Follicular Unit Extraction for Hair Transplantation: An Update

Abstract

Follicular unit extraction (FUE) is a hair transplantation technique that uses small punches (0.8-1 mm in diameter) to extract the follicular units (FUs). Though initially the technique was not widely accepted because of the difficulty of extracting intact follicular units with such small punches, it has since gained in popularity due mainly to rising patient demand, the availability of better instrumentation and greater surgical skill acquired from experience. It is now a recognised alternative to follicular unit transplantation (FUT), a technique based on harvesting the FUs from a strip of tissue. Among the advantages of FUE are less post-procedural discomfort in the donor zone and the barely visible scarring from the punches. However, FUE is a more laborious, time-consuming procedure that involves a long learning curve for the surgeon.

Full text

Actas
Dermosifiliogr.
2017;108(6):532---537
PRACTICAL
DERMATOLOGY
Follicular
Unit
Extraction
for
Hair
Transplantation:
An
Update夽
F.
Jiménez-Acosta,∗I.
Ponce-Rodríguez
Clinica
Mediteknia
de
Dermatología
y
Trasplante
Capilar
,
Las
Palmas
de
Gran
Canaria,
Spain
Received
14
August
2016;
accepted
24
February
2017
Available
online
11
June
2017
KEYWORDS
Follicular
unit
extraction;
Hair
transplant;
Follicular
unit
hair
transplantation
Abstract
Follicular
unit
extraction
(FUE)
is
a
hair
transplantation
technique
that
uses
small
punches
(0.8-1
mm
in
diameter)
to
extract
the
follicular
units
(FUs).
Though
initially
the
tech-
nique
was
not
widely
accepted
because
of
the
difficulty
of
extracting
intact
follicular
units
with
such
small
punches,
it
has
since
gained
in
popularity
due
mainly
to
rising
patient
demand,
the
availability
of
better
instrumentation
and
greater
surgical
skill
acquired
from
experience.
It
is
now
a
recognised
alternative
to
follicular
unit
transplantation
(FUT),
a
technique
based
on
harvesting
the
FUs
from
a
strip
of
tissue.
Among
the
advantages
of
FUE
are
less
post-procedural
discomfort
in
the
donor
zone
and
the
barely
visible
scarring
from
the
punches.
However,
FUE
is
a
more
laborious,
time-consuming
procedure
that
involves
a
long
learning
curve
for
the
surgeon.
©
2017
Elsevier
Espa˜
na,
S.L.U.
and
AEDV.
All
rights
reserved.
PALABRAS
CLAVE
Extracción
de
unidades
foliculares;
Trasplante
de
pelo;
Trasplante
de
unidades
foliculares
Actualización
del
método
Follicular
Unit
Extraction
(FUE)
del
trasplante
de
pelo
Resumen
La
follicular
unit
extraction
(FUE)
es
una
técnica
de
trasplante
capilar
que
utiliza
punches
de
peque˜
no
diámetro
(0,8-1
mm)
para
extraer
las
unidades
foliculares.
Aunque
en
sus
primeros
a˜
nos
tuvo
escasa
aceptación
debido
a
la
dificultad
en
extraer
unidades
foliculares
intactas
con
un
punch
tan
peque˜
no,
la
FUE
se
ha
popularizado
y
es
ya
una
alternativa
a
la
técnica
clásica
de
la
tira
(FUT).
Entre
los
motivos,
la
cada
vez
mayor
demanda
por
parte
de
los
pacientes
y
la
mayor
habilidad
de
los
cirujanos
en
las
extracciones
al
contar
con
mejor
instrumental
y
más
experiencia.
Entre
las
ventajas
de
la
FUE
destaca
la
reducción
de
molestias
postoperatorias
en
la
zona
donante
y
el
aspecto
muy
poco
visible
de
las
cicatrices
puntiformes
residuales.
Sin
embargo,
la
FUE
requiere
una
mayor
laboriosidad,
aumentando
el
tiempo
operatorio,
y
una
larga
curva
de
aprendizaje
por
parte
del
cirujano.
©
2017
Elsevier
Espa˜
na,
S.L.U.
y
AEDV.
