High-Definition 3D Exoscope in Thyroid Surgery

Introduction

Several exoscopic devices have been developed during the last decade such as the VITOM^® 3D (Karl Storz, Tuttlingen, Germany), Orbeye^® (Olympus, Tokyo, Japan) and Modus V^TM (Synaptive Medical). In particular, Karl Storz’s video telescope operating monitor (VITOM^®) was released in 2011 as a two-dimensional (2D) high definition exoscope. The telescope was characterized by a 10 mm outer diameter and a shaft length of 14 cm, allowing for mean focal distance is 200 mm with the depth of field of 12 mm. It was connected to a high-definition (HD) digitized camera with an optical zoom and focus features, providing high-resolution image with minimal spherical aberrations or chromatic distortions, and a wide viewing angle comparable to the operating microscope. However, the main limitation was the lack of stereopsis compared to the operating microscope, resulting in a reduced image depth on the screen. The introduction of three-dimensional systems (VITOM^® 3D operating exoscope) aimed to improve the depth perception during surgery allowing for planning, targeting and controlling fine hand movements. ¹

The high-definition (HD) VITOM^® 3D operating exoscope is an innovative and promising tool that was recently introduced in the otorhinolaryngologist – head and neck surgeon’s clinical practice. The exoscope was developed to substitute the operating microscope in performing microsurgical procedures such as microvascular anastomoses, laryngeal and lateral skull base surgery.^2-4 Nevertheless, the possibility to employ this new technology during other surgeries should be further investigated.

Technological advancements have been introduced in thyroid surgery with the purpose of better cosmetics results and less postoperative pain. However, the primary aim during a thyroidectomy is to completely remove the thyroid gland preserving recurrent laryngeal nerves (RLNs) and parathyroid glands (PGs). After a preliminary dissection, the RLN should be adequately identified to reduce the risk of iatrogenic damage. Although various medical devices have been developed over the past two decades for intraoperative use to simplify the RLN preservation, the visual nerve identification still represents the gold standard.^5,6 Loupes are widely used to enhance the surgical field magnification, improving the ability to perform tissue dissection in the area of the RLNs and PGs, consequently reducing the risk of nerve tearing and PGs devascularization. However, the magnification is restricted to the surgeon unless the loupes are coupled to a microcamera. Moreover, a three-dimensional endoscopic-assisted thyroidectomy was already introduced in the clinical practice. ⁷ In this context, the introduction of the 3D exoscope as a new visualization and magnification tool represents an innovative way to improve the identification and preservation of the RLNs and the PGs during conventional open thyroidectomy. This system projects the surgical image onto a large 32 inch monitor which can be easily seen by all the operators and other surgical staff. The 3D image of the exoscope allows the surgeon to have a better view of the surgical field associated to depth perception thanks to a 4K screen. Moreover, image magnification could be adjusted to the specific procedure, and it could be modulated during surgery to focus anatomical structures of interest. Thanks to these features, the 3D exoscope could be used during open surgical procedures to enhance the ability to perform precise dissection of fine structures.^8,9 Finally, the possibility to easily record images of the surgical field showing intact RLN and PGs could have an impact also from a medicolegal perspective.

The aim of this paper is to describe our preliminary experience with the 3D exoscope in thyroid surgery, discussing potential advantages of this system.

Methods

The Institutional Ethic Committee of Humanitas Clinical and Research Center approved the study (Prot. Ne. CE Humanitas 478/19 06/2019). Informed consent was obtained from patients.

Results

Three (females: 2; mean age: 47.0, range 42-56) total thyroidectomies with or without central compartment neck dissection were performed. The 3D exoscope was used without significant intra-operative delay or complications compared to the standard procedure without the exoscope. The exoscope set-up time was approximately 5 min in all the procedures. Mean operative time was 96 min (range 81-119).

Table 1 shows the frequency of responses for each of the 12 survey items of the Exoscope Quality Assessment Tool. The majority of the individual items were judged “good” (n = 82, 75.9%). “Magnification rate,” “temperature of the surgical field,” and “surgical working space,” and “ease of set up and joystick use” represented the best-rated items, judged “very good” by all participants. On the other hand, “image quality” and “luminance” were the less-rated items, judged “very good” only by one (11.1%) and three (33.3%) participants, respectively.

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Table 1.

Exoscope Quality Assessment Tool results. Data are Reported as Counts and Percentage for Each Item.

