Follicular Unit Hair Transplantation

Patient evaluation and surgical planning

Diagnosis and classification of androgenetic alopecia

The diagnosis of androgenetic alopecia in men is usually straightforward. It is made by observing a “patterned” distribution of hair loss. It is confirmed by the presence of miniaturized hairs in the areas of thinning. The diagnosis is supported by a history of baldness in the family. In women, the diagnosis is more complex since the most common presentation, a diffuse pattern, can be mimicked by a host of non-androgenetic etiologies.

Miniaturization – the progressive diminution of the hair shaft's diameter and length in response to androgens – can be most readily observed with a densitometer, a hand-held instrument that magnifies a small area of the scalp where the hair has been clipped to about 1 mm. One type, the Rassman densitometer, magnifies by ×30 in a visual field of 10 mm ² , making it easy to identify miniaturization and calculate hair density ( Figs 30.1–30.3 ). With video-densitometry ( Fig. 30.1B ), the doctor can project the image onto a computer screen so that it is immediately visible to the patient. It can also provide a permanent digital record of the person's density and miniaturization status.

When describing hair loss, particularly in the early phases, it is preferable to think in terms of changes in volume rather than density. Density is simply the number of hairs per unit area, whereas volume reflects both hair shaft diameter as well as the absolute numbers of hairs.

A new device, called the Cross Section Trichometer, takes both of these factors into account by measuring the cross-sectional area of a demarcated bundle of hair. This instrument measures hair mass – the cross-sectional area of a bundle of hair present in a premeasured area of scalp. It detects small changes in both hair density and diameter. Since the earliest sign of hair loss results in volume changes caused by individual hairs decreasing in size (miniaturization) without a decrease in number, devices that can assess hair shaft diameter are useful for identifying early hair loss. Only in more advanced balding will the actual number of hairs start to decrease.

The Norwood classification of male pattern hair loss, published in 1975, remains the most widely used. It defines two major patterns and several less common types ( Fig. 30.4 ). In the regular Norwood pattern, two areas of hair loss – a bitemporal recession and thinning crown – gradually enlarge and coalesce until the entire front, top, and crown (vertex) of the scalp are bald. A less common Norwood variety, Norwood class A, is characterized by a distinctly anterior-to-posterior progression, usually resulting in baldness on the front and top of the scalp, but more limited loss in the crown. In both patterns, the sides and back tend to resist androgenetic changes, though the sides may exhibit significant thinning in senile alopecia.

Two other types of genetic hair loss not emphasized in the literature – diffuse patterned alopecia (DPA) and diffuse unpatterned alopecia (DUPA) – pose the greatest challenge both for diagnosis and patient management. A thorough familiarity with all of these patterns is essential for diagnosing androgenetic alopecia and planning FUHT ( Table 30.1 ).

Table 30.1

Classification of androgenetic alopecia

Norwood classes	Regular classes I –VII
	Type A variant (IIA–VA)
	Variations: persistent frontal forelock; persistent frontal hairline
Diffuse androgenic alopecias	Diffuse patterned alopecia (DPA)
	Diffuse unpatterned alopecia (DUPA)
Senile alopecia
Female pattern alopecia	Ludwig classes I–III

DPA is an androgenetic alopecia that manifests as diffuse thinning in the front, top, and vertex, with a stable permanent zone. In DPA, the entire top of the scalp gradually miniaturizes without passing through the typical Norwood stages. DUPA is also androgenetic but lacks a stable permanent zone. It affects men much less often than DPA. DUPA tends to progress more rapidly than DPA and eventuates in a horseshoe pattern resembling the Norwood class VII. However, unlike the Norwood class VII, the DUPA horseshoe can look almost transparent due to the low density of the back and sides. Differentiating between DPA and DUPA is very important because DPA patients often make good transplant candidates, whereas DUPA patients almost never do, as they inevitably have extensive hair loss without a stable zone for harvesting.

The early warning signs of DUPA include:

• A rapid decrease in hair volume and a change in hair texture at an early age, often in the teens

• The maintenance of an adolescent hair pattern and persistent frontal hairline in spite of dramatic volume change

• A see-through donor area (most easily visualized when the hair is wet or lifted up)

• Significant miniaturization of the donor area (>35%)

• A donor density of <1.5 hairs per mm ² .

