INTRODUCTION
Having beautiful and harmonious breasts is a legitimate right that cannot be overlooked1. Hence, the concept of breast reconstruction is within the scope of repair surgeries
for a special group of patients, including those with breast cancer2.
Breast cancer remains among the most common cancers in women, trailing only non-melanoma
skin cancer and representing about 25% of new cancer cases each year in the country3. International oncology, mastology, and plastic surgery entities combat breast cancer
with the objective of restoring the patient's dignity and feminine identity4,5.
Among the various surgical breast reconstruction techniques, the following stand out:
transverse rectus abdominis muscle (TRAM) flap developed by Hartrampf, Sheflan, and
Black in 19826; the large dorsal muscle flap (or latissimus dorsi) developed by Tanzini in 19067; and breast expanders developed by Radovan in 19828. Silicone implants and lipografting are surgical options with the same indications2.
Anatomically, it is important to note that the female breast has a conical shape with
a circular base, and the apex is represented by a thinner skin structure, usually
of a more hyperchromic color in relation to the rest of the body. The presence of
the oral accommodation of the infant, called the nipple-areolar complex (NAC)1, is fundamental to a reconstructed breast since it serves three functions: lactation,
morphology (shape, size, and aesthetic proportions), and sexuality (sensitivity and
sensuality). Therefore, when approaching the theme breast reconstruction, we must
include that of the NAC2,9.
When approaching blepharoplasty, it is understood that the surgical procedure is an
aesthetic and/or reparative resolution. This procedure consists of reconstruction
of the tissues that cover the eyeball for numerous causes, such as congenital or tumor
diseases, and flaccid disorders of eyelid structures related to age that affect or
reduce the patient's visual field. However, in addition to functional repair, it also
attenuates aging-related stigmas in the upper third of the face and is a cosmetic
surgery in high demand by female patients, especially the elderly10,11,12,13,14.
Histologically, the eyelid skin is also similar to the areolar skin because it is
thin and has an epithelium classified as stratified squamous keratinized with considerable
melanin presence in the basal blade and the absence of hair, making it a good donating
area for the creation of a "neo-areola"15.
Given such theoretical, statistical, and anato-histological concepts, the eyelid skin
is an excellent graft option for areolar reconstruction, which we will demonstrate
here by addressing aspects already mentioned in the literature, evaluating cases corrected
using the proposed technique, and analyzing the psychological aspect of all patients
studied.
OBJECTIVE
General Objective
To demonstrate a viable option for areolar reconstruction using bilateral total eyelid
skin grafts.
Specific Objectives
Analyze the applicability of the technique; and
Compare its effectiveness to those of other reconstruction methods.
METHODS
Study Design
This retrospective descriptive clinical study included patients who underwent surgery
performed by a male senior plastic surgeon and assistant professor of the plastic
surgery service of the Santa Casa de Misericórdia of Rio de Janeiro, Brazil (former
38th ward).
Data collection
We surveyed the data of operated patients from a databank of digitized medical records.
All medical records with "breast reconstruction" or "reconstruction of the nipple-areolar
complex" performed by the same senior surgeon in 1995-2015 were collected.
Sample
The inclusion criteria were applied to the study sample, so our obtained data set
included medical records of patients who underwent areolar reconstruction for whom
complete pre- and postoperative color images (minimum 6 months of evolution) taken
by the institution's professional team of photographers or the senior surgeon, with
surgical descriptions, medical evolution, and telephone contact information were available.
The exclusion criteria were incomplete medical records; black and white or absent
photographs; absence of surgical descriptions or medical progress; absence of patients'
telephone contact; no areolar reconstruction during evolution; and different breast
or areolar reconstruction after breast cancer.
Photographic evaluation
Among the selected patients, 10 medical records from the "reconstructed with eyelid
skin group" and 10 medical records from "reconstructed with other techniques group"
were randomly chosen by digital drawing for a total 20 patients whose photographs
(n = 20) were subjected to macroscopic analysis by professionals.
The digital cash program "random.org - Random Integer Generator" was used to make the random drawings of the study's allocations.
The 20 photographs were presented to five male Brazilian plastic surgeons recognized
as specialists by the Brazilian Society of Plastic Surgery (SBCP) with at least 10
years of experience in breast reconstruction. We queried their satisfaction with the
neo-areolas without disclosing which were reconstructed using eyelid skin.
Among these images, photographs A, B, C, D, E, F, G, and H were used; I and J represented
areolas reconstructed with eyelid skin; and L, M, N, O, P, Q, R, S, T, and U represented
areolas reconstructed with skin of the upper internal region of the thigh and inguinal
area. The evaluators graded each photographic result on a scale from 1 to 5 points
in whole values for each photographic result considering three criteria: color; texture;
and symmetry.
