A Safe and Effective Lip Augmentation Method: The Step-by-Step Φ (Phi) Technique

Abstract

The shape and fullness of the lips are essential in facial aesthetics. We describe a safe injection technique of hyaluronic acid (HA), based on the well-known golden number Φ (phi), for lip augmentation.

Methods:
The name given to that procedure is "the step-by-step Φ technique." Firstly, "step-by-step" because we never inject more than 1-1.5 ml of HA in 1 session, and "phi" because we apply the golden ratio 1.618-broadly known as Φ-to identify the proper points for injection. Using a specific caliper, we identified 3-4 points in each upper half of the lip. We injected 0.01-0.05 ml of lower concentration (25 mg/g) HA in these particular areas of the upper lip, from the vermillion border into the vermillion. We took into consideration the existing lip volume to decide the proper amount of HA to be injected in every single site, as lips are often asymmetric. On the lower lip, we use the same caliper to identify again the proper injection points. If necessary, the next 2 sessions are performed at an interval of 15-30 days.

Results:
Our technique was performed in 833 patients. Mean age was 30.2 years (range: 18-72 years), and most patients were very satisfied. With this technique, we avoid severe complications such as arterial embolism or venous occlusion and unnatural results. The most common side effects were swelling, redness, and mild pain.

Conclusion:
The step-by-step Φ technique is safe, easy to learn and perform, and can provide natural results in lip augmentation.

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Cosmetic
From the Kosmesis Aesthetic Plastic Surgery Center, Athens, Greece.
Received for publication September 29, 2020; accepted October 28,
2020.
Presented at 13th Hespras, October 16–19, 2019, Athens, Greece; at
Hands-on-Course on hyaluronic acid injections using the “Step by
Step Φ Technique,” Bucharest, 2019; at ISAPS Athens, November
24, 2018; and at IMCAS Bangkok, July 13–15, 2018.
Copyright © 2021 The Authors. Published by Wolters Kluwer Health,
Inc. on behalf of The American Society of Plastic Surgeons. This
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Commons Attribution-Non Commercial-No Derivatives License 4.0
(CCBY-NC-ND), where it is permissible to download and share the
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DOI: 10.1097/GOX.0000000000003332
INTRODUCTION
Lips are located at the center of the lower face and,
together with the eyes and nose, comprise “the triangle
of beauty.”1,2 According to the American Society of Plastic
Surgeons, there is tremendous and ongoing growth in
lip augmentation procedures. Specically, lip injections
between botulinum toxin A injections and a variety of soft
tissue llers were part of nearly 2.6 million injection pro-
cedures in 2018, with a total increase of 312% between
2000 and 2017.3–5 Lip injections can be quick, lunchtime
procedures, but the results from less-qualied providers
can often be obvious and unappealing.6 The vast major-
ity of severe complications are imputable to unauthorized
non-medic injectors,7–11 and thus, there is an emerging
need in this skyrocketing ller industry for well-trained
board-certied plastic surgeons. This article explains and
provides an easy way to master a safe and effective lip aug-
mentation technique, the step-by-step Φ (phi) technique,
based on and inspired by the Greek golden ratio of beauty.
MATERIALS AND METHODS
In total, 833 patients underwent lip augmentation from
June 2013 to March 2019, in our private clinic located in
Athens, Greece. Patients enrolled for this study were aged
from 18 to 72 years, were in general good health, and were
having lip augmentation for the rst time. Pre-procedure
and post-procedure frontal, prole, and oblique view
photographs and videos of the patients were obtained.
Following fundamental references to lip anatomy, the
golden ratio, and lip aesthetics, we describe the step-by-
step Φ technique.
Evangelos Keramidas, MD,
FEBOPRAS
Stavroula Rodopoulou, MD,
FEBOPRAS
Maria-Ioanna Gavala, MD
Background: The shape and fullness of the lips are essential in facial aesthetics.
We describe a safe injection technique of hyaluronic acid (HA), based on the well-
known golden number Φ (phi), for lip augmentation.
Methods: The name given to that procedure is “the step-by-step Φ technique.”
Firstly, “step-by-step” because we never inject more than 1–1.5 ml of HA in 1 ses-
sion, and “phi” because we apply the golden ratio 1.618—broadly known as Φ—to
identify the proper points for injection. Using a specic caliper, we identied 3–4
points in each upper half of the lip. We injected 0.01–0.05 ml of lower concentra-
tion (25 mg/g) HA in these particular areas of the upper lip, from the vermillion
border into the vermillion. We took into consideration the existing lip volume to
decide the proper amount of HA to be injected in every single site, as lips are often
asymmetric. On the lower lip, we use the same caliper to identify again the proper
injection points. If necessary, the next 2 sessions are performed at an interval of
15–30 days.
Results: Our technique was performed in 833 patients. Mean age was 30.2 years
(range: 18–72 years), and most patients were very satised. With this technique,
we avoid severe complications such as arterial embolism or venous occlusion and
unnatural results. The most common side effects were swelling, redness, and mild
pain.
Conclusion: The step-by-step Φ technique is safe, easy to learn and perform, and
can provide natural results in lip augmentation. (Plast Reconstr Surg Glob Open
2021;9:e3332; doi: 10.1097/GOX.0000000000003332; Published online 2 February 2021.)
A Safe and Effective Lip Augmentation Method:
The Step-by-Step Φ (Phi) Technique
LWW
ORIGINAL ARTICLE