Todos
los
derechos
reservados.
夽Please
cite
this
article
as:
Jiménez-Acosta
F,
Ponce-Rodríguez
I.
Actualización
del
método
Follicular
Unit
Extraction
(FUE)
del
trasplante
de
pelo.
Actas
Dermosifiliogr.
2017;108:532---537.
∗Corresponding
author.
E-mail
address:
fjimenez@mediteknia.com
(F.
Jiménez-Acosta).
1578-2190/©
2017
Elsevier
Espa˜
na,
S.L.U.
and
AEDV.
All
rights
reserved.

Follicular
Unit
Extraction
for
Hair
Transplantation:
An
Update
533
Introduction
Seven
years
ago
in
this
journal,
we
published
a
review
of
the
technique
for
hair
transplant
using
follicular
units
(FU).1
Although
the
basic
concepts
of
hair
transplant
regarding
the
design
of
the
frontal
hairline
and
implantation
in
the
recep-
tor
zones
described
in
that
review
are
still
applicable,
very
significant
changes
have
occurred
in
the
method
of
extrac-
tion
of
the
FUs
from
the
donor
area
(known
as
follicular
unit
extraction
[FUE]),
which
justify
this
update.
These
days,
the
majority
of
transplant
surgeons
use
2
techniques
indistinctly,
the
classic
strip
technique,
also
known
as
follicular
unit
transplant
(FUT)
or
strip
harvest-
ing,
and
the
FUE
technique,
though
popularity
of
the
FUE
technique
and
patient
demand
has
increased
as
it
is
a
much
less
invasive
method
and
this
is
perceived
by
the
patient.
In
this
update
we
describe
the
general
features
of
the
FUE
technique
and
its
advantages,
disadvantages,
and
con-
troversies.
Concept
of
Follicular
Unit
Extraction
FUE
is
an
FU
transplant
technique
in
which
extraction
of
the
FUs
from
the
donor
area
is
performed
using
a
punch
with
a
diameter
of
approximately
1
mm.
In
the
FUT
technique,
the
FUs
are
harvested
from
a
surgically
excised
strip
of
skin
using
a
stereomicroscope
whereas,
in
the
FUE
technique,
FU
extraction
is
performed
blind,
directly
from
the
donor
area,
using
a
cylindric
punch,
guided
only
by
the
direction
of
the
hair
shafts
as
they
emerge
through
the
skin
surface.
It
must
therefore
first
be
understood
that
FUE
differs
from
FUT
only
in
the
method
of
FU
extraction;
the
implantation
process
in
the
recipient
area
is
identical
in
the
2
methods.
FUE
is
similar
to
the
punch
grafting
technique
described
by
Okuda2,3 in
1939
and
Orentreich4in
1959,
the
main
dif-
ference
being
the
size
of
the
punch
used
for
the
extraction.
Whilst
Okuda
used
punches
of
2.5
to
3
mm
and
Orentreich
punches
of
4
mm
(containing
10
to
20
hairs
per
punch),
the
ones
in
FUE
are
much
smaller,
because
the
aim
is
to
extract
only
FUs
(1
to
4
hairs
per
punch).
The
first
article
on
FUE
was
published
in
2002
by
Rass-
man
et
al.5In
its
early
years,
the
technique
was
not
widely
adopted
by
transplant
surgeons,
mainly
because
of
the
dif-
ficulty
of
extracting
intact
FUs
with
such
a
small-diameter
punch.
However,
over
the
past
decade,
after
its
challenging
initiation
in
which
few
surgeons
believed
it
would
become
established
as
an
alternative
to
the
strip
technique,
FUE
has
grown
in
popularity.
There
are
several
reasons
for
this:
increased
patient
demand;
improved
surgeon
proficiency
in
the
extractions,
acquired
through
greater
experience
and
the
availability
of
better
instruments;
results
that,
in
the
hands
of
experienced
surgeons,
are
comparable
to
those
of
the
strip
technique;
and
greater
interest
of
physicians
new
to
this
field
to
learn
the
technique,
as
FUE
is
a
method
that
does
not
require
microscopy
or
technicians
trained
in
graft
dissection.6
Instruments
Employed
in
Follicular
Unit
Extraction
The
FU
extraction
process
using
the
FUE
technique
involves
2
actions:
the
circular
incision
with
the
punch
around
the
FU
to
Table
1
Follicular
Unit
Extraction
Instruments.
