Follicular Unit Extraction (FUE)

Improvements in instrument technology and technique have made follicular unit extraction (FUE) a procedure competitive with strip harvesting for obtaining donor hair for hair transplantation.

Follicular unit extraction (FUE) is one of the techniques for obtaining donor hair for hair transplantation. FUE is a technique Hair Follicular Units that requires more skill on the part of the physician hair restoration specialist and more cost on the part of the patient than the technique of strip harvesting (removal of a strip of scalp tissue bearing hundreds of follicular units). It is also a technique with potential benefit for the patient in less donor-site scarring, although small polka-dot scars may appear at sites of follicular unit extraction. If technical advances in FUE instruments make the procedure competitive with strip harvesting in the number of intact follicles that can be harvested per session, FUE may become a procedure of choice for more patients.

FUE is a newer technique than strip harvesting. As FUE evolved, so did the development of instruments for harvesting follicular units (FUs)--technical evolution from the original manual instruments, to more technically sophisticated, mechanically or electronically-assisted instruments, to the latest development of a robotic FUE device.

What is the effect of his instrument evolution on improving the advantages and lessening the disadvantages of FUE over strip harvesting? Before addressing the question, a recap of basic information about FUE and the follicular unit may be helpful.

The Follicular Unit (FU) and FUE

Follicular unit (FU) is a term that describes how scalp hair normally grows. Scalp hair is not evenly distributed across the scalp like corn in a cornfield. It grows in clusters of follicles, little islands of one to four follicles on a plane of scalp skin. Each FU has a distinct anatomic and physiologic identity, and a micro-environment of cells, nerves and blood vessels.

Strip harvesting of donor hair takes a strip of scalp tissue bearing hundreds of FUs for use in transplantation. The FUs in the harvested strip may or may not be transplanted as FUs; the FUs may be divided into individual follicles for transplantation.

FUE removes one FU at a time, targeting the FUs that appear most likely to thrive and produce hair in a transplant recipient site.

In strip harvesting, a team of trained technicians removes follicles from the strip of harvested scalp tissue and prepares them for transplantation by the physician hair restoration specialist at a recipient site. In FUE, the physician hair restoration specialist removes follicular units one at a time from the donor site until there are enough for a transplant session. A drawback of FUE has been that one-by-one harvest of FUs may produce less than one-half the number obtained by strip harvesting. FUE is slower and more labor-intensive for the physician hair restoration specialist, and thus more costly for the patient.

Physicians who favor FUE cite evidence to indicate that the cosmetic outcome of FUE can justify its greater cost to the patient. Instruments that make FUE faster and more efficient are marketed with the claim that they benefit both patient and physician hair restoration specialist.

Transection: An FUE Complication

When hair follicles in an FU are removed from a donor site and transplanted to a recipient site, the follicles should be all physiologically healthy and anatomically intact. Healthy, intact follicles are more likely to thrive and produce hair at the transplant recipient site.

A problem for FUE from its beginning has been the transection of follicles during the FUE procedure. A transection is a cross-sectional cut; the transection of a hair follicle is slicing or tearing it at a cross-sectional angle.

Why It Is Important to Keep a Hair Follicle Intact

A hair follicle is an elegantly complex biological entity. The more that is learned about it, the more elegant and complex its biological functions are found to be. That's why it is important to avoid physical damage to the follicle that is meant for transplantation—for instance, by transection during the FUE procedure.

FUE Procedure

Under microscopic examination, the hair follicle is seen to be made up of layers of specialized cells that provide the specialized functions necessary for growth and for scalp hair's unique anagen-catagen-telogen growth cycling. Located under the follicle structure called "the bulge" is a permanent nest of stem cells that provide regenerative capacity. Running from "the bulge" to the skin surface is the erector pili muscle that causes "goose bumps" and makes hair stand erect in response to cold or to strong emotion such as anger or fear. The erector pili is attached to the follicle but stands separate from the follicle in its route to the skin surface, making it vulnerable to damage during FUE.

The FUE surgical instrument is essentially a hollow sharp punch that is designed to incise the skin around a FU from surrounding tissue. In manual FUE, the freed FU is extracted from its bed with forceps. The procedure sounds simple enough, but the apparent simplicity can be illusionary. The apparent simple procedure of incising and extracting a FU can go awry with transection of the FU.

Transection occurs when the circular sharp blade of the hollow FUE punch fails to completely enclose the FU, and slices off a part of it. Transection can also occur when the FU is pulled apart when it is gripped and pulled with forceps. The damaged follicle(s) in the FU may be useless for transplantation, or fail to thrive if transplanted.

In strip harvesting, a few transected follicles present no problem because the tissue strip contains hundreds of intact follicles. FUE has been unable to harvest large numbers of follicles, so each FU has value in assuring a successful transplant session.

Attempt to avoid transection by blunt dissection—using a blunt instrument to free the FU from surrounding tissue—can occasionally "bury" a FU by pushing it deeper into surrounding tissue. A buried FU can become a focus for infection or cyst formation if not completely removed.

Some confounding issues of FUE are inherent to the patient—e.g., follicles that take an unforeseen direction under the skin, so a punch aligned with visible hair above the skin makes an inadvertent cut into invisible follicles. Some issues are inherent to the physician—e.g., lack of skill and/or experience.

When the number of transected follicles amounts to a substantial percentage of harvested FUs, a transplant session may be less than optimal and additional cost may fall on the patient. Thus, a patient who is considering FUE for harvest of donor hair should ask for the physician's FUE transection rate. A transection rate of 3% or lower can be considered good to excellent; a transection rate of more than 5% can be considered poor. The patient should remember that follicle transection is not unique to FUE. Transection also occurs with strip harvesting.

Newer FUE instruments and techniques claim to lessen the problem of transection and improve the efficiency of FUE.