PRS Global Open • 2021
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Key Points in Vascular Lip Anatomy
The inferior (lower lip) and superior labial (upper lip)
arteries arise from the facial artery approximately 1.5 mm
superolateral to the oral commissure.12 Anatomic varia-
tions are commonly the rule and vary among 3 positions:
the superior labial artery is located 78.1% between the
orbicularis oris and the oral mucosa, 17.6% intramuscu-
larly, and 2.6% between the skin and the muscle, whereas
the inferior labial artery is located 78.1% between the orbi-
cularis oris and the oral mucosa, 17.3% intramuscularly,
and 1.7% between the skin and the muscle.13 These arter-
ies form a circular vascular network around the mouth
and are ordinarily located posterior to the wet-dry border;
thus, treating this area should be avoided.14 Moreover,
the superior labial artery is more frequently supercial in
the midline; thus, extra caution is needed when treating
cupid’s bow area. Both in the upper and lower lip, median
areas are important danger zones, whereas paramedian
areas are considered safer locations when injecting the
ller supercially.13 A general rule to ensure safety at most
times, as stated in many anatomical studies, is puncturing
the lips from the vermillion border and to never inject
ller deeper than 2.5 mm at any point.12,14–16
The Metric System
Our technique was developed by using a specic cali-
per (as shown in Fig.1) and the golden ratio as a guide.
The golden ratio or phi number is symbolized by the
Greek letter Φ, as a contribution to Phidias (Φειδίας), the
sculptor and architect of the Parthenon, and many other
classical era Greek masterpieces. The Phi number, rst
described as the golden ratio by the Greek mathematician
Euclid in the 10th of his 13 books of Elements, is an irra-
tional number of the order 1.618033988 and is obtained
when a line a + b is sectioned such that (a + b)/a = 1.618.
Over centuries, evidence of its presence in a wide variety
of mathematical, biological, and natural systems has been
recorded, derived from the idea that it represents the
perfect beauty.17 It has also appeared throughout history
in many artistic masterpieces and architectural creations
such as Da Vinci’s paintings and the Parthenon, and it is,
in brief, an attempt to mathematically and geometrically
interpret the captivating mystery of beauty.18,19 Undeterred
by its subjective nature,20 we applied this number in our
way: to identify the proper points for injection.
Lip Aesthetics
The basic principles of ideal lips include the following:
a pronounced cupid’s bow, a well-dened vermillion bor-
der, upturned corners of the mouth, fullness in the center
that fades out toward the mouth, symmetry between the
left and the right sides, philtrum length of 12–15 mm, a
thinner upper lip protrusion compared with the larger
lower lip, and a balanced upper and lower lip. Specically,
on the frontal view, the ratio of ideal upper lip to lower
lip is determined by the golden ratio, which is 1:1.6.1,21,22
However, it cannot be ignored that lip aesthetics change
throughout history, eras, and races; however, voluptuous
lips with an accentuated volume are delightful and very
popular as well.2,23 Specically, the current contemporary
preferred female-lip ratio has recently been found to be
1:1 in White women.23 To clarify what is considered the
best lip ratio among patients, we conducted a survey in
2008 to evaluate their preferences compared with experts’
opinions and use it as a guiding tool during the patient–
doctor consultation process. Figure 2 shows a photo-
shopped image of different lips ratios, and each patient
(Greek, white women) could choose her preferred lip
ratio. Among 700 participants, 70% chose the 0.85:1 ratio,
20% the 1:1, and 6% the 0.65:1. In 2019 we started the
same survey again, which is still ongoing, aiming to exam-
ine the stability of these results throughout time.
The Step-by-Step Φ Technique
Denition
The step-by-step Φ technique consists of 2 essential
parts. The rst one is the “step-by-step” because we inject
gradually and only 1–1.5 ml of hyaluronic acid (HA) in
each session. The next session is 15–30 days after, and the
third, if needed, is 15–30 days after the second session.
The second part of our technique is the “Φ” because we
apply the number Phi ratio to identify the proper injec-
tion points.
Patient Preparation
• Obtain signed informed consent;
• Discuss the desirable lip ratio using practical examples
(Fig.2);
• Obtain photographs/videos;
• Position patient in a comfortable supine or semi-sitting
position;
• Administer anesthetic lidocaine/tetracaine cream
mixture;
• Disinfect using chlorhexidine solution.
Marking the Lips
A specic phi caliper (9 cm × 2 cm, manufactured by
Golden Mean Calipers) that can expand to t an individu-
al’s lips is required. The injection points are marked with
the following order: the caliper is placed at the outer cor-
ner of the upper right side of the lip, with the total length
of the caliper extending from the outer corner to the right
philtrum ridge, and then 3 injection points are marked. If
Fig. 1. The Φ caliper.

