In Follicular Unit Hair Transplantation, the goal should be to achieve the best possible cosmetic result in the context of the patient’s total donor reserves, rather than trying to place as many grafts as possible in one session. Hair transplantation is not a marathon where the winner takes all and where the losers can die of exhaustion. It is a surgical procedure where the survival and placement of every graft counts.

The benefits of using large sessions of follicular units are numerous. They were first described in the publication Follicular Transplantation (Bernstein and Rassman, 1995). They include:

Advantages of Large Hair Transplant Sessions

  • Accomplishes the main goals of hair restoration i.e. establishes a hairline, frames the face and provides coverage to the bald scalp
  • Creates a distribution that can “stand on its own”
  • Minimal interruption of patient’s daily work and social routine
  • Surgical advantages of transplanting into virgin scalp:
    • The original blood supply is intact
    • Connective tissue has normal elasticity
    • Grafts can be placed close together
    • Graft survival is optimized
  • Surgical advantages of using a virgin donor area:
    • Because the density is at a maximum, the greatest number of grafts can be obtained per unit area, thus conserving on the size of the donor strip
    • Maximum scalp mobility = greatest chance of a hairline donor closure
    • Absence of donor scarring = larger follicular units and greater follicular unit yield
    • Normal angle of hair = less follicular transection

Almost a decade ago, we wrote in Follicular Transplantation: Patient Evaluation and Surgical Planning (Dermatol Surgery 1997): “One should attempt to achieve, in the first session, as many of the patient’s goals as possible. In our opinion, what can safely be accomplished in one procedure is best done in one procedure, and should not be spread out over two or more.”

That said, judgment must be used in deciding just what constitutes a large session and in which situations/persons they are appropriate. With new techniques and new instrumentation, many more grafts can be safely transplanted at one time; however, there are certain problems and limitations associated with very large sessions and these increase exponentially as the size of the sessions increase.

Disadvantages of “Excessively” Large Sessions

  • In order to densely pack grafts one must make recipient sites very small. In order to fit grafts into these very small sites, one needs to dissect away much of the dermis around the follicular unit, but this is the tissue that helps protect FUs from desiccation, warming and mechanical trauma.
  • In order to very densely pack grafts, 4-hair follicular units (which provide the most density and fullness) often must be sub-divided into smaller units. This subdivision of follicular units increases the risk of transection and increases graft numbers and the cost of the procedure (when charged by the graft) without yielding more density or coverage.
  • With one large session, one can’t create the “central” density of two procedures where one has the option of adding additional grafts to this critical area in the second session. The appearance of central density mist closely mimics nature and, in a hair transplant, is critical to achieving the most natural result.
  • The central scalp is the least vascular and most subject to the vascular compromise that can be caused by very dense packing, but this is the area that should have the greatest hair density. Greater central density can be consistently achieved with two sessions, without the risk of compromising graft growth, by transplanting the largest naturally occurring follicular units in the central forelock area in sites that are close, but not very densely packed.
  • One doesn’t have the ability to do a second procedure using information from the first session, particularly with respect to grooming preferences.
  • Very large sessions run the risk of wide donor scarring — the problem is that you can’t always judge in advance who this person may be. Particularly, scalp laxity may not be a reliable indicator, since those with very loose scalps may be the poorest healers. With a very large first procedure, there is greater risk of an unacceptable scar and fewer options to correct it.
  • This greater risk of donor scarring, represents a trend in the opposite direction of Follicular Unit Extraction (FUE) where trying to minimize donor scarring is the primary goal.
  • Very large sessions use up donor supply and limit graft availability for future sessions needed to address additional hair loss.
  • Many patients seeking surgical hair restoration do not need very large sessions and performing sessions that are too large forces the surgeon to place graft is areas that are less than ideal just to fit the grafts in somewhere. Not only is this hair wasted but, at times, it can cause long-term cosmetic problems.
  • Increased risk of popping when grafts are placed very close together and this increases the risk of graft desiccation as they sit on the surface of the scalp. Unlike chilled grafts in a holding solution, grafts that have already been placed in the scalp are metabolically active are, therefore, at greater risk of injury.
  • There is increased surgical time and when excessive, this may result in decreased graft survival.
  • Very dense packing requires the use of chisel blades, and in some situations these may cause more damage than a hypodermic needle (the later has the advantage of dilating the recipient site and is designed to minimize tissue trauma). Hypodermic needles are also much easier to use when working through existing hair.
  • A grid-like pattern (rows) is needed to pack grafts very densely and this can look unnatural in certain lighting.
  • Must clip the patient’s hair very short for the procedure — which is cosmetically unacceptable for many patients.
  • Dense packing and excessively large sessions go hand-in-hand and the potential problems associated with dense packing (particularly popping and vascular compromise) are compounded when large sessions are used.
  • Poor growth is not an all-or-none phenomena and sub-optimal growth is literally impossible to detect.
  • There is great patient variability in hair transplantation, particularly with respect to the tendency towards popping, scalp laxity, and the effects of long-standing sun exposure on the scalp blood supply. Not all of these variables can be completely accounted for prior to surgery. Once a very large donor strip is removed, there is no turning back and any problem that can easily be managed in a large session will be compounded in an excessively large session.

The message for patients is that accomplishing the hair restoration in as few sessions as possible is an important goal, but insuring the maximal growth of every graft and having the best long-term cosmetic result is the ideal.

Robert M. Bernstein, M.D.


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