On the Origin of The Follicular
Unit Hair Transplant
M. Bernstein, MD
It is wonderful to see that follicular unit 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
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
Looking forward to hearing from you.
Robert M. Bernstein, M.D.
I first presented the 1995 "Follicular Transplantation"
paper at the 1996 ISHRS in Nashville. At that same meeting,
Dr. David Seager gave two pivotal presentations "Does
the Size of the Graft Matter?" in which he showed
that intact follicular units actually grew better than
when they were split, and "Dissection with binocular
stereoscopic dissecting microscope" in which he
ran a video displaying, in vivid detail, the technique
that he had learned from Dr. Limmer. As a result of
this meeting the concept of follicular unit transplantation
was launched, and the impressive nature of microscopic
dissection was illustrated to hair transplant surgeons
from around the world.
As I was preparing references for the "paired"
follicular transplantation articles titled Follicular
Transplantation: Patient Evaluation and Surgical Planning,
and The Aesthetics of Follicular Transplantation, Dermatologic
Surgery 1997;23:771-799, I again scanned the hair transplant
literature for relevant articles, and specifically reviewed
the article that Dr. Limmer had sent me titled "Elliptical
donor stereoscopically assisted micrografting as an
approach to further refinement in hair transplantation"
Dermatol Surg 1994;20:789-793 (the one that Dr. Marritt
quoted in his commentary). I included this reference
in our publication as well as another article by Dr.
Limmer "Relating Hair Growth Theory and Experimental
Evidence to Practical Hair Transplantation" (references
6 and 8). In body of the text, near the beginning of
the first article, I commented:
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
I find it surprising that Dr. Marritt would adamantly
state in a publication with the stature of Dermatologic
Surgery that "In twenty-eight pages of text the
word Limmer, appears not once," without carefully
reading the article. In any event, although we referenced
Dr. Limmer for microscopic dissection, his article did
not discuss the actual use of individual follicular
units. The single statement "depending upon the
density of the individual follicular groupings within
the donor area, such as an ellipse will bear approximately
1200-2400 hairs" did not give us, nor other readers,
the impression that this was an article suggesting that
individual follicular units be used in the surgery.
There is a difference between noting that natural groupings
exist, and recommending the use of intact, individual
units in the transplant. I think that this is part of
the problem that Dr. Marritt discussed in Dr. Limmer
not receiving enough recognition for his work., and,
despite Dr. Marritt's repeated proclamations in his
commentary, I do believe that it is accurate to state
that the 1995 "Follicular Transplantation"
article introduced both the concept, and the term "follicular
unit," to the hair transplantation literature for
the first time.
Our impression from carefully reviewing the writings
of Dr. Limmer, and with conversations with those that
he trained, was that at least until Dr. Seager's 1996
ISHRS presentation, his primary focus in using stereo-microscopic
dissection was to preserve the integrity of the hair
follicle, and that the generation of follicular units
was the natural outcome of meticulous microscopic dissection,
rather than an end in, and of, itself. In fact, this
was the impetus for Dr. Seager conducting his study
on the importance of maintaining the integrity of the
follicular unit. For example, in the technique of micrografting,
one might divide a larger group to generate singe hair
grafts, or to combine single units to produce larger
units, especially when 16 gauge needle sites were used,
as this size wound is large enough to accommodate multiple
follicular units. In contrast, individual follicular
units, even containing four hairs, will readily fit
into an 18 gauge Nokor needle site due to their compact
nature, and the ability to use the smallest possible
wounding is their unique advantage.
Dr. Marritt recently sent me the 1992 tape that he
mentioned in his commentary "Elliptical Donor Stereoscopically
Assisted Micrografting." To my surprise "the
close, careful, dissection of the conical, tapered follicular
bundles" that Dr. Marritt describes was actually
performed in the video with scissors, without specifically
isolating individual follicular units, and without removing
any intervening tissue. All micrografts have a somewhat
conical appearance (due to the relative contraction
of the dermis with respect to the fat), regardless of
how they are dissected. The definition of Follicular
Unit Transplantation is "A method of hair restoration
surgery where hair is transplanted exclusively in its
naturally occurring, individual follicular units."
In Follicular Unit Dissection "Some non-hair bearing
tissue is removed to decrease the overall bulk of the
implant." In contrast, "Mini-Micrografts Cut
to Size" is a dissection technique whereby "the
donor strip is subdivided to produce grafts of specific
sizes as defined by the number of hairs they contain
and/or the size of tissue that will fit into a specific
recipient site. The removal of excess skin is not required.
The dissection can be carried out with or without magnification."
Clearly the latter is what was shown in the video and
that is why the video is appropriately named "Micrografting,"
rather than Follicular Unit Transplantation.
Regardless of this follicular nit-picking, as I mentioned
at the outset, I feel the exclusive use of individual
follicular units is actually less important than the
innovative techniques of single strip harvesting and
microscopic dissection. However, the clear articulation
of follicular unit transplantation, in it's pure form,
is what seemed to ultimately allow the hair transplant
community at large to understand the concept, and it's
As a final note, Dr. Limmer and I, in conjunction with
18 of our colleagues, have recently completed an article
to clearly define follicular unit transplantation with
all of it's essential components, and to differentiate
it from the technique of mini-micrografting where the
grafts are "cut to size." As you can imagine,
almost every issue was debated, and our e-mails and
faxes were running at full steam for months. No issue,
however, was as hotly debated as the term itself. I
represented the camp that wanted to keep the original
name "follicular transplantation" unchanged,
as I felt that the term had already received wide acceptance,
and was short and sweet. Dr. Limmer represented the
group that wanted to change the name to the more precise
"follicular unit transplantation" and we each
fervently lobbied the other authors. From the title
of this commentary, the outcome should be obvious.
For those who have continued to read on, let me conclude
by saying, that for someone relatively new in this field,
it has been exciting to see changes occur so rapidly,
and it has been an incredible experience to interact
so closely with such wonderful colleagues as Drs. Limmer,
Seager, Norwood, Shapiro, Stough, and all the other
people that have been involved with follicular unit
transplanting, and of course with Bill Rassman, from
whom I have learned so much.
ROBERT M. BERNSTEIN, MD
Fort Lee, New Jersey