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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5214_Библиотеки_им_академика_М_И_Перельмана.pdf
118
Fig. 4.43 Pain from angular artery irritation. (With kind
permission of MANIAMIND)
Fig. 4.44 Entry point of chin ller with cannula
F. Chin Filler
(i) Cannula
(a) Useful when injection is needed over
a large area.
(b) Create an entry point on the side of
the chin line or just below the chin
tip, insert the cannula deeply, and
proceed after touching the bone
(Fig.4.44).
(c) The deep layer is a safe area free of
dangerous vessels, and bruising during the chin ller procedure is minimal. However, large vessels may
pass through the center of the chin in
some cases, so gentle manipulation
is required to minimize vascular
damage.
(ii) Needle
(a) Useful when injection is needed in a
narrow area.
(b) Deep layer injections are relatively
safe.
(c) Perform an aspiration test before
injecting.
4 Basic Techniques forFiller Procedures
4.6 Considerations
forMechanical Properties
ofFiller Injection Process
4.6.1 Understanding Injection
andEjection Pressure
forSafety Procedures
4.6.1.1 Injection andEjection Pressure
The increased frequency of medical procedures,
particularly those involving injectable llers, has
heightened the focus on procedural safety. This
chapter explores the dynamics of injection and
ejection pressures during the administration of
hyaluronic acid (HA) llers. The foundation of
this discussion is based on a pivotal study by
author published in 2020 in the Journal of
Cosmetic Dermatology (https://doi.org/10.1111/
jocd.14064).
Although it is generally considered safe to
perform procedures with low injection pressure,
it is difcult to assert this as a denitive truth
without understanding the corresponding ejection pressure. Therefore, the researchers measured the injection pressure values under various
conditions and the corresponding ejection
pressures.
Injection force and ejection force refer to the
manual efforts exerted during the injection process and the expulsion of ller from the syringe,
respectively. Injection pressure and ejection pressure refer to the pressures exerted during these
processes. Understanding and controlling these
forces and pressures are essential for safe and
effective ller procedures (Fig.4.45).
The researchers conducted a comprehensive
assessment involving 12 combinations of four
different HA llers with varied rheological properties. They used needles of different gauges
(30 G, 27 G, and 25 G) to evaluate the corresponding ejection pressures under controlled
injection forces.
4.6.1.2 Key Methodological Steps
Selection of Fillers: Four HA llers with distinct
rheological properties were chosen.
4.6 Considerations forMechanical Properties ofFiller Injection Process
119
Needle Gauges: Three needle gauges (30 G,
27G, and 25G) were used to determine the
effect on injection force and ejection
pressure.
Measurement: The ejection pressures corre-
sponding to various injection forces were
measured using a standardized injection
model.
4.6.1.3 Study Result
The study revealed a clear relationship between
needle gauge, injection force, and ejection pressure. Key ndings include:
Needle Gauge Impact: The highest and lowest
injection forces were observed with 30G and
25G needles, respectively.
Injection Force Correlation: High ejection pres-
sures were achieved by administering HA llers under high injection forces, consistent
with the expected ejection force.
Pressure Comparison: Regardless of the injec-
tion force, ejection pressure often exceeded
the vascular pressure at the point of vessel
entry, highlighting potential risks.
4.6.1.4 Conclusion ofStudy
These ndings demonstrate that even if the injection pressure is low, the ejection pressure can be
much higher than blood pressure. This means
that in ller injection environments created with
low injection pressure, it is still not possible to
prevent vascular accidents in situations where
intra-vascular ller injection occurs (e.g., when a
cannula or needle is already inserted into a blood
vessel).
Therefore, for a safe ller procedure, practitioners should conrm the location of blood vessels based on anatomical knowledge and exercise
gentle manipulation to ensure that needles or
cannulas do not penetrate the vessel wall and
inject ller inside the blood vessel.
4.6.2 Various Physical Conditions
That Determine Injection
andEjection Force
andPressure
4.6.2.1 Factors Related totheInjection
Force
Filler injections involve the use of needles or
cannulas to implant materials into the soft tissues of the face or body. The ease of these procedures is signicantly inuenced by the injection
force. Lower injection force generally facilitates
smoother procedures. This chapter delves into
the mechanisms that dictate injection and ejection pressures, drawing insights from key studies, including the 2024 publication by Seung
Min Oh et al. in Plastic and Reconstructive
Surgery Global Open and the 2020 study by
Yongkoo Lee etal. in the Journal of Cosmetic
Dermatology.
