Hair transplantation began as a dermatologic surgery procedure when New York dermatologist Norman Orentreich, MD reported on the successful growth of 4mm ‘plugs' transplanted from hair bearing scalp to bald areas.1 For many years, dermatologists included this procedure on their ‘menu' of services, as it was relatively easy for the surgeon to transplant 50-100 plugs with the help of one or two assistants. However, in the last 15 years, grafts have gotten progressively smaller and graft counts have risen into the thousands. This procedure has evolved to such an extent that modern hair transplantation requires not only an experienced surgeon, but also a large, highly trained staff with sufficient equipment and facilities. This evolution has been greatly facilitated through the educational activities of the International Society of Hair Restoration Surgery (ISHRS), the largest hair transplant society worldwide. Through their annual scientific meeting and bimonthly journal, The Hair Transplant Forum International, new techniques and theories have been disseminated, facilitating the rapid evolution of this specialty. There has been a significant growth in these procedures around the world, particularly in the Middle East and Asia. The ISHRS reported from a survey of its members that approximately 250,000 procedures are performed worldwide annually, with 100,000 of these being done in the United States alone.2 One unfortunate side effect of the increasing specialization in the hair transplant field is that this evolution has occurred outside the view of the dermatology and dermatologic surgery community. Dermatology residents rarely receive training in this procedure and only a minority of busy hair transplant surgeons today are dermatologists. Most dermatologists are simply not aware of the rapid strides in hair transplant techniques.

Early Strides
In the 1980s, the standard round graft plug gave way to the minigraft. Instead of harvesting individual plugs, surgeons would take out the donor tissue as numerous thin strips with the aid of a multibladed scalpel. These strips were then rapidly cut like scallions and placed in small incisions or holes. In the early 1990s, numerous clinics were experimenting with extensive micrografting, including those of Carlos Uebel,3 and Bobby Limmer.4 Limmer is credited with introducing the technique that has become the basis for modern follicular unit transplantation. He described harvesting the donor tissue as a single strip, from which the natural groupings of one to four hair follicle groupings (“follicular units”) were separated with the aid of a dissecting stereo microscope. These small grafts were then placed into incisions made with 16-20-gauge needles.

In the mid-90s, this procedure gained more widespread attention with the promotion of “follicular unit transplantation,” a concept promulgated and articulated by Robert Bernstein, MD and William Rassman, MD.5 The logic behind using the natural anatomical groupings was appealing and gradually garnered widespread acceptance as the standard of care today. Over the last 10 years, the trend has been toward ever increasing size of ‘sessions' so that 2,000-4,000 grafts are the norm in dedicated hair transplant centers, and sessions of up to 7,000 grafts have been reported.

Patient Management Today
To understand the status of hair transplantation today, we can follow a typical procedure of 3,000 grafts for male pattern hair loss. The selection of appropriate candidates and planning of the procedure is a complicated topic in its own right. During the consultation, finasteride is usually prescribed to halt further hair loss, and topical minoxidil solution is often recommended, as well. Careful consideration of the patient's current goals must be balanced with the progressive nature of androgenetic alopecia and the potential for continued hair loss to make the grafts look unnatural. It is emphasized that medical treatment preserves existing hair while transplantation restores density to the hairline and thinning or bald areas, and that use of these complementary approaches is essential to long term satisfaction.

The planning of the procedure is conceptualized as an evaluation of supply (donor hair) and demand (balding area). Evaluation of the donor area includes determination of donor density, hair density, hair curl and texture (fine, medium, or coarse). This task has been greatly aided by the use of video microscopy (Fig. 1a).7 The greatly magnified image of the donor area can be seen by the surgeon and patient so that these characteristics can be discussed in preparation for surgery. In addition, the balding areas can be assessed for miniaturization and signs of ongoing hair loss (Fig. 1b,c). The benefits of finasteride and minoxidil are often better appreciated by the patient when they can see the extent of their miniaturizing hairs. In one recent encounter, a patient informed me that he believed he had lost all his native hair and that the only hair on the top of his scalp was from previous transplants. Looking through his scalp with the video microscope showed him that this simply was not the case. After seeing this, he readily agreed to go on medical treatment in conjunction with the planned surgery. The video microscope can also be useful in evaluating patients with all forms of hair loss, as cases of telogen effluvium and scarring alopecia can be readily differentiated from pattern hair loss.