The sensitivity of densitometry in detecting early DUPA justifies its routine use in the evaluation of hair loss. Once a diagnosis of DUPA is considered, any decisions regarding surgical hair restoration should be postponed. The possibility of missing a DUPA diagnosis is one of the most powerful arguments against performing hair transplantation at an early age.

Both DPA and DUPA occur in women but, in contrast to men, DUPA is far more common. As with men, women with DUPA do not make good transplant candidates (except possibly when donor hair is used solely to soften the frontal edge of a wig). Indeed, the higher DUPA incidence in women explains why a smaller proportion of women than men qualify as transplant candidates. Interestingly, the most common classification used for women, the Ludwig classification, does not differentiate between DPA and DUPA.

There is a home test that screens for variations in the androgen receptor gene on the X chromosome, a gene associated with male pattern hair loss. Its purpose is to identify persons at increased risk of developing hair loss before it is clinically apparent so that medical intervention can be started early, when it is most effective. The presence of one of the variants indicates a moderately increased risk for the development of androgenetic alopecia and the other indicates a substantially decreased risk of becoming bald. A similar screening test is also available for the detection of hair loss in women.

It is important to realize that these markers reveal an association with hair loss and that a cause and effect relationship has not been proven. A danger is that patients may overreact to this relatively incomplete information. It is best to have the tests performed under a doctor's supervision so that the results can be put in the context of other information that the physician gleans through a careful history and physical and so that the patient may be properly counselled.

It is important to emphasize that a non-androgenetic differential must be considered in all cases of unpatterned alopecia because a wide variety of medical conditions can produce diffuse hair loss. This is particularly relevant in evaluating women since unpatterned hair loss is the rule rather than the exception ( Box 30.1 ). The following laboratory tests are often useful when a non-androgenetic cause for diffuse hair loss is suspected: chemistry screen, complete blood count, serum iron, total iron-binding capacity, tri-iodothyronine, thyroxine, thyroid-stimulating hormone, antinuclear antibody, and serologic test for syphilis.

Box 30.1

Non-androgenetic causes of diffuse hair loss in women

• Anemia.

• Endocrine diseases (especially thyroid)

• Connective tissue disease

• Obstetric/gynecologic conditions (e.g., postpartum, polycystic ovarian disease)

• Weight loss (especially crash diets)

• Emotional and physical stress (e.g., surgery, anesthesia)

• Medications: oral contraceptives, thyroid drugs, anti-hypertensives (especially β-blockers), psychotropics, anticoagulants, antilipemics, gout therapy, prednisone, excessive vitamin A or tryptophan use

In women, diffuse or patterned hair loss may be a sign of excessive androgen production. A further medical evaluation is indicated when the hair loss is associated with any of the following: cystic acne, irregular menses, hirsutism, virilization, infertility, or galactorrhea. Serum levels of dehydroepiandrosterone (DHEA) sulfate, androstenedione, total and free testosterone, and prolactin can serve as a useful screen.

When the diagnosis of androgenetic alopecia is uncertain, further diagnostic information can be gleaned from a hair-pull test for telogen effluvium, a potassium hydroxide mount and culture for fungus, a microscopic examination of the hair bulb and shaft, and a scalp biopsy (sectioned horizontally). A dermatologic consultation is warranted whenever the diagnosis of hair loss is unclear.

Assessing the patient's donor supply

The main factors in determining total donor reserves are donor density, scalp laxity, and the physical size of the donor area.

Planning the first hair transplant session

Ideally, the main goals of the first transplant session should be:

• To establish the frontal hairline and frame the face

• To provide coverage to all bald areas of the scalp, from the frontal hairline to the vertex transition point

• To create sufficient density so that the results will look natural after one session, though additional sessions may be desired.

These goals should be the ultimate aim of those performing hair restoration surgery, but may not be achievable with a small or inexperienced surgical team. In this author's opinion, there is little medical or aesthetic justification for performing the surgery in arbitrarily small sessions. It is preferable that each procedure cover the entire area of hair loss intended to be treated and be designed to “stand-alone.”

