Making an Incision

Many of the procedures explained in subsequent chapters of this book
involve making incisions into the skin. Whether it be to remove a suspicious
lesion or to create a flap for wound coverage, you must learn
how to make an incision safely and efficiently. You will use a knife with
a very sharp blade. It is important to know how to use the knife properly
to prevent accidental injury to the patient or yourself.
Which Blade to Use
Knife blades come in various sizes (see figure below). There is no orderly
scale to follow as with needle sizes. A no. 11 blade comes to a sharp
point, whereas a no. 15 blade has a rounded end. A no. 10 blade is twice
the size of the no. 15, and a no. 20 blade is bigger than the no. 10. It can
be confusing, but most blades come with a picture on the packaging.

Commonly used knife blades. A, no. 11 blade; B, no. 15 blade; C, no. 10 blade.

Table 1. Deciding Which Blade to Use


* This table describes the optimal knife blade to use if you have a choice of sizes. If you do not have
the luxury of choice, any blade can be used for almost any situation.

Holding the Knife
For safety, use a blade only when it is attached to a handle. Some disposable
knives come with the blade already attached to the handle.
When they are not available, you may have to put the blade onto a
knife handle yourself. Never touch the blade with your fingers; it is
very sharp. Use a clamp or needle holder to grasp the blade, and position
it onto the handle.
Hold the handle with your dominant hand, as if you were using a writing
instrument. To have the best control over the instrument, hold the
handle 3–4 cm away from where the blade meets the handle.


Hold the knife like a writing instrument 3–4 cm behind the point where the
blade meets the handle.

Using the Knife
When you are about to make the incision, place the tissue under some
tension. Use the index finger and thumb of your nondominant hand to
push down on the skin, spread it apart, and make the skin taut. This
technique makes the skin easier to incise.

Make the incision with the flat part of the knife, not the very tip. Push
the blade down with just enough pressure to cut through the skin. You
do not have to go exactly to the proper depth with the first cut. It is
better to be too timid than too forceful. If you use too much force to
make the incision, your knife may penetrate too deeply into the tissues
and accidentally cut an important structure.
Which Side to Incise First
When you have to make two incisions (for example, to remove a suspicious
skin lesion), look at their orientation. If they are to be made one
above the other (for example, if you are working on the side of the leg),
do the bottom skin incision first. If the top incision is made first, blood
from the skin edges will drip down and obscure the area below. The presence
of the blood makes it more difficult to perform the lower incision.