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
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
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
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
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
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.
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.
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.