2 Neurosurgical Instrumentation
Guilherme Henrique Weiler Ceccato, Jean G. de Oliveira, and Luis A. B. Borba
Abstract
Neurosurgical instrumentation is a field with which every member of the surgical team must be familiarized. This is even more important when considering skull base procedures, as working with deep approaches requires skillful handling of instruments. Neurosurgery significantly evolved in the last decades and aims to be as precise as possible. Nowadays the ability of image acquisition by the microscope allows the surgeon to accurately identify anatomical structures; and the instrument’s efficiency has also evolved. In order to perform high-quality neurosurgical procedures, it is mandatory to have appropriate knowledge of surgical instruments, especially microsurgical instruments. Complementary to an in-depth knowledge on how to operate, it is crucial to have advanced knowledge about with what instruments to operate. This chapter presents an overview of general microsurgery techniques and surgical instrumentation.
Keywords: Keywords: instrumentation, microsurgery, skull base, microscope, neuroendoscopy, bipolar coagulator, dissectors, needle holder, brain retractor, drill
2.1 Operating Room
There is a basic setup of the operating rooms (ORs) to allow suitable workflow before, during, and following every surgical procedure (Fig. 2.1). Most ORs include a circulating nurse, a scrub nurse, an anesthesia team, and the surgical team itself. The scrub nurse should be able to handle a variety of steps of each procedure, and should be skillful in handling from the drape of microscope to advanced knowledge of the microsurgical instruments, and also should be familiarized with the surgeon’s techniques. It is important to accurately deliver the instruments to the surgeon’s hand and minimize his/her need to look away from the microscope, and in this way the surgical team should follow the surgical procedure closely in the video system. For the adequate workflow during every surgical procedure it is crucial to check if all the suitable instruments are available before beginning the procedure, and be prepared to circumvent unexpected situations, such as malfunctioning or broken equipment.
Fig. 2.1 (a) Operating room during resection of a meningioma. The senior surgeon (Dr. Luis A. B. Borba) is operating assisted by an auxiliary surgeon and the scrub nurse, who has quick and easy access both to the surgeon and the surgical instrumentation table. The team watches the procedure wearing 3D glasses, and the anesthesia team is positioned near the foot of the patient, with easy access to the ventilator tube and venous accesses. (b–e) The operating room must be large enough, well equipped, and keep the main neurosurgical apparatus in the room, such as the surgical microscope. The operating table should be able to adopt different conformations according to the surgical needs, and must be well padded.
The surgical team, instrumentation table, and microscope must be arranged in order to ensure quick and fine movement to deliver the instruments to the surgeon and also enable the team to adequately visualize the procedure.1
The ORs should be large enough to accommodate all the staff and equipment (Fig. 2.1) and also a well-equipped storage room is required to supply the surgeon’s needs. It is very useful for the surgeon to know the possible resource limitations of each institution.
Another important aspect is the surgical ergonomics that have direct impact on the quality of the procedure.2 The surgeon must pay attention to adopt the most comfortable position to operate, in order to concentrate his or her efforts in the procedure itself and not spend energy trying to find the best position during the procedure. The surgeon’s hands and elbows should be well supported, the shoulder should be relaxed and must feel comfortable. To operate in seated or standing position depends upon the surgeon’s preferences, and the best position should be chosen by him/her. Operating in seated position has the potential to provide more support to hands and arms, but working in standing position can deliver more dynamics from the surgeon’s perspective and allow easier changes of microscope position in some situations. However, a position should not to be imposed against the surgeon’s comfort, beliefs, and efficacy.
2.2 Microscope
The microscopes used in neurosurgical procedures significantly evolved in the last few years, with great increase in image quality and additional resources, improving the quality of the procedures (Fig. 2.2).
