2 Day 1: The Organization of the Microsurgical Laboratory: Necessary Tools and Equipment
Abstract
The organization of the microneurosurgical training laboratory is essential to an effective neurosurgical training program. In this chapter, we review key organizational aspects, list the necessary equipment, and discuss principal microneurosurgical instruments.
2.1 Organization of the Microsurgical Training Laboratory
The microsurgical laboratory should be headed by a qualified neurosurgeon who has microsurgical experience, who can provide oversight and guidance for such work, and who has an established record of service and rapport with trainees. Work in the modern microsurgical laboratory can range from training only with artificial materials to working with biological materials (e.g., animal and human placentas), cadaveric tissues, and animals. Training exercises that involve more than artificial materials will require appropriate facilities, staff, and institutional approvals and inspections, especially for the use of live animals or cadaveric tissues as a part of the training.
Because the activities of the laboratory center on learning specific neurosurgical techniques or maneuvers, these are best coordinated by the neurosurgical department of the sponsoring hospital or university. Most laboratories allow shared access to the facilities by various clinical and educational departments in different specialties. Allowing 24-hour access (including on weekends) helps to make the microsurgical practice opportunities available to as many busy specialists as possible, which maximizes the use of expensive microscope and laboratory resources. Ideally, a coordinating administrator will design a well-defined program and training schedule for the trainees. As interns or junior residents master their basic microsurgical skills, they are not yet performing the corresponding operations in patients, and they may continue their education and practice their skills during more flexible hours. 1 , 2 , 3 , 4 Even experienced neurosurgeons will benefit from performing “off-the-job training” to maintain their microsurgical skills. 5 Such ongoing practice increases efficiency in an operating room and raises the incidence of technical success. 6 It has been suggested that a neurosurgeon needs at least 10,000 hours of training, including on decision-making, to become competent, confident, and technically skilled. 7
2.2 Laboratory Setup
Ideally, the laboratory should be set up away from the clinical departments in its own space near the vivarium. Because of regulations and the obvious potential for contamination from animal, cadaveric, and other biological tissues, training activities using these materials must be isolated from patient care areas. A well-outfitted bioskills laboratory also has operating rooms and conference rooms within the same facility. The conference room should include a library (with microsurgical videos, books, and articles) equipped with computer workstations that provide access to the medical literature and have servers for data storage. Such a facility may be difficult to establish, given the already high demand for research space in many medical institutions. At a minimum, the goal should be to designate an area where the trainee will be undisturbed and will have access to the appropriate instruments and visualization, including an operative microscope, to perform the required procedures.
The ideal operating room in a practice laboratory is a space with an area of more than 20 square meters (just over 215 square feet), in an illuminated, well-ventilated room equipped with a microscope with excellent optical performance and an operative table. Surgical chairs should be placed in such a way that two people (trainer and trainee) can perform each exercise together opposite to each other. Optimally, the surgical chairs should be the same type used in the operating room. The chairs should be comfortable, should have armrests, and should be able to have the height adjusted. A sink with a water supply system and a basin for washing and cleaning (i.e., sanitizing) instruments is essential. The special sterilization equipment and sterile space necessary for research projects involving survival experiments are not routinely needed for training purposes involving animal sacrifice (Fig. 2.1). Ideally, the laboratory should have storage for biological tissues used for training, such as a dedicated refrigerator and freezer, and cabinets for formaldehyde-preserved specimens.
The ethical and responsible conduct of research and training in the laboratory should be followed by all trainees who work and train in the laboratory. The laboratory staff and trainees should complete regular certification courses (online Collaborative Institutional Training Initiative [CITI] training or equivalent) on biosafety and biosecurity, on responsible conduct of research, and on animal care and use. In most instances, the trainee should also be briefly instructed by a local veterinarian before working with animals.
Because it contains expensive equipment and instruments, the laboratory should support an appropriate level of electronic security and should be kept locked when not in use. Only approved personnel should have access to the laboratory. Residents and other trainees should be in constant contact with the staff and manager of the laboratory to make sure that lost and damaged instruments are replaced.
