head and neck" specimens) whose policy, protocols, and logistics have already been elucidated in previous works. Five fresh-frozen adult specimens were dissected adopting an FLA. In these specimens, a TOA was also performed, as well as a neuronavigation-assisted comparison between transoral and transnasal explorable distances.A complete decompression along with stable instrumentation and fusion of the CVJ was accomplished in all the cases at the maximum follow-up (mean: 25.3 months). In two cases, the O-arm navigation allowed the identification of residual compression that was not clearly visible using the microscope alone. In four cases, it was not possible to navigate C1 lateral masses and C2 isthmi due to the angled projection unfitting with the neuronavigation optical system, so misleading the surgeon and strongly suggesting changing surgical strategy intraoperatively. In another case (case 4), it was possible to navigate and perform both C1 lateral masses and C2 isthmi screwing, but the screw placement was suboptimal at the immediate postoperative radiological assessment. In this case, the hardware displacement occurred 2 months later requiring reoperation.

New surgical frontiers for 4K 3D-exoscope in paediatric head and neck surgery

PURPOSE

To define the interest, advantages, and disadvantages of the use of a 3D-exoscope in paediatric ENT surgery.

METHODS

Four surgeons with experience in paediatric surgery completed a questionnaire following each surgery performed under 3D-exoscope to evaluate the contribution of the tool compared to the usual practice (microscope or magnifying loupes). Surgeries were separated into three groups: otology, transoral and cleft palate surgery, and open head and neck surgery.

RESULTS

Between June 2021 and June 2022, 151 paediatric surgeries were included in this study. Among them, 93 (62%) otologic surgeries, 35 (23%) transoral surgeries, and 23 (15%) head and neck surgeries were performed. The median age at surgery was 68 months (interquartile range 19-135 months). For otologic surgeries, the mean scores (/100) for the contribution of the exoscope compared to the microscope were 68.4(± 23.2). For transoral and cleft palate surgery, the mean score (/100) for the contribution of the use of the exoscope compared to the magnifying loupes was 92.9 (± 8.6), whereas for open head and neck surgeries, the mean score (/100) was 89.5 (± 7.2).

CONCLUSION

3D-exoscopy appears to be a relevant tool for paediatric head and neck surgery, applicable in otologic, transoral, and cervical fields. It presents educational and ergonomic advantages and improves surgical team communication.

Improvement of Surgical View and Working Space at the Lower Pole by Three-Dimensional Exoscope-Assisted Coblation Tonsillectomy: A Case Series

Advantages of hot devices for tonsillectomy, represented by coblation, have been highlighted in recent years. During hot technique tonsillectomy it is important to identify and coagulate the vessels of the tonsillar capsule, especially at the lower pole of the tonsil. Hot technique tonsillectomy under microscope or endoscope has therefore been recommended to achieve accurate identification of the microstructure of the surgical field. We have applied ORBEYE, a three-dimensional surgical exoscope system, to coblation tonsillectomy. Advantages of using ORBEYE include high definition and high magnification images, and flexibility of camera position and angle. This means there is an improved surgical view and working space, particularly at the lower pole during performance of coblation tonsillectomy. Here, we demonstrate that ORBEYE can be an effective surgical instrument in coblation tonsillectomy.

The Impact of a Robotic Digital Microscope on the Ergonomics in a Neurosurgical Operating Theatre (A Single-Centre Experience)

