Minimally Invasive Surgery for Hair Transplantation
BACKGROUND. Follicular Unit Transplantation (FUT) is performed using large numbers of naturally occurring, individual follicular units obtained by single-strip harvesting and stereo-microscopic dissection. Donor wound scarring from strip excision, although an infrequent complication still concerns enough patients that an alternative solution is warranted.
OBJECTIVE. The purpose of this paper is to introduce Follicular Unit Extraction (The FOX Procedure) in which individual follicular units are removed directly from the donor region through very small punch excisions, and to describe a test (The FOX Test) that determines which patients are candidates for this procedure. This paper explores the nuances, limitations and practical aspects of Follicular Unit Extraction.
METHODS. Follicular Unit Extraction was performed using 1mm punches to separate follicular units from the surrounding tissue down to the level of the mid dermis. This was followed by extraction of the follicular units with forceps. The FOX test was developed to determine which patients would be good candidates for the procedure. The test was performed on 200 patients. Representative patients who were FOX positive and FOX negative were studied histologically.
RESULTS. The FOX Test can determine which patients are suitable candidates for Follicular Unit Extraction. Approximately 25% of the patients biopsied were ideal candidates for FUE and 35% of the patients biopsied were good candidates for extraction.
CONCLUSION. Follicular Unit Extraction is a minimally invasive approach to hair transplantation that obviates the need for a linear donor incision. This technique can serve as an important alternative to traditional hair transplantation in certain patients.
Introduction
MODERN HAIR transplantation began in the 1950s with an open donor method of harvesting using the “standard” 4mm punch based upon the pioneering work of Dr. Norman Orentreich.1 The size of the punch was gradually reduced in order to improve the survival of the hairs in the central part of the graft that had been subject to poor oxygenation (the donuting effect), and to make the hair transplant look more natural. Mini-micrografting, the use of large numbers of small grafts, harvested with a multi-bladed knife, rather than a punch, and then cut to the size the physician needed, became the standard for hair transplantation in the late 1980s and early 1990s. 2 Follicular Unit Transplantation (FUT), a procedure in which hair is transplanted in its naturally occurring, individual follicular units, became state-of-the-art in the later half of the 1990s.3-7
Punch harvesting was abandoned in favor of donor strip excision to maximize yield and minimize damage to the donor follicles. Punch harvesting became impractical for smaller grafts, as small changes in the incident angle of the punch transected proportionally more hair as the diameter of the punch was reduced. Generating grafts from a donor strip harvested with a multi-bladed knife was superior to the punch graft technique because it allowed in-vitro visualization of the tissue during the dissection process, but still caused a significant amount of transection. Precise control of graft dissection through direct visualization of the tissue was maximized using single-strip harvesting and stereo-microscopic techniques3. These techniques allowed for the removal of intact individual follicular units from the donor strip and were the enabling technologies for Follicular Unit Transplantation.
The only significant disadvantage to single-strip harvesting is the resultant donor scar. Although the scar usually heals as a nearly undetectable fine line, such a scar can potentially present cosmetic problems in patients who choose to wear their hair very short or in the rare individual who heals with a widened scar. Additionally, single strip harvesting can sometimes be problematic in patients with very tight scalps where a primary closure is difficult.
To circumvent the necessity of producing a linear donor incision, these authors began exploring variations of the punch technique. However, instead of using these punches to merely remove small pieces of hair bearing tissue, we have attempted to directly extract intact individual follicular units from the donor area without significant follicular transection; in effect, creating grafts that are identical to those generated by single-strip harvesting and stereo-microscopic dissection.
There are several problems inherent in removing individual follicular units with small punches. First, any significant variation between the incident angle of the punch and the exiting hair can result in graft transection. Keeping the punch parallel to the follicles throughout the entire length of the graft is difficult, as the visual cues used to guide one’s hand are lost once the punch passes into the depths of the tissue. Second, it is difficult to keep the punch perfectly oriented along a single axis when advancement into the tissue requires a back and forth twisting motion between the fingers. Third, the anatomic characteristics of follicular units are problematic for direct extraction.
