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.

Follicular Unit Transplantation is a technique, 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 transplanted. 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.

Note: this material is based on publication authored by Dr. Rassman, Dr. Bernstain and Dr. Cole.