Multiportal Retrograde Endoscopy to Enhance Surgical Target Visualization: A Pilot Study

Introduction: Current transnasal endoscopic techniques for sinus and skull base surgery use a single endoscope to provide target visualization from one perspective curtailing depth perception and compromising visualization of the instrument-target interface. Furthermore, the view can be blocked by instruments, and collisions between instruments often occur. We investigated the use of multiportal surgical pathways to provide more accurate manipulation of the surgical target. The goal of the current study is to determine if (1) flexible endoscopy can augment rigid endoscopy to allow for enhanced visualization of obstructed surgical targets, (2) multiple synchronous endoscopic views can be displayed without exacerbating mental workload, and (3) synchronous retrograde endoscopy can provide beneficial anatomic information to the surgeon.

Methods: Surgeries were performed in three different cadaver heads by three different surgeons. A zero-degree rigid endoscope was introduced through the nose for the standard transnasal approach. A flexible endoscope was introduced transorally, directed past the palate superiorly, and then flexed 180 degrees for the retrograde view ([Fig. 1]). A maxillary antrostomy and frontal sinusotomy were performed bilaterally on each cadaver head (total 12 sinuses) with dual screen viewing. Videos of the standard transnasal view from the rigid endoscope and retrograde view from the flexible endoscope were recorded simultaneously.

Results: [Fig. 2] depicts the view of the uncinate process from the standard transnasal view (rigid endoscope) and retrograde view (flexible endoscope) while using the backbiter for resection. [Fig. 3] compares views of the frontal sinus outflow tract from the transnasal, retrograde, and transorbital portals. The surgeons who operated noted that they utilized the retrograde view to adjust the location of ends/tips of their instruments. Four surgeons reviewed the videos and individually agreed that the visualization achieved provided a perspective otherwise not attainable with rigid transnasal endoscopy alone.

Conclusion: High-quality visualization of surgical targets such as the frontal or maxillary ostia can be challenging with rigid endoscopes alone. Multiportal retrograde endoscopy as demonstrated here provides proof of concept that additional views of a surgical target can be achieved. Additional work is needed to further develop indications, techniques, and generalizability to targets beyond those investigated here.

Fig. 1 (A) Transnasal rigid endoscopic view of the left middle meatus with instrument (*) against lateral nasal sidewall anterior to uncinate (U). (B) Flexible endoscope passed through choana to obtain retrograde view visualizing the same instrument and the medial aspect of the middle turbinate (MT) and ethmoid bulla (E). (C) Combined image.

Fig. 2 (A) Endoscopic transnasal view of backbiter instrument (*) in place to incise uncinate (U). (B) Retrograde endoscopic view confirming placement of instrument with improved view posterior and medial to the uncinate and middle turbinate (MT). (C) Combined view.

Fig. 3 (A) Transnasal 0-degree rigid endoscopic view of frontal sinus seeker (*) within the frontal outflow. (B) 70-degree transnasal. The flexible endoscope (F) was passed through choana along anterior ethmoid cells to obtain a view into frontal outflow tract shown in (C). (D) Superior transorbital endoscopic view looking inferiorly into frontal outflow visualizing the same instrument (*).

Publication History

Article published online:
12 February 2021