Ergonomics is an emerging concept in the neurosurgical operating theatre, where neurosurgeons work under great concentration and frequently neglect their uncomfortable body posture. Work-related musculoskeletal disorders (WMSD) are becoming a widespread burden in the neurosurgical community. WMSD have a negative impact on surgical performance and decrease the surgeons' quality of life. Here we present our single-centre 2-month experience with the Aesculap AEOS® Robotic Digital Microscope (RDM) and prospectively calculate the REBA (Rapid Entire Body Assessment) scores and compare them with similar neurosurgical cases operated with a conventional operative microscope (OPMI).Materials and Methods: For a period of 2 months at the Department of Neurosurgery of the University Hospital Pirogov, Sofia, Bulgaria, 41 consecutive patients were operated on using RDM. The REBA employee assessment worksheets were filled in prospectively to assess the ergonomics of the senior author (N.G.) while using the RDM and the OPMI.Results and Conclusion: The ergonomics during neurosurgical operations could be substantially improved with the implementation of the exoscope. For challenging cranial approaches, where the operator must frequently "look around corners" the exoscope has a major advantage compared with the OPMI-the REBA score is 2.6 times lower for the exoscope and reaches a low risk for WMSD. For spinal operations, the neck score as part of the REBA score is three times lower for the exoscope.

Combined Transoral Exoscope and OARM-Assisted Approach for Craniovertebral Junction Surgery. New Trends in an Old-Fashioned Approach

BACKGROUND

The introduction of recent innovations in the field of intraoperative imaging and neuronavigation, such as the O-arm StealthStation, allows for obtaining crucial intraoperative data by performing safer and controlled surgical procedures. As part of the improvement of surgical visual magnification and wide expansion of surgical corridors, the 3D 4 K exoscope (EX) has nowadays become an interesting and useful tool. The transoral approach (TOA) is the historical gold-standard direct microsurgical route to ventral craniovertebral junction (CVJ).

METHODS

We herein report our experience, consisting of ten cases via TOA concerning the simultaneous application of an O-arm with a StealthStation navigation system (Medtronic, Memphis, TN) and an imaging system, along with the 3D 4 K exoscopes in the TOA, for the treatment of CVJ pathologies.

RESULTS

No intraoperative neurophysiological changes or postoperative infections occurred, but neurological improvement was evident in all the patients. A complete decompression and a stable instrumentation and fusion of the CVJ were accomplished in all cases at the maximum follow-up time.

CONCLUSIONS

With EX, the role of the surgeon becomes self-sufficient with better individual surgical freedom compared to endoscopic surgery and excellent 3D vision and magnification. O-arms offer absolutely reliable intraoperative support for more-effective CVJ decompression. Nevertheless, with O-arm-assisted neuronavigation, it can be difficult to navigate C1 lateral masses and C2 isthmi, and converting 3D into 2D real-time navigation can be quite complicated. Finally, the combination of an EX with an O-arm appears more time-consuming compared to the old-fashion one.

A new era in teaching: how advanced optical recording technology could change the postcesarean delivery complication conundrum

BACKGROUND

The last 4 decades have seen increased complications after cesarean deliveries. Despite an incomplete understanding of their etiology, surgical practices have been adopted, creating disproportionate morbidity and the absence of preventive strategies. Additional research tools are needed for further investigation.

OBJECTIVE

This study aimed to evaluate the VITOM high-definition optical recording system as a tool to highlight cesarean operative steps and surgical techniques and assess the use of its video recordings for operating room team teaching and research potential.

STUDY DESIGN

Contemporaneous cesarean delivery techniques offer no resolution to long-term postcesarean sequelae. From March 2015 to February 2022, a novel tool, VITOM exoscope, was evaluated and used to photograph and video record 104 elective cesarean deliveries. The images were projected on a large screen to be viewed by scrubbed-in and unscrubbed personnel and recorded for future use. During this period, staff participants in 3 designated operating rooms reached 514, including 168 trainee residents, 5 nurse practitioners, 6 physician assistants, 21 medical students, 70 surgical technicians, and 110 circulating nurses. The maternal ages of patients varied from 21 to 49 years. Gestational ages ranged from 28 0/7 to 41 6/7 weeks of gestation. Selected photographs of crucial cesarean surgical steps were taken and printed. Video recordings were stored in designated institutional data storage and uploaded onto a secure drive for further use. After every case, debriefing was held, and subjective opinions were obtained from the various participants.