According to the research, there are four conditions that can reduce the injection force
(Table4.3) (Figs.4.45, 4.46, 4.47, and 4.48).
So to make ller procedures more comfortable
by reducing the injection force, it is important to
carefully consider and optimize the above four
factors in the procedure environment.
4.6.2.2 Factors Related totheEjection
Force
Factors related to ller ejection pressure include
both the injection force and the resistance of the
surrounding tissue.
Table 4.3 Four conditions that can reduce the injection
force
Smaller diameter of the syringe (Fig.4.46)
Low viscosity of ller (Fig.4.47)
Shorter length of the needle or cannula (Fig.4.47)
Larger inner diameter of the needle or cannula
120
Fig. 4.45 Injection and ejection force
4 Basic Techniques forFiller Procedures
Fig. 4.47 Filler viscosity vs injection force
When considering ller ejection pressure,
both the injection force and tissue resistance play
crucial roles. An optimal injection process
involves:
Balancing the injection force involves using
the minimum necessary force to reduce ejection
pressure without compromising the delivery of
the ller. Assessing tissue resistance requires
understanding the type of tissue being treated and
adjusting the injection technique accordingly to
minimize resistance.
By carefully considering both the injection
force and the surrounding tissue resistance, practitioners can better control ejection pressure,
enhancing the safety and effectiveness of ller
procedures.
Fig. 4.46 Syringe diameter vs injection force
High tissue resistance occurs in denser or
more brous tissues, requiring higher ejection
pressure to overcome the resistance and deliver
the ller. This can lead to potential complications
such as tissue trauma or an increased risk of intravascular injection. In contrast, low tissue resistance is found in less dense, more pliable tissues,
which allows for lower ejection pressures.
4.7 Filler Molding andFiller
Degradation Test
4.7.1 Filler Molding
A. Fillers are semisolid materials with uidity.
Due to this characteristic, injection is possible through thin tubes such as needles or cannula. After injection into the tissue, it is
restored to its original form and functions as
an implant. The physical properties of the
Needle Lengthe [mm]
Injection force
4.7 Filler Molding andFiller Degradation Test
Fig. 4.48 Needle length
vs injection force
121
25G
11 12
ller are determined by the aforementioned
rheology values. In particular, these gures
relate to elasticity and viscosity, expressed in
terms of G′, G″, and G*.
B. There are two main uses of llers. The rst is
depression correction of the dermis, and the
second is increasing volume of the face.
Clinically, there are many more cases and
types of llers to increase the volume of the
face.
C. When ller is used to increase the volume of
a facial area, it is mainly injected in the deep
layers. The ller must not only resist the pressure exerted on the face, but also the pressures exerted by the facial muscles. From a
clinical point of view, llers with low elasticity have low resistance to external forces. The
shape of the rst injection is not well maintained and changes easily. Low elastic and
soft llers are easily made into the desired
shape after ller injection. However, the
shape created is not well maintained and
changes or migrates easily.
D. On the other hand, elastic and hard llers are
difcult to inject and require more force to
produce the desired shape. However, once
you mold the shape, deformation is not easy
and thus the shape is well maintained. Highly
elastic llers are generally preferred for the
purpose of increasing volume by injecting
13 14 15 16 17
into deeper layers. When injecting a ller into
the nose, a ller that can maintain a good
shape and resistance to external forces is suitable. However, the greater the elasticity of the
ller, the greater the possibility of vascular
compression by the product. This in turn
increases the risk of developing ischemic side
effects. Depending on the skill or preference
of the physician, the ller with the appropriate rheology should be selected.
E. On the other hand, if the ller is to be injected
into a shallow layer and then evenly spread
out, a less elastic ller is preferred. A representative indication would be for infraorbital
dark circles. This is because it should be
injected just below the skin and then spread
evenly. However, well spreading llers are
easily changed by external forces. Due to the
high probability of ruggedness after the procedure, patients who have undergone the
procedure should be thoroughly trained in
postoperative care.
F. Each ller company produces a variety of ll-
ers by adjusting the cross-linking ratio or by
adjusting the concentration of hyaluronic
acid. Therefore, relatively high elastic llers
are recommended for volumizing through
deep layer injection and low elastic llers for
wrinkle correction through shallow layer
injection.
