INTRODUCTION

Within the past decade, Follicular Unit Transplantation has transformed hair transplantation from a cosmetically unpredictable procedure to one that can produce consistently natural results. The key to its effectiveness lies in the fact that scalp hair tends to grow in tiny bundles, called "follicular units," rather than individually. By working with these naturally occurring units, instead of larger or smaller grafts, Follicular Unit Transplantation creates as natural a look as possible while minimizing the transplant wound size and accelerating post-operative healing. A recently developed refinement, Follicular Unit Extraction, promises to eliminate, for select candidates, the procedure's most invasive aspect: the surgical removal of a strip of tissue from which the units are harvested.

Follicular units are made up of one to four terminal hairs, one to two vellus hairs, their associated sebaceous glands, neurovascular plexus, an erector pilorum muscle, and a circumferential band of adventitial collagen, the perifolliculum. The tendency of scalp hair to grow in this way, rather than in single hairs, can be most easily demonstrated by clipping the hair to approximately 1 mm in length and then viewing it with a densitometer at x 30 magnification in a 10-mm field. What this also reveals is that these compact units are surrounded by significant amounts of non-hair-bearing scalp. Including this extra skin in the dissection -- as do hair transplants with larger grafts, such as plugs and minigrafts -- requires a larger recipient wound, as well as risking visible scarring in the skin around the grafts and distortions of the growing hair.

Although simple in concept, Follicular Unit Transplantation has many nuances and complexities. Those wishing to perform Follicular Unit Transplantation in their clinical practice are encouraged to join the International Society of Hair Restoration Surgery (ISHRS) and attend its annual meeting, subscribe to Hair Transplant Forum International (the trade publication for hair transplant surgeons), and follow relevant medical literature (particularly Dermatologic Surgery). Although it is not an accredited board, certification by the American Board of Hair Restoration Surgery (ABHRS) indicates a basic competency in the field and requires three years of clinical experience and passing both oral and written examinations. The process of preparing for ABHRS certification is a worthwhile endeavor and recommended for those serious about surgical hair restoration.

HISTORICAL VIGNETTE

Reports of successful hair transplants appeared as early as 1930 in Japanese literature, beginning with Sasagawa's hair-shaft insertion procedure and then Okuda's success in pioneering 2- to 4-mm punches for the treatment of various alopecias of the scalp, eyebrows and moustache. Okuda made the important observation that using smaller punches in the recipient area improved cosmetic results.

By 1943, Tamura had treated 137 cases of non-androgenetic alopecia of various etiologies using techniques very similar to modern-day hair transplantation. For instance, he harvested donor grafts by making an elliptical incision that was sutured closed, prepared recipient sites with a thick needle, stored grafts in physiologic saline, and observed post-operative telogen effluvium. Most significantly, Tamura demonstrated that single-hair grafting resulted in growth practically indistinguishable from naturally grown hair -- and much more natural-looking than hair transplants using larger grafts. But it took several decades before Western surgeons would apply Tamura's insights to their hair restoration procedures.

The first hair transplant surgery in the United States was performed by Dr. Norman Orentreich in 1952 with grafts measuring 6 to 8 mm in diameter, significantly larger than those of either Tamura or Okuda. At first, incredulous editors rejected Orentreich's work, not believing that hair transplantation was even possible. He finally found a publisher in 1959, in the Annals of the New York Academy of Science. The paper laid out the concept of "donor dominance" -- the idea that grafts continue to show the characteristics of the donor site after they have been transplanted to a new site. This remains the basic tenet of all hair transplantation surgery. Yet while donor dominance insured that transplanted hair could grow, it did not guarantee that the results would look natural.

Not until 40 years later would hair transplants in the United States start to produce consistently natural-looking results and promise predictable cosmetic improvements in most patients. It was a slow evolution, but the large grafts used throughout the sixties and seventies eventually gave way to minigrafts in the eighties and mini-micrografting in the early nineties. The stage was then set for Follicular Unit Transplantation. First appearing in the medical literature in 1991 it quickly emerged as the standard in hair restoration -- supplanting mini-micrografting in the treatment of androgenetic alopecia and rendering other well-established procedures such as scalp reductions, scalp lifts and flaps virtually obsolete.

So swift was Follicular Unit Transplantation's ascent that the two standard textbooks on surgical hair restoration, published in 1995 and 1996, as well as the most comprehensive text on trichology, published in 1997, make not one mention of the terms "follicular unit" or "Follicular Unit Transplantation." At the 1996 meeting of the International Society of Hair Restoration Surgeons, three seven-minute presentations on the procedure were given; but at the 2002 meeting, Follicular Unit Transplantation was the subject of entire seminars and workshops and suffused every aspect of the weeklong gathering.

The follicular unit was first defined by Headington in his landmark 1984 paper "Transverse Microscopic Anatomy of the Human Scalp." Follicular Unit Transplantation had its origins in the microscopic dissection techniques of Dr. Limmer in 1988 that was described in his paper "Elliptical Donor Stereoscopically Assisted Micrografting as an Approach to Further Refinement in Hair Transplantation" in 1994. The term "follicular unit" was introduced into the hair transplant literature by Bernstein and Rassman in 1995. The conceptual framework for Follicular Unit Transplantation was mapped out by these authors in the publication "Follicular Transplantation" and in the paired articles, "Follicular Transplantation: Patient Evaluation and Surgical Planning" and "The Aesthetics of Follicular Transplantation" (1997).

The name "Follicular Unit Transplantation" was formalized by a group of hair restoration surgeons in a 1998 publication in Dermatologic Surgery. In this paper, the procedure was precisely defined and included the two basic techniques, single-strip harvesting and stereo-microscopic dissection, as integral parts of the procedure. However, since follicular units can now be harvested directly from the donor area without the necessity of a strip incision (using Follicular Unit Extraction) the original definition has become too restrictive.

The term Follicular Unit Transplantation should now be used to encompass all hair restoration procedures that utilize naturally occurring, individual follicular units exclusively in the surgery, regardless of how these units are harvested. The caveat, of course, is that the harvesting technique must always maintain the follicular unit's integrity.