Punches
Sharp
punches
Titanium
(www.mediquipsurgical.com)
Cole
serrated
punch
(www.coleinstruments.com)
Ertip
punch
(Turkish)
(www.ertipmedical.com)
Ring
punch
(Dr.
Roberto
Trivellini)
Blunt
punches
Hex
punch
(flat
tip)
(www.harrisfueinstruments.com)
Hybrid
punches
Hybrid
trumpet
punch
(www.devroyeinstruments.com)
Motorized
devices
SAFE
System
(www.harrisfueinstruments.com)
CDD-Vortex
and
PCID
(www.coleinstruments.com)
WAW
system
(www.devroyeinstruments.com)
Mamba
(Dr.
Roberto
Trivellini)
Ertip
FUE
micromotor
(www.ertipmedical.com)
Dr.
Jack’s
E-FUE
device
(Robbinsinstruments.com)
4D
FUE
(folliculartech.com)
Smartgraft
Neograft
liberate
it
from
the
adjacent
dermal
tissue;
and
extraction
of
the
FU,
usually
performed
with
forceps.
The
circular
incision
with
the
punch
is
the
most
difficult
and
delicate
part
of
the
extraction.
The
first
instrument
used
to
perform
the
incisions
in
FUE
was
the
traditional
1-mm
skin
biopsy
punch.
The
problem
was
that
the
only
guide
available
to
the
surgeon
to
direct
the
punch
was
the
angle
of
the
hair
as
it
emerged
through
the
skin.
The
punch
must
cut
around
the
whole
FU,
which
is
formed
of
follicles
4
to
5
mm
deep.
As
the
FUs
are
not
rigid
structures
but
can
subtly
change
angle,
irreversible
damage
due
to
follicle
transection
was
very
common.
Because
of
this,
early
attempts
were
made
to
extract
the
FUs
using
larger
punches
(1.25
mm,
1.5
mm,
and
up
to
2
mm),
but
this
forfeited
the
concept
of
natural
and
undetectable
FU
transplant
and
furthermore,
the
scars
left
by
the
punches
in
the
donor
area
were
larger
and
were
visible.
Today,
FU
extraction
using
the
FUE
technique
is
per-
formed
with
punches
between
0.8
and
1.15
mm
in
diameter,
the
most
widely
used
being
0.9
mm.
Instruments
used
in
FUE
can
be
divided
into
3
types:
manual
(Fig.
1A),
motorized
(Fig.
1B),
and
the
robotic
arm
(Table
1).
With
the
manual
system,
the
surgeon
introduces
the
tip
of
the
punch
by
hand
and
makes
the
incision
around
the
follicular
unit.
With
the
motorized
systems,
the
punch
is
introduced
into
a
handpiece
held
by
the
surgeon
and
attached
to
a
motor
that
rotates
or
oscillates
the
head
of
the
punch
at
a
given
number
of
revolutions.
With
the
robotic
system,
the
surgeon
selects
the
UF
to
be
extracted
on
a
screen
and
the
robotic
arm
makes
the
circular
incision
around
the
unit.
The
Artas
System
(Restoration
Robotics,
San
Jose,
California,
US)
is
the
only
robot
manufactured
and
marketed
exclusively
for
FUE.7,8
A
wide
variety
of
punches
are
available
commercially,
dif-
fering
in
the
design
of
the
punch
tip.
They
are
classified
into
sharp
punches,
blunt
punches,
and
hybrid
punches
(Table
1).
Sharp
punches
have
greater
cutting
ability,
while
the
blunt
and
hybrid
punches
are
better
for
tissue
dissection.9---11The
extraction
technique
varies
according
to
the
type
of
punch

534
F.
Jiménez-Acosta,
I.
Ponce-Rodríguez
Figure
1
FUE
systems.
A,
Manual
punch.