122
4 Basic Techniques forFiller Procedures
Filler procedure considerations should
include:
(i) Is the area to be treated an area that requires
a molding process?
(ii) Is it exposed to pressure from external forces
or facial expressions after the procedure?
(iii) How will the change in volume of the ller
itself after the procedure affect the outcome
of the procedure?
For example, in the case of nasal dorsum,
asymmetry is likely to occur when injecting without sufciently considering symmetry during the
procedure. If asymmetry occurs, the molding
process should be used to correct it after the procedure. From the initial start of injection, it is
good practice to perform molding concurrently
while watching for asymmetry.
The nasal dorsum area tends to be deformed
due to facial expressions of the eyebrows and
nose itself and wearing glasses/sunglasses after
the procedure. The patient’s facial expression
should be carefully observed during the design
and consultation before the procedure, along with
predicting the possible change in the shape of the
ller after the procedure. During the examination
of the patient, if the patient has high utilization of
glabella or nasal muscles, pretreatment with botulinum toxin is necessary.
It must also be noted that llers change in volume after being injected into the body. In the case
of biphasic llers, the free HA component is
absorbed between 2–3days, leaving less than the
volume actually injected. After the procedure, the
result is satisfactory, but a patient may complain
that the ller disappeared after 1–2weeks.
Even when the tissue pressure of the area to be
injected is high, it is difcult to maintain the
appearance immediately after the procedure due
to the compressing phenomenon after the procedure. For example, if you are performing a procedure to correct the depression of the nose, it is a
good idea to evaluate the tissue pressure in the
area before the procedure. It is possible to estimate the pressure through a pinch maneuver.
If the operator feels that the pressure at the site
to be treated is high, the ller shape is not likely
to remain after the procedure and the area is
likely to sink again. One should decide whether
to use a harder ller or just accept a mild
correction.
Some monophasic llers contain mannitol.
Mannitol acts as an antioxidant, draws water as a
polymer, and acts as a diuretic. The physician
must understand and select the characteristics of
each product. This will produce better results and
will eliminate the need for unnecessary additional procedures. Even if the same procedure is
performed using the same technique, the result
may vary depending on the characteristics of the
product.
When treating with antioxidant llers containing mannitol, the scope of the procedure should
be well designed and planned.
G. Molding process
(i) Molding of pre-tarsal roll
The pre-tarsal roll area is a difcult area to
mold. When molding, it is good practice
to aim for the hard tissue to hold the
product inside. However, during the pretarsal roll area procedure, there is a risk
of pressure (and product) passing to the
eye when molding. Therefore, it is necessary to mold using special equipment
(Figs.4.49 and 4.50).
(ii) Molding of the lateral cheek area
When injecting ller into the lateral cheek
area, the operator should inject at the correct
depth. The brous connective tissue in the subSMAS layer must be dissected using the cannula. This will prevent the lateral cheeks from
becoming bumpy after ller injection. The pinch
maneuver is used to determine the depth of the
SMAS and the location of the parotid gland,
assisting the dissection of the sub-SMAS layer.
The physician should not completely dissect the
entire site to be injected. Instead, it should be
partially dissected to just weaken the connective
tissue. The dissection area should be the entire
area designed to inject ller. After dissection,
ller is injected and molding is performed.
Specially designed equipment may be used
(Figs.4.51 and 4.52).
4.7 Filler Molding andFiller Degradation Test
Fig. 4.49 Special equipment used for molding pre-tarsal roll
123
Fig. 4.50 How to use a guider. (With kind permission of DAEHAN medbook)
4.7.2 Filler Degradation Test
uronidase in the event of adverse events
will be discussed in detail later.
A. Hyaluronic acid ller and hyaluronidase
(i) The physician can solve side effects or
unsatisfactory procedures of hyaluronic
acid ller injection by dissolving the
ller. In particular, hyaluronidase can be
used for side effects caused by intravascular ller injection. The use of hyal-
(ii) There are two types of hyaluronic acid
ller. The rst is a biphasic type, and the
second is a monophasic type. Whether
these two types of llers differ in their
dissolution is worth investigating. The
situation in which the ller must be dissolved is often an emergency. Therefore,
124
Fig. 4.51 Equipment for lateral cheek area molding
Fig. 4.52 Lateral cheek molding
understanding the characteristics of the
dissolution process according to
hyaluronic acid ller type is meaningful
in that it helps physicians effectively treat
side effects. The authors tested how
biphasic and monophasic llers respond
to hyaluronidase. In addition, we tested
how polycaprolactone llers respond to
hyaluronidase.
