Seven years ago in this journal, we published a review of the technique for hair transplant using follicular units (FU).1 Although the basic concepts of hair transplant regarding the design of the frontal hairline and implantation in the receptor zones described in that review are still applicable, very significant changes have occurred in the method of extraction of the FUs from the donor area (known as follicular unit extraction [FUE]), which justify this update.

These days, the majority of transplant surgeons use 2 techniques indistinctly, the classic strip technique, also known as follicular unit transplant (FUT) or strip harvesting, and the FUE technique, though popularity of the FUE technique and patient demand has increased as it is a much less invasive method and this is perceived by the patient.

In this update we describe the general features of the FUE technique and its advantages, disadvantages, and controversies.

FUE is an FU transplant technique in which extraction of the FUs from the donor area is performed using a punch with a diameter of approximately 1mm. In the FUT technique, the FUs are harvested from a surgically excised strip of skin using a stereomicroscope whereas, in the FUE technique, FU extraction is performed blind, directly from the donor area, using a cylindric punch, guided only by the direction of the hair shafts as they emerge through the skin surface. It must therefore first be understood that FUE differs from FUT only in the method of FU extraction; the implantation process in the recipient area is identical in the 2 methods.

FUE is similar to the punch grafting technique described by Okuda2,3 in 1939 and Orentreich4 in 1959, the main difference being the size of the punch used for the extraction. Whilst Okuda used punches of 2.5 to 3mm and Orentreich punches of 4mm (containing 10 to 20 hairs per punch), the ones in FUE are much smaller, because the aim is to extract only FUs (1 to 4 hairs per punch).

The first article on FUE was published in 2002 by Rassman et al.5 In its early years, the technique was not widely adopted by transplant surgeons, mainly because of the difficulty of extracting intact FUs with such a small-diameter punch. However, over the past decade, after its challenging initiation in which few surgeons believed it would become established as an alternative to the strip technique, FUE has grown in popularity. There are several reasons for this: increased patient demand; improved surgeon proficiency in the extractions, acquired through greater experience and the availability of better instruments; results that, in the hands of experienced surgeons, are comparable to those of the strip technique; and greater interest of physicians new to this field to learn the technique, as FUE is a method that does not require microscopy or technicians trained in graft dissection.6

The FU extraction process using the FUE technique involves 2 actions: the circular incision with the punch around the FU to liberate it from the adjacent dermal tissue; and extraction of the FU, usually performed with forceps.

The circular incision with the punch is the most difficult and delicate part of the extraction. The first instrument used to perform the incisions in FUE was the traditional 1-mm skin biopsy punch. The problem was that the only guide available to the surgeon to direct the punch was the angle of the hair as it emerged through the skin. The punch must cut around the whole FU, which is formed of follicles 4 to 5mm deep. As the FUs are not rigid structures but can subtly change angle, irreversible damage due to follicle transection was very common. Because of this, early attempts were made to extract the FUs using larger punches (1.25mm, 1.5mm, and up to 2mm), but this forfeited the concept of natural and undetectable FU transplant and furthermore, the scars left by the punches in the donor area were larger and were visible. Today, FU extraction using the FUE technique is performed with punches between 0.8 and 1.15mm in diameter, the most widely used being 0.9mm.

Instruments used in FUE can be divided into 3 types: manual (Fig. 1A), motorized (Fig. 1B), and the robotic arm (Table 1). With the manual system, the surgeon introduces the tip of the punch by hand and makes the incision around the follicular unit. With the motorized systems, the punch is introduced into a handpiece held by the surgeon and attached to a motor that rotates or oscillates the head of the punch at a given number of revolutions. With the robotic system, the surgeon selects the UF to be extracted on a screen and the robotic arm makes the circular incision around the unit. The Artas System (Restoration Robotics, San Jose, California, US) is the only robot manufactured and marketed exclusively for FUE.7,8

Figure 1.

FUE systems.