Extraction
of
the
follicular
unit
requires
align-
ment
of
the
punch
with
the
angle
and
direction
of
emergence
of
the
hair
shaft,
which
must
be
kept
in
the
center
of
the
punch.
B,
Tw o
motorized
systems:
the
SAFE
device
by
Harris
(HSC
Devel-
opment,
Colorado,
US)
(1)
and
the
Vortex
device
by
Cole
(Cole
Instruments,
Georgia,
US)
(2).
employed,
as
we
explain
in
the
following
section.
In
the
com-
ing
years,
new
punches
will
appear
on
the
market,
designed
to
facilitate
extraction
of
the
FU
and
reduce
the
percentage
of
transected
follicles
to
minimum
acceptable
levels,
simi-
lar
to
those
of
the
strip
method
(less
than
5%
to
10%).
The
Artas
system
uses
a
blunt
punch
that
slides
within
a
sharp
punch.
In
the
authors’
opinion,
the
instruments
are
very
impor-
tant,
but
so
is
the
surgeon’s
experience
and
expertise.
There
are
surgeons
who
only
use
manual
sharp
punches
and
achieve
results
as
good
as
surgeons
who
use
motorized
systems
with
blunt
or
hybrid
punches.
Results
thus
depend
not
only
on
the
type
of
instrument
but
also
on
the
surgeon.
Correct
Extraction
of
Follicular
Units
Using
Follicular
Unit
Extraction
To
extract
FUs
with
FUE,
the
punch
must
be
aligned
with
the
direction
of
emergence
of
the
hair
shaft,
which
must
remain
in
the
center
of
the
punch
(Fig.
2).
The
use
of
high-
power
magnification
glasses
(4-5x)
is
important
because
they
make
greater
precision
possible
in
the
extraction.
With
mod-
ern
punches,
the
hair
must
be
cut
to
a
length
of
1
to
2
mm
to
see
the
angle
of
emergence;
however,
new
punches
not
Figure
2
Incisions
made
with
the
punch
around
the
follicular
unit,
with
the
hair
in
the
center
of
the
surface
of
the
punch
sections.
yet
available
commercially
are
being
developed
to
per-
mit
extractions
with
long
hair.
The
angle
of
emergence
of
the
hair
changes
depending
on
the
area
of
extraction.
The
hair
emerges
at
a
more
acute
angle
in
the
temporal
region
and
at
the
borders
of
the
scalp.
One
of
the
rec-
ommended
techniques
to
make
the
follicle
adopt
a
more
vertical
position
and
thus
facilitate
extraction
is
to
inject
saline
solution
(tumescence)
immediately
prior
to
incision
with
the
punch.12
The
depth
to
which
the
punch
should
be
introduced
varies
depending
on
whether
a
sharp,
blunt,
or
hybrid
punch
is
being
used.
Sharp
punches
are
usually
introduced
to
a
depth
of
2.5
to
3
mm;
deeper
than
this
(below
the
level
of
inser-
tion
of
the
arrector
pili
muscle),
the
deeper
segments
of
follicles
in
anagen
diverge,
increasing
the
risk
of
transec-
tion
(Figs.
3
and
4).
Blunt
and
hybrid
punches,
because
of
their
greater
dissecting
and
lesser
cutting
effects,
can
be
introduced
deeper
(>
4
mm)
with
less
risk
of
transection.
However,
blunt
punches
have
a
higher
risk
of
pushing
the
graft
into
the
dermis
(buried
grafts).10
Advantages
and
Disadvantages
of
Follicular
Unit
Extraction
One
of
the
novelties
of
FUE
has
been
the
possibility
to
extract
FUs
from
other
body
areas.
This
is
useful
in
patients
in
whom
the
donor
area
of
the
scalp
has
a
low
density
of
FUs,
as
often
occurs
in
patients
who
have
undergone
a
number
of
previous
transplants.
The
area
of
body
hair
most
commonly
used
is
the
beard,
especially
the
subman-
dibular
region
(Fig.
5).
Other
areas
from
which
follicles
can
be
extracted
are
the
chest,
abdomen,
pubis,
legs,
and
axillas
(Table
2).13,14
One
undeniable
disadvantage
of
FUE
is
that
the
pro-
cedure
is
very
laborious
and
demanding
on
the
surgeon.
