The Angelina Dissectors: A Novel Design of Dissectors for Endoscopic Endonasal Approaches

Abstract

Background  The description and refinement of the transsphenoidal approach would not be possible without new tools and technologies developed by surgeons to facilitate this approach, which is nowadays the standard procedure for more than 90% of sellar lesions. The latest major change in transsphenoidal surgery was the introduction of the rigid endoscope and the subsequent description of the endoscopic endonasal approach. Traditional bayoneted instruments, when used for this technique, were inadequate. New instruments designed, specifically for this technique, are necessary to facilitate the surgeon's work and improve patient outcome.

Objective  This study describes a novel design of dissectors created specifically for endoscopic endonasal approaches.

Methods  To develop and design the Angelina dissectors, we used our extensive surgical experience to identify the shortcomings of the available dissectors used for transsphenoidal surgery and created the Angelina dissectors.

Results  The Angelina dissector was designed with a unique shaft shape which facilitates endoscopic endonasal surgery.

Conclusion  Even though an endoscopic endonasal approach is possible using other instruments, the design of these dissectors aids the surgeon's work. It is our impression, based on personal experience that it allows more freedom of movement and dexterity during the procedure, which could translate as an improved patient outcome.

Introduction

The historical background and evolution of pituitary surgery and the advances in equipment have been reviewed and highlighted on many articles in the past two decades. The description and refinement of the transsphenoidal approach would not be possible without new tools and technologies developed by surgeons to facilitate this approach which is nowadays the standard procedure for more than 90% of sellar lesions. ^{1 2}

The current technique of the transsphenoidal procedure is, like many advances in medicine, the result of a long and relentless process and it is still ongoing. It has taken open transcranial sellar approaches, marked by the pioneer work of Sir Victor Horsley who performed the first pituitary surgery in 1889 to the current endoscopic endonasal procedure. ³ The limitations of the transcranial approach inspired the development of the transsphenoidal procedure that evolved from the simultaneous work of Oskar Hirsch in Vienna ⁴ and of Harvey Cushing in Boston. ⁵ Cushing's pioneer work to developed this procedure could have been lost when, in 1929, he abandoned the transsphenoidal procedure in favor of a transcranial one, leading most surgeons at the time to follow suit. Hirsch, Hannibal Hamlin, Norman Dott, and a few others are notable exceptions that kept performing and refining this procedure and the tools available for it. ³

The work of Norman Dott and Gerard Guiot returned attention to the transsphenoidal procedure for sellar lesions. Both were noted not only for their surgical ability but also for their ingenuity. Dott and Guiot created new tools and instruments to overcome the limitations of the time for the transsphenoidal approach. ^{6 7} Norman Dott was a neurosurgeon in the Royal Infirmary of Edinburgh. He spent a year in Dr. Cushing's service in 1923 to 1924 where he learned and studied the transsphenoidal technique and its benefits, despite the difficulties encountered at the time. One of the main problems was the dark and narrow surgical field and Dott designed a modified speculum with lights attached to it to improve lighting. ^{3 8}

After learning the transsphenoidal technique from Norman Dott in 1956, Gerard Guiot returned to France and started using it in lieu of the transcranial approach. He created several surgical instruments to meet his needs during surgery contributing for the advancement of this technique. His group went on working performed approximately 5,500 transsphenoidal surgeries. ^{3 8 9}

Optimization of operative results requires the careful selection of instruments. ¹⁰ Many of the breakthroughs and improvements in techniques were possible because of new technologies and tools created, often by or with the assistance of experienced surgeons. The latest advancement in transsphenoidal surgery was the introduction of the rigid endoscope and the subsequent description of the endoscopic endonasal approach by Jho and Carrau, where the “eye” of the surgeon (the endoscope) is in the sinonasal cavity. ^{11 12} The endoscopic endonasal approach has been growing since and again, instruments designed specifically for this technique are necessary to facilitate the surgeon's work.

In this article, we described the rationale and recommended uses of a novel instrument design, created from the senior authors' experiences which are successfully used in our institution for endoscopic endonasal approaches.

Instrument Design Rationale

Traditional straight instruments, used in open transcranial surgery, were initially modified to a bayonet shape ( Fig. 1A , B ) so they could be used in the narrow nasal speculum, while moving the surgeon's hands to the side, no longer blocking the microscope's lens and illumination ( Fig. 2A ). During surgery, it is frequently necessary to rotate a dissector along its longitudinal axis. The bayonet disrupts this axis between the dissector's handle and its tip, not allowing adequate rotation of the instrument ( Fig. 3A ). Despite this, the bayonet was necessary to avoid blocking the line of sight of the microscope and of the surgeon.

Fig. 1.

Schematic representations of different dissector designs. ( A ) Bayonet dissector; ( B ) straight dissector; ( C ) single-angle dissector (theoretical); ( D ) The Angelina dissector.