Fig. 2.2 (a) Example of used surgical microscope, in the case model Leica M530 OHX. Nowadays high-definition images can be provided by the microscopes, both intraoperative and recording. (b) Attached to the microscope, there is a three-dimensional apparatus that allows capturing the surgery in three-dimensional format. Some microscopes have an already coupled three-dimensional apparatus; others require attaching an external system to capture the procedure in that format. The image shows the screen to watch in 3D real time the procedure, as well a Sony MCC-3000 MT 3D Full HD video camera, which capture video of the procedure and a Sony HVO-3300 MT 3D video recorder, which stores the surgical videos. (c) The educational value of each surgical procedure increased significantly in the last few years, and each course or lecture can be enriched with three-dimensional and high-quality media. (d) Another feature of recent microscopes is the fluorescence system. The use of indocyanine green videoangiography after clipping an aneurysm is demonstrated.
The eyepieces can correct refractory defects and the surgeon may choose to correct directly in the microscope or use his or her own corrective glasses. Another feature is the mouth switch that enables the surgeon to finely adjust the microscope position hands-free. This feature can bring more naturalness and efficiency to the procedure, such as the surgeons can follow structures in the surgical field keeping his/her hands under the microscope.
The working distance is another important element, especially considering skull base procedures occurring deeper to surface, such as the transsphenoidal approach. As deep regions need to be reached, the microscope must provide greater working distance in order to achieve adequate focus. Recent microscopes reach working distances from 200 to 500–600 mm, so the structures between this range will be at focus. Focal lengths of the objective lens (working distance) are automatically adjusted and around 200 mm is suitable for superficial procedures such as peripheral nerve surgeries, 275 mm for the majority of intracranial procedures, and greater than 300 mm for deeper approaches, such as transsphenoidal or pineal surgeries.1,3
The magnification is given by the objective and ocular lens, with motorized lens interposed between them in order to enable changing the magnification.3 The field of view is another important variable and has an inverse relation with magnification.
Recent microscopes have different fluorescence modalities available in the microscope, such as the 5-aminolevulinic acid (5-ALA) or the sodium fluorescein for brain tumor surgeries and indocyanine green (ICG) videoangiography for cerebrovascular surgery (Fig. 2.2). These technologies enhanced the surgeon’s ability to see the same surgical field from different perspectives, and may improve the quality of the procedure.
Modern microscopes are able to acquire high-quality images and videos of the procedure, and can transmit for screens in the OR or to distant places, and some of them are capable of capturing the procedure in a three-dimensional format. The advancements in the quality of the imaging acquired allow the surgical team to follow the procedure in depth with a perception similar to the surgeon. And the educational value of each operation for teaching the technique employed is much more evident nowadays (Fig. 2.2).
2.3 Neuroendoscopy
The introduction of endoscopy in neurosurgery increased the quality of the procedures, especially considering deep approaches. It allows achievement of minimally invasive surgery and also better inspection of surgical cavities after tumor resections, looking for residual lesions not seen through the microscope (Fig. 2.3). The current endoscopes usually have a diameter of 2.7 or 4.0 mm and a usual length of 18 cm.4 With larger endoscopes it is possible to obtain better quality of images and improve illumination of surgical field; so the 4 mm endoscopes are more frequently used. The endoscopes commonly used present an angle of 0 degree along its long axis and provide a straight view (Fig. 2.4). Endoscopes of 30, 45, 70, and 90 degrees are less used because they are more disorienting, but are preferred in select situations, especially when it is necessary inspect the corners of a cavity, such as the sella turcica or the internal auditory canal. Modern endoscopes have coupled irrigation sheaths for cleaning the lens and minimize the need to remove them from the surgical field for cleaning, which arises because of the contact with blood or debris.4,5,6
Fig. 2.3 Endonasal approach can be performed using only the microscope, the endoscope, or both, using the microscope for resecting the tumor and the endoscope for inspecting the corners, for example. In images (a) and (b), we observe the resection of a pituitary adenoma using the microscope and in image (b) both the three-dimensional and two-dimensional screens are visible, giving the opportunity to everyone in the room to watch the procedure. The scrub nurse does not wear 3D glasses because it can disturb while handling the microinstruments; so the procedure can be watched in the two-dimensional screen. In image (c) the endoscope is used to inspect the surgical cavity following resection of the lesion with microscope.