Depending
on
the
surgeon’s
expertise,
it
can
take
1.5
to
3
hours
to
obtain
1000
grafts
using
FUE,
making
this
is
a
very
surgeon-dependent
technique.
Most
surgeons
limit
sessions
of
FUE
to
a
maximum
of
1500
to
2000
FUs
per
day
so
as
not
to
excessively
prolong
operating
times.15 In
the
experience
of

Follicular
Unit
Extraction
for
Hair
Transplantation:
An
Update
535
Figure
3
Punches
with
a
sharp
tip
should
only
be
introduced
to
a
depth
of
2
to
3
mm
to
minimize
the
risk
of
follicle
transec-
tion.
Blunt
and
hybrid
punches
can
be
introduced
to
a
greater
depth
(>
4
mm)
a:
Sebaceous
gland.
Figure
4
Follicular
units.
A,
Normal,
undamaged.
B,
Partial
transection
of
2
follicles.
C,
Complete
transection
of
the
follicular
unit.
the
authors,
when
2000
or
more
FUs
need
to
be
extracted,
it
is
preferable
to
do
this
on
2
consecutive
days
not
only
to
limit
operating
times
but
also
to
minimize
potential
damage
to
the
grafts.
Choosing
Between
Follicular
Unit
Extraction
and
the
Strip
Technique
Almost
any
patient
who
is
a
candidate
for
strip
transplant
can
also
be
a
candidate
for
the
FUE
procedure
(Fig.
6).
However,
there
are
situations
in
which
the
choice
between
Figure
5
Beard
as
the
donor
area;
1100
extractions
per-
formed
using
the
sharp
0.9-mm
Cole
punch
in
the
Vortex®
motorized
system
(Cole
Instruments,
Georgia,
US).
Table
2
Advantages
and
Disadvantages
of
the
Follicular
Unit
Extraction
Technique.
Advantages
of
Follicular
Unit
Extraction
Reduction
of
postoperative
discomfort
and
of
donor
area
healing
time
Almost
imperceptible
pinpoint
scars
Disadvantages
of
Follicular
Unit
Extraction
Slower,
more
laborious
technique
that
is
more
demanding
on
the
surgeon
Requires
shaving
of
the
donor
area
before
performing
extractions
Finer
and
more
delicate
follicular
units
(higher
risk
of
damage
during
implantation)
Table
3
Preferences
for
Use
of
Follicular
Unit
Extraction
or
the
Strip
Technique.
Preference
for
Follicular
Unit
Extraction
Patients
with
very
short
hair
Young
patients
with
a
small
recipient
area
Patients
with
considerable
tension
in
the
scalp
skin
Correction
of
scars
from
a
previous
transplant
performed
using
the
strip
technique
Preference
for
the
strip
technique
Sessions
of
more
than
2500
follicular
units
in
a
single
day
Patients
who
do
not
want
to
shave
their
hair
for
the
operation
techniques
can
be
important
(Table
3).
For
example,
in
young
patients
with
small
recipient
areas,
FUE
gives
much
more
freedom
to
cut
the
hair
very
short
in
the
future
and
also
allows
additional
sessions
to
be
performed,
when
nec-
essary,
without
obliging
the
patient
wear
long
hair
to
cover
the
linear
scar
of
the
strip.
However,
patients
who
do
not
wish
to
cut
their
hair
very
short
for
the
operation
prefer
the
strip
technique,
as
the
linear
scar
will
be
covered
by
the
remaining
hair.
FUE
is
also
indicated
particularly
when
scars
from
a
previous
strip
transplant
cause
tension
in
the
scalp
skin.
Additionally,
FUE
is
very
useful
to
correct
hypertrophic

536
F.
Jiménez-Acosta,
I.
Ponce-Rodríguez
Figure
6
Good
candidate
patient
for
either
follicular
unit
extraction
(FUE)
or
the
strip
technique.
This
patient
received
2000
transplanted
follicular
units
using
the
FUE
method
with
the
sharp
0.95-mm
Cole
punch
in
the
Vortex
system
(Cole
Instru-
ments,
Georgia,
US).
