What is Follicular Unit Transplantation
By Robert M. Bernstein, MD & William Rassman, MD

What are Follicular Units?

Human hair grows in tiny bundles called follicular units. Although this fact had been recognized for some time by histologists (doctors who study human tissue), the existence of follicular units has been largely ignored by physicians performing hair restoration surgery.

The follicular unit of the adult human scalp consists of 1-4 terminal (full thickness) hair follicles. In areas of the scalp affected by genetic balding, the healthy terminal hairs are gradually replaced by hairs of smaller diameter and length called "miniaturized" hairs.

In addition to the full terminal hairs, the follicular unit contains 1-2 fine vellus hairs, sebaceous (oil) glands, a small muscle, tiny nerves and blood vessels, and a fine band of collagen that surrounds the unit (the perifolliculum). The follicular unit is thus the hair bearing structure of the skin and should be kept intact to insure maximum growth.

The follicular unit is seen on the surface of the scalp as a tiny group of hairs that appear to be growing together. They are best viewed under a microscope where they are seen as well-formed structures in the skin.

What is Follicular Unit Transplantation?

Follicular Unit Transplantation is a technique, pioneered by the physicians at the New Hair Institute, in which hair is transplanted from the permanent zone in the back of the scalp into areas affected by genetic balding (and some other types of hair loss), using only the naturally occurring, individual follicular units. In order to remove follicular units from the back of the scalp without damaging them, the donor tissue must be removed in one piece. This technique, "single strip harvesting," is an essential component of follicular unit transplantation as it not only preserves the follicular units, but also prevents damage (transection) to the individual hair follicles. It differs dramatically from the minigrafting and micrografting technique of using a multi-bladed knife that breaks up follicular units and causes unacceptable levels of transection of hair follicles.

Another essential component of Follicular Unit Transplantation is "stereomicroscopic dissection." In this technique all of the follicular units are removed from the donor tissue under total microscopic control to avoid damage. Complete stereomicroscopic dissection has been shown to produce an increased yield (as much as 30%) of both the absolute number of follicular units, as well as the total amount of hair. (This procedure differs from minigrafting and micrografting in which grafts are cut using minimal or no magnification.)

A major advantage of follicular unit transplantation (besides preserving follicular units and maximizing growth) is that it allows the surgeon to use small recipient sites. Grafts
comprised of individual follicular units are small because follicular units are small, and because the surrounding non-hair bearing tissue is removed under the microscope is not trans-
planted. Follicular unit grafts can be inserted into tiny needle-
sized sites in the recipient area, that heal in just a few days, without leaving any marks.

When performed by a skilled surgical team, Follicular Unit Transplantation can produce totally natural-looking hair transplants that maximize the yield from the patient's donor supply to give the best possible cosmetic results. Because the tiny follicular unit grafts (and the very small wounds they are placed in) allow large number of grafts to be safely transplanted in one procedure, the total restoration can be completed in the fewest possible sessions.

The reason for using only Follicular Units

The fact that scalp hair grows in follicular units, rather than individually, is most easily observed by densitometry, a
simple technique whereby scalp hair is clipped short in a very
small area and then observed via magnification in a 10mm2 field. What is very obvious when one examines the scalp by this method, is that follicular units are relatively compact, but
are surrounded by substantial amounts of non-hair bearing
skin. The actual proportion of non-hair bearing skin is probably on the order of 50%, so that its inclusion in the dissection (or, conversely, its removal) will have a substantial effect upon the outcome of the surgery. When multiple follicular units are used (as in minigrafting and micrografting) the additional skin that is included will adversely affect the outcome of the surgery, by necessitating larger wounds, making the healing slower and often causing irregularities of the skin surface.

A great advantage of using individual follicular units is that the wound size can be kept to a minimum, while at the same time maximizing the amount of hair that can be placed into it. Having the flexibility to place up to 4 hairs in a tiny recipient site has important implications for the design and overall cosmetic impact of the surgery. This is one major advantage that follicular unit transplantation has over extensive micrografting. Follicular Unit Transplantation can minimize or eliminate the "see through" look that is so characteristic of micrografting.