Fig. 2.

Schematic representations of different dissectors in endonasal approaches, where the shaded area represents the sinonasal cavity. ( A ) Microscope-assisted approach using the bayonet dissector; ( B – D ) endoscope-assisted approaches using the straight dissector ( B ), the single angle dissector ( C ), and the Angelina dissector ( D ).

Fig. 3.

Schematic representation of the different dissector designs when rotated. ( A and C ) The bayonet and single angle dissectors do not allow rotation because the longitudinal axis is disrupted. ( B and D ) The straight and the Angelina dissectors have the longitudinal axis aligned, allowing rotation of the dissector.

In the endoscopic endonasal technique, the surgeon's “eye” and lighting are in the sinonasal cavity and the bayonet is no longer necessary, which allows the use of straight dissectors ( Fig. 2B ) that allow free rotation of the tool ( Fig. 3B ). The endoscope in the narrow surgical field can collide with the dissectors, creating imprecise and jagged movements (we refer to this as “swording”), mainly when working on the right and superior quadrant of the sella and parasellar region ( Fig. 4A and Video 1 ).

Fig. 4.

Schematic representation of an endoscope assisted approach to a target to the right superior half (shaded area) of the sphenoid roof, divided diagonally with the sella as center. ( A ) Straight dissector interferes with the endoscope (“swording”) and obstructs the field of vision. ( B ) The Angelina dissector design avoids the endoscope improving precision and dexterity during surgery.

Video 1

This video demonstrates our intraoperative use of the Angelina Dissectors for different tasks and situations. At 0m22s a straight dissector is used to show the limitation of this tool, particularly when compared to the Angelina Dissector, as presented at 0m55s.

Download video file ^{(44.3MB, mp4)}

The senior authors' experience with endoscopic endonasal approaches called for a new type of dissector specifically designed for this type of surgery. Initially, a single distal angle in the dissector's shaft seemed as a simple solution ( Fig. 1C ). However, this design would lead to a converging angle between the handles when using two instruments, making the surgeon's hands clash, and interfere with one another and the distal part of the endoscope ( Fig. 2C ). The longitudinal axis between the handle and the tip would also lose its alignment, not allowing rotation of the dissector ( Fig. 3C ).

The Angelina dissectors (so named after the senior author's daughter) resolved these issues associating a proximal angle in its shaft to a distal bayonet ( Fig. 1D ). The proximal bend moves the shaft away from the endoscope and from the visual field, thus avoiding “swording” ( Fig. 4B ). The distal bayonet, near the edge, realigns the axis of the handle, and of the tip of the dissector ( Fig. 3D ), and brings it back into the visual field without blocking the view. This design also moves the handle of the dissector away from the endoscope and/or from a second instrument being used ( Fig. 2D ).

In the traditional four-hand technique used in endoscopic endonasal approaches, the endoscope is inserted in the sinonasal cavity through the right nostril by the cosurgeon and held in the superior portion. In this approach, the surgeon uses the left nostril to gain access to the sinonasal cavity and the inferior portion of the right nostril (usually, a sucker). In this technique, the right superior quadrant is occupied by the endoscope. The Angelina design is ideal for working on lesions in the superior right half of the sphenoid, imagining a diagonal division using the sella as center ( Fig. 4 ) because its design avoids “swording” or interfering with the field of vision.

The Angelina design was matched with different tips (dissector, ring curette, ball probe) that the senior authors deemed necessary during their surgical cases. Using the initial dissectors made in the anatomy laboratory and in the operating room, they refined the design by adjusting the size, length, or angle of each one. Currently, the Angelina dissector set (KLS-Martin Group, Jacksonville, Florida; Fig. 5 ) is used routinely in our institution for every endoscopic endonasal approach, allowing improved precision and dexterity during the procedure, which may reflect in improved patient outcomes ( Video 1 ).

Fig. 5.

( A ) The complete Angelina dissector set (KLS-Martin, Jacksonville, Florida) currently used in our institution. ( B ) Different tips perfected by use in the anatomy laboratory and operating room by the senior authors.

Conclusions

The endoscopic endonasal approach brought great advances to transsphenoidal surgeries, increasing the reach of skull base surgeons through the nose. This relatively new technique requires surgical instruments designed to meet its needs. The surgeons with the most experience in this field can use their experience to design these instruments and to create better tools for less experience surgeons.

The Angelina dissector ( Fig. 6 ) was designed for endoscopic endonasal approach and, in our opinion, it is a valuable tool. Even though an endoscopic endonasal approach can be done using others instruments, these dissectors facilitate the surgery, regardless of the level of experience of the surgeon.

Fig. 6.

Comparing the Angelina dissector schematic design and the finalized Angelina number 1 dissector from KLS-Martin (Jacksonville, Florida).

Funding Statement

Funding No funding was obtained for this study.