Microsurgery Exercises

Training in a laboratory with an operating microscope often takes long hours of concentrated work. This task is impossible to accomplish unless the surgeon has a comfortable and perfectly balanced position.
Position of the legs
One should remove every object from the way of the legs on the ground which can disturb convenience. It is also important to have enough place for the knees, hence sitting at a table with drawers is not always suitable.
The way of sitting
It determines two very important issues. On one hand, it affects the ability of manipulation, on the other hand it affects how we see through the microscope. We can only work without hand tremor if both forearms are resting on the table (Yasargil 1975). One should not achieve this immobility by leaning on the elbows, as it quickly leads to fatigue and tremor of the hands. Turn the light source on, focus on the filed and instruments held in both hands into the middle of the field trying different magnifications. The final adjustment is provided by the conformity of body position and microscope adjustments. After a few occasions, we just briefly and routinely perform these procedures.

Adjusting the microscope
1.  Position the eyepieces at 0 diopter.
2.  Adjust the fine focus.
3.  Set the interpupillary distance.
4.  Choose the lowest magnification and focus on the spot that you previously marked by using the coarse focus.
5.  Choose the highest magnification and adjust the fine focus also for this magnification. The reason for starting the fine focusing at the highest magnification is that the microscope will be focused in the smallest depth of the field, thus allowing a perfect focus at all magnifications.
6.  Switch to the lowest magnification without modifying the focus, and set the eyepieces to the lowest possible diopter. Adjust the diopters separately for each eye by rotating the lens of the eyepiece clockwise.

Advices
·  The operating microscope is a complex, expensive and delicate instrument. When adjusting the knobs use only your index finger and thumb so that you will not over-tighten the screw mechanism.
·  When turning the light source on or off, make sure that the light intensity is set to minimum. By doing so the life of the light bulb will be prolonged by almost 50%.
·  While working, adjust the light to the lowest comfortable level. This protects your eyes from exhaustion.

Appropriate position of the hands and tools are very important in microsurgery. Please note that only the fingers are allowed to move during work and the arm shoulders rest on a solid surface. This way we can cancel unnecessary movements. The instruments are held like we hold the pen using three fingers, the thumb, the index and the middle fingers. The elbows, the wrists and the ulnar sides of the forearms should lie on the table. The arms should include a 60 degree angle with each other, so the arms get into a slightly supined position.

		Hold the instruments as a pen (Acland 1989).

		If we do not have a chance to support the forarms properly, touching middle fingers with each other improves comfort and stability (Acland 1989).

During microsurgery, the eye-hand coordination can be practiced and well improved by scraping off printed letters from a sheet of paper using an approx. 20 G needle under the microscope. First we practice how to bring the tool into the microscopic field, then using the tip of the needle, we slowly remove separate letters. With small, horizontal movements we sweep off the removed dye spots using a cotton tip applicator held in the left hand. Use low amplitude movements and high frequency. Speed is unimportant! Avoid puncturing of the paper. The goal is to remove the letter leaving a macroscopically invisible spot behind.

Using two forceps, we remove a vertical thread from a gauze dressing. Next we put it back into its original location in the net. Pay attention, you should use both hands equally for grabbing the thread. Grab the thread as many times as possible. The aim is to achieve a state where the previously removed vertical thread is indistinguishable from the rest of the net.

It is particularly important to practice the stitching and knotting in microsurgery. We use 10/0-7/0 atraumatic needles which are permanently attached to a fine monofilament thread. The cross section of the needle is somewhat flat so it cannot turn around along its axis when held in the needle holder. We grab the needle closed to the thread (at 1/3 of the needle). At the beginning even grabbing of the needle represents a problem. The recommended technique is shown here:

Holding the thread in the left hand, lay the greater curvature of needle on the surface a way it gets into position where it is suitable to grab it with and instrument held in the right hand (Acland 1989).

		For a right-handed person the steps are as follows: the needle is held in the forceps in the right hand, the forceps in the left hand is put under the incision (to expose the wound on the right side). Never grab the edge of the structure to be sutured with the forceps. The axis of the needle should be held perpendicularly to the surface to be sutured. The distance from the edge should be approx. two times the diameter of the needle (Acland 1989).

		On the left side: Let us make the tip of the needle get out exactly in line with the stitch on the right side. (Acland 1989).

		When the tip of the needle is visible on the left side, we grab it with the left forceps and pull the needle out. Be careful and do not disconnect the thread from the needle. Let us try to avoid surface friction by retracting with the left forceps when the needle is pulled through the rubber. (Acland 1989).

		When we pull the thread through counteract the friction by retracting with a forcep held int he right hand (Acland 1989).

Microsurgical knotting evolves the simultaneous use of two instruments, similarly to the laparoscopic approach. In the clinical practice, two major methods of tying knots are applied: the one-handed and the two-handed versions. The one-handed version resembles the method used in macroscopic instrument-aided knotting procedures, because the long part of the thread is held always in the same hand, whereby the thread is passed into the other hand during the two-handed procedure.