2.3 Materials and Equipment
To effectively perform microsurgical operations, even in practice sessions, neurosurgeons must have at least a minimal set of essential equipment. The essentials include an operative microscope, microsurgical instruments, and suture material. Any instrument used in microsurgery training should meet the technical conditions required for those used in clinical surgery. When the quality of the microsurgical instruments used in training is as high as that of those used in clinical surgery, the training will prepare the neurosurgeon better for actual surgery. The main types of equipment used in the training laboratory are the operative microscope, surgical loupes, exoscope, microsurgical instruments (needle holder, forceps, scissors, vascular clips, clip applier, scalpel), bipolar coagulation, retractors, irrigator and solutions for irrigation, suction devices and suction cannulas, sponges and gauze, sutures and needles, dyes, background material, high-speed drill, and various stimulation devices.
2.3.1 Operative Microscopes
Optimally, the training operative microscope should be the same as or similar to the type of microscope used in surgery. Efficient manipulation of the modern operative microscope requires some training, so similarity allows the trainee to build skills that will translate more smoothly to the operating suite. The principal structure of the microscope resembles that of the microscopes that many students use in high school or college biology classes, with some important differences. The main parts of the microscope are shown in Fig. 2.2.
The trainee must be able to adjust and confidently operate the microscope. Most neurosurgery is performed under substantial magnification (within the range of 4x to 40x). Thus, a byproduct of practicing surgical hand skills in the neurosurgical training laboratory should be the attainment of familiarity and expertise with working in a magnified anatomical environment.
The operative microscope should be firmly affixed to the table or it should have a heavy base with a hard platform to hold it steady and minimize oscillations. Modern microscopes have a built-in computer with dedicated software that controls the positioning of the microscope head and the camera that records video. The working head of the microscope includes a main objective lens and a magnification changer directed at the operative field, two sets of binocular eyepieces for the surgeon and the surgical assistant with switchable positions, and handgrips with multiple programmable buttons to release and reposition the microscope, change focus and magnification, start and stop video recording, and activate fluorescence (Fig. 2.3). Operative microscopes are also equipped with a portable foot control panel (also called foot pedal or foot switch) with programmable buttons and functions similar to the handgrips.
Modern operative microscopes have an electric motor that affords smooth movements for repositioning the microscope. A well-balanced microscope head can be moved in multiple directions with handgrips, a foot control panel, or a mouth switch (Fig. 2.4). Although not included with the standard microscope configuration, a headpiece device for the surgeon has been developed that allows hands-free positioning of the microscope. 8 The surgeon’s and face-to-face observer’s microscopic views are three-dimensional because of the two space-separated beams of light projecting in two eyepieces separately (Fig. 2.5). However, the side observer’s view is not three-dimensional because both observers eyepieces receive the same one beam of light from a side beam splitter (Fig. 2.5). The operative field is illuminated coaxially through the objective lens from a built-in light source. Coaxial lighting is absolutely essential for reaching deep lesions; thus, it is also needed in training exercises involving a deep operative field.
Despite the complex structure of the various types of modern microscopes, the principles of working with them remain the same. The basic adjustments of the microscope for obtaining an optimal view include adjustment of (1) the interpupillary distance of the eyepieces; (2) the individual eyepiece magnification with the diopter setting ring for sight correction; (3) the zoom (magnification); and (4) the focal distance, either manually (basic models) or automatically (advanced models).
The surgeon sets the appropriate interpupillary distance by positioning his or her eyes about 1 inch from the eyepiece. The small round optical fields should be visible separately. The adjusting knob is then turned until the two circles overlap completely. Most microscopes have an interpupillary distance scale near the knob for fast settings. With repeated practice, trainees will begin to remember the exact value of their own interpupillary distance.
The eyepiece diopter correction is essential for maintaining the focus of the microscope whenever the magnification is changed. If the operator needs no correction for his or her vision, the eyepiece should be set at zero. Nearsighted or farsighted operators who wish to operate without glasses should adjust the diopter setting of the eyepiece according to their individual eyeglasses prescription. Alternatively, the microscope can be used while wearing eyeglasses, especially if the correction is more than 3 diopters. When using eyeglasses, the eyecaps on the eyepieces should be adjusted to a minimum to ensure the full field of view is visible. On some microscopes, the rubber eyecup should be removed from the eyepieces in order to see the full field of view when wearing eyeglasses.