Keramidas et al. • The Step-by-Step Lip Augmentation
3
more volume is needed and depending on the patient’s
lip length, the caliper is placed at the right side of the
upper lip, with its length extending from the outer corner
of the lip up to the previously marked middle injection
point. Then, a fourth injection point is marked between
the 2 initial marked points. The same marking is repeated
for the upper left side of the lip. For the lower lip, a line
is drawn from the philtrum columns to the lower lip, an
area that could be injected at the end to achieve a better
projection, and we repeat the same 4 steps, leaving the lips
with a total of 12 or 16 needle entry points: 6 or 8 on the
upper and 6 or 8 on the lower lip, as shown in Figure3.
Typically, 12 points of injection (6 in the upper and 6 in
the lower lip) are needed.
The Injection Technique
• Between various dermal llers, HA is the most
commonly used because it is considered safe and
effective.24,25 In our patients, we used HA with the fol-
lowing characteristics: cross-linking 3/6, concentration
25 mg/g.
• When aiming to restore the volume, the injection is
performed into the vermillion through the vermillion
border. Insert a 30-gauge needle at each marked
point of the vermillion border at an oblique angle
(30 degrees) no more than 2.5-mm deep to avoid lip
vessels. To maintain the right needle depth measure,
bend the needle at 2.5 mm. Proceed slowly. At each
needle’s point, small boluses of 0.05–0.1 ml of HA are
slowly injected with a total amount of 1–1.5 ml in both
lips per session. Injection of HA is performed in a ret-
rograde linear threading fashion.
• When aiming to restore the shape, the injection is per-
formed into the vermillion border. At this point, it is
important to avoid injections into the white roll because
the hydrophilic HA leads to a blunted lip margin pos-
sibly due to the different histological characteristics of
this area. Insert a 30-gauge needle at each marked point
of the vermillion border at a parallel angle. This deli-
cate part of the lip is more prone to unnatural results;
thus, we strongly recommend using a modest amount of
0.02–0.4 ml of HA. Injection of HA is performed slowly
in a retrograde linear threading fashion.
• Assess the lips for any asymmetry depending on the
individual’s anatomy and, if needed, inject 0.05 to
0.1 ml in the intended area.
A helpful tool in the injection technique is categoriz-
ing the lips according to their needs and tissue proper-
ties. Although many validated classications exist,26–28 we
proposed a simple categorization method to organize and
simplify the lip shaping process:
1. Normal-volume lips
Delightful volume (vermillion) and denition (vermillion
border) exist but patients are requesting a more projected
view. Injection is performed into the vermillion to enhance
volume and correct any asymmetries. Reassessment is
Fig. 2. Photoshopped images of dierent lip ratios for patient consultation.
Fig. 3. Marking the injection points.