In an alternate approach to surgical planning, the objective is to achieve final density in a one-pass procedure by creating high density in a more limited area and then transplanting another area in a subsequent session. This is accomplished in part by using very small recipient sites, limiting graft size to three hairs and using the stick-and-place method, in which grafts are inserted as soon as the recipient sites are made.

As the number of grafts placed per unit area (density) rises, so too does the risk of vascular compromise that may result in suboptimal graft growth. Technical problems of popping that may cause the grafts to become desiccated or that expose the grafts to mechanical injury on reinsertion also become more likely. Proper patient selection and technical expertise help avoid such problems, but the risks are increased nevertheless. It certainly behoves those with more limited experience to be conservative when determining the number of grafts to be transplanted.

Because the blood supply to the scalp is extensively collateralized, the risk of vascular compromise is related more to the density of grafts in a specific area and the size of the recipient wounds, than the absolute number of grafts placed. For this reason, the transplantation of a large number of grafts over a broad area does not seem to pose the same problems as producing very high densities in specific areas. In addition, popping becomes less of a technical issue when the same numbers of grafts are placed over a larger area. However, transplanting a large number of grafts (in “mega-sessions”) poses its own challenges, such as increasing the time the grafts remain outside the body, requiring more staff, contributing to patient and staff fatigue, and creating organizational issues. As with dense packing, the use of very large sessions should be reserved for only the most experienced surgical teams.

Though the amount of hair needed to cover the front and top of the patient's scalp will vary, an attempt should be made to achieve this coverage, if only lightly, in the first session. Crown coverage should not be a goal of the first session unless the patient has an above-average donor supply; if it is attempted in the first session, the patient's options will be more limited and the chances for an aesthetically balanced transplant may be permanently compromised.

Table 30.2 offers general guidelines as to the number of follicular units recommended for the first hair transplant procedure.

Planning a second session

Subsequent transplant sessions

The surgeon should make every attempt to accomplish the restoration in as few sessions as possible, rather than putting patients through an unnecessarily protracted course of multiple surgeries that can adversely affect their donor area and their lifestyle. The number of grafts required to achieve patient satisfaction varies widely due to the great variability in hair characteristics and patient tastes. Moreover, because hair loss patterns form a continuum, the number of grafts necessary for each discrete Norwood class can vary significantly. Table 30.3 shows the approximate number of follicular unit grafts necessary for a complete restoration, with and without crown coverage.

The patient

It is common practice for doctors to place patients on finasteride before surgery to minimize the chance of post-surgical effluvium (shedding). Although there are no scientific studies confirming that it is effective for this purpose, it would seem that if the goal is to prevent post-surgical shedding, the medication should be prescribed at least a month before the procedure. If, however, the intent is to postpone or obviate the need for surgery, then it should be taken for a minimum of 1 year to allow sufficient time for the patient's hair to regrow.

Patients using topical minoxidil are advised to discontinue its use several days before surgery (because of its vasodilator properties) and wait until a week after the procedure before resuming it (to avoid the irritating effects of the alcohol in the 2% solution or the propylene glycol in the 5% solution). Although we suggest minoxidil in combination with finasteride for patients with early hair loss, we generally do not recommend the use of minoxidil after a hair transplant, unless it is being used in an area other than that which was transplanted (such as the crown). We feel that minoxidil has little added value for the average post-transplant patient. We do, however, encourage the continued use of finasteride to help retard further balding. Those who do not plan to use minoxidil after surgery should discontinue it immediately, so that any of its beneficial effects may be reversed by the time of surgery and the true extent of a person's hair loss be more easily appreciated.

Patients are advised to avoid products that are used to thicken the hair or that stain the scalp for 3 days before the procedure, as these often take several days to completely wash out of the scalp. Their presence during surgery can decrease visibility and make placing more difficult. Hair systems should be removed before surgery and be replaced with, or converted to, a clip-on system. The front edge of the piece can be kept in place with a stiffening rod, obviating the need for tape or glue. However, any form of attachment at or near the frontal hairline risks dislodging grafts. Patients are encouraged to permanently discontinue the system after the procedure, but those who feel the need to use them until their hair grows in should wait at least 10 days postoperatively when the grafts are secure.