A, Manual punch. Extraction of the follicular unit requires alignment of the punch with the angle and direction of emergence of the hair shaft, which must be kept in the center of the punch.

B, Two motorized systems: the SAFE device by Harris (HSC Development, Colorado, US) (1) and the Vortex device by Cole (Cole Instruments, Georgia, US) (2).

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A wide variety of punches are available commercially, differing in the design of the punch tip. They are classified into sharp punches, blunt punches, and hybrid punches (Table 1). Sharp punches have greater cutting ability, while the blunt and hybrid punches are better for tissue dissection.9–11The extraction technique varies according to the type of punch employed, as we explain in the following section. In the coming years, new punches will appear on the market, designed to facilitate extraction of the FU and reduce the percentage of transected follicles to minimum acceptable levels, similar to those of the strip method (less than 5% to 10%). The Artas system uses a blunt punch that slides within a sharp punch.

In the authors’ opinion, the instruments are very important, but so is the surgeon's experience and expertise. There are surgeons who only use manual sharp punches and achieve results as good as surgeons who use motorized systems with blunt or hybrid punches. Results thus depend not only on the type of instrument but also on the surgeon.

To extract FUs with FUE, the punch must be aligned with the direction of emergence of the hair shaft, which must remain in the center of the punch (Fig. 2). The use of high-power magnification glasses (4-5x) is important because they make greater precision possible in the extraction. With modern punches, the hair must be cut to a length of 1 to 2mm to see the angle of emergence; however, new punches not yet available commercially are being developed to permit extractions with long hair. The angle of emergence of the hair changes depending on the area of extraction. The hair emerges at a more acute angle in the temporal region and at the borders of the scalp. One of the recommended techniques to make the follicle adopt a more vertical position and thus facilitate extraction is to inject saline solution (tumescence) immediately prior to incision with the punch.12

Figure 2.

Incisions made with the punch around the follicular unit, with the hair in the center of the surface of the punch sections.

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The depth to which the punch should be introduced varies depending on whether a sharp, blunt, or hybrid punch is being used. Sharp punches are usually introduced to a depth of 2.5 to 3mm; deeper than this (below the level of insertion of the arrector pili muscle), the deeper segments of follicles in anagen diverge, increasing the risk of transection (Figs. 3 and 4). Blunt and hybrid punches, because of their greater dissecting and lesser cutting effects, can be introduced deeper (>4mm) with less risk of transection. However, blunt punches have a higher risk of pushing the graft into the dermis (buried grafts).10

Figure 3.

Punches with a sharp tip should only be introduced to a depth of 2 to 3mm to minimize the risk of follicle transection. Blunt and hybrid punches can be introduced to a greater depth (>4mm)

a: Sebaceous gland.

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Figure 4.

Follicular units.

A, Normal, undamaged. B, Partial transection of 2 follicles. C, Complete transection of the follicular unit.

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One of the novelties of FUE has been the possibility to extract FUs from other body areas. This is useful in patients in whom the donor area of the scalp has a low density of FUs, as often occurs in patients who have undergone a number of previous transplants. The area of body hair most commonly used is the beard, especially the submandibular region (Fig. 5). Other areas from which follicles can be extracted are the chest, abdomen, pubis, legs, and axillas (Table 2).13,14

Figure 5.

Beard as the donor area; 1100 extractions performed using the sharp 0.9-mm Cole punch in the Vortex® motorized system (Cole Instruments, Georgia, US).

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One undeniable disadvantage of FUE is that the procedure is very laborious and demanding on the surgeon. Depending on the surgeon's expertise, it can take 1.5 to 3hours to obtain 1000 grafts using FUE, making this is a very surgeon-dependent technique. Most surgeons limit sessions of FUE to a maximum of 1500 to 2000FUs per day so as not to excessively prolong operating times.15 In the experience of the authors, when 2000 or more FUs need to be extracted, it is preferable to do this on 2 consecutive days not only to limit operating times but also to minimize potential damage to the grafts.

