Follicular Implants: The Basic Building Block

Follicular Transplantation is based upon the fact that hair emerges from the scalp in naturally occurring groups called follicular units, which are comprised of 1 to 4 terminal hairs 1 . By using follicular units exclusively in the transplant, the surgeon can safely move large quantities of implants in a single session and can create hair patterns that most closely mimic nature. The essence of the follicular approach is that the natural hair groupings of the patient's hair dictate the size of the implant, rather than the doctor.

The sole use of large numbers of very small grafts for the treatment of androgenic alopecia is not new. First described by Carlos Ubel in Brazil in the early 1980's, its benefits were more recently popularized by one of us 3 . Although micrografts represented a significant improvement over the larger grafts, they were not ideal. As the profession gained experience with micrografts, a number of observations were made which suggested that this procedure needed refinement. Micrografts: 1) had a tendency to produce a look that was too thin, 2) often had inconsistent graft growth, and 3) at times required larger sites to accommodate the extraneous skin that was also transplanted.

The advantages of Follicular Transplantation over micrografting are that: 1) a fuller look is achieved, since the grafts are of the same size as seen in nature, 2) growth is more consistent, since the follicular units are left intact, and 3) the results are always natural, since follicular implantation allows the doctor to follow the pattern set by nature in a distribution that mimics the way hair grows in the patient's own scalp.

Follicular Transplantation enables the surgeon to restore more hair with a minimum amount of transplanted skin. In this procedure, the tissue between the follicular groups is dissected away, while the vital support structures around the units are preserved 1 . This produces very small "physiologic" implants which, in turn, can be inserted into very small needle sites. By keeping the recipient wounds small, the total surface area of the wound is often significantly less in large sessions of follicular implants than in smaller sessions using larger grafts. Because of the smaller wound size, greater amounts of hair can be safely moved per session. With follicular implants, the accelerated wound healing time and the smaller number of total surgeries required are of great benefit to the patient.

Figure 1. Micrografting vs. Follicular Transplantation. A three hair micrograft (A) that is derived from two separate follicular units may be only 50% wider than a follicular implant (B) derived from a naturally occurring three hair follicular unit, but can have 2 ¼ times the volume of tissue. These differences may be even more dramatic with larger grafts that include multiple follicular units.

Follicular implants differ from traditional 2-4 mm grafts or minigrafts in that the latter types consist of multiple, partial, or complete follicular units along with the intervening skin. Even micrografts, containing as little as two or three hairs may contain unnecessary tissue if the hair was derived from two or more distinct follicular units (figure 1). Hair moved in non-follicular units (grafts) results in transplanted tissue containing the same ratio of follicles to skin present in the donor area. As healing occurs, the fibrosis that forms around the larger graft contracts bringing the follicular units closer together. This contraction may increase the density of the hair within the graft to the point where it can exceed the density of the donor source. Conversely, if single hair micrografts are derived from splitting up 2 or 3 hair follicular units, the growth may be compromised. In Follicular Transplantation, single hair implants are derived from naturally occurring single hair follicular units so that all the germinative and support structures are left intact.

In all hair restoration surgery, the surgeon is confronted with the problem of having a relatively small amount of donor hair to cover a much larger recipient area (in a patient whose total volume of hair is inexorably dwindling). Therefore, the recipient density should not equal the donor density, much less exceed it. The pluggy appearance of traditional grafts are the inevitable consequence of ignoring this basic principle. If the follicular unit is maintained, the natural hair groups will be held in their normal anatomic relationship, and the appearance will be normal (figure 2).

Figure 2. A) Natural hair density. B) Grafts consisting of multiple follicular units. C) Coverage with follicular implants.

The follicular unit, the basic building block of Follicular Transplantation, consists of 1 to 3, less commonly 4, and occasionally 5 terminal hair follicles. It also includes 1 to 2 vellus hairs, the associated sebaceous glands, subcutaneous fat, and a circumferential band of collagen which defines the unit 1 . It is essential to have all these elements intact in order to ensure the optimal growth of the implants. The average density of hair in a Caucasian male is 2.0 hairs/mm 2 and the average density of follicular units is 1 unit/mm 2 . Although the density of hair can vary from greater than 3 hairs/mm 2 to less than 1 hair/mm 2 , the density of follicular units is relatively constant. 1, 4 Figure 3 illustrates the follicular groupings in a non-balding Caucasian male.

Figure 3. Densitometry showing the natural follicular groupings in a Caucasian male with a density of 2.0 hairs/mm 2 .

The germinative center of the hair follicle is now felt to lie along the region of the follicle, extending from the insertion of the sebaceous glands down to the dermal papillae (rather than just in the matrix), 5, 6 but it is clear that the other elements of the follicular unit must also be intact to ensure maximum growth. Whether these supporting structures are directly involved in growth or merely provide protection to the germinative elements during surgery has not been resolved, but it is clear that they are necessary to insure follicular survival in the transplant process. 7 The recognition that this naturally occurring biologic unit must be kept "whole" is the fundamental principle of follicular transplantation. Dr. Bobby Limmer has long used, and strongly advocated, stereoscopically assisted microscopic dissection to improve the quality of micrografts. 8 This is equally valuable when follicular implants are used exclusively in the transplant, as it significantly increases the visibility of the follicular anatomy.

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