follicular units for minimally invasive hair restoration
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Follicular units for minimally invasive hair restoration

If we recall early hair transplant procedures, one of the pioneering techniques, known as punch grafting, was that proposed by Dr. Norman Orentreich. He punched hair grafts as large as 10 mm in diameter for grafting. This punch graft method of hair transplantation was practiced for many years. Over time the size of the grafts became progressively smaller until the follicular transplant technique replaced this conventional grafting method.

Amongst all the different viable hair transplant techniques that have been used so far, follicular unit transplantation, combined with the single scar technique for donor skin harvesting, has been the most favored in the recent times given its minimal postoperative complications. When the patient, however, is undergoing a severe and extensive hair loss that is rapidly progressing, even this single scar approach tends to be visibly ugly. Also, a patient’s scalp laxity plays an important role in determining how the donor region may heal and reveal itself when the hair style is short. A tight scalp generally results in widening of scars. To avoid these problems, Dr. Rassman and his colleagues have formulated a new method called the FOX procedure or the follicular unit extraction (FUE) technique.

In this technique, grafts of 1 mm diameter containing individual follicular units are punched and they are pulled out from the scalp along with the follicles. Effectively, these units resemble the same kind of minigrafts that are harvested from the donor strip harvesting technique. This FUE approach would in principle result in decrease in the time spent on dissection and there would be no scar since the small area of the punches would close on their own and leave just very small spots, the scars of which diminish with time. The other advantages of this technique is that it can be used on patients who have smaller areas to be treated such as the front lock, eyebrows and the temple peaks, those who have tendency to develop wide scars as evident from previous surgeries or hair transplants and sports persons who need to resume their activities without post operative delay.

This technique however does have some inherent difficulties and differs from patient to patient. Scalp anatomy plays an important role in the harvesting of the grafts. Sometimes it can be very difficult for the hair surgeon to predict the position of the follicles in the scalp. This is very important while harvesting follicles with the FUE technique as the punch must be inserted such that it does not cut through the hair follicles - it is very important to obtain undamaged follicles.

When the hair surgeon plans a punch, he has to first find the angle in which the hairs have grown. This he can determine only to a certain extent as the distribution and other vital components of the graft is embedded in the scalp layers. In the skin, the hair follicles actually look like a monocotyledonous crop with fibrous roots. So the idea of simple graft removal is in reality a rather tedious one involving a lot of evaluatory procedures before the punch can be correctly inserted into the skin.

Dr. Masumi Inaba had already formulated a similar follicular unit harvesting technique some time ago in which he removed grafts directly from the donor sites. This was similar to the old punch grafting technique developed by Dr Orentreich, but with a variation in that the grafts were removed with the follicles as one would get when follicular unit transplants are dissected from strips. For this approach Dr Inaba punched the hair follicle donor site only to a certain depth and then pulled out the graft gently without damaging the follicles. While punching an area, the hair surgeon is able to feel a change in pressure when he/she reaches the subcutaneous layer and stops pushing the punch further into the skin. With the help of a forceps, he/she can pull out the hair with intact follicles.

When this procedure was tried by Dr. Rassman and his group, it was seen that although this method was an effective one, better in many ways than their technique of punching to the far end of the follicles to remove them intact, the procedure varied between patients and the possibility of fragmenting of follicles was very evident. Different hair characteristics were evaluated to confront this problem and the shaft diameter was seen to have some correlation with the risk of hair fragmentation. Thicker shaft diameter seemed to allow reduced follicular damage (on average Asians have thicker hair follicles and hair fiber than Caucasians) and this was probably the reason why Dr. Inaba could get good results in his patients.

Since there was lot of variation in the final grafts removed for transplantation, the histological aspects of the donor grafts were studied using a method called the FOX test. The FOX test also doubles up as an evaluation procedure to select suitable candidates for follicular unit extraction (FUE).

The FOX test

1. The donor area hair is cut to a length of 2mm and the area anesthetized.
2. Using Ringer solution, a type of salt solution which is used in intravenous administrations, the donor area is injected and “puffed up” for easy extraction of the follicles.
3. Each of the hair follicle bunches extracted were subjected to microscopic analyses to determine the amount of damage caused to the follicles and graded along a scale of 1-5. Grade 1 meant the follicles were intact and 5 where the follicles were 80% and above destroyed.
4. The patients were classified according to the above findings as positive (suitable candidates), moderately positive and negative (not suitable candidates) for the FOX procedure. Grade 1 and 2 were positive, 3 moderate or neutral and 4 and 5 negative for FOX procedure.
5. Histological studies especially using staining to find the different components of the dermal sheath were conducted to find any correlation in the anchoring patterns of the follicles to ease the extraction procedure.

FOX procedure

In comparison with the strip harvesting approach, the FOX procedure requires a larger area of donor region for hair follicle extraction, at least 8-10 times more area. 100 follicular unit grafts can be obtained from a 5 square centimeter area of donor hair in the strip harvesting method while a similar amount of grafts from the FOX procedure is probable from about 50 square centimeters of donor area.

Staining dermal layers using hematoxylin, eosin and orcein have revealed differences in FOX positive or type 1 and FOX negative or type 5 patients. The size of the dermal sheath is thick in FOX negative and thin in FOX positive patients. Further investigation involved staining the dermal sheath with orcein to study the other components present such as elastin, smooth muscles and fibroblasts. The elastin stained heavy in FOX positive patients but not as much in FOX negative patients while no significant differences were seen in the other two components.

Based on the above findings, it is very difficult to come to a conclusion that any one of the above factors determines the anchoring of hair follicles. A detailed study of the dermal layer and its composition could definitely enrich the understanding of evaluating patients for the FOX procedure.

The FOX procedure has a few advantages with regard to scarring but many significant disadvantages which need to be evaluated before it can be popularized amongst patients and surgeons. According to Dr. Walter Unger the following points need to be evaluated before the FOX procedure can replace follicular unit transplants harvested from donor skin strips.

1. Donor area damage can be very obvious in this method when the area to be grafted is large because the number of punches necessary to extract the required number of donor hair follicles is significantly large. If one were to calculate the total length of surgical incision necessary, a requirement of 500 follicles would involve about 1560 mm of skin incisions for punch invasions while in strip harvesting the same amount can be harvested with incisions totaling just 200 mm.

2. During the FOX procedure it is necessary that the hair in the donor region be cut to 2mm length. Since the area involved is large, there is no method available to cover these harvested areas. The patient has to wait until the hair grows. But in strip harvest technique, only the 1 cm X 20 cm donor area is prepared for harvesting and the hair above the region is combed over the harvested area as temporary coverage.

3. Prediction of follicle damage is not possible and hence the amount of transplantable hair that can be retrieved with FUE is also a question. Strip harvesting however yields good donor hair follicles and has a higher success rate.

4. The angle of hair growth of existing hairs near the harvested regions could be affected by the FOX procedure. Also the possibility of bacterial infection may increase, although this can be prevented by leaving a time gap between the procedures.

5. The time involved in punching and harvesting follicles with FUE is definitely more as compared to follicular unit transplants.

Follicular units for minimally invasive hair restoration references

  • Rassman WR, Bernstein RM, McClellan R, Jones R, Worton E, Uyttendaele H. Follicular unit extraction: minimally invasive surgery for hair transplantation. Dermatol Surg. 2002 Aug;28(8):720-8. PMID: 12174065
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