Cases
In the results, five complete cases will be illustrated, showing pre- and postoperative
photographic files (some perioperative) of patients who underwent treatment using
the proposed technique of areolar reconstruction.
Application of questionnaire
Telephone contact was made with the selected patients for the administration of a
satisfaction questionnaire (Appendix 1) by the author. This questionnaire followed
the SATIS-BR satisfaction scale.
The study included only patients for whom telephone number was available in the medical
records. We did not attempt to call them more than five times in 24 hours. Patients
for whom there was no longer a medical record or there was care of others due to absence
did not participate in the study.
Surgical description
The surgical descriptions of all studied patients were analyzed for safety. This sequence
can be summarized as follows:
Dorsal decubitus;
Cushion under popliteus;
Calf electric scalpel plate;
Venoclysis in the contralateral upper limb to the mastectomized side;
General anesthesia;
Antisepsis with chlorhexidine;
Surgical drapes;
Infiltration with xylocaine 2% + adrenaline (1:200,000) + 0.9% saline solution + sodium
bicarbonate;
NAC reconstruction as follows:
Resection of bilateral upper palpebral total skin band + hemostasis + running edge
bearing suture with a 6-0 nylon;
Placement of resected skin in a solution of 0.9% saline solution;
Pitanguy's "Point A" marking in "neo-mama" + production of cutaneous flap for papilla
reconstruction + decortication of areolar area;
Skin grafting of upper bilateral palpebral skin, filling of the entire decorticated
circular area; and
Suturing with mononylon and monocryl + Brown dressing.
RESULTS
Digital medical records were available for 74 patients; of them, 33 described areolar
reconstruction using an eyelid skin graft and 41 described areolar reconstruction
using other techniques, all performed by the senior surgeon as mentioned in the methodology.
Among the 74 related cases, 58 patients underwent post-mastectomy breast reconstruction,
while 16 underwent NAC reconstructions due to total necrosis after reduction mammoplasties
performed in the service and were, therefore, excluded.
After application of the exclusion criteria, 50 medical records were selected for
the study; of them, 21 detailed reconstruction with palpebral skin and 29 involved
reconstruction using other techniques.
Of the patients who underwent breast reconstruction (n = 50), 12 were treated with
TRAM, 10 with pedicle flaps with large dorsal muscle (latissimus dorsi), and 28 with
tissue expansion (Table 1).
Table 1 - Number of cases by breast reconstruction type.
Técnicas de Rec. Mamária |
Nº de casos |
TRAM |
12 |
L. Dorsi |
10 |
Expansores |
28 |
Table 1 - Number of cases by breast reconstruction type.
The results obtained in the macroscopic evaluation by five professionals were graded
on a scale of 1 to 5 on 20 photographs (A to U) of areolar reconstructions (Table 2). Photos A to J, referring to the group of areolar reconstructions with palpebral
skin, received scores of 3-5 points. Photos H to U, reconstructions using other techniques,
also received scores of 3-5 points.
Tabela 2 - Distribuição de notas de 1 a 5 pontos para resultados de reconstrução areolar com
enxertos cutâneos de áreas doadoras variadas, através de fotografias
|
Professional 1 |
Professional 2 |
Professional 3 |
Professional 4 |
Professional 5 |
Photo A |
4 |
4 |
3 |
4 |
4 |
Photo B |
5 |
5 |
4 |
5 |
5 |
Photo C |
5 |
4 |
4 |
3 |
5 |
Photo D |
4 |
5 |
5 |
4 |
4 |
Photo E |
4 |
4 |
5 |
5 |
4 |
Photo F |
5 |
4 |
4 |
3 |
4 |
Photo G |
4 |
4 |
5 |
4 |
4 |
Photo H |
4 |
5 |
5 |
4 |
4 |
Photo I |
5 |
3 |
3 |
4 |
3 |
Photo J |
4 |
4 |
4 |
4 |
4 |
Photo L |
3 |
3 |
3 |
3 |
4 |
Photo M |
4 |
5 |
4 |
4 |
5 |
Photo N |
5 |
4 |
4 |
5 |
4 |
Photo O |
5 |
4 |
4 |
4 |
4 |
Photo P |
4 |
4 |
3 |
3 |
3 |
Photo Q |
4 |
4 |
3 |
3 |
3 |
Photo R |
3 |
5 |
4 |
5 |
4 |
Photo S |
4 |
4 |
4 |
5 |
4 |
Photo T |
5 |
4 |
4 |
3 |
3 |
Photo U |
3 |
4 |
3 |
3 |
4 |
Tabela 2 - Distribuição de notas de 1 a 5 pontos para resultados de reconstrução areolar com
enxertos cutâneos de áreas doadoras variadas, através de fotografias
The scores of the eyelid skin reconstruction group and the other graft techniques
group compared the arithmetic mean of the groups and applied a parametric and non-paired
test, Student's t-test, demonstrated that the evaluation values were equivalent between
the eyelid skin reconstruction group and the other graft techniques group with no
statistically significant intergroup difference (p = 0.1036) (Figure 1).