The first knot
Grab the long thread with the right needle holder at a distance which can be easily looped around the tip of the left forceps (direction: towards the “short end”, distance: 3 times the length of the “short end”) (A). Reach and pull the “short end” through the loop with the left forceps (meanwhile do not let the loop slip off) (B). Pull only the “long end” while firmly holding the “short end”, and tighten the knot (C).

Attention
1. When the knot is tightened, the edges of the rubber should only touch each other - do not overlap! In order to achieve this, the distance of the stitch from the edge should not be large and the knot must not be very much tightened.
2. Do not pull the “short end”, pull only the “long end” otherwise the knot looses its ideal structure.

The second half of the knot
Move the”long thread” to the side of the short end (D), grab the “long end” now with the left hand (distance: 3 times the length of the “sort end”) (E) and wrap it around the right forceps (direction: opposite to the “short end”) than grab the “short end” with the right forceps and pull it through the loop (F), and tighten the knot. Eventually, cut both the “short and long” ends approx. 3 mm long.

We should distinguish the two ends of the thread as “long end” (to which the needle is connected) and “short end” (which resides on the right side after the stitching).
We grab the long thread with the left forceps (A) at a distance which can be easily looped around the tip of the needle holder held in the right hand (direction: towards the “short end”, distance: 3 times the length of the “short end”). This way a loop is created around the tip of the instrument held in the right hand (B-C). We grab the “short end” with the right instrument and move it to the opposite side (D-E).
The thread resides in the left forceps, and looping the long thread in the direction of the short end we create a second loop (G-I). By moving the short end to the other side we tighten the loop. This square knot is created similar to that of used in the macrosurgery.

Surgeons’ knot
If the first loop is doubled, a surgeons’ knot is created which is less likely to get loose during the second knot is performed.

Attention
The knot is not twisting/ turning aside (stays a real square knot) if the long thread is pulled when the knot is tightened.

Preparation
• The prepared vessel is first placed on a moistened gauze sheet. We keep it always wet in order to prevent drying out of the vessel wall.
• The isolated vessel should be clamped with two clips at a set and stable distance and cut completely trough perpendicularly to its axis.
• The lumen should be rinsed in both directions with a solution containing high concentration of heparin.
• The adventitia (a thin, fiber-rich layer on the surface) should be removed in a few millimeter distances from the edges (using forceps and scissors) (Eisenhardt 1980).

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The technique of the stitching and knotting (demonstration of the “3 o’clock-stitch”)

	First we expose the right side of the vessel with the left forceps. We stitch into the right side of the vessel with the needle held in the right forceps (distance: two times the diameter of the needle) and we exit the vessel wall reaching the lumen. We leave an approx. 1 cm long “short end”.

	When stitching the left side, grab the needle with a needle holder held in the right hand, and stitch from the lumen toward the adventitia in this case. Knotting is performed according to the instructions detailed above (Yonekawa 1999).

Frontal surface:
                            (1) stitch at „12 o’clock”,
                            (2) stitch at „6 o’clock”,
                            (3) we place a silastic cannula into the lumen

                            (4) stitch at „3 o’clock”,
                            (5) stitch at “1.5 o’clock”,
                            (6) stitch at „4.5 o’clock”,

Dorsal surface:
                            (7) stitch at 1.5 o’clock”,
                            (8) continuous suture which consists of 2 steps:
                                    stitch at „3 o’clock”,
                                    stitch at „4.5 o’clock”,
                            (9) removal of the silastic cannula, knotting.

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                            The steps of the stitches at the dorsal wall

The first stitch is placed at the upper 1/3 (7. step), which is followed by a regular knot. At the last two stitches, we apply a continuous suture (8), this enables us to remove the silastic cannula without the necessity of putting in further stitches. First we knot the upper loop, than we cut it and we finish with the lower loop.
We can check the tightness of the stitches by careful pulling of the vessel. By flushing the lumen, we can make sure the water-tightness of the anastomosis in vitro. To this end, we insert a longer piece of the afore-mentioned silastic cannula into the lumen and tie it to the vessel. We flush the system with a saline solution from a syringe and check if the solution is leaking. If the saline is dripping only from the other end of the vessel, it shows that the vessel permeable and the stitches are tight. Under in vivo conditions, we always have some leakage among the stitches (owing to the high intraluminal pressure in the arterioles), which is clotted in a few minutes due to normal coagulation processes. A fibrotic tissue formation will later develop, and after its resorption, the lumen will stay fully permeable.
We have to take care about the following factors during microvascular anastomosis preparation:
• The adventitia should be carefully removed. Adventitia entering the reconstructed vessel lumen causes microtrombus formation. If the stitch is placed into the adventitia, the knot splits easily.
• If the stitch is placed far from the edge of the vessel, or if the knot is very much tightened, the vessel edges overlap which reduce the lumen of the vessel.
• Let us not stitch too deep, because we may include the dorsal wall into the stitch. This can also be avoided when the needle is grabbed not very far from its tip.
• It is characteristic feature of the microsurgical stitches that those should be placed faultlessly (to the right spot) for the first time, because repeated stitches make more holes and deteriorate the structure of the microvessel.

A.	B.
C.	D.
E.	F.

A.	B.	C.

D.	E.	F.