THE LOGIC OF TRANSPLANTING INDIVIDUAL FOLLICULAR UNITS

That scalp hair grows in follicular units, rather than individually, is most easily observed by densitometry, a simple technique whereby scalp hair is clipped to approximately 1mm in length and then observed via magnification in a 10mm field22. What is strikingly obvious when one examines the scalp by this method, is that follicular units are relatively compact, but are surrounded by substantial amounts of non-hair bearing skin. The actual proportion of non-hair bearing skin is probably on the order of 50%, 16 so that its inclusion in the dissection will have a substantial effect upon the outcome of the surgery. When multiple follicular units are used, and the skin is included, these effects may be profound.

Figure 2-A. Low Density


Figure 2-B. Average Density


Figure 2-C. High Density

To illustrate this point, use any of the "videografts" in figures 2 and draw a circle around a single follicular unit, and then draw a circle encompassing two units, then three etc. What one observes is that, as single follicular units are combined to form larger groups, the total volume of tissue included is not additive, but geometric.

When the actual transplant is performed, two additional factors act to compound the effects of this increased volume. The first is that the donor and recipient sites are not always a perfect match for one another. In many ways, transplanting skin from the back of the scalp to the front can be as different as using a graft from the inner thigh to fill in a defect on the lower leg. The reason is that bald scalp becomes atrophic over time, as the diminution of the follicular appendages are associated with a decrease in the other cutaneous elements.15

The other problem is that the transplantation of multiple follicular units, often requires recipient skin to be removed (via punch or laser) to allow this new volume of tissue to fit into the recipient site and/or to avoid unsightly compression of the newly transplanted grafts. In effect, richly vascular scalp, of maximum thickness, is transplanted into a somewhat atrophic recipient area, in which tissue is further removed to accommodate the graft. Not surprisingly, the results of this technique will often look unnatural!

The great benefit of using individual follicular units is that the wound size can be kept to a minimum, while at the same time maximizing the amount of hair that can be placed into it. Having the flexibility to place up to 4 hairs in a tiny recipient site has important implications for the design and overall cosmetic impact of the surgery. It is a major advantage that follicular unit transplantation has over extensive micrografting in minimizing or eliminating the "see through" look that is so characteristic of the latter procedure.

THE LOGIC OF KEEPING RECIPIENT SITES SMALL
The importance of minimizing the wound size in any surgical procedure can not be over emphasized and hair transplantation is no exception. The effects of recipient wounding are felt at many levels. Large wounds can lacerate blood vessels and although the blood supply of the scalp is extensively collateralized, any damage to these vessels will have an impact on local tissue perfusion. An equally important issue is to minimize the disruption of the microcirculation. This is an unavoidable aspect of all scalp surgery, regardless of the size or depth of the wounds, but keeping this disruption to a minimum is a crucial part of the surgery. This is especially important when transplanting grafts in large quantities. The compact follicular unit is, of course, the ideal way to permit the use of the smallest possible recipient site, and has made the transplantation of large numbers of grafts technically feasible.9

Clearly, excision (removing tissue via a punch or laser) causes more damage to tissue then an incision (slit), but it is important to stress that all the parameters affecting recipient wounds have not been determined. As such, there are no absolute guidelines as to the ideal number, or densities of grafts, that can be used and still ensure maximum growth. The practitioner must rely on his clinical judgement in this regard, and it is suggested that one be conservative until one has significant clinical experience with the close placement of large numbers of grafts. In addition, there are a host of systemic and local factors that should be taken into account when planning the number and spacing of the recipient sites, regardless of their size.7

Another important advantage of the small wound is a factor that can be referred to as the "snug fit." Unlike the punch, which destroys recipient connective tissue, a small incision, made with a needle, retains the basic elasticity of the recipient site. When a properly fitted graft is inserted, the recipient site will then hold it snugly in place. This "snug fit" has several advantages. During surgery, it minimizes popping, and the need for the sometimes-traumatic re-insertion of grafts. After the procedure, it ensures maximum contact of the implant with the surrounding tissue, so that oxygenation can be quickly re-established. In addition, by eliminating dead space, there is less coagulum formed, and wound healing is facilitated.

Since oxygen reaches the follicle by simple diffusion, its ability to do so is a function of tissue mass. Unlike larger grafts whose centers can become hypoxic, the slender follicular unit presents little barrier to this diffusion, thus ensuring uniform oxygenation.

It is important to note that when using larger grafts, either round or linear, compression is an undesirable consequence, and may result in a tufted appearance. In contrast, when transplanting follicular units, there are no adverse cosmetic effects of compression, since follicular units are already tightly compacted structures.

Another aspect of wound healing is the concept of "memory." All of us who routinely perform cutaneous surgery, understand the advantage of wounds healing by primary intention. When tissue is removed by a punch, or destroyed by laser, the resulting defect heals by secondary intention. One can justifiably argue that when a graft is placed in the defect, the area doesn’t need to granulate in. However, because the underlying defect is still present, the wound invariably causes more scarring than when a simple incision is made (thus the term "memory"). This is readily evidenced in the scarred skin around the healed punch or laser sites. Although, not always visible, this tissue has lost its resiliency and cannot support the same density of grafts in subsequent procedures.