B. Organization of the Experiment
(i) The hyaluronidase used in the experi-
ment consisted of 1500units in one vial.
Generally, hyaluronidase used in the
United States or Europe is 150–200units
per vial. The hyaluronidase used in this
4 Basic Techniques forFiller Procedures
experiment is higher in dosage than the
product used in the United States or
Europe.
(ii) It was mixed with 2cc of saline solution
and prepared at a concentration of
75units/0.1cc.
(iii) After placing 1cc of ller in a Petri dish,
we mixed various concentrations of
hyaluronidase or saline solution.
C. Biphasic ller dissolution experiment.
(i) Different concentrations of hyaluronidase
and saline were mixed with 1cc of biphasic ller.
(a) Biphasic ller 1cc + hyaluronidase
0.1cc (75units) (Fig.4.53)
– 0.1 cc 75 units of hyaluronidase
hardly dissolve 1 cc of biphasic
ller.
(b) Biphasic ller 1 cc+ hyaluronidase
0.5cc (375units) (Fig.4.54)
– Hyaluronidase 0.5cc (375units) is
insufcient to dissolve 1 cc of
biphasic ller.
(c) Biphasic ller 1cc + hyaluronidase
1cc (750units) (Fig.4.55)
– For dissolving 1 cc of biphasic
ller, a dose of hyaluronidase 750
unit (1cc) can be considered sufcient. Of course, the experimental results invitro and invivo are
4.7 Filler Molding andFiller Degradation Test
Fig. 4.53 Before mix versus after 5min of mix
125
Fig. 4.54 Before mixing versus after 5min of mix
Fig. 4.55 Before mixing versus after 5min of mix
126
4 Basic Techniques forFiller Procedures
known to be different. This is
because the degree of degradation
by hyaluronidase will vary invivo
and invitro.
(d) Biphasic ller 1 cc + Saline 1 cc
(Fig.4.56)
– When biphasic ller is mixed with
saline, it is mixed homogeneously
and reaches a new equilibrium. At
rst glance it appears to be dissolved, but not in actuality. This
shows that the dose of hyaluronidase is important in dissolving the
ller (especially in the case of
biphasic ller), but the amount of
saline mixed together is also
important. This experiment shows
two functions of saline. The rst is
the dilution effect of the ller
component, and the second is the
effect of lowering the viscoelastic-
ity of the ller.
D. Monophasic ller dissolution test
(i) Various concentrations of hyaluronidase
and saline were mixed with 1cc of monophasic ller.
(a) Monophasic ller 1cc + hyaluroni-
dase 0.1cc (75units) (Fig.4.57)
Fig. 4.56 Before mix versus after 5min of mix
Fig. 4.57 Before mix versus after 5min
4.7 Filler Molding andFiller Degradation Test
127
– The amount of hyaluronidase is
insufcient to dissolve the ller. It
is different from when dissolving
the biphasic ller. It is observed
that hyaluronidase does not mix
uniformly with the ller and is
present in a separate state.
(b) Monophasic ller 1 cc+ hyaluroni-
dase 0.5cc (375units) (Fig.4.58)
– It can be seen that 0.5cc 375units
of hyaluronidase cannot completely dissolve 1cc of monophasic ller. Since the action time of
the hyaluronidase in the body lasts
more than 5min, the actual dissolution invivo will proceed further.
However, assuming an emergency,
the 375 units of hyaluronidase
were insufcient to dissolve 1cc
ller immediately.
(c) Monophasic ller 1cc + hyaluroni-
dase 1cc (750units) (Fig.4.59)
– The results are quite different from
the dissolution of the biphasic
ller shown above. Biphasic llers
become homogeneously mixed
with the hyaluronidase solution,
whereas monophasic llers sepa-
rate from the hyaluronidase solu-
tion. At 5 min, there were no
signicant effects, and after 1h of
observation, dissolution proceeded
Fig. 4.58 Before mix versus after 5min
Fig. 4.59 Before mix versus after 5min vs after mix 1 h