Although it is now widely known that hair follicles in the human scalp grow in groups of 1-4 hairs, rather than as randomly spaced individual follicles, it is less well known that this grouping is a characteristic of the dermal component of the follicles only (Figure 1A). If one examines the subcutaneous layer of the scalp, one notes the distinctly random distribution of the bulbs8 (Figure 1B). In order for follicles to be grouped on the surface of the scalp and be random in the fat, the follicles take a curved path through the skin. To visualize it another way, follicular units resemble a small bundle of wheat gathered at the top and splayed apart at the bottom.
Figure 1. Cross-section views of follicular units at different levels in the skin. A) Level of mid-dermis: Follicular units are seen as highly organized groups of 1-4 hairs. B) Subcutaneous fat layer: Hair bulbs have a distinctly random distribution with organization into follicular units that are not readily apparent.
The clinical implication of this is that a punch that neatly encompasses a follicular unit on the surface will amputate the splayed bulbs as it cuts through the deeper tissues. Our experience in trying to simply “punch out” follicular units with a small punch yielded results that would be anticipated from these anatomical considerations. It resulted in an unacceptable rate of transection (about 30%) with wide patient-to-patient variability.
In 1997, we began working on tools to circumvent the problem of follicular unit “splay.” Variations in instrument design, however, were not able to obviate the problem. Through correspondence with Dr. Richard Shiell in early 2001, it was brought to our attention that Dr. Masumi Inaba had described a unique process of removing hair from the donor area in which the punch was used to cut only part of the way down the follicle. The remainder of the follicle was then literally pulled from the scalp. A review of Inaba’s textbook produced an epiphany. It became clear that by cutting only partially into the dermis, many of the problems we were experiencing could be circumvented and transection could be reduced or eliminated.
We soon realized, however, that even with this “extraction” technique there was considerable patient-to-patient variability in obtaining intact follicular units. In some patients, follicular units could be removed completely intact. In others, the grafts pulled apart during their removal, resulting in the follicles being fragmented. We searched to find different hair characteristics that would account for this variability. The most obvious was hair shaft diameter. It was felt that thick, coarse hair would act to hold the graft together as it was extracted. It was also assumed that Inaba’s positive experience with the technique was based upon a select patient population, i.e., Japanese patients who characteristically have thick, coarse hair.
Unfortunately, the problem was not as straightforward as we had thought. Although successful extraction occasionally did correlate positively with hair shaft diameter, we found a number of Asian patients whose grafts fragmented during extraction and some fine-haired Caucasian patients in whom extraction was relatively easy. It was apparent that other factors were involved. It seemed that the dermis might be as important as the hair shaft in providing integrity to the graft during extraction. In conjunction with the Department of Dermatology of Columbia University, we began to study the donor tissue histologically to see what specific factors contributed to the integrity of the graft and could account for differences in their ability to be extracted.
We have defined FOllicular Unit EXtraction (The FOX ProcedureTM) as a technique of harvesting intact individual follicular units directly from the donor area using a small punch. In the procedure, a 1mm punch is placed directly over an individual follicular unit and, following the angle of the emergent hairs, the punch is passed partially through the dermis. Once the initial advancement is made, the bulk of the follicle is pulled with forceps, literally “extracting” the follicular unit from the scalp. It is important that the punch is small enough to leave an imperceptible donor scar.
The FOX TestTM allows the physician to determine which patients will be good candidates for the procedure. The FOX Test involves 5 or more small biopsies taken from the back of the scalp in the same manner as in The FOX Procedure. The extracted grafts are examined under a stereomicroscope for their integrity and/or sent for histologic examination.
This paper describes the FOX Procedure and the FOX Test, the indications for its use, and the limitations of the technique. It also attempts to explain why only select patients are good candidates for the technique.