Large wounds cause a host of other cosmetic problems including dimpling, pigmentary alteration, depression or elevation of the grafts, or a thinned, atrophic look. The key to a natural appearing hair transplant is to have the hair emerge from perfectly normal skin. The only way to ensure this is to keep the recipient wounds small.

THE LOGIC OF CREATING SITES WITH COLD STEEL
In the public’s mind, no single word in medicine evokes a stronger image of "state-of the art" than the word "Laser, " and "Laser Hair Transplantation" is no exception.6 But, when the image begins to fade, and we examine its actions logically, we see that not only is the laser inappropriate for follicular unit transplantation, but that it is actually detrimental.

Lasers are used in hair transplantation to create recipient sites. In contrast to other fields of medicine where its properties of selective photo-thermolysis play a role, in hair transplantation the role is purely destructive. That lasers can create a hole with little surrounding thermal injury is little consolation to the surgeon who would prefer to have none. And the claim of the newest lasers, that they can make a recipient site with no thermal burn at all, is well and good, but it is missing the whole point. That point is that no matter how precise the laser is, it is still making a hole by removing tissue, and is, therefore, a throwback to the old punch technique.

Just to remind the reader, removing tissue destroys blood vessels and collagen, weakens the elastic support, increases the coagulum, decreases perfusion, and retards healing. Essentially, the laser "loosens" the "snug fit" that is such a benefit in follicular unit transplantation. If one merely wants to create a slit, which supposedly looks more natural than a hole, then lasers will do just fine. If one needs to remove tissue, to make room for a large graft, or prevent compression, then lasers may be the tools of choice. And, if one is more concerned that blood will cloud the view during surgery, rather than nourish the implants afterwards, then the laser should be given a try. But, if one wants to maximize the growth of follicular units, and keep recipient wounds to a minimum, then the beam should be pointed the other way.

THE LOGIC FOR TRANSPLANTING FOLLICULAR UNITS IN LARGE SESSIONS
Although larger sessions are made possible by the ability of follicular units to fit into very small recipient sites, and to minimize wounding, the next logical question to ask is "What is the actual advantage of performing these large sessions?" After all, they are time consuming, require a larger staff, and are more expensive for the patient (at least at the outset).

There are a number of very important reasons to transplant in large sessions. Some of them are specifically related to the use of follicular units, and some to hair transplantation in general, but all significantly affect our patient’s wellbeing. They may be summarized as follows:

Social reasons
Planning for telogen effluvium
Economizing the donor supply
Enhancing the complexion of the follicular units
The social implications of the surgery are uncommonly discussed at medical meetings, but are in the forefront of almost every balding patient’s mind. Putting aside anatomic, physiologic and technical issues for the moment, it is important to emphasize the practical reasons to strive toward large sessions. The specific events that bring a balding patient to the doctor for hair loss will vary, but the common denominator of those seeking hair restoration is to improve their appearance, and (although generally unspoken), to improve the quality of their life, be it personal, professional, or social.

Figure 3A & 3B: Before & After 1 session


Figure 4A & 4B: Before & After 1 session


Figure 5A & 5B: Before & After 2 sessions


Figure 6A & 6B: Before & After 2 sessions

There is probably no better way for a surgeon to undermine this goal than to subject an already self conscious patient to a protracted course of small, incomplete procedures. Until the transplant is cosmetically acceptable, the disruptions from the scheduling of multiple surgeries, the limitations in activity, and the concern about their discovery, can place a patient’s life "on hold." It should therefore be incumbent upon the physician to accomplish their objectives as quickly as possible. Figures 3 and 4 show what is possible using follicular units in large numbers in just one session, and figures 5 and 6 show what is possible in two sessions. The important point is that, even if one or two transplant sessions does not accomplish all of a patients goals, he still can continue with normal activities while awaiting subsequent procedures.

Telogen Effluvium
Balding is a progressive process by which full-thickness terminal hairs gradually decrease in length and diameter in a process called miniaturization. This is a consequence of both the shortening of the anagen (growing) phase of the hair cycle and the diminution of the germinative elements in the follicle. Miniaturization is a universal aspect of androgenetic alopecia and accounts for most of the early cosmetic changes in hair loss. In other words, early in balding, the "thinning" that one notes is really due to thinning (i.e. miniaturization) of the hair shafts, rather than the actual loss of hair itself.9

Regardless of the technique, an inevitable aspect of hair transplant surgery is that the patient’s existing hair in, and around, the transplanted area has a chance of being shed as a result of the procedure. The hair that is at greatest risk of being lost is the hair that has already begun the process of miniaturization and, if this hair is at, or near the end of its normal life span, it may not return.

Often this shedding is mild and insignificant, but at times is can be substantial enough to leave the patient with a thinner look after the procedure than before he started. The reason is that in some patients (especially those that are younger and in very active stages of hair loss) large amounts of hair can be undergoing this process of miniaturization. Identifying those patients especially at risk, educating all patients that this process can occur, and planning for it surgically are thus integral parts of hair transplantation.12

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Designing the Hairline | Follicular units minigrafts | Future hair transplantation | Hair loss women | Hairline placement | Hairloss why | Logic Folicular Unit Transplantation | Natural Hairline Dr Shapiro | Origin of Folicular Unit Transplantation | Support of Folicular Unit Transplantation | Surgical Planning | Correction of Corn Row
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