Fig. 2.4 (a–h) In this CT–MRI fused image the corridor used during the transsphenoidal approach toward sella turcica is seen. Different angles of view according to the lens angulation are demonstrated; special forceps are used during this kind of approach. In the inset image we have the measurement of the length of corridor toward the sphenoid sinus and anterior wall of sella turcica in this patient. Some intraoperative images of the resection of a pituitary adenoma using the microscope are demonstrated, including the placement of the nasal speculum, drilling the anterior wall of sella turcica and removing bony tips circumferentially with a Kerrison rongeur, the incision of the dura mater, and then the removal of the tumor using different types of ring curettes.
When performing a transsphenoidal approach using microscope, the bayoneted instruments are preferred because the surgeon’s hands are out of the line of view (Fig. 2.5). However, when using the endoscope, as the camera is inside the surgical field, straight instruments can be used because they are more easily managed and do not block the surgeon’s view. A different set of endoscopic microsurgical instruments with greater length need to be used, including special scissors and forceps, and also ring curettes to be employed when removing tumors from inside the sella turcica.
Fig. 2.5 (a) Different types of bayonet instruments, especially ring curettes, are demonstrated, with different sizes and with straight or angled tips. (b) Different sizes of nasal speculums should be available to choose the best one for each case, and the Kerrison rongeurs are also seen. (c) We demonstrate different types of optic lens, with 0, 30, and 45 degrees. (d) Here some special scissors used during endonasal approaches are demonstrated, with straight or angled tips, greater lengths, and special design. (e) Different kinds of suction tubes used during endonasal approaches are seen, with different diameters, lengths, and curved tips. (f) A suction tube is demonstrated, with the thumb hole evident, through which it is possible to control the power of suction. A complete set of suction tubes is demonstrated, with straight and curved tips, lengths of 8, 10, and 13 cm, and diameters ranging between 3 and 12 French. Courtesy from The Rhoton Collection®. ©2019 by the American Association of Neurological Surgeons. Reprinted with permission of the American Association of Neurological Surgeons.
During endoscopy it is important to avoid instrument conflict inside the narrow corridor toward sella turcica, by keeping the endoscope in a superior orientation considering the other instruments, for example. Also, when performing an endoscopic approach, the surgeon should handle the endoscope in the left hand and the instrument in the right one, with the assistant manipulating the suction tube. The endoscope should be white balanced, focused, and tested before use to ensure high quality.7 In some cases it is possible to use a four-hand technique through the two nostrils, with one surgeon holding the endoscope and suction tube and the other dissecting with two hands, for example, and allowing to alternate between the first and second surgeons regarding the surgical task.
There is a range of microinstruments for transsphenoidal approaches. This includes a wide range of curettes and blunt ring curettes, especially forceps to hold tissue inside the sella turcica, a three-pronged fork to manipulate cartilage into sellar opening, malleable loop and spoon, and an osteotome to open the sellar wall. Also, different speculums exist for exposure of the nasal corridor toward the sphenoid sinus, with thicker or thinner spatula widths.8
The blunt ring curettes contain circular loops on the dissecting tip and present different angles for long axis of the instrument. The rings present with 3, 5, and 9 mm in diameter, and have a 12 cm shaft in order to reach the sellar region successfully.8
2.4 Patient Positioning
Especially considering skull base surgery, patient positioning is essential, in order to ensure the best possible surgical field and guarantee patient comfort and safety to endure long operating times. Also, head fixation for microscopic procedures is almost always mandatory as even a minimal movement is magnified under the view of microscope.
Head fixation usually can be achieved using a three-point fixation system (Mayfield® head holder).2 The posterior pins are positioned in the occipital protuberance and mastoid process and the anterior pin behind the hairline in the frontal region, and it is important to place these pins within the sweatband region, along the superior temporal and nuchal lines9 (Fig. 2.6). It is important to remind that the head holder must be applied in such a way as not to hide the incision or obstruct the surgical field. The three sharp pins are intended to penetrate until the outer table of skull, and it is important to avoid placing them over spinal fluid shunts, thin bones (such as those over the frontal and mastoid sinus), or scalp vessels (such as the superficial temporal or occipital arteries). Also, avoid placing over the temporalis muscle, as they can remain unstable after placement and slip. There are special pins designed for pediatric patients population.7,9,10,11
