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Size
of donor area and tissue to be collected
The donor strip of skin is then taken to a preparation room. Here
the skin is dissected into grafts ready for implantation. In modern
clinics the donor skin is dissected by a team of highly trained
assistants. There can be three to five, and sometimes even seven
or eight, technicians dissecting the skin simultaneously. Arguably
the best, hair transplant clinics have their technicians divide
up the donor skin using stereo dissecting microscopes.
Using the binocular microscope, the assistants subdivide the single
strip into thin slivers 2 to 3 follicular units wide. These individual
slivers are then further dissected into individual follicular units.
The tissue is handled with fine forceps and
cut with small scalpels.
The tissue is held with forceps on one side, the scalpel is angled
parallel to the angle of the hair follicles, and the skin is cut
to the side of a follicular unit. If the technicians see significantly
damaged hair follicles or hair follicle missing a bulb, they will
cut these away from the follicular units and discard them. They
cut off much of the non hair bearing scalp skin around the hair
follicles. The smaller the follicular unit the quicker and better
it will heal into the skin once it is implanted. It is also less
likely to leave a visible scar. The grafts, separated by numbers
of hairs, are kept in chilled saline until the time of implantation,
separated by hair number. The mean number of hairs per graft is
2.2 to 2.3, so most grafts contain 2 or 3 hairs. Follicular units
of ones and twos will be used towards the front to make the hair
line, while follicular units of three and four hair follicles will
be used to fill in behind the implanted hair line.
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Above
is a typical stereo microdissecting microscope set up for
dissecting hair follicles. The box to the left is a cold
light supply, the light is guided through optical fibers
in the flexible metal arms that are positioned either side
of the microscope to feed light onto the dissecting dish
under the microscope.
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The use of dissecting stereo microscopes during hair transplant
graft dissection has only recently been advocated as a means of
reducing hair follicle damage and improving graft growth. The first
publication on their use was in 1994 although the top hair transplant
doctors were using microscopes for dissection since about 1990.
If a dissecting microscope is not used to cut up the donor skin
strip, it has been found that it is much more likely that hair
follicles will be cut and damaged. Using the microscope, technicians
can see the hair follicles much better and so are less likely to
cut through a hair follicle. One study evaluated the prevalence
of hair follicle transection in grafts prepared with and without
the dissecting stereomicroscope. Half as much transection (10%
vs 20%) was noted in grafts prepared with microscopes, suggesting
their use may be associated with less hair follicle trauma and
improved hair growth (Cooley 1999).
To be fair to those surgeons that do not have their technicians
use microscopes when they cut up the donor skin into grafts, some
studies have shown that implanted hair follicles can grow even
after sustaining mild to moderate damage and that sometimes cutting
the hair follicles in two can actually lead to two hair follicles
being produced from one! The issue is how much damage a hair follicle
can sustain before it becomes so damaged that it cannot grow. Those
follicles from which more than a third of the lower follicle and
bulb region have been cut will not grow. In light of this, dissecting
hair follicles under a microscope is probably the safest way to
ensure that the dissected hair follicles are healthy and will survive
and grow after implantation. One study that compared implanted
hair follicles that had been dissected with microscopes or loupes
suggested microscope use increased the hair yield by as much as
20% (Berstein 1998).
Dissecting the hair follicles under a microscope also enables
a relatively new development in hair restoration to take place – follicular
unit grafting. Hair follicles often grow in natural clusters of
twos, threes, and fours. Using the stereo dissecting microscope,
the hair follicles in the donor skin can be divided into their
natural “follicular units” and implanted in these units.
This makes for a much more natural looking transplant result. So
in short, microscopic dissection results in grafts that are smaller
and contain a minimum amount of scalp skin. These grafts can be
placed into smaller recipient sites, and this theoretically allows
for a greater hair density, faster healing, and less trauma to
any existing hairs in the implant recipient area. In addition,
transplanting grafts with a limited amount of skin around them
minimizes any changes in pigmentation and texture of the recipient
scalp skin. So with the donor skin now dissected into follicular
units the next part of the procedure, the implantation, can begin.
Dissection
of the donor skin strip to make grafts ready for implantation
references
- Bernstein RM, Rassman WR. Dissecting microscope versus magnifying
loupes with transillumination in the preparation of follicular
unit grafts. A bilateral controlled study.
Dermatol Surg. 1998 Aug;24(8):875-80. PMID: 9723053
- Cooley JE, Vogel JE. Follicle
trauma and the role of the dissecting microscope in hair transplantation.
A multicenter study. Dermatol
Clin. 1999 Apr;17(2):307-12, viii; discussion 312-3. PMID: 10327300
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