PRS Global Open • 2021
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scheduled after 15 days and if needed more volume is added.
Do not inject more than 1–1.5 ml of HA in each session.
2. Thin lips
Patients present with hereditary acquired atrophic lips,
opting for a luscious pout.Volume is usually insufcient in
the upper lip and less frequently in both lips or in the lower
lip. The goal is to achieve the desired result while respect-
ing soft tissue’s expansion properties. To accomplish that,
address the ratio by injecting into the vermillion of the
thinner lip 0.5–1 ml of HA in the rst session. As soon as
the desired ratio is acquired, inject 0.5–1 ml of HA in both
lips usually in the second or third session. Sessions interval
is 30 days so that the tissues adjust to the placed HA and
continue until the desired volume is achieved. If any asym-
metries are present, we correct them by injecting more HA
on the proper side of the lip. The next goal is dening and
shaping the lips with the same step-by-step philosophy, by
injecting into the vermillion border a moderate amount
(0.02–0.4 ml) of HA. Reassess after 15 days and, if needed,
add more HA to establish a better denition.
3. Aged thin lips
Vermillion border disappearance, soft tissue volume
loss, lengthening of the upper lip, and vertical lines are
only some aging signs. These patients desire a more youth-
ful appearance. Similarly to thin lips shaping procedure,
we prefer to rst correct the volume by injecting HA into
the vermillion and then correct the shape by injecting HA
into the vermillion border. Again, the use of 0.5–1 ml in
each session, every 30 days is essential because lips have
limited expansion properties. In contrast to thin lips,
aged lips should be injected with less HA (up to 0.5 ml)
in each session; thus, more sessions are needed to achieve
the desired natural results. Moreover, even from the rst
session, HA can be injected into the vertical lines of the
upper lip.
• Assess at all times for any signs of intravascular injec-
tions: immediate blanching, extreme pain. If present,
treat with hyaluronidase, massage, warm compresses,
and aspirin administration until the capillary rell is
back to normal.24,29,30
Aftercare
• Lightly massage the treated area.
• Cleanse the skin with saline 0.9%.
• Apply ice packs for a few minutes to reduce pain and
the risk of edema and bruising.
• Patients were advised to avoid excessive exercise, hot tem-
peratures, and/or hot beverages for the next 24 hours.
• The next session is 15 days after, and the third, if
needed, 30 days after the rst one.
(See Video 1 [online], which demonstrates the tech-
nique in 3D animation.)
RESULTS
An estimated 833 patients underwent the “step-by-step
Φ technique’’ lip augmentation from June 2013 to March
2019. Patients’ medical records were reviewed retrospec-
tively. The mean age was 30.2 years, with a range of 18–72
years.
Approximately 3 ml of HA (range: 1–12)was injected into
each patient. The majority of patients required 3 sessions to
achieve the optimum result spaced in 1-month interval. The
time until the desired result was achieved ranged between 1
and 16 months. The results were evaluated immediately after
the procedure, 15 days later to assess the results, correct any
asymmetries, and schedule the next session, if needed. From
a total of 833 patients, the 623 continuously revisited our
ofce every year or two to repeat the treatment in different
degrees to maintain their results. All 833 patients revisited
our ofce at least one more time and were asked to ll out a
written questionnaire. We evaluated their results using a GAIS
5-point scale evaluation system. In total, 92.4% of patients
marked the results as exceptional, 7.56% as very improved
or improved, 0% as no result, and 0% as worse. Figures4–7
show representative participants.
In terms of the adverse effects, minimal pain, mild
swelling, and a fair degree of redness were observed.
Severe bruising was observed in 8 patients, mild bruis-
ingin 15 patients, and all developed bruising in the upper
lip. Severe swelling occurred in 10 patients and mildswell-
ingin 50 patients. However, no severe complications such
as infection, vascular occlusion, necrosis, discoloration, or
granuloma formation occurred.
Regarding the duration of the results, as per our expe-
rience, after using 3 syringes of 1 ml, the desired results
can be long-lasting, and the mean time for a patient to
revisit our ofce to maintain the initial result was 12–18
months.
Case 1
Lip category: normal lips
Number of sessions: 2
Total amount of HA: 2 ml
Time period to achieve the desired result: 2 months
Figure4 shows a participant representing normal-vol-
ume lips.
Case 2
Lip category: thin lips
Number of sessions: 9
Total amount of HA: 9 ml
Time period to achieve the desired result: 12 months
Figures5 and 6 show a thin lips category patient’s aug-
mentation process. (See Video 2 [online], which displays
the patient talking and smiling, demonstrating natural lip
movement.)
Case 3
Lip category: aged lips
Number of sessions: 2
Total amount of HA: 2 ml
Time period to achieve the desired result: 2 months
Figure 8 shows an aged-lips category participant.