RESULTS

The VITOM was used for 104 cesarean deliveries. Setup time was reduced from 7 minutes initially to 3 minutes with more experience. All staff participants had only positive evaluations and remarks about the image quality and the clear delineation of specific anatomic landmarks. By polling medical students and residents in training, the VITOM experience was described as very useful and, in a few cases, only somewhat useful. The scrubbed surgical technicians and circulating nurses gained a better understanding of surgical layers, improving their ability to anticipate subsequent surgical steps, thereby streamlining operating flow and efficiency. Unscrubbed personnel could also follow the operation's progression despite being remote from the sterile field. Anesthesiologists could follow the operative field and eventual blood loss in plain view. Recorded videos and still photographs were used at clinical teaching conferences and in peer-reviewed publications, enhancing understanding of cesarean delivery techniques.

CONCLUSION

The VITOM exoscope provided superb image quality, enabling a clear vision of the anatomic structures of the cesarean operation. It is a promising additional research tool to capture important details of the employed surgical techniques and provides a possible insight into long-term postcesarean sequelae.

High Definition Three-Dimensional Exoscope (VITOM 3D) in E.N.T. Surgery: A Systematic Review of Current Experience

Over the last decade, technological growth has developed new devices for more precise surgery based on improved maneuverability, minimally invasive approaches, and magnification of the operating field. In this context, the exoscope has opened a new phase for more accurate and safer microsurgery, improving the perception of the volume of objects and the depth of structures for planning, targeting, and controlling fine movements. The exoscope could be used for middle ear, transcanal, transmastoid, and craniotomy procedures that require two-handed dissection, both to perform both totally VITOM-based techniques and coupled to traditional procedures with an operating microscope or endoscope. In addition, the VITOM 3D system allows the surgeon to work with high-definition images, which is essential in facial nerve surgery or submandibular salivary stone or tear surgery approaches, where magnification plays a fundamental role in surgical success and in reducing operating times. The 3D exoscope approach could also be included in traditional transoral procedures for oropharyngeal carcinoma. The exoscope may provide a relevant approach in teaching surgeons and nurses, allowing adequate training in non-oncological surgical procedures such as a tonsillectomy or lateral pharyngoplasty.

Live-streaming otolaryngology surgical procedures for virtual medical student rotations

Background

The coronavirus disease 2019 pandemic created challenges in surgical education that expedited the development of virtual learning. Virtual rotations have been one such solution. However, they require co-ordination and technological equipment to create a meaningful, interactive experience for students.

Methods

Various otolaryngology surgical procedures were live-streamed during a two-week virtual rotation for medical students. A mobile audiovisual cart comprising a computer mounted with a webcam and microphone/speaker were utilised to live-stream from four sources: video-assisted telescope operating monitor (‘VITOM’) exoscope, microscope, endoscope and room camera. A dedicated faculty member, who was not the operating surgeon, was present to facilitate students’ understanding of the procedure.

Conclusion

A wide breadth of otolaryngology surgical procedures were live-streamed via a mobile audiovisual computer, including views of the room, endoscopic views, microscopic views and open views via an exoscope (video-assisted telescope operating monitor). This virtual rotation set-up, along with the dedicated faculty facilitator, reduced the burden on the operating surgeon and enhanced students’ learning experience.

Is the exoscope ready to replace the operative microscope in transoral surgery?

PURPOSE OF REVIEW

Exoscopes are external digital devices that provide enhanced and magnified visualization of the surgical field. They usually have dedicated digital controls and a more compact mechanical structure than operative microscopes and current robotic surgical systems. This technology has significant potential in otolaryngology - head and neck surgery, especially concerning the field of transoral approaches. We herein analysed the overall technical characteristics of currently available exoscopic systems and contextualized their advantages and drawbacks in the setting of transoral surgery.