Systemic antibiotics are not indicated for clean surgical wounds in healthy patients, so their routine use in hair transplantation is not necessary; however, many doctors routinely use them. Because there are no specific guidelines for antibiotic prophylaxis in hair transplantation for patients with a history of endocarditis or mitral valve prolapse, the decision to use them must be based on the individual patient's risk factors.

Other preoperative instructions are relatively straightforward and will depend to some degree on the preferences of the operating surgeon. Patients should be notified well in advance of the procedure date regarding the need to discontinue certain medications, to stop smoking, and abstain from alcohol. Box 30.3 is a summary of the main preoperative instructions.

All patients undergoing hair transplantation should be treated with universal precautions. Although there is no consensus on the need to perform routine blood tests before the procedure, the following tests provide an additional level of safety:

• Complete blood count

• Metabolic panel

• Hepatitis B surface antigen and antibody

• Hepatitis C antibody

• HIV screen.

One should obtain medical clearance for HIV-positive patients to make sure that they are immunocompetent enough to withstand a potential series of procedures. With hepatitis antigen positivity, one should inform the patient's primary physician to rule out active disease. Other tests, such as a platelet count and prothrombin and thromboplastin times, are performed only if warranted by the history and physical exam.

The surgical consent form should be given to patients to read at their leisure well in advance of the procedure and should be signed by the patient before taking any medications that can cause drowsiness or impair judgment. The exact time of signing should be indicated. The major elements of the consent form are listed in Box 30.4 .

Although not universally recommended, some doctors have the patient shower the morning of surgery using a chlorhexidine surgical scrub as shampoo. Though it does not sterilize the scalp, the chlorhexidine binds to the stratum corneum, decreasing transient and pathogenic microorganisms and resident skin flora. Caution is advised as it can be toxic to the middle ear and irritating to the eyes. In our practice, we advise patients to use a simple baby shampoo. After showering, the patient should dress in comfortable clothes and wear a button-down shirt.

Donor harvest

In preparation for the donor harvest, patients are seated upright on the operating table. The hair in the donor area (hair in the proposed donor strip plus 0.5 cm above and below the strip to facilitate suturing or stapling) is then cut to a length of 2 mm using electric clippers. The trimmings are thoroughly vacuumed away and the hair above the strip is held back with paper tape, fully exposing the donor area. A gauze headband is placed around the patient's head just below the clipped area and sterile drapes are taped to the headband.

In the first session of FUT, in a patient with average scalp laxity, we generally harvest a donor strip that is 1.2–1.4 cm wide. In calculating the length, we use the general rule of 70–95 follicular units/cm ² . For example, if a 2000-follicular unit graft hair transplant is planned for a non-Hispanic white male with an average density of 85 FU/cm ² , a 1.2 cm-wide strip would need to be about 20 cm in length (plus tapered corners to allow a flat closure). People of African and Asian descent characteristically have a lower follicular unit density and a strip of this dimension will yield a lower number of follicular unit grafts.

When performing follicular unit extraction, one can generally extract about 18 FU/cm ² , so the surgeon would need about five times the area of an FUT strip to get the equivalent number of grafts. Thus, to extract the 2000 grafts in the above example, one would need an area measuring 1.2 × 20 × 5 cm or 120 cm ² . In FUE, the hair should be clipped to a length of 1 mm (half the length of the 2 mm needed for FUT).

Local anesthesia

A ring block is established using an anesthetic mixture of lidocaine, bupivacaine, and epinephrine (see Table 30.4 ). The anesthetic solution is injected into the subcutaneous fat layer approximately 1 cm below the lower portion of the clipped area and extending several centimeters past it on either side. In addition to buffering the anesthetic, already discussed, discomfort from the injections can be reduced by pressing a vibrating hand massager to the skin below the area of insertion of the needle. The sting of the injection can also be reduced by a device that controls the flow of the anesthetic solution.

Approximately 0.75 mL of anesthesia is used per centimeter of donor area, so that a 25 cm-long incision would require slightly less than 20 mL of anesthetic solution. It is important to avoid injecting into the muscle, as epinephrine will cause vasodilatation, due to the action on β ₂ -receptors, quickly dissipating the local effects of the anesthetic and increasing its toxicity.