Figure 1 - Distribution of mean graft assessment scores.
Figure 1 - Distribution of mean graft assessment scores.
Among the results obtained from the evaluation of patient satisfaction, referring
to the areolar results, of the 50 telephone numbers registered, only 32 patients could
be contacted. Of the contacted patients, 21 were "very satisfied," 4 were "satisfied,"
4 were "indifferent," and 3 were "dissatisfied." None of the patients were "very dissatisfied."
All patients who were contacted and underwent reconstruction using eyelid skin answered
"very satisfied" or "satisfied" (Figure 2).
Figure 2 - Distribution of patients by degree of satisfaction with areolar reconstruction result.
Figure 2 - Distribution of patients by degree of satisfaction with areolar reconstruction result.
All surgery plans of breast reconstruction at the first surgery used one of the cited
techniques; at the second surgery, symmetrization and reconstruction of the NAC were
applied.
Among the complications, there were two cases of partial graft loss (less than 10%
of the grafted area), one case of hypochromia, and one case of hyperchromia (Figure 3).
Figure 3 - Distribution of complications of eyelid reconstructions.
Figure 3 - Distribution of complications of eyelid reconstructions.
Below are photos of five patients who underwent breast reconstruction and NAC reconstruction
using total eyelid skin grafts (Figures 4-8).
Figure 4 - A. Preoperative view of left breast planned for expander and nipple-areolar complex
reconstruction. B Postoperative (5 months) view of left breast reconstruction with expander and nipple-areolar
complex reconstruction using bilateral upper eyelid skin. C. Photo of nipple-areolar complex reconstruction using eyelid skin at 5 months postoperative
showing assumed coloration.
Figure 4 - A. Preoperative view of left breast planned for expander and nipple-areolar complex
reconstruction. B Postoperative (5 months) view of left breast reconstruction with expander and nipple-areolar
complex reconstruction using bilateral upper eyelid skin. C. Photo of nipple-areolar complex reconstruction using eyelid skin at 5 months postoperative
showing assumed coloration.
Figure 5 - A. Preoperative image of breast reconstruction of the left breast using a transverse
rectus abdominis muscle flap. B. Postoperative image (3 months) of mammary reconstruction using an expander and nipple-areolar
complex reconstruction.
Figure 5 - A. Preoperative image of breast reconstruction of the left breast using a transverse
rectus abdominis muscle flap. B. Postoperative image (3 months) of mammary reconstruction using an expander and nipple-areolar
complex reconstruction.
Figure 6 - A. Preoperative image of second breast reconstruction using a left transverse rectus
abdominis muscle flap. B. Postoperative image (4 years) of second breast reconstruction using a transverse
rectus abdominis muscle flap on the left with nipple-areolar complex
Figure 6 - A. Preoperative image of second breast reconstruction using a left transverse rectus
abdominis muscle flap. B. Postoperative image (4 years) of second breast reconstruction using a transverse
rectus abdominis muscle flap on the left with nipple-areolar complex
Figure 7 - A. Preoperative image of second breast reconstruction using a breast expander. B. Surgical plan of second breast reconstruction using an expander to achieve greater
symmetry along with nipple-areolar complex reconstruction. C. Perioperative view of second time mammary gland reconstruction with an expander
on the left demonstrating better symmetry and nipple-areolar complex reconstruction
with eyelid skin. D. Perioperative image of nipple-areolar complex reconstruction using palpebral skin.
E. Postoperative image (17 months) showing the nipple-areolar complex reconstruction
using eyelid skin.
Figure 7 - A. Preoperative image of second breast reconstruction using a breast expander. B. Surgical plan of second breast reconstruction using an expander to achieve greater
symmetry along with nipple-areolar complex reconstruction. C. Perioperative view of second time mammary gland reconstruction with an expander
on the left demonstrating better symmetry and nipple-areolar complex reconstruction
with eyelid skin. D. Perioperative image of nipple-areolar complex reconstruction using palpebral skin.
E. Postoperative image (17 months) showing the nipple-areolar complex reconstruction
using eyelid skin.