The main reason for transplanting only individual follicular units is to duplicate the way hair naturally grows. By mimicking the way hair grows in nature, the doctor can insure that the transplant will look totally natural. Any grouping larger than the naturally occurring follicular unit will run the risk of a pluggy, tufted look.

The Importance of Keeping Recipient Sites Small

Using only follicular units enables the recipient sites to be kept very small. In fact, in Follicular Unit Transplantation, the sites are so small that they are made with specialized instruments that are the size of 18-20 gauge needles. This is about the size that is used in routine blood tests.

The importance of minimizing the wound size in any surgical procedure cannot be over emphasized. This, of course, includes hair transplantation as well. The effects of recipient wounding impact many aspects of the surgery. Larger wounds tend to injure larger blood vessels and although the blood supply of the scalp is extensive, the damage to these vessels can have a deleterious impact on blood flow to the tissues.

Especially when transplanting large numbers of grafts per session, it is important to keep the recipient wounds as small as possible so that growth will be maximized. The compact follicular unit is the ideal way to permit the use of the smallest possible recipient site, and has made the transplantation of large numbers of grafts technically feasible. Another important advantage of the small wound is a factor that can be referred to as the "snug fit." A follicular unit graft is so small that it can always fit into a tiny wound without having to remove tissue. Unlike the punch, which destroys recipient collagen and elastic tissue, a small incision, made with a needle, retains the basic elasticity (recoil) of the recipient site. When a properly fitted graft is inserted, the recipient site will then hold it snugly in place. This "snug fit" has several advantages. During surgery, it minimizes popping and the need for the sometimes traumatic re-insertion or re-positioning of grafts. After the procedure, it ensures maximum contact of the graft with the surrounding tissue, so that oxygenation can be quickly re-established. In addition, by eliminating empty space around the graft, microscopic clots are minimized and wound healing is facilitated.

It is important to note that when trying to place larger grafts (either round or linear), into a small site (kept small to minimize tissue injury) compression of the grafts is an undesirable consequence, and may result in a tufted appearance. In contrast, when transplanting follicular units, there are no adverse cosmetic effects of compression, since follicular units are already tightly compacted structures.

Finally, large wounds cause a host of other cosmetic problems including dimpling, pigmentary alteration, depression or elevation of the grafts, or a thinned, atrophic look. The key to a natural appearing hair transplant is to have the hair emerge from perfectly normal skin. The only way to ensure this is to keep the recipient wounds small.

How is Follicular Unit Transplantation Different from
Mini-Micrografting?

This is one of the most commonly asked questions and it is a very important one for those deciding which hair restoration procedure to choose. In contrast to Follicular Unit Transplantation, where the graft sizes are determined by nature, in mini-micrografting (the combination of minigrafts and micrografts as defined in Chapter 6) the graft sizes are arbitrarily determined by the doctor who cuts the donor tissue into the size pieces that he wants. Another name for this technique is mini-micrografts "cut to size."

In mini-micrografting, neither preserving follicular units, nor even keeping hair follicles intact, are felt to be that important. Rather, the speed and economics of the procedure are the deciding factors. Mini-micrografters use a multi-bladed knife to quickly generate thin strips of tissue and then use direct visualization (rather than microscopic control) to cut the tissue. The resulting grafts are generally larger than follicular units and since the excess skin is not trimmed away the donor sites (wounds) are also larger.

It should be apparent from the comparison shown on the next page that Follicular Unit Transplantation is superior in producing a natural, undetectable result, in maximizing healing, and preserving precious donor hair. Mini-micrografting, however, requires a smaller staff and each procedure is cheaper and shorter (although in the end it takes more procedures and therefore may cost just as much for this technique).

For more detailed information on NHI's Follicular Unit Transplantation, please see the reference section in the back of the book. Many of the original articles can be found on our web site www.newhair.com in the section, NHI Medical Publications

The following table summarizes the major differences between Follicular Unit Transplantation (FUT) and Mini-Micrografting