6.1 Microsurgical Training in a Deep Surgical Field

Each of the techniques described in this chapter should be mastered using both short and long microsurgery instruments. A deep surgical corridor can be simulated using different tools. The basic exercises to be practiced in deep field include dissection, tying knots on gauze, and performing anastomoses (both wet and dry laboratory training). For example, an end-to-side anastomosis can be performed on silicone tubes that are placed in a model of a skull (about 6 cm deep). A skull model with a craniotomy limits the possible movements of the instruments and the hands (Fig. 6.1). We have found plastic toy building bricks (Lego, The Lego Group) to be very convenient for assembling customized stands that can be used to help simulate the restrictions of working through a craniotomy and at depth in the surgical field during these exercises (Fig. 6.2).

6.2 Exercise: Deep Operative Field Dissection

The deep operative field dissection exercise is essential for microneurosurgical training. It must be mastered because the skills of sharp dissection in a deep operative wound are among the most essential for successful performance of microneurosurgical procedures in patients.

The following materials are necessary to perform the deep operative field dissection exercise:

1. 
   

   A customized stand, up to 10 cm in height, with an opening about 4 cm above the planned abdominal approach. The depth between the laboratory animal and the opening in the stand should be about 6 cm, which corresponds to the depth of the center of the skull base.

   
   
2. 
   

   Bayonetted microsurgery instruments of the appropriate length: needle holder, forceps, and scissors

   
   
3. 
   

   A microscope objective lens with a focal length of not less than 270 mm. Note that small laboratory stereomicroscopes may not have enough focal distance to allow dissection in a simulated deep operative field.

   
   
4. 
   

   Laboratory animal (e.g., rat) or other simulation model

After the rat is anesthetized, a median laparotomy is performed. The contents of the abdominal cavity are then carefully removed, retracted to the left, and placed on the moistened gauze.

Use bayonetted microsurgery scissors to perform sharp dissection and a suction tip to apply counterpressure. Then separate the abdominal aorta from the neighboring vena cava (Fig. 6.3, Video 6.1).

6.3 Exercise: Anastomosis in a Deep Operative Field

Neurosurgical trainees should have technical practice in performing microvascular anastomoses in a deep operative field. There are several clinical situations in which such skills are indispensable, such as anastomoses inside the interhemispheric fissure or deep inside the sylvian fissure and subtemporal approaches or anastomoses involving posterior fossa arteries. For experimental surgery in the laboratory setting, these situations can be simulated using a special stand to support the hands and to increase the depth of the operative field (Fig. 6.4).

Training for conducting anastomoses in the deep operative field can be done using any type of blood vessel. Rat carotids may be preferable to other rat vessels because their size more nearly matches the cerebral arteries of the human patient than other alternatives. However, exercises on the rat femoral vascular bundle are more demanding and therefore more challenging for training. For example, we describe an end-to-side anastomosis on a femoral vascular bundle that creates an arteriovenous fistula (Fig. 6.5).

The femoral vascular bundle is dissected in a standard fashion, and a small triangle of colored latex (i.e., a piece of a surgical glove) is placed under the vessels for better visualization. The temporary clips are applied to both the artery and the vein approximately 1 cm apart from each other. The end-to-side (end of artery to side of vein) anastomosis is then created using interrupted sutures. It is easier to make the opening in the vein when a traction suture is applied first to lift the vessel wall. The vein opening should not be too long, however, because the vein tends to collapse and shrink without the tension provided by blood flow. On the bloodless vein, the length of the incision may look appropriate, but it distends with arterial pressure, which can result in a much larger opening than originally thought.

To avoid a mismatch of the joining vessels, mark the planned arteriotomies on the distended vessels. Before tying the last suture, release the distal clip temporarily to wash out any thromboses and air. Then release the proximal clip temporarily for the same purpose before finally tying the last suture. After the anastomosis is completed, remove the distal clip first. Blood will fill the vein and the artery up to the arterial clip, which will then reveal any leakage. To stop a leak, place additional stitches at the site of the leak. In the final step, remove the arterial clip to allow the vein to fill with arterial blood, which causes it to become red and pulsatile. The change in color and the pulsation of the vein confirm the patency of the anastomosis.