The ring block takes approximately 15 min to induce anesthesia. As soon as the donor-area skin becomes numb, tumescent anesthesia is administered by injecting larger quantities of a more dilute lidocaine–epinephrine solution into the mid-fat to make the area firm. The tumescence serves six purposes: (1) to widen the distance from the follicles residing in the upper fat to the nerves and larger blood vessels lying just above the fascia; (2) to increase the rigidity of the donor area; (3) to decrease follicular transection; (4) to decrease bleeding; (5) to produce more uniform anesthesia; and (6) to reduce the amount of anesthetic required.

Tumescence can be achieved using a dilute solution of epinephrine and lidocaine (see Table 30.4 ). This will provide additional anesthesia that is particularly important in repeat procedures, or for patients with significant donor scarring. In situations where there is prior surgery, direct cutaneous innervation to the donor area from the occipital branches can be blocked by scar tissue, so that innervation to the donor area arrives in a rostral–caudal direction, rendering inferiorly placed ring block anesthesia alone ineffective. At times, when there is an excessive amount of donor scarring, the anesthetic mixture must be injected above or directly into the scarred area to make it numb.

Strip excision

The ideal position for the donor incision is in the mid-portion of the permanent zone. This generally lies at the level of the external occipital protuberance (at the midline). The donor strip can be excised using two parallel blades set 1.0–1.5 cm apart or the strip can be harvested using a single blade. When using the parallel blade technique, a convenient harvesting device is the Rassman handle that is loaded with two no.10 blades. The handle holds the blades at an angle of 30°, making them parallel to the emergent hair. The handle should hold the blades in a pre-angled position to allow both blades to lie flush with the skin surface when aligned with the hair follicles; otherwise, the surgeon may cut too superficially with the upper blade and too deep into the scalp with the lower ( Fig. 30.7 ). Once the main parallel portion of the incision is complete, a single scalpel blade is used to taper the ends into an ellipse and to dissect the base of the strip in mid-fat, just below the level of the follicles. In general, the length of each tapered end should measure at least 1.5 times the width of the strip, so that the ends lie flat ( Fig. 30.8 ).

Alternatively, the skin can be marked and the entire excision can be made with a long free-hand ellipse. This has the advantage of allowing the angle of the blade to be adjusted to the angle of the follicles as each edge is cut. However, this technique makes it harder to keep the width uniform, which is necessary for predictable graft yields. In addition, the first incision causes the strip to lose its rigidity, making the cutting the second edge more difficult

Regardless of the harvesting method, once the strip is removed it is immediately placed into a holding solution.

Donor closure

The most common types of closures include metal staples, a running non-absorbable suture, or a running absorbable suture. If staples are used to close the wound edges, it is important to be certain that the wound edges are flush before the staples are applied. The edges can be approximated by grasping the lower edge with a skin hook and using rat-toothed forceps to hold and slightly evert the upper edge (this requires the help of an assistant) ( Fig. 30.9 ). The staples should then be placed approximately 0.6 cm apart. Staples have very little tissue reactivity, but they make flush apposition of wound edges a little more difficult and can be uncomfortable in the postoperative period. In the author's practice, we routinely remove alternating staples at 10 days and the remainder at 18–25 days postoperatively, depending on the degree of tension, the patient's age and the amount of anticipated activity. We feel that leaving in staples for this longer period of time leads to a finer donor scar, particularly in younger or active patients and in those with tighter than average closures.

Non-absorbable sutures, of either nylon or polypropylene, are usually placed using a single running stitch and are removed in 10–14 days. A problem is that if they are placed too far from the wound edge, they entrap hair follicles and this may result in the destruction of donor hair if there is significant postoperative edema. If placed too close to the wound edge, they can become buried and difficult to remove. These two problems are avoided with the use of staples and probably speak to why staples are used by so many hair transplant surgeons in spite of the preference that patients have for the more comfortable sutured closure.