The focal distance of the microscope lens is one of its most important features. In older models of the operative microscope and in the most current laboratory-grade stereomicroscopes, the total focal distance is significantly affected by the focal distance of the objective lens. In such microscopes, the focal distance is indicated on the frame of the lens, and it must correspond to the distance between the lens and the planned surgical target. Objective lenses are available with various focal distances (e.g., 200 mm, 250 mm, 300 mm, 400 mm, etc.) and can be interchanged before surgery to accommodate longer (~40–50 cm in spine surgery) and shorter (~20–40 cm in cranial surgery) working distances. Most modern operative microscopes incorporate a variable focusing system (varioscope) that allows for continuous adjustment of the working distance and magnification for near distance positioning and for far distance positioning, without the need to change the objective lens.
The total magnification of the microscope depends on the focal distance of the objective lens and on the magnification factor of the three key optical components: the eyepieces, the magnification changer, and the objective lens (Fig. 2.6). Eyepieces usually have a magnification of 10x or 12.5x for operative microscopes, although higher magnifications (20x) may be chosen for custom-built training stereomicroscopes.
The magnification changer assemblies of operative microscopes differ significantly from those of laboratory stereomicroscopes. Depending on the configuration of the operative microscope, the magnification changer assembly may include up to three components for magnification adjustment: a foldable binocular tube with an integrated two-step manual magnification changer (Promag [Carl Zeiss Meditec, Inc.], 1.0x or 1.5x magnification); an additional three-step manual magnification changer (1x, 0.6x, and 1.6x); and a motorized zoom lens mechanism. The zoom lens mechanism provides a stepless change of magnification from 0.4x to 2.4x. The field of view diameter depends on the magnification and is between 1 and 10 cm.
The field of clear view (i.e., the focal depth) is the range of depth of the operative wound that is clearly visible at a given distance through the microscope. This depth depends on the focal distance of the lens, the degree of magnification, and the optical system of the microscope. In modern microscopes, the field of clear view is deep enough to provide a clear and in-focus view of both deep and shallow structures in the surgical landscape. The focal distance must be adjusted such that most of the field of clear view is slightly higher than the object, which allows the surgeon to clearly see the tips of the instruments and the operative field. The surgeon should first adjust the focus to the highest magnification and then return the setting to the lower magnification. Doing so allows the object to remain in focus when the magnification is subsequently changed. This algorithm for adjusting the microscope is essential knowledge for any trainee (Table 2.1).
Control of light intensity and magnification are essential for microscopes used in training. The most suitable microscopes for laboratory use have a built-in white light source (typically halogen), a magnification of 2x to 40x, and a focal distance of 200 to 400 mm. The training microscope should also have a double optical system or a built-in video camera connected to a monitor to enable the instructor and the trainee to observe each other’s technique. This system enables the instructor to coach the trainee and to evaluate the trainee’s skills.
The use of video recording can facilitate the post-training assessment of the technique. It allows trainees to film their microsurgical practice sessions for self-analysis and for later discussion with the instructor. Videos from practice sessions can be used to capture photographs, which can be used for publications. In addition, intraoperative images can form the basis for artist’s illustrations.
A portable benchtop stereomicroscope is suitable for initial and continuing dry microsurgical training (Fig. 2.2a). However, unless they are customized, benchtop stereomicroscopes usually have a short focal distance that does not allow training with long instruments in a deep operative field. In contrast, simple operative microscopes, such as OPMI 1 (Carl Zeiss Meditec, Inc.) and higher-grade microscopes, have a longer focal length and a flexible suspension system and are considered optimal for a training laboratory (Fig. 2.2b–d).