A,
Before
transplant.
B,
Twenty-four
hours
after
follicular
unit
extraction.
C,
Result
a
year
after
the
intervention.
scars
from
a
previous
transplant
performed
using
the
strip
technique.16
Controversies
in
Follicular
Unit
Extraction
Many
patients
have
the
mistaken
idea
that
the
FUE
tech-
nique
does
not
leave
scars,
as
has
been
stated
on
some
websites
and
internet
blogs.
This
is
not
the
case.
Any
extrac-
tion
performed
with
a
punch,
however
small,
will
leave
a
Figure
7
Hypopigmented
pinpoint
scars
in
the
donor
area
of
a
patient
who
underwent
follicular
unit
extraction
with
a
blunt
0.9-mm
punch
(Harris
SAFE
system,
HSC
Development,
Colorado,
US).
Figure
8
Excessive
number
of
extractions
causing
thinning
of
the
hair
in
the
donor
area
leading
to
a
moth-eaten
appearance.
pinpoint
scar.
These
scars
are
usually
very
hard
to
see,
even
with
very
short
hair,
but
this
is
not
necessarily
the
case
in
all
patients
(Fig.
7).
One
of
the
most
debated
aspects
of
FUE
is
damage
to
the
donor
area
when
a
very
large
number
of
extractions
are
performed.
In
other
words,
what
is
the
maximum
number
of
extractions
that
can
be
taken
from
the
donor
area
without
the
damage
becoming
clinically
visible?
In
theory,
taking
into
account
that
most
individuals
have
an
FU
density
between
70
and
80
FUs
per
square
centimeter
and
that
up
to
15
to
20
FUs
per
square
centimeter
can
be
extracted
in
each
session,
it
is
estimated
that
the
maximum
recommended
limit
is
of
approximately
3000
to
4000
FU
extractions
per
session.15 However,
after
several
sessions
of
FUE,
each
one
with
thousands
of
extractions,
the
donor
area
can
be
left
with
a
very
low
hair
density
and
acquire
a
moth-
eaten
appearance
(Fig.
8).
It
is
also
important
to
perform
the
extractions
uniformly
across
the
whole
donor
area,
so
as
not
to
leave
some
areas
with
a
lower
density
than
others.
Finally,
some
experts
still
doubt
that
growth
of
the
FUE
grafts
is
the
same
as
is
achieved
with
the
strip
technique.17

Follicular
Unit
Extraction
for
Hair
Transplantation:
An
Update
537
The
controversy
arises
because
FUs
extracted
using
FUE
are
typically
smaller
(skeletonized),
while
those
dissected
by
microscopy
are
thicker
and
include
more
of
the
surrounding
adipose
tissue.
Perhaps
the
poor
growth
observed
in
some
cases
of
FUE
occurs
because
the
smaller
FUs
require
more
delicate
handling
during
implantation,
as
there
is
a
higher
risk
of
damaging
the
hair
bulbs
and
dermal
papillas,
the
most
sensitive
part
of
the
follicle.
Controlled
studies
comparing
graft
survival
after
extraction
using
each
technique
need
to
be
performed
to
resolve
this
controversy.
How
to
Learn
and
Start
to
Practice
FUE
The
appearance
of
FUE
has
led
to
increased
interest
in
learn-
ing
hair
transplant
techniques.
However,
FUE
has
a
long
learning
curve
and
sufficient
knowledge
cannot
be
acquired
in
a
weekend
workshop.
Furthermore,
as
there
is
a
signifi-
cant
delay
until
results
are
seen
(between
6
and
12
months),
surgeons
can
take
a
long
time,
sometimes
years,
to
develop
the
competence
required
for
this
procedure
and
to
imple-
ment
appropriate
quality
controls.
One
of
the
best
ways
to
learn
FUE
is
to
attend
the
annual
workshops
and
conferences
organized
by
the
International
Society
of
Hair
Restoration
Surgery
(www.ISHRS.org).
This
Society
also
offers
1-
or
2-year
fellowships
in
a
number
of
accredited
clinics.
