8.1.1 Dry-Laboratory Training

Many training centers use silicone tubing to model blood vessels to help students perfect their suturing techniques at the beginning of microsurgical training. Synthetic models are recommended for studying the basic steps and techniques of performing different types of anastomoses. Dry training may be included in the curriculum for beginning students and for the first day of intensive microsurgical courses.

The primary disadvantage of synthetic models is that they do not allow the student to feel the real resistance and tension that living tissue provides when the student is practicing suturing, dissecting, and tightening knots. For this reason, nonliving tissue models can be used in the later stages of dry training after the theoretical basics and sequence of surgical steps has been covered.

Laboratory animals should not be used in the first few days of training for several reasons. First, at the beginning of training, working under “real” conditions is not so important; second, ethical guidelines favor reducing the use of animals; and third, using fewer animals will reduce the cost of training. Dry training may also be useful in the later stages of training when the same anastomosis is to be performed in a deep operative field or other inconvenient environment where the instrument positions and moves differ from what was initially mastered.

After trainees study the technique of performing microanastomosis on nonliving tissue models, they can begin to practice on live animals. It is better to use recycled laboratory animal material from the training of more experienced trainees first, as prepared animals can be kept refrigerated (at about 4°C) for up to 1 week after defrosting without losing the natural elasticity of the tissues.

Poultry Arteries

Chicken wings and legs are easily accessible material for learning to perform microvascular anastomoses ^{1 ,​ 2} (Fig. 8.1). A characteristic of tissue that is not fixed in formalin is that it dries out quickly; therefore, the anastomosed vessels should be regularly moistened with an isotonic solution. Turkey wings and necks have larger arteries than chicken wings and necks. The turkey arteries are similar in diameter to the human middle cerebral artery and superficial temporal artery and may also be used for microsurgical practice. ^{3 ,​ 4}

8.1.2 Wet Training

For optimal use of laboratory animals, a single animal may be used to perform several different anastomoses. Bypass exercises can also be performed on tissue-based models other than live laboratory animals.

Human Placenta

Human placenta is a good source of small vessels for microsurgical practice. The human placenta has an oval shape with a diameter of 16 to 20 cm, a thickness of 2 to 3 cm, and weight of 500 to 600 g. The fetal surface of the placenta is covered with two closely adherent membranes, the chorion and amnion, which are similar to the arachnoid membrane and contain many vessels with diameters ranging from 1 to 6 mm. After approval is received from the local ethics committee, a placenta can be successfully used for microsurgical training (Fig. 8.2). ^{10 ,​ 11 ,​ 12}

To prepare a placenta for use in microsurgical training, the student should remove the fetal allantoic sac and cut the umbilical cord, leaving a stump of about 5 cm length for insertion of the catheters for flushing the vascular beds and for pressurized infusion. The outer surface of the placenta then should be cleaned from blood products using tap water. Infusion of the cannulated umbilical cord arteries and veins with water or normal saline using a 50 mL syringe washes the blood clots from the vasculature. Cleaned placentas may be stored dry in a closed container under refrigeration (about 4°C), but not frozen, for approximately 1 week during the training and then appropriately discarded. ¹⁰ We have attempted to store the placentas in isotonic solution, but we found that they are better preserved when stored without any solution.

8.2.1 When to Start Microsurgical Practice

Microsurgical training should begin as early as possible and include theoretical and practical courses. These courses should be divided into general and specialized training. General training is not dependent on the surgical specialization of a trainee and consists of learning laboratory animal care, anesthesia, microsurgical dissection, and suturing on synthetic and real tissue models. After learning these techniques, the curriculum should be directed toward learning specialized skills that are germane to the specific clinical goals of the trainee. Specialized training is conducted to gain proficiency in microsurgical techniques. The learning of difficult or specific skills and techniques is conducted purposefully to meet the requirements of a particular subspecialization or operation that the surgeon expects to perform.

8.2.2 Regularity

The educational process is most productive when the training sessions occur regularly and are of an appropriate duration. Training sessions should not be too short (shorter than 1 hour) or too long (longer than 4 hours), because fatigue will prevent optimal skill development. The most favorable duration for a dedicated session is 1 to 3 hours, with short rest periods every 40 minutes, or as necessary. The optimal time for practice is summer or holiday seasons when staff neurosurgeons take vacations and the volume of cases decreases. Many short courses offer basic 2-day microsurgical training. However, we believe that such training is less effective than ongoing, periodic training that occurs over a long period, despite the financial and logistical attractiveness of the shorter programs.

After 2 hours of working with a surgical microscope, a trainee may have difficulty with visual accommodation, which decreases the ability to focus, making training less effective. Additionally, microsurgery is full of details and subtleties that must be ingrained into habits, which are difficult to learn in such a short training period.

Approaches to microneurosurgical training schedules vary by nation, institution, and mentor. Good examples are neurosurgery departments and laboratories at universities in Kyoto, Fujita, and Fukui (Japan), where students and neurosurgery residents undergo rigorous and continuous training to master the basics of microsurgical training. The residents attend 2 classes of basic dry microsurgical training and practice 2 or 3 times per week in the laboratory over the course of their 7-year neurosurgical residency. Attending physicians and professors have free access to the laboratory and may also maintain their skills with regular exercises in addition to clinical practice.

8.2.3 Sample Structure of Microsurgical Training

The training begins with introductory lectures on the microsurgical tools and equipment (Chapters 1 and 2) and then 4 to 6 hours of dry training practice on knot tying and instrument handling (Chapter 3). The next 2 days are devoted to learning principles of work with laboratory animals, anesthesia, surgical approaches, and simple vascular anastomoses on a tissue model (Chapters 4 and 5). The following days are aimed to secure acquired skills and study more complex anastomoses on smaller arteries, veins, and in a deep operative field (Chapters 6 and 7).

Microsurgical training courses (Chapters 4–7) should be set at least annually and be performed along with cadaveric courses on neurosurgical anatomy and procedural simulation on computer virtual reality models. The dry training (Chapter 3) is then regularly used as a tool for rehearsal before an operation and to maintain microsurgical suturing skills. Finally, the microsurgical skills are refined in the operating room during real surgeries.

8.2.4 How to Get Involved

Training time goes by fast, and there is never enough time for regular training and practice in the laboratory. Several approaches may help the trainee to stay on schedule. If you want to pursue a career in cerebrovascular surgery, one good option is to seek an opportunity to collaborate with colleagues in the research department and to ask if you can work on a project that involves vascular surgery in rodents, such as arterial anastomoses or transplantations. Such research would result in the accumulation of necessary manual skills over time.

Trainees should practice microsurgery using the operative microscope whenever possible to develop the skills required for work under high magnification. Suturing the dura mater and closing wounds will initially take a long time under the microscope. As microsurgery skills are acquired, these procedures can be performed more quickly and with better precision and accuracy while the trainee’s comfort with working with the operative microscope improves significantly. ¹⁶ Participate in advanced training courses on a regular basis, at least once per year. These practices are unique opportunities to go beyond the usual intraoperative scenarios and try new techniques.

Dry microsurgical training should be easily accessible in the resident’s room. It should not take longer than moving a chair and turning on the light of the microscope to start a knot-tying practice session. The deliberate and focused practice of knotting techniques on a regular basis allows the student to sustain and advance their bypass skills. This practice may be performed every day even at home as off-the-job training. ¹⁷