Once the donor hair has been evaluated, the scalp laxity is assessed to determine how much can be removed safely, without causing excess tension when the donor strip is removed. In the past, when sessions of 1,000 grafts and less were the norm, there was a common practice to keep the width of the donor strip at 1cm or less. Nowadays, it is common to remove up to 2cm in width in order to harvest the maximum number of grafts. To accomplish this, a careful assessment of scalp laxity is necessary to avoid excess tension on closure, the leading culprit in wide donor scars.

The typical donor density is 75-85 follicular units per cm2, but the range can be 50 to over 100. After this is determined, the amount of tissue that must be removed can be calculated. For a typical patient with 80 follicular units/cm2, 37.5cm2 of donor tissue must be removed to give 3,000 follicular unit grafts (3,000/80 FU/cm2 = 37.5cm2). The dimensions of the strip are then determined by assessing the scalp laxity and looking at where the best hair is. Typically, the strongest, best quality hair is in the mid-occipital scalp, so the strip is widest here (1.5-2cm) and made thinner in the parietal and temporal regions. A strip with dimensions of 10 x 2cm in the occipital area, and 9 x 1cm in each parietal-temporal area, will yield at least 3,000 grafts.

The donor harvest has received considerable attention recently, partly because of the use of longer, wider strips, but also because of the public attention given to donor scarring. Just as patients today will not accept pluggy, unnatural looking transplants, they have become increasingly concerned about wide donor scars. Most surgeons will use two layers of sutures, and recently some have adopted a running subcutaneous stitch. Efforts to reduce tension have led to descriptions of various undermining techniques as well. In addition, a technique referred to as the ‘trichophytic closure' has gained widespread acceptance. In this technique, either the superior or inferior wound edge is trimmed superficially to allow for a row of hair to grow through the scar during the healing process (Fig. 2).

The problem of donor scarring has led to the development of technique called follicular unit extraction,7 in which the follicular units are removed by punch of 1mm or smaller. While a linear scar is not produced by this technique, it is possible for patients to heal with small depigmented scars where the extractions took place. In addition, it is time consuming and technically demanding to remove these grafts individually without damaging them. Nonetheless, a small niche has developed for this technique, particularly among younger patients who wish to wear their hair short and are worried about a linear scar.

The strip is then handled by the team of assistants to create microscopically dissected follicular units. The first step is to create ‘slivers' from the strip, which requires gently cutting between follicular units to create thin slices. These are then divided further into the follicular unit grafts (Fig. 3). Some clinics prefer to create very skinny grafts with all peri-follicular tissue trimmed away, while others prefer ‘chubbier' grafts, which they believe provide a protective cushion to enhance survival. There is widespread consensus that using all microscopic dissection allows for the best quality grafts, with the least amount of transaction and waste. I supervised a multicenter study comparing clinics that did or did not use the microscope in their practices and found that there was on average 50 percent less transaction when microscopes were used.8 Because the large procedures routinely performed today may take eight to 15 hours to complete, considerable attention has been given to what holding solution to hold the tissue in prior to implantation. Most surgeons use chilled saline, although others prefer lactated ringers or a saline with a more physiologic pH (e.g., PlasmaLyte A). I have studied various holding solutions over the years and prefer to use a transplant media designed to hold tissue at cold temperatures (HypoThermosol-FRS, BioLife Solutions, Inc.). Using this solution, I have found that assays for ischemia-reperfusion injury are lower9, and there is enhanced graft survival compared to saline when studied over extended ex vivo holding times. Future research will hopefully clarify this issue, as there is currently no well accepted standard.