	Not Acceptable	Acceptable	Good
Image quality	—	66.7% (n = 6)	33.3% (n = 3)
Stereoscopic effect	—	44.4% (n = 4)	55.6% (n = 5)
Magnification rate	—	—	100% (n = 9)
Range of motion of the holding system	—	11.1% (n = 1)	88.9% (n = 8)
Luminance	—	88.9% (n = 8)	11.1% (n = 1)
Eye strain	—	33.3% (n = 3)	66.7% (n = 6)
Temperature of the surgical field	—	—	100% (n = 9)
Natural posture	—	33.3% (n = 3)	66.7% (n = 6)
Surgical working space	—	—	100% (n = 9)
Joystick ease of use	—	—	100% (n = 9)
Same field of view as the surgeon	—	11.1% (n = 1)	88.9% (n = 8)
Ease of set-up	—	—	100% (n = 9)

Discussion

In this paper we showed the feasibility of 3D exoscope-assisted thyroid surgery. The implementation of lighting and magnification of the surgical field determined by the exoscope could improve the ability to perform precise dissection of fine structures. In particular, this technology allowed the identification of the RLNs and the preservation of the PGs without complications.

Although the exoscope was developed to substitute the operating microscope in microsurgical procedures, several papers have been recently published demonstrating the usefulness of exoscope-assisted open surgery. In particular, the exoscope was used for parotid surgery ⁸ and upper airway stimulation ⁹ during the identification and dissection of the facial and hypoglossal nerves, respectively.

The Exoscope Quality Assessment Tool was used to better define advantages and disadvantages of this system in open thyroid surgery, as already performed in other clinical and pre-clinical contexts. In particular, the questionnaire was proposed to both main and assistant surgeons, and scrub nurses to identify any differences during exoscope-assisted thyroid surgery.

One of the main advantage of this system is surely the possibility to share the same vision of the main surgeon during the procedure.^10,11 As shown in Video 1, the first part of the thyroidectomy was not performed under exoscopic vision, but the exoscope was only used to share the surgical vision and to record the surgical steps for educational purposes. The optimal ergonomics of the small 3D camera, associated to the slim holding system, allowed the exoscope to be placed above the surgical field without interfering with surgical maneuvers. In addition, both the 3D camera and the IMAGE1 PILOT could be equipped with sterile covers. In fact, both items “range of motion of the holding system” and “surgical working space” were judges “very good” by almost all participants. Once the macroscopic dissection was carried out as conventional open thyroidectomy, the main surgeon and the assistant could wear the 3D glasses and switched to exoscopic vision. Also, the scrub nurse could benefit from the 3D vision on the HD screen to better understand surgical steps, and to anticipate the surgeon’s next choice of instrument. From this perspective, we should mention that an additional screen should be placed in front of the assistant and the scrub nurse (Fig. 1), given that the optimal 3D vision could be achieved only with the gaze perpendicular to the screen.

The “image quality” and especially the “luminance” are the exoscope’s features that need an improvement according to both surgeons and nurses responses. Even if the 3D vision enhance the perception of objects volume and the depth of structures for planning, targeting and controlling fine movements, the use of 3D glasses probably reduce the luminance of the surgical field compared to conventional shadowless operating lamps. Moreover, the scrub nurses reported a not negligible eye strain due to the 3D glasses.

Even if the image quality is expected to improve thanks to technological advancements, the “magnification rate” was considered adequate by all participants to improve the definition of fine structures during the identification and preservation of the RLNs and the PGs. Another aspect that should be mentioned was the possibility to modulate the image magnification dynamically during the procedure. The joystick was easy to use, allowing movement of the camera and magnification of the area of interest during the procedure, and assisting the surgeon during fine dissection. This could represent an advantage compared to surgical loupes given their fixed magnification. Moreover, the image orientation could be changed without moving the camera, and there was no loss of time in the transition to the contralateral side during total thyroidectomy. In general, the exoscope set-up was rated “very good” by all participants, as demonstrated by the fast set-up time of approximately 5 min. Some differences in terms of OR set-up are encountered depending on the surgical procedure, but the system is surely intuitive and easy to prepare for thyroid surgery with no intra-operative delay.

A central compartment neck dissection was performed in one patient after thyroidectomy. Exoscopic assistance was useful during the first part of the dissection when the RLN should be separated from the lymph nodes along its course. Then, the exoscope was not strictly necessary and the dissection could be completed on a direct vision. In our opinion, if only crucial surgical steps are performed with the aid of the exoscope, the operative time could be comparable to a conventional thyroidectomy. However, a learning curve may be expected in first-time users.

Some concerns should be raised from the economic perspective. Given the widespread of surgical procedures performed in the otolaryngology field (eg microvascular anastomoses, laryngeal and lateral skull base surgery), the possibility to use the exoscope also for thyroid surgery will may be encouraged in the future. On the other hand, exoscope-assisted thyroid surgery seems to present an unfavorable cost-benefit ratio in other settings, such as general surgery, where the exoscopic system has not been introduced at this time.

Conclusion

3D Exoscope-assisted thyroid surgery seems to be feasible and safe. The high-definition 3D exoscope could be used to perform precise dissection in the identification and preservation of the RLNs and the PGs. Further studies should be encouraged to analyze potential clinical benefit in the post-operative period.