Keramidas et al. • The Step-by-Step Lip Augmentation
5
DISCUSSION
There are quite a few remarkable techniques that
already exist concerning lip augmentation.22,24,31 However
we feel that the “step-by-step Φ” technique is designed to
assist junior practitioners to simplify and senior practitio-
ners to optimize their own lip augmentation procedure.
This method has a short learning curve and it is easy and
safe for even a resident plastic surgeon to master. As per
our experience, the most challenging parts of lip aug-
mentation are maintaining safety at all times; nding the
proper injection points; choosing the appropriate HA and
the amount that should be injected in each marking point
and in total in each session; planning the frequency of
the sessions until the desirable goal in ratio, volume, and
shape is achieved; and, last but not least, consulting the
patient.
Safety is established by: keeping the needle at 2.5-mm
depth when injecting through the vermillion border at an
oblique angle (30 degrees), by avoiding injecting poste-
rior to the wet line border, and by slowly injecting the HA
in a retrograde manner. Slow injection in each marked
point helps prevent intravascular injections of a signi-
cant amount of HA. If an intra-arterial injection is admin-
istered accidentally, immediate acute pain and blanching
will warn us to stop the procedure. Also, using a needle
(instead of a cannula)—especially for beginners—helps
the injector to become familiar with the most precise
placement of HA.32
Fig. 4. Participant with normal-volume lips category before (A) and 2 months after applying the tech-
nique (B).
Fig. 5. Monthly spaced lip augmentation stages on a typical thin lips category participant.
Fig. 6. Image of the patient in Figure5 just before her rst session of HA lips injection (A) using the step-
by-step Φ technique and 18 months following her last session (B).