Absorbable sutures should be placed close to the wound edge ( Fig. 30.10 ). This will tend to minimize the amount of suture material used, decrease the entrapment of follicles and avoid strangulation if there is significant postoperative edema. To further limit damage to follicles, the sutures should be placed approximately 4.5 mm apart and the suture should be advanced on the surface, rather than under the skin, as this will minimize the amount of suture in contact with the follicles ( Fig. 30.11 ). With this technique, the needle should be passed through the full thickness of the dermis and exit the wound edge, just below the level of the bulbs, without incorporating any significant amount of subcutaneous tissue. The needle track must be kept parallel to, and within, 1.5 mm of the wound edge. Particular attention should be paid to placing the needle parallel to the upper wound edge where the angle is very acute. Although hypoallergenic, in our experience, poliglecaprone can cause allergic reactions in some patients. Basic guidelines for using poliglecaprone 25 sutures can be found in Box 30.5 .

Graft dissection

Once the donor strip is removed, it is immediately placed into the holding solution and passed to the surgical team leader stationed at a stereomicroscope ( Fig. 30.12 ). The strip dimensions are measured and recorded. The next step is performed under strict stereomicroscopic control in a process called “slivering.”

In one method of slivering, the donor strip is placed on its side, on a wooden tongue-depressor blade, soaked in Ringer's, with the hair pointing away from the dissector and the convex surface of the strip facing upward. For a right-handed person performing dissection, the left end of the strip is held with rat-toothed forceps in the dissector's left hand. An assistant applies tension to the strip, holding it a few centimeters away from the area being cut with rat-toothed forceps held in the right hand. Using a Persona no.10 blade on a no.3 blade handle held in the right hand, the dissector begins to cut the strip into 2–2.5 mm-wide sections, by guiding the blade between follicular units using a one-directional fillet-like movement from the epidermal side to the subcutaneous surface. A back-and-forth sawing motion should be avoided, as it will increase the risk of transection ( Figs 30.13 , 30.14 ). The pieces generated are then distributed to the other members of the surgical team who complete the dissection. In the last step, the individual pieces are placed on their sides, stabilized with straight jeweler's forceps, and then dissected under the stereo­microscope with a scalpel into individual follicular units of one to four hairs each ( Figs 30.15 , 30.16 ).

Next, the units are sorted according to the number of hairs they contain and placed into Petri dishes with 4-quadrant dividers to hold separate the different size follicular units. The Petri dishes containing holding solution are placed on a cooling unit to keep the solution at a specified temperature ( Fig. 30.17 ). The temperature is monitored with a digital sensing device.

An alternate slivering method involves dissecting the donor strip into slivers as wide as one follicular unit, approximately 1 mm. The units are then isolated from the very thin strip. The key to either method is that every step is performed under stereomicroscopic control, which keeps the units intact and avoids follicular transection. It is also vital that all the pieces of the strip remain in chilled Ringer's lactate, except when they are being cut. While under the microscope they should be kept well hydrated using 10-mL syringes containing Ringer's lactate that is kept at each cutting station.

Follicular unit extraction

Follicular unit extraction (FUE) is a conceptually simple procedure, where individual follicular units are harvested through small circular incisions created by a trephine or similar round instrument. In FUE, the punch cuts down through the reticular dermis and the follicular unit is pulled (extracted) from the scalp. The advantage of this procedure is that it obviates the need for a linear incision. Difficulties lie in the increased risk of follicular transection compared to strip harvesting, the inability to harvest all the hair from the mid-portion of the donor area, and the intrinsic variability of each patient with respect to the ease of extraction. There are also the organizational challenges of not being able to have multiple persons working in parallel (as can be done with the microscopic dissection of a harvested strip) and the inability to easily harvest and place grafts at the same time. Both of these constraints serve to increase the length of the FUE procedure.

The main indication for FUE is for patients who want to wear their hair so short that the linear donor scar of FUT may become visible. FUE is also useful in patients who are at risk of having a widened donor scar. This includes very athletic patients, particularly those engaged in contact sports, bodybuilders, and younger patients in general. Other indications include patients with very tight scalps (in whom a strip excision is not practical) and those with a history of healing poorly, i.e., those that heal with stretched or hypertrophic scars, or with keloids. Some patients simply prefer not to have a linear donor scar.