RECENT FINDINGS

The actual advantages of exoscopy are still indeterminate, as it has only been applied to limited surgical series. However, its specific properties are herein compared with conventional transoral microsurgery and transoral robotic surgery, discussing the available literature on such a topic, filtered on the basis of the authors' experience and its possible future evolutions. Finally, a summary of current experiences in the field of three-dimensional (3D) transoral exoscopic surgery is presented, highlighting differences compared with standard approaches.

SUMMARY

3D-exoscopic transoral surgery will possibly play an essential role in future management of early laryngeal and oropharyngeal lesions, significantly shifting the paradigms of this type of procedures.

Subjective workload measurement of the transition from a conventional operative microscope to a Robotic Digital Microscope. A pilot study

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Evaluate the subjective workload for transition of an experienced neurosurgeon from a conventional operative microscope /OPMI/ to a Robotic Digital Microscope /RDM/.

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Show a single center initial experience of the use an exoscope.

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The exoscope improves ergonomics.

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Operative exoscope could reduce work-related musculoskeletal disorders.

VITOM-3D assisted neck dissection via a retroauricular approach (RAND-3D): a preclinical investigation in a cadaver lab

Objective

The recent introduction of 3D exoscopic surgery has allowed interesting technical improvements in head and neck surgery resulting in technical solutions that are also applicable to neck dissection. The aim is to replace robotic surgery while minimising the costs of the procedure.

Methods

Based on these considerations, we conducted a preclinical investigation in the cadaver lab focused on approaching conventional neck dissection using a retroauricular incision, and evalute the applications and usefulness of the Storz 3D Exoscopic System at different stages of the surgical procedure. The acronym RAND-3D (3D exoscopic surgery) was coined to describe the application of this optical tool in neck dissection.

Results

The current study in the cadaver lab indicates that RAND-3D is an acceptable alternative operating technique in performing neck dissection by a retroauricular approach. Technically feasible and safe, this technique assures a complete compartment-oriented dissection without damaging major vascular or nervous structures.

Conclusions

This approach can be used in selected cases with a clear cosmetic benefit and represents a valid alternative to endoscopic- and robotic-assisted neck dissection.

Application of a new computer-assisted robotic visualization system in cochlear implantation-Proof of concept

BACKGROUND

Over the last decades conventional cochlear implant (CI) surgery has remained essentially unchanged. Nevertheless, alternative implantation techniques to further improve patient outcomes such as endaural implantation or robot-assisted surgery have been proposed in recent years. However, none of these have gained acceptance in clinical routine, thus confirming a demand for new developments.

METHODS

Cochlear implant surgery was performed in two mastoid bones obtained from body donors using a novel hands-free exoscope. Advantages and disadvantages of the system were evaluated.

RESULTS

In all cases, implantation of the electrode was feasible. The system allowed for hands-free movement and adjustment of the exoscope by the head-mounted display. Network connectivity of the system leaves room for improvement.

CONCLUSION

The RoboticScope is an innovative tool and can be used supportively in conventional CI surgery in the experimental setting. Although operating the device requires a certain learning curve, the usability is intuitive for every ear surgeon.

Using a 4K three-dimensional exoscope system (Vitom 3D) for mastoid surgery during the coronavirus disease 2019 pandemic

Objective

Microscopic surgery is currently considered the ‘gold standard’ for middle-ear, mastoid and lateral skull base surgery. The coronavirus disease 2019 pandemic has made microscopic surgery more challenging to perform. This work aimed to demonstrate the feasibility of the Vitom 3D system, which integrates a high-definition (4K) view and three-dimensional technology for ear surgery, within the context of the pandemic.

Method

Combined approach tympanoplasty and ossiculoplasty were performed for cholesteatoma using the Vitom 3D system exclusively.

Results

Surgery was performed successfully. The patient made a good recovery, with no evidence of residual disease at follow up. The compact system has excellent depth of field, magnification and colour. It enables ergonomic work, improved work flow, and is ideal for teaching and training.