In some ways, the surgeon can be compared to a fighter pilot, who must study the operation of the aircraft engine in order to become intimately familiar with it, even if someone else performs the actual engine maintenance. Learning the proper operation, care, and maintenance of the microscope is part of the surgeon’s job, simply because the microscope is such an essential part of the operating room armamentarium. Preoperatively, the surgeon should check three important systems of the microscope: the electrical, mechanical, and optical systems. The electrical components include the manipulators, the foot control panel, and the light source. The handgrips and the foot control panel should be tested to ensure that the microscope will respond to their commands. Buttons and switches on the handgrips and foot control panel should be programmed beforehand in the way that is most comfortable for the neurosurgeon (Fig. 2.3c,d, Fig. 2.4). If the microscope light is not bright enough or if the remaining lamp life is short (based on the total hours used, usually 500 h maximum), it should be replaced beforehand to prevent the loss of illumination during a critical step of the operation. Other checks include the proper positioning of the microscope in the operating room, the proper placement of the eyepieces for the surgical assistant, and the balancing of the microscope head to ensure its smooth and easy movement. Finally, all the lenses should be cleaned, especially the objective lens, which often becomes soiled by droplets of blood and solutions. Any necessary optical adjustments can be made to the lenses after they are cleaned.
Setting Up the Operative Microscope
When preparing the operative microscope for use, the following sequence should be observed:
Change the objective lens to one with a focal distance (f) that corresponds to the distance from the microscope to the operative field. Typically, a lens with f = 20 cm is used for surface operations, one with f = 40 cm is used for spinal surgery, and one with f = 30 cm is used for cranial operations.
Position the co-observation tube for the surgical assistant in accordance with the operation: face to face (for spine and microsurgery training) or to the side beam splitter port (for cranial and microsurgery training). The side is usually opposite to the hemisphere being operated, that is, the co-observation tube will be on the left for a right-sided approach.
Check the functionality of all the electrical, mechanical, and optical parts of the microscope, including the knobs and electronic switches that control the light, magnification, focus, and release of the magnetic brakes.
Balance the microscope.
Adjust the interpupillary distance of the eyepieces.
Adjust the eyecup so the entire field of view is visible.
Adjust the diopter setting on the eyepieces separately for each eye.
Set the microscope to the lowest magnification.
Cover the microscope with a sterile drape.
2.3.2 Surgical Loupes
Unlike high-cost microscopes (that may cost anywhere from US $10,000–$500,000), surgical loupes (that usually cost from US $20–$1,000) are a cheaper and more mobile instrument. However, surgical loupes are not adjustable and they lack the necessary magnification to support many microsurgical manipulations. They provide only low-resolution views (the usual magnification is 2x to 8x), which make it difficult to maintain a clear view during some manipulations. Loupes can have either a fixed working distance or an adjustable working distance (the distance between the eyes and the operational field). Before purchasing personal loupes, surgeons should determine their individual optimal working distance. Although loupes are considered a personal item, those with adjustable intrapupillary distance can be shared by several users, which can be economically advantageous.
2.3.3 Exoscopes
The exoscope is another technologically advanced tool in the surgeon’s armamentarium that is used to provide a magnified view of the operative field. The exoscope combines the features of an endoscope and a microscope. The optics of the exoscope are positioned outside of the wound, like a microscope, but the image is displayed on a monitor similar to the way an endoscope functions. Exoscopes display high-quality two-dimensional or three-dimensional video with acceptable visualization of the surgical field and a wide range of magnification from 2x to 40x. (Fig. 2.7). Exoscopic technologies are only now being integrated into operating room equipment used by neurosurgeons but will likely be routinely used alongside the operative microscope in the near future. 9 , 10 Some exoscopes have a robotic positioning arm that automatically aligns the exoscope with the desired trajectory by using neuronavigation input or by using controls on the foot pedal. This hands-free positioning function presents a completely new way of providing visualization in the operating room, which increases the surgeon’s comfort when working on deep structures within narrow and complex anatomical corridors. Our laboratory experience with the exoscope indicates that its combination of high magnification with a high-resolution stereoscopic view facilitates the performance of microsurgical steps, with technical results comparable to those with the use of a standard operative microscope.