An important application of FUE is to camouflage a widened linear donor scar from prior hair transplant procedures. As stated earlier in this chapter, it is unfortunate that patients with very loose scalps are at risk of healing with widened scars but may also be poor candidates for FUE due to a difficulty in adequately stabilizing the scalp.

FUE's main limitation is that it is less efficient in harvesting hair than FUT performed with strip harvesting. In FUT, all the hair from the optimal (central) part of the donor region can be removed and transplanted, and the resulting defect is sewn closed. In contrast, the FUE defects remain open to heal by second intention with significant amounts of intervening hair left behind and, therefore, a much larger region of the scalp must be accessed to harvest the necessary amount of donor hair. In a single procedure, to obtain the equivalent number of grafts, FUE requires approximately five times the area needed when using a strip. In FUE, the greater area required significantly increases the risk of harvesting hair from non-permanent areas of the scalp or from areas where the hair is of poorer quality. Figure 30.18 shows the donor area immediately after the extraction of 1891 follicular unit grafts and the same area 1 and 2 weeks postoperatively.

As mentioned, transection during the harvest is greater in FUE than with stereomicroscopically controlled FUT. This is due to the inability of the instruments used in FUE to fully account for the variable angles and curved path of the individual follicles that comprise each follicular unit as they pass deeper in the skin. With FUE, the second intention healing causes microscopic fibrotic changes in the donor area, distorting adjacent follicular units and making subsequent sessions more difficult. Taken together, these factors limit the total number of intact follicles that can be harvested through FUE, rendering it a less robust procedure than FUT. In a procedure where a finite donor supply is the main constraint, the inefficient use of donor tissue poses a significant problem. Table 30.5 summarizes the pros and cons of FUE.

The ability to perform FUE with minimal transection varies significantly among patients and in different regions of the scalp. Because of this, a test measuring the ease of extraction (the FOX Test) should be performed prior to recommending the procedure in patients where extraction is likely to be difficult. Patients undergoing FUT can easily be tested for FUE at the time of surgery in case the latter procedure is considered at a future date.

A significant advance in the technique of FUE is to first score the top of the follicular unit with a sharp punch and then use a blunt instrument to separate the follicular unit from the surrounding tissue, thereby minimizing follicular transection. The main limitations of this technique are the increased incidence of buried grafts and increased surgical time in an already very laborious process. Robotic FUE, based on this two-step concept, addresses the limitations of conventional techniques.

Robotic FUE (see Video 30.1 )

Follicular unit extraction consists of two main steps: (1) separation of the follicular units from the surrounding skin, and (2) extraction (removal) of the follicular units from the scalp. Step one is a highly repetitive and labor-intensive process that requires great precision. This step requires the centering of the punch over a follicular unit and the alignment of the dissecting instrument parallel to the follicles. Since this process must be repeated hundreds to thousands of times in a typical FUE hair transplant, it is subject to significant human variability and error.

A major advance in follicular unit extraction is the use of a robotically controlled extraction device that automates this crucial first step of FUE. The robotic system increases the accuracy of graft harvesting, which in turn minimizes damage to hair follicles, potentially increasing graft survival.

The current robotic technology is based on the two-step method of extraction, namely, it uses a sharp punch to penetrate the skin and a dull rotating punch to separate the deeper part of the follicular unit from the surrounding tissue. The main improvement is a very precise, image-guided robotic arm that operates a dual-needle punch mechanism in order to increase the accuracy of extraction ( Fig. 30.19 ).

Compared with manual systems, the robot is more versatile in its ability to harvest grafts from patients with different hair characteristics, patients from various ethnic backgrounds, and hair from different parts of the scalp. It is particularly useful in extracting grafts from the sides of the scalp, where the hair lies flatter on the skin.

Introduction of the robotic system into a physician's practice can present a formidable challenge. Besides the expense of the technology, the robot requires an operating room larger than those that exist in many doctors' offices and requires that the room be dedicated to this purpose. In addition to special training required to operate the system, the FUE procedure itself should be modified, so that grafts are kept out of the body for as short a time as possible and kept in an environment that will ensure maximum growth. This can be accomplished by making recipient sites prior to the robotic harvesting and by using special biologic solutions to hold the grafts.