Conclusion

The Vitom 3D system is considered a revolutionary alternative to microscope-assisted surgery, particularly in light of coronavirus disease 2019. It allows delivery of safe otological surgery, which may aid in continuing elective surgery.

[Surgical treatment of chronic otitis media in children using three-dimensional imaging]

The introduction of three-dimensional exoscopy has opened a new stage in microsurgery in recent years. Researchers from various specialties give mostly positive reviews. There are very few works on the use of three-dimensional imaging in otorhinolaryngology, and there are practically no such works on otosurgery. This article presents a short review of publications and our own clinical examples, which are the first detailed description of VITOM 3D KARL STORZ exoscope use for cholesteatoma surgery in children, published in the available world literature. The first experience allowed us to draw preliminary conclusions about the comparability of this method of intraoperative imaging with a microscope. In addition, we have identified additional benefits of the exoscope. Further research will make it possible to better adapt the technique to the peculiarities of otosurgery, and it should take its place in the arsenal of ENT surgeons, along with microscopy.

Transoral laser microsurgery: feasibility of a new exoscopic HD-3D system coupled with free beam or fiber laser

In the last decades, new technological devices and instruments have been developed to overcome the technical limits of transoral laser microsurgery. The recent introduction of 3D endoscopy seems to be a promising tool in the field of diagnostic and operative laryngology as an alternative to the traditional microlaryngoscopy. Our work aims to present a novel transoral microsurgical setting that expands the use of exoscopic systems (in this case the VITOM® 3D-HD) as an alternative to the standard operating microscope. A customized support arm and an adaptor to firmly connect the VITOM® 3D-HD camera to the laser micromanipulator were specially designed. This setup was used as an alternative to the standard operating microscope in a cohort of 17 patients affected by suspicious early to intermediate pharyngo-laryngeal neoplasms. A historical cohort of patients treated with the traditional setting and matching the same inclusion criteria was used as a reference for the duration of surgical procedures. The surgical procedures comprised 7 cordectomies, 2 endoscopic partial supraglottic laryngectomies, 4 tongue base resections, and 4 lateral oropharyngectomies or hypopharyngectomies. In 6 cases (35%), a simultaneous neck dissection was performed. The low rate of positive deep (6%) or superficial (12%) margins reinforced the safety of this platform, and the results obtained in terms of operating time were comparable to the control group (p > 0.05), which confirms the feasibility of the system. Our surgical setting setup is a convincing alternative to traditional transoral laser microsurgery for early to intermediate pharyngo-laryngeal neoplasms. The main advantages of this system are comfortable ergonomics for the first surgeon and a potential benefit in terms of teaching if applied in university hospitals, since the entire surgical team can view the same surgical 3D-HD view of the first operator. Further work is still needed to objectively compare the traditional and new technique, and to validate our preliminary clinical findings.

Combined transoral exoscope and OArm-assisted approach for craniovertebral junction surgery: Light and shadows in single-center experience with improving technologies

Background

The introduction of recent innovations in the field of intraoperative imaging and neuronavigation, such as OArm Stealth Station, allows to obtain crucial intraoperative data by performing safer and controlled surgical procedures. As part of the improvement of surgical visual magnification and wide expansion of surgical corridors, the 3D-4K exoscope (EX) represents nowadays an interesting and useful tool. Transoral approach (TOA) represents the historical gold standard direct microsurgical route to ventral craniovertebral junction (CVJ).

Methods

We herein report a preliminary experience on 6 cases of 33 patients operated by TOA concerning the simultaneous application of OArm with Stealth Navigation system (Medtronic, Memphis, TN) and imaging system along with the 3D-4K EXs in TOA for the treatment of CVJ pathologies.

Results

Neither intraoperative neurophysiological changes nor postoperative infections occurred, but a neurological improvement was evident in all the patients. A complete decompression along with stable instrumentation and fusion of the CVJ was accomplished in all cases at the maximum follow-up (mean: 16.8 months).