Conclusions
Ideally
the
transplant
surgeon
should
know
and
be
able
to
perform
the
2
techniques
(FUE
and
strip)
to
be
able
to
use
the
most
appropriate
one
for
each
patient
and
not
the
most
convenient
one
for
the
surgeon.
The
most
interesting
advantages
of
FUE
compared
to
FUT
are
the
reduction
in
postoperative
discomfort
in
the
donor
area
and
the
lower
visibility
of
the
pinpoint
scars.
The
main
disadvantages
of
FUE
are
that
it
is
more
laborious,
leading
to
longer
operating
times,
and
its
long
learning
curve.
Conflicts
of
Interest
The
authors
declare
that
they
have
no
conflicts
of
interest
References
1.
Jimenez
F,
Ponce
I.
Técnica
actual
del
trasplante
de
pelo
de
unidades
foliculares.
Actas
Dermosifiliogr.
2010;101:291---306.
2.
Okuda
S.
Clinical
and
experimental
studies
of
transplantation
of
living
hairs.
Jpn
J
Dermatol
Urol.
1939;46:135---8.
3.
Jimenez
F,
Shiell
RC.
The
Okuda
Papers:
An
extraordinary
---but
unfortunately
unrecognized---
piece
of
work
that
could
have
changed
the
history
of
hair
transplantation.
Exp
Dermatol.
2015;24:185---6.
4.
Orentreich
N.
Autografts
in
alopecias
and
other
selected
der-
matologic
conditions.
Ann
NY
Acad
Sci.
1959;83:463---79.
5.
Rassman
WR,
Bernstein
RM,
McClellan
R,
Jones
R,
Worton
E,
Uyttendaele
H.
Follicular
unit
extraction:
Minimally
inva-
sive
surgery
for
hair
transplantation.
Dermatol
Surg.
2002;28:
720---8.
6.
Rassman
W,
Pak
J,
Kim
J.
Follicular
unit
extraction:
Evolution
of
a
technology.
J
Transplant
Technol
Res.
2016;6:158.
7.
Avram
MR,
Watkins
SA.
Robotic
follicular
unit
extraction
in
hair
transplantation.
Dermatol
Surg.
2014;40:1319---27.
8.
Berstein
RM,
Wolfeld
MB.
Robotic
follicular
unit
graft
selection.
Dematol
Surg.
2016;42:710---4.
9.
Cole
J.
An
analysis
of
follicular
punches,
mechanics,
and
dynam-
ics
in
follicular
unit
extraction.
Facial
Plast
Surg
Clin
North
Amer.
2013;21:437---47.
10.
Harris
JA.
The
SAFE
system:
New
instrumentation
and
methodol-
ogy
to
improve
follicular
unit
extraction
(FUE).
Hair
Transplant
Forum
Int.
2004;14:157.
11.
Devroye
J.
Powered
FUE
extraction
with
the
short
arc
oscilla-
tion
flat
punch
FUE
system
(SFFS).
Hair
Transplant
Forum
Int.
2016;26:34---6.
12.
Zontos
G,
Rose
PT,
Nikiforidis
G.
A
mathematical
proof
of
how
the
outgrowth
angle
of
hair
follicles
influences
the
injury
to
the
donor
area
in
FUE
harvesting.
Dermatol
Surg.
2014;40:
1147---50.
13.
Umar
S.
The
transplanted
hairline:
Leg
room
for
improvement.
Arch
Dermatol.
2012;148:239---42.
14.
Umar
S.
Body
hair
transplant
by
follicular
unit
extrac-
tion:
My
experience
with
122
patients.
Aesthetic
Surg
J.
2016;36:1101---10.
15.
Ors
S,
Ozkose
M,
Ors
S.
Follicular
unit
extraction
hair
transplan-
tation
with
micromotor:
Eight
years
experience.
Aesthetic
Plast
Surg.
2015;39:589---96.
16.
Harris
JA.
Follicular
unit
extraction.
Facial
Plast
Surg
Clin
North
Am.
2013;21:375---84.
17.
Beehner
ML.
FUE
vs
FUT-MD:
Study
of
1,780
follicles
in
four
patients.
Hair
Transplant
Forum
Int.
2016;26:160---1.