2.3.4 Microsurgical Instruments
The ability to properly perform microsurgical techniques depends not only on the extent of the surgeon’s training, but also on the quality of the instruments the surgeon uses. The actual effects of surgery are actuated by the use of the microsurgical instruments, so the better the instruments, the better the microsurgical results. The extremely thin tips of the instruments can be easily bent, making it impossible for them to properly hold suture materials and tissues. Having to work with damaged instruments—even during microsurgical practice—can create unnecessary difficulties, frustration, and anxiety. The end result is often a lesson on how not to perform better; instead, the surgeon or trainee must focus only on how to overcome the obstacles that might otherwise have been easily prevented. Thus, trying to practice with less than perfect microinstruments is simply a waste of precious time. There is no nobility in working with bad instruments, even in the laboratory.
Ideally, each trainee should have a personal set of microsurgical instruments, with a customized case and rack for them. Each trainee should also have an individual microscope, or an assigned and protected time to work with the laboratory microscope during training. In some neurosurgical centers in Japan, the United States, and China, trainees are provided with personal microsurgical instruments that are paid for by the clinic or university. However, the high cost of microsurgical instruments precludes such largesse in every case. Thus, the training laboratory should always have on hand several sets of the basic microinstruments for common use. Microsurgical instruments produced by different companies differ greatly in quality and price. We recommend nonmagnetic titanium or high-grade stainless steel corrosion-proof microsurgical instruments. 11
In choosing the microsurgical instruments they will use, surgeons should pay attention to the shape of the handle, because the shape influences the surgeon’s ability to manipulate the instrument as needed without losing control of it. Most handle shapes are either flat or round. Instruments with a bayonet-like shape are used for microsurgery in a deep and narrow operative wound. Bayoneted instruments prevent the hand and the handle from overlapping with the microscopic field of view during surgical maneuvers. Most instruments have fluted or corrugated surfaces on the handles to increase friction and resistance to slipping. With increasing experience, each neurosurgeon develops his or her own preferences regarding the types of instruments and the methods for holding them.
One of the most important characteristics of microsurgical instruments is their fragility. The tip of an instrument can be measured in thousandths of an inch, which corresponds to the thickness of the 10–0 suture. Following several simple rules will keep instruments in perfect condition for a long time:
Do not transport an instrument outside the case, which makes it more vulnerable to being bent if it is accidentally dropped. Always transport the instruments in the carrying case, whether they are dirty or clean.
Do not hold more than one instrument in one hand.
Always clean the instruments one by one.
Do not mix microsurgical instruments with other surgical instruments.
Do not touch the tips of the microsurgical instruments to other hard metal objects.
To avoid rust, do not keep the instruments moist for a long time or autoclave the instruments far in advance of use.
Do not use the instruments for work on cadavers or other non-living biological tissues, because by regulation they must be cleaned and stored separately from instruments used in survival animal surgery. All instruments used in survival animal surgery must be sterile.
Following these simple rules will help to maintain the microsurgical instruments in perfect condition over a longer period of time. Doing so will also lead to a better training experience and will facilitate many surgeries.
Needle Holders
The needle holder is optional for microneurosurgical training, because in most cases a needle can be handled with forceps. Many neurosurgeons use microforceps as needle holders, partly because it rules out the necessity of choosing the proper instrument to perform surgical manipulations between suturing. Needle holders come with and without a locking mechanism. Locking needle holders are not used for microsurgery, because their tips shift when the locking mechanism is opened or closed. Standard small stainless steel microsurgical needle holders with curved tips are good enough for initial microsurgical training (Fig. 2.8). The sole advantage of needle holders over microforceps is the solid fixation of the needle. However, in some cases, the use of a needle holder can be advantageous. For example, a needle holder with long rounded handles and curved tips (Fig. 2.8e) might be particularly useful for performing anastomosis in a deep and narrow operative corridor.
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3 Day 2: Dry-Laboratory Microsurgical Training: Techniques and Manual Skills
7 Day 6: Exercises: Kidney Autotransplantation, Supermicrosurgery, and Aneurysm Clipping
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