Almost any patient who is a candidate for strip transplant can also be a candidate for the FUE procedure (Fig. 6). However, there are situations in which the choice between techniques can be important (Table 3). For example, in young patients with small recipient areas, FUE gives much more freedom to cut the hair very short in the future and also allows additional sessions to be performed, when necessary, without obliging the patient wear long hair to cover the linear scar of the strip. However, patients who do not wish to cut their hair very short for the operation prefer the strip technique, as the linear scar will be covered by the remaining hair.

Figure 6.

Good candidate patient for either follicular unit extraction (FUE) or the strip technique. This patient received 2000 transplanted follicular units using the FUE method with the sharp 0.95-mm Cole punch in the Vortex system (Cole Instruments, Georgia, US).

A, Before transplant.

B, Twenty-four hours after follicular unit extraction.

C, Result a year after the intervention.

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FUE is also indicated particularly when scars from a previous strip transplant cause tension in the scalp skin. Additionally, FUE is very useful to correct hypertrophic scars from a previous transplant performed using the strip technique.16

Many patients have the mistaken idea that the FUE technique does not leave scars, as has been stated on some websites and internet blogs. This is not the case. Any extraction performed with a punch, however small, will leave a pinpoint scar. These scars are usually very hard to see, even with very short hair, but this is not necessarily the case in all patients (Fig. 7). One of the most debated aspects of FUE is damage to the donor area when a very large number of extractions are performed. In other words, what is the maximum number of extractions that can be taken from the donor area without the damage becoming clinically visible? In theory, taking into account that most individuals have an FU density between 70 and 80 FUs per square centimeter and that up to 15 to 20FUs per square centimeter can be extracted in each session, it is estimated that the maximum recommended limit is of approximately 3000 to 4000FU extractions per session.15 However, after several sessions of FUE, each one with thousands of extractions, the donor area can be left with a very low hair density and acquire a moth-eaten appearance (Fig. 8). It is also important to perform the extractions uniformly across the whole donor area, so as not to leave some areas with a lower density than others.

Figure 7.

Hypopigmented pinpoint scars in the donor area of a patient who underwent follicular unit extraction with a blunt 0.9-mm punch (Harris SAFE system, HSC Development, Colorado, US).

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Figure 8.

Excessive number of extractions causing thinning of the hair in the donor area leading to a moth-eaten appearance.

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Finally, some experts still doubt that growth of the FUE grafts is the same as is achieved with the strip technique.17 The controversy arises because FUs extracted using FUE are typically smaller (skeletonized), while those dissected by microscopy are thicker and include more of the surrounding adipose tissue. Perhaps the poor growth observed in some cases of FUE occurs because the smaller FUs require more delicate handling during implantation, as there is a higher risk of damaging the hair bulbs and dermal papillas, the most sensitive part of the follicle. Controlled studies comparing graft survival after extraction using each technique need to be performed to resolve this controversy.

The appearance of FUE has led to increased interest in learning hair transplant techniques. However, FUE has a long learning curve and sufficient knowledge cannot be acquired in a weekend workshop. Furthermore, as there is a significant delay until results are seen (between 6 and 12 months), surgeons can take a long time, sometimes years, to develop the competence required for this procedure and to implement appropriate quality controls.

One of the best ways to learn FUE is to attend the annual workshops and conferences organized by the International Society of Hair Restoration Surgery (www.ISHRS.org). This Society also offers 1- or 2-year fellowships in a number of accredited clinics.

Ideally the transplant surgeon should know and be able to perform the 2 techniques (FUE and strip) to be able to use the most appropriate one for each patient and not the most convenient one for the surgeon.

The most interesting advantages of FUE compared to FUT are the reduction in postoperative discomfort in the donor area and the lower visibility of the pinpoint scars. The main disadvantages of FUE are that it is more laborious, leading to longer operating times, and its long learning curve.

The authors declare that they have no conflicts of interest