Conclusions

With EX, the role of surgeon become self-sufficient with a better individual surgical freedom compared to endoscopic surgery and excellent 3D vision and magnification. OArm allows an absolutely reliable intraoperative support for a more effective CVJ decompression. Nevertheless, with OArm-assisted neuronavigation, it can be difficult to navigate C1 lateral masses and C2 isthmi, and to convert 3D into 2D real-time navigation, it can become quite complicate. Finally, the association of EX and OArm appears more time consuming compared to the old fashion one.

A high-definition 3D exoscope as an alternative to the operating microscope in spinal microsurgery

OBJECTIVE

Since the 1970s, the operating microscope (OM) has been a standard for visualization and illumination of the surgical field in spinal microsurgery. However, due to its limitations (e.g., size, costliness, and the limited movability of the binocular lenses, in addition to discomfort experienced by surgeons due to the posture required), there are efforts to replace the OM with exoscopic video telescopes. The authors evaluated the feasibility of a new 3D exoscope as an alternative to the OM in spine surgeries.

METHODS

Patients with degenerative pathologies scheduled for single-level lumbar or cervical spinal surgery with use of a high-definition 3D exoscope were enrolled in a prospective cohort study between January 2019 and September 2019. Age-, sex-, body mass index-, and procedure-matched patients surgically treated with the assistance of the OM served as the control group. Operative baseline and postoperative outcome parameters were assessed. Periprocedural handling, visualization, and illumination by the exoscope, as well as surgeons' comfort level in terms of posture, were scored using a questionnaire.

RESULTS

A 3D exoscope was used in 40 patients undergoing lumbar posterior decompression (LPD) and 20 patients undergoing anterior cervical discectomy and fusion (ACDF); an equal number of controls in whom an OM was used were studied. Compared with controls, there were no significant differences for mean operative time (ACDF: 132 vs 116 minutes; LPD: 112 vs 113 minutes) and blood loss (ACDF: 97 vs 93 ml; LPD: 109 vs 55 ml) as well as postoperative improvement of symptoms (ACDF/Neck Disability Index: p = 0.43; LPD/Oswestry Disability Index: p = 0.76). No intraoperative complications occurred in either group. According to the attending surgeon, the intraoperative handling of instruments was rated to be comparable to that of the OM, while the comfort level of the surgeon's posture intraoperatively (especially during "undercutting" procedures) was rated as superior. In cases of ACDF procedures and long approaches, depth perception, image quality, and illumination were rated as inferior when compared with the OM. By contrast, for operating room nursing staff participating in 3D exoscope procedures, the visualization of intraoperative process flow and surgical situs was rated to be superior to the OM, especially for ACDF procedures.

CONCLUSIONS

A 3D exoscope seems to be a safe alternative for common spinal procedures with the unique advantage of excellent comfort for the surgical team, but the drawback is the still slightly inferior visualization/illumination quality compared with the OM.

Microsurgical procedures during COVID-19 pandemic: the VITOM® 3D-HD exoscopic system as alternative to the operating microscope to properly use personal protective equipment (PPE)

PURPOSE

In the field of microsurgery, the use of conventional operating microscope, adopted in several disciplines, is not suitable with the full adoption of appropriate personal protective equipment (PPE), as goggles and face shields, needing the eyes to be at close contact with oculars.

METHODS

Herein we present an exoscopic surgical setup, implemented for transoral laser microsurgery, by the VITOM® 3D-HD system.

RESULTS

Our proposed exoscopic setting overcomes safety limits of the conventional operating microscope, being suitable with the adoption of full PPE necessary facing with suspected or confirmed positive SARS-CoV-2 patients needing urgent microsurgical procedures.

CONCLUSION

The use of protocols to reduce the virus spreading is mandatory to safely treat also patients potentially SARS-CoV-2 infected. The described surgical setup is advisable to manage urgent microsurgical procedures along the duration of the COVID-19 pandemic, being applicable PPE necessary to treat potentially or confirmed SARS-CoV-2-infected patients.