Dermatologic Surgery 1998; 24: 929-932

On the Origin of Follicular Unit Hair Transplantation
Commentary by ROBERT M. BERNSTEIN, MD
Fort Lee, New Jersey

It is wonderful to see that follicular unit hair transplantation has reached such a level of importance that a lengthy commentary has been devoted to assigning credit to its origins. From the tone of his dissertation, however, Dr. Marritt seems to be defending Dr. Limmer from an enemy camp. This is, of course, unnecessary as my commentary will hopefully show. The important point is that we should all be delighted that, with its increasing popularity, more of our patients can benefit from the follicular unit transplantation procedure.

This writing is a result of being asked to comment on some of the opinions and exuberances expressed in Dr. Marritt's flamboyant letter. If the reader expects this to be anything other than light-hearted commentary, please read no further.

Before I begin, I want to emphatically express my personal feeling that Dr. Limmer's contributions to follicular unit transplantation are immeasurable. Dr. Limmer had the incredible foresight to be performing transplants, largely using follicular units, many years before anyone else had even considered it. His recognition that stereo-microscopic dissection and single strip harvesting are the only ways to insure maximum yield from the donor supply, even exceeds in importance follicular unit transplantation itself. Stated another way, follicular unit transplantation can not truly be performed unless microscopic dissection and single strip harvesting have been implemented. Dr. Limmer has been encouraging the hair transplant community to adapt these techniques almost as soon as he began using them (which goes as far back as 1988), and he has been the sole spokesperson on these ideas for much of this time.

Once these issues are respectfully acknowledged, one can chat about the much less significant issue of how the concept of follicular unit transplantation evolved. After observing literally thousands of patients scalps through the densitometer (that was originally designed to simply measure hair density), Dr. Rassman and I came upon the idea of building the entire transplant around the exclusive use of individual follicular units. This was approximately the same time we were exploring transplanting in very large sessions. Using individual follicular units seemed to be the ideal way to minimize total wounding in these larger procedures (initially performed, by the way, with a multi-bladed knife and loop magnification). We also felt it would address the issue of the "thin look" seen with extensive micrografting, since now each implant could contain more hair and still fit into a very small site. In addition, we were surprised to note that not only were these naturally occurring groups distinct, but their spacing in the scalp seemed to be relatively constant, and practically independent of the density of the patient's hair.

The idea of a follicular constant added simplicity to the surgical planning as pretty much the same number of grafts would be needed to cover a given area regardless of the patients hair density. The size of the donor harvest could be simply calculated, since the spacing of the follicular units was relatively constant (at 1 per mm2). In addition, follicular units could be "sorted" according to size in order to maximize the cosmetic impact of the transplant. For example, those containing 3 and 4 hairs might be placed in the forelock region for greater density and the smaller units in the transition zones. Most importantly, this sorting allowed us to increase hair density in certain areas without having to make the sites closer together. Sessions involving larger numbers of grafts had the additional benefit of generating more units of each size that could be used for these aesthetic decisions.

A more subtle revelation was that patients with only a few hairs per follicular unit would have a more thin look and this would be an essential characteristic of their transplant, since combining these units would not produce more hair, but only significantly increase wound size. At the other end of the spectrum, patients with greater numbers of hair per follicular unit could have dramatic results from a single session, given that their other hair characteristics were also favorable. These issues have the greatest significance in subsequent transplant sessions, and their understanding would be needed for setting realistic goals and for appropriate long-term planning.

We called this procedure, which involved the movement of large numbers of individual follicular units into very small recipient sites "Follicular Transplantation" and published it in 1995 in the Journal of Aesthetic and Restorative Surgery. The article, besides defining the follicular unit, and stressing the importance of very small wounding, discussed practical and aesthetic issues to be considered when these implants were transplanted in large sessions. Prior to publishing the article, I searched for other references in the hair transplant literature that discussed transplanting with individual follicular units, but found none. Unfortunately, being relatively new in the hair transplant field, at that the time of the writing, I had no first hand knowledge of Dr. Limmer's work.

While preparing the follicular transplantation article, I called Dr. Alan Halperin who was head of dermatopathology at the Albert Einstein College of Medicine in NYC, and asked him to put together a series of very thin horizontal and vertical sections of the scalp so that we could examine histologically the orientation of follicular units at different levels in the skin. Samples of these histologic sections were included in the original 1995 paper of which Dr. Halperin was a co-author. The following is the abstract of that original 14 page paper:

ABSTRACT: Follicular Transplantation is a method of hair restoration surgery which recognizes the follicular unit as the basic element of tissue to be moved in the transplant. The anatomic and physiologic basis of this procedure, as well as its potential advantages, are discussed. We then describe in detail how follicular implants may be used in extensive quantities for the treatment of androgenetic alopecia.
Bernstein RM, Rassman WR, Szaniawski W, Halperin A: Follicular Transplantation. International Journal of Aesthetic and Restorative Surgery 1995;3:119-132.

Dr. Halperin mentioned that Dr. John Headington, a dermatopathologist at the University of Michigan had done extensive work with horizontal scalp sections. I spoke with Dr. Headington about our project and he sent me an article that he had written in 1984 entitled "Transverse microscopic anatomy of the human scalp." To my surprise, not only had Headington defined the follicular unit histologically, but noted the same follicular unit constant that we had observed clinically. Clearly, he is responsible for originating the term "follicular unit" back in 1984.

I sent Dr. Headington a letter and reprint of the 1995 Follicular Transplantation article thinking that he would be impressed that we applied his histologic observations to hair transplantation, but he never responded. I later learned that he had retired from practice. The following is a copy of that letter:

May 6, 1996
Dear Dr. Headington:

I have enclosed a reprint of an article that we recently published quoting your "Transverse Microscopic Anatomy of the Human Scalp" that you wrote in 1984. I hope we were able to capture the essence of your basic science research and put it to good clinical use. I would greatly appreciate your comments.

Since the publication of Follicular Transplantation, we have become more observant of the natural hair patterns of patients and have found significant racial differences in density. Preliminary observations suggest the following:

Caucasians have an average density of 1 follicular unit/mm2 and 2.0 hairs/mm2. Asians have an average density of 1 follicular unit/mm2 with 1.75 hairs/mm2. Africans have an average density of 0.65 follicular units/mm2 with 1.6 hairs/mm2.

It is apparent that Asians have an average of 1.75 hairs per follicular, Caucasians 2.0 and unit and Africans 2.46 hairs per follicular unit. Could it be that in Africans, the low density in high follicular groups with darkly pigmented hair, enhance photo-protection and minimize heating of the skin? Curly hair in tight groups of 3 may act like a scaffolding that holds the hair off the surface of the scalp (to cool it), and in a tight meshwork (that blocks the sun).

We are in the process of examining racial variation in natural hair groupings and density. If you would like to be involved in our future work, please let me know.

Looking forward to hearing from you.
Sincerely,
Robert M. Bernstein, M.D.

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