Hair Transplant Surgery
Step by Step - Follicular Units

What are Follicular Units?

Most people imagine that hair grows individually, one by one, and that the closer they are, the greater the density (hair volume). Wrong.

Hairs do not grow from your scalp one by one as many believe, but rather in groups of 1, 2, 3, and rarely 4, hairs, called follicular units (FUs).

*normal scalp magnified 50x under a microscope

Therefore, the concept of “hair by hair transplant” is not only wrong in terms of how the procedure is performed, but also does not provide volume in the final result, as we would damage the FUs with more than one strand of hair.

Each FU is composed of, besides hair follicles, a sebaceous gland, bulbs (root of hair) and arrector pili muscle.

FU types

Therefore, there are four types of follicular units (FUs) as follows:

1-hair FU or single hair – among these we find Ultrafine single hairs (finer hairs – click here to read more about Ultrafines)

2-hair FU

3-hair FU

Follicular Group – FU with up to 4 hairs (rare)

Follicular units: 1 and 2, 3 hairs, ultrafine (left) and follicular group (right)

Everyone has follicular units of 1, 2, 3 and up to 4 (more rarely) hairs.

However, the higher the percentage of 3-hair FUs, the greater the density and hair volume, and the higher the percentage of 1 and 2-hair FUs, the lower the density.

Patients who have a higher number of 3-hair FUs will have better results in terms of fuller hair, and those who have a higher number of 1 and 2-hair FUs (therefore a lower percentage of 3-hair FUs), will have “less fullness” in their results.

To illustrate, imagine a forest in which 80% of the trees have 3 branches and the other 20% are trees with 1 or 2 branches. In second forest, the opposite occurs, only 20% of the trees have 3 branches and 80% have 1 or 2 branches. If you were to fly over these two forests, which would you see more green and less soil?

Obviously, it would be the forest that has a higher percentage of trees with 3 branches. The same thing happens with hair on the scalp.

*Donor area with high density vs. Donor area with low density

The correct procedure then is to transplant follicular units or grafts.

At the end of a megasession we determine the exact number of FUs. After we multiply by the number of hairs in each graft and therefore we have the exact number of hairs.

The average number transplanted in a megasession is 2000 to 2500 follicular units, with corresponds to 4500 to 5500 hairs varying from patient to patient in accordance with:

· the distance between the FUs.

The closer the FUs are to one another, the greater the density, in other words, the closer the hairs, the greater the density. To give you an idea, the number of FUs per square centimeter may vary between 50 and 100, depending on each patient and each area.

Consider the following situations:

Patient A has 100 FUs per cm2: 50 3-hair FUs, 30 2-hair FUs and 20 1-hair FUs.

The total is: (50 x 3) + (30 x 2) + (20 x 1) = 150 + 60 + 20 = 230 hairs.

Patient B has 70 FUs per cm2, (because the distance between the FUs is greater). Of this total, 20 are 3-hair FUs, 20 are 2-hair FUs and 30 are 1-hair FUs.

The total is: (20 x 3) + (20 x 2) + (30 x 1) = 60 + 40 + 30 = 130 hairs.

See the difference? There are 100 hairs less in Patient B in a scalp area the same size. Patient B therefore will not have the same result as Patient A in terms of “fullness” and coverage.

See examples below of 3 different patients with donor areas of low, medium and high density.

Low density | Medium density | High density

Separating Follicular Units

After removing the donor area, it is divided into increasingly smaller fragments until obtaining the Follicular Units.

Slivers
In the first step, using a powerful (high magnification) microscope, two assistants begin to fragment the donor area removed by transversely cutting it into very thin “slices” (less than 1 mm) of one follicular unit of thickness. These fragments are called slivers and should be very thin so that you can see translucently the FUs and their roots. This step is very important and requires extreme concentration and care from the person who is making the slivers so that no roots are transected, resulting in their loss. A good sliver is key to preparing a good graft.

*Donor area removed, transversal cut (sliver) and separated FUs

Preserving the Slivers and FUs
Both the slivers as well as the FUs are preserved in a refrigerated saline solution during the entire surgical procedure so that they do not dry out and we may therefore obtain the integration of 100% of the FUs.

Placement
The FUs should be handled with extreme care so that they are not damaged, especially their roots.

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There are two techniques for placing the FUs:

The first is to do a micro-perforation and place the FU immediately after (stick and place technique).

The second is to create all of the incisions and after insert the FUs.

Each patient has an appropriate indication for surgical technique and each surgeon has his or her preferred technique.

The important thing is that the first FUs to be made are the first to be placed so that they spend the least time possible outside the body, increasing their chances of integration, which nowadays may be 100% of the transplanted FUs, as long as all the necessary precautions are taken.