PRS Global Open • 2021
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The Φ caliper provides a practical and reproducible
way of nding and marking the correct injection points.
The golden ratio has proved its aesthetic value and has
had numerous applications throughout the centuries. By
using the Φ caliper in a modern, different way, we identi-
ed which points/parts of the lips—if enhanced—would
atter them the most. As per our experience, a standard-
ized lip-marking pattern with xed injection sites, that can
be applied even in quite asymmetric lips, not only allows
safe aesthetic outcomes, but also provides condence to
the injector in training. However, if any asymmetries are
present, customization, according to the individual’s anat-
omy, can be achieved by injecting only 0.05–0.1 ml in the
intended areas.
Classifying patients in normal-volume, thin, and aged
lips is a useful tool that helps the physician planning the
procedure. In normal-volume lips, we propose enhanc-
ing volume by injecting into the vermillion. In thin lips,
we prefer to address rst the ratio by injecting into the
thinner lip, then the volume by injecting into the vermil-
lion, and lastly the shape by injecting into the vermillion
border when necessary.33 In aged lips, we proceed as in
thin lips, but we also inject HA into the vertical upper
lip lines in a particularly modest manner to avoid distor-
tions. Moreover, each target group has different reasons
for undergoing this cosmetic procedure, and the injector
should take these into consideration to better educate the
patients, manage their expectations2,6,21 and set accord-
ingly their aesthetic goals.21,34
Obtaining the desirable volume at the adequate time
is essential and it is summarized in the step-by-step part of
this technique. The delicate lip tissue should be treated
with respect, mildness, and caution. Gentle manipula-
tions are recommended, and overlling in a single session
should be avoided because it increases the risk of compli-
cations and creates a counterfeit, “sausage,” or “duck-like”
appearance. In each marking point, it is advised to inject
no more than 0.05–0.1 ml of HA, and in each session,
the maximum amount of HA should be no more than
1–1.5 ml.6 These 2 measures of quantity could allow the tis-
sues, especially in thin and aged lips, to gradually “expand”
and provide space for the HA to settle.21 The ller proper
adjustment provides natural lip movements and an overall
natural appearance to the lips, but prevents premature lip
philtrum prolongation. Undetectable results are eventu-
ally achieved by gradually injecting HA in separate 15- to
30-day sessions, according to our experience, especially in
thin and aged-lips categories.
Considering the ratios of the perfect lips, the deni-
tion of ideal proportions has been attempted since ancient
times, but the perception of beauty depends on aesthetic
trends, which are only a snapshot in time and may be
subject to change. Moreover, social media preferences of
how the lips should look vary in different countries and
cultures; thus, golden ratios and ideal proportions are
not universally applicable and need to be seen in this
context.2,35 However, we believe they can serve as a very
helpful tool, especially in achieving aesthetically pleasant
and natural results. In our technique, we use our survey’s
photoshopped image as a guide when discussing lip aug-
mentation with our patients. The majority nd it pleas-
ing and helpful in managing their expectations regarding
the immediate and long-term procedure’s aftermath.
Tailoring treatment to individual patient’s needs is one of
the most important steps in every technique; after all, the
relative attractiveness of the lips is a matter of just a few
millimeters or even less.
It is our hope that this article will help physicians, who
are just starting to learn how to perform lip augmentation
procedures or want to update their technique, to treat their
patients effectively and in an aesthetically pleasing way.
CONCLUSIONS
We present the step-by-step Φ technique as a safe and
effective method to create attractive lips. There is no sin-
gle way to achieve the intended results; however, anatomi-
cal knowledge and the use of the appropriate technique
are essential for an optimal and safe result.
Evangelos Keramidas, MD, FEBOPRAS
Kosmesis Aesthetic Plastic Surgery Center
Ethnikis Antistaseos 9-11
Chalandri, Athens 15232
Greece
E-mail: plastker@yahoo.com
PATIENT CONSENT
Patients provided written consent for the use of their images.
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7
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