Follicular Unit Transplantation Today - Achieving Natural Results with Hair Transplants by:Robert M. Bernstein, M.D., F.A.A.D.

Follicular unit transplantation had its origins in the microscopic dissection techniques of Limmer

, developed in 1988. The conceptual framework for follicular unit transplantation was introduced in the hair transplant literature by the authors in their 1995 publication Follicular Transplantation and further detailed in 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, an attempt was made to precisely define follicular unit transplantation and included the two basic techniques of Limmer, single-strip harvesting and stereomicroscopic dissection, as integral parts of the procedure. 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 of follicular unit transplantation has become obsolete. Follicular unit transplantation is simply the transplantation of follicular units by any means.

Other surgeons have regarded follicular unit transplantation as simply the transplantation of follicular units by any means, thus a strict definition of this involving strip harvesting and stereomicroscopic dissection was never accepted by all. Follicular units can be produced by many methods, one of which is follicular unit extraction. Transplantation of grafts obtained by follicular unit extraction is still regarded as a form of follicular unit transplantation.

In order to produce hair transplant grafts in very high densities or in very large numbers per session, some practitioners have limited follicular units to those containing a maximum of three hairs, particularly in those patients with coarse hair. This would necessitate dividing a naturally occurring four-hair follicular unit into smaller grafts, essentially creating micrografts. Other practitioners of follicular unit transplantation occasionally combine two follicular units with the intention of creating more density in the forelock area, particularly in patients with fine or light-colored hair. Other physicians may combine one-hair follicular units into 'twos' simply to minimize the number of recipient sites needed. Finally, unlike strip harvesting with stereomicroscopes, where intact naturally occurring follicular units are generated, for the vast majority of the time with follicular unit extraction techniques the physician is not always able to harvest intact units and therefore must work with partial groups or groups devoid of some of the connective tissue support structures.

Considering these relatively common variations on follicular unit transplantation and the often imperfect follicular units that are generated in the increasingly popular technique of follicular unit extraction, follicular unit transplantation should be considered as any procedure in which the goal is hair restoration using predominantly naturally occurring individual follicular units. It is important that where significant exceptions or deviations are made from the pure follicular unit transplantation procedure these modifications are clearly explained.

Follicular unit extraction may be considered a specific harvesting method in follicular unit transplantation in which follicular units are obtained directly through small circular incisions rather than through a microscopically dissected donor strip. However, the nature of this hair transplant technique itself can have a significant impact on other aspects of the surgery, including the quality of the grafts, their number, the organizational aspects of the surgery, and possibly its design.

Transplanting Individual Follicular Units

There are two central arguments for transplanting individual follicular units. The first is that using individual follicular units will produce the most natural results. The second is that it allows the practitioner to transplant the maximum amount of hair into the smallest possible wound.

Natural results

Since hair naturally grows as individual follicular units, it is logical to conclude that transplanting hair exactly the way it grows would produce the most natural results. This apparently obvious conclusion however may not always be true. As will be discussed in a subsequent section, the normal density of follicular units is approximately 100/cm2. If an average follicular unit contains 2.3 hairs, there will be 230 hairs/cm2. In the context of this density, follicular units of any size will look natural. However, if 2400 follicular units are transplanted evenly over the front and top of a bald scalp (excluding the crown), an area that generally measures 150 cm2, the new transplanted density is 16 follicular units/cm2 or 16% of the original density. A second procedure of 2000 grafts, evenly distributed, will increase the average density to just under 30% of the original density. However, most physicians transplant greater densities toward the front part of the scalp (40-50%), leaving the area toward back of the scalp thinner. Therefore, even with two sessions totaling 4400 grafts, there may be as little as 20% of the original density on the top of the scalp and as little as 10% towards the back. If the crown is transplanted, these numbers will be even lower.

At low densities, there may not be enough hair to 'visually support' the larger follicular units and four-hair grafts may have a slightly unnatural look. This may present a particular problem in patients with coarse, dark hair and light skin. One solution is to try and bury the larger units in areas of greater density, such as in the forelock area, and use the smaller grafts towards the periphery, but in patients with extreme skin/hair color contrast this may not be enough and it may be appropriate to split some of the four-hair units into two, two-hair grafts.

A second issue is that merely using individual follicular units will not insure that the grafts look natural. The right-sized units must be placed in the right place. Since the normal hairline consists mainly of single-hair follicular units, so must the transplant. This, however, is not always easy to do. Transplanting the naturally occurring follicular unit implies keeping the support structures intact, which is best accomplished using a 'chubby' graft. Chubby grafts, however, increase the chance that empty telogen follicles are included in the dissection. Although this is beneficial to achieve maximum fullness for most of the scalp, at the hairline this may result in two-hair grafts. To avoid this problem, follicular units at the hairline should be trimmed 'thin,' which may expose the graft to mechanical injury and desiccation.

Another problem occurs when small transplant sessions are performed. This may due to a demand issue (i.e. if the patient is a Norwood Class III and only requires 800 grafts) or a supply issue (i.e. if the patient can only afford a small number of grafts or follicular unit extraction is planned and a limited number of grafts is a constraint due to the capabilities of the surgical team).

Since the normal donor scalp contains only around 10-15% one-hair follicular units, a donor strip of 800 grafts would only yield 100-150 single-hair follicular units, far short of the 250-300 generally needed for the frontal hairline.

In strip harvesting, if the surgeon desires to restore a hairline in one session then he or she must resort to splitting larger follicular units into one-hair grafts. Follicular unit extraction presents another problem since harvesting single-hair follicular units with this technique greatly increases the number of the recipient wounds. In follicular unit extraction, in order to minimize injury to the donor area, it may be beneficial to harvest the largest follicular units and then divide them into one-hair grafts for the hairline. This has been a common practice for over a decade among transplant surgeons and is a minor departure from pure follicular unit transplantation.

About the author

Dr. Bernstein is recognized worldwide for pioneering Follicular Unit Hair Transplantation. Dr. Bernstein's hair restoration center in Manhattan is devoted to the treatment of hair loss using his state-of-the-art hair transplant techniques. Dr. Bernstein has been named "Best Doctor" in New York Magazine for 10 Consecutive Years. Read more at http://www.bernsteinmedical.com/.

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