Looking at the recipient area, there is a consensus that there must be a sufficient density of grafting to achieve a look that will satisfy patients. I use the following protocol: for patients with normal texture hair, I aim for 50 grafts/cm2; this is increased to 60/cm2 for patients with fine hair (Fig. 4), and decreased to 40/cm2 for those with coarse hair. If the patient has existing hair in the recipient area, then these numbers adjusted downward accordingly. These density goals must be balanced with the overall plan for coverage. For example, a patient who simply has frontal recession, with a surface area of 60cm2 can achieve the target density of 50 FU/cm2 with 3,000 grafts. Another patient with more extensive hair loss who wants an area of 100cm2 covered will only achieve a density of 30/cm2 with the same number of grafts. There is often a compromise between coverage and density in the typical case.

Most surgeons use incisions, rather than punch holes, but there is disagreement over whether these should be with needles or blades. Furthermore, some surgeons prefer to orient the incision perpendicular to the direction of hair flow (‘lateral slits'), a technique described by Jerry Wong, MD,10 while others prefer the standard ‘sagital' incision. The implantation of these small grafts is perhaps the most technically demanding part of the procedure, as graft sites typically measure only 0.5-1.0mm. Grafts are prone to drying during both the dissection and placement phase of the procedure, and I have found it helpful to keep ambient humidity in the surgery room greater than 50 percent with a humidifier.

Even though graft numbers are much greater than in the past, the size and depth of these incisions are much smaller, producing a less invasive procedure that heals more quickly with less scabbing. This allows for a more rapid recovery and return to work. The typical post operative appearance is depicted in Figure 5.

Considerations Regarding Women
While the typical patient is a male in his 30s to 50s with androgenetic alopecia, a significant number of patients are female and/or have non-androgenetic hair loss. The issue of hair transplantation in women is a complicated and often controversial issue, with some surgeons claiming that a large percentage of women are candidates, while others claim just the opposite. In my practice, I find that I can reliably produce satisfactory results in women who have the following characteristics: 1.) moderate hair loss (as opposed to too little or too much); 2.) medium to coarse hair 3.) excellent donor density and scalp laxity 4.) realistic expectations. I will typically do fewer grafts (e.g. 1,500-2,000 vs. 2,000-4,000 in men) and take great care to avoid damage to existing hair in the recipient area that could lead to post-operative shedding (“shock loss”).

Repair of older work is a situation frequently encountered by the hair restoration surgeon. In some situations, simply adding large numbers of follicular units will camouflage older, pluggy looking work. However it is often necessary to ‘core out' old plugs with a punch to get the best results (Fig. 6). These holes may be sutured or left to heal by secondary intention.

Non-androgenetic hair loss includes hair loss due to trauma (Fig. 7), burns, and radiation (Fig. 8). Contrary to the commonly held notion, follicular unit grafts generally grow well in scar tissue as long as incision sites are relatively small and not placed too densely. These are often some of the happiest patients. In addition, patients with trichotillomania and traction alopecia may be good candidates if the practices that originally caused the hair loss are no longer present. Central centrifugal cicatricial alopecia (CCCA) may also be treated with hair transplantation as long as all signs of inflammation (redness, scaling, burning) have been treated and are no longer present. Even so, such patients must be instructed that the condition may reactivate, resulting in loss of the grafts. I place these patients on an indefinite regimen of once or twice weekly application of super potent topical steroids and intralesional triamcinolone injections if there is any flare up.

Future Directions
The rapid evolution in hair restoration surgery will continue as improvements in technique allow for faster, more efficient transplantation. New instruments are being developed to facilitate and speed up the surgery and there are even efforts to introduce robotics into the field. Scientific advancements will likely lead to adoption of optimized graft holding solutions and post-operative care products, both of which will result in greater graft survival and improved healing. New products emerging from regenerative medicine research may make donor scarring much less of a problem. Without a doubt, new pharmaceuticals will be introduced that offer alternatives to finasteride and minoxidil. And finally, research in cell therapy (a.k.a. “hair cloning”) and regenerative medicine may make the goal of unlimited donor hair a reality. 11 For those suffering with hair loss, the future is indeed bright.