Figure 8 - A. Surgical plan of second breast reconstruction using an expander to increase symmetry
and reconstruct the nipple-areolar complex using left eyelid skin. B. Perioperative image demonstrating nipple-areolar complex reconstruction using eyelid
skin.
Figure 8 - A. Surgical plan of second breast reconstruction using an expander to increase symmetry
and reconstruct the nipple-areolar complex using left eyelid skin. B. Perioperative image demonstrating nipple-areolar complex reconstruction using eyelid
skin.
DISCUSSION
With the evolution of studies on mastectomy surgical techniques, the great resections
attributed by Halsted, gave rise to less radical surgeries associated with parallel
therapies, such as chemotherapy and radiotherapy, saving the thoracic muscles, and
several times, mammary skin, as in the cases of subcutaneous skin saving adenomastectomy,
when well indicated, and quadrantectomies16.
This evolution makes breast reconstruction surgeries using expanders comprise more
space in the surgeon's arsenal of operative techniques, leaving the options of autogenic
pedicle flaps as a second option due to the higher morbidity rate, which may explain
the greater number of breast reconstructions using expanders8.
Although it is a topic of great discussion, it is clear that immediate or late post-mastectomy
breast reconstruction in two surgeries or a single surgery is performed in accordance
with the surgeon's experience. The following factors are considered: 1) guarantee
of a completely resected tumor; 2) guarantee of resolved cancer disease; 3) maximum
gradual tissue expansion; 4) guarantee of rotated pedicle flap without suffering;
and 5) surgical and anesthetic time. Of the patients evaluated for breast reconstruction,
all underwent NAC reconstruction using eyelid skin in a second surgery. The senior
surgeon who performed the procedures aimed to give volume to the breast-free area
and then ensure NAC2 symmetry and reconstruction.
The evaluations of photographs by professionals showed that areolar reconstructions
with palpebral graft can present good morphological aspects compared to other reconstructions.
It cannot be said that this is a better surgical technique than the others since the
results shown in the different photographs were equivalent. However, we can state
that the proposed technique is capable of reproducing results as accepted as those
of other areolar reconstruction techniques, making it one more option within the plastic
surgeon's technical arsenal17.
Comparison of the scores assigned by professionals with the patients' answers in the
satisfaction questionnaire revealed divergences in the results. One case achieved
the highest score (5 points) by the professional and moderate satisfaction ("satisfied")
from the patient. The same occurred inversely in two cases in which professionals
assigned regular scores (i.e., 3 points) and the respective patients answered "very
satisfied." These comparisons showed possible bias due to subjective analysis of the
results, which may be linked to the professional's technical criteria and the patient's
expectations.
Another important fact is the low complication rates, which remain at 2% for hyperchromia
and hypochromia, or partial loss of less than 10% of the grafted area, seen in 4%
of the studied cases. The proportions of skin grafts to total skin were compatible
to those in the literature. It is also believed that after resection of the palpebral
skin band resulting from superior blepharoplasty, refinement of the flap resecting
connective tissue promotes better results in terms of texture and staining18,19. The psychological evaluation of selected patients revealed that the technique fills
an important social function since it is directly linked to improved self-esteem and
satisfaction with the results. Blepharoplasty performance, an aesthetic procedure,
in favor of a final reconstruction of the female anatomy, enables the technique to
provide an aesthetic improvement of its donor area, bringing signs of rejuvenation
on the upper third of the face and achieving patient satisfaction11,19.
Blepharoplasty is considered one of the most common aesthetic plastic surgeries worldwide,
with low rates of complications, most of which consist of hematomas and kemoses20. Nonetheless, Beier, Breuel, and Leffler, in 200920, showed a very low rate of complications with good to very good aesthetic results
for areolar reconstruction using compound flaps (local or contralateral nipple) with
total grafts of eyelid skin21. In 2009, Kruavit21 showed a complication rate of 3.8% post-blepharoplasty in 6215 patients over an 18-year
period.
Among the study limitations, we cite the total sample number of medical records evaluated
since it was not performed in a reference oncologic service for breast reconstruction
surgeries and because only patients operated upon by a single professional were included.
Photograph quality differed over 20 years (1995-2015) of follow-up. This is explained
by technological advances and the existence of more modern resources, which can create
a comparison bias among the professionals' grades. Another negative factor is the
low number of specific studies on areolar reconstruction from its inception to the
most commonly used techniques, hindering dissertations and subject development, unlike
papillary reconstruction techniques.
The 16 records of areolar reconstruction with eyelid skin in patients with NAC necrosis,
post-mammoplasty, were not included in the sample due to the possibility of bias of
results considering graft receptor sites in different situations.
The satisfaction questionnaire was not applied to the entire sample number due to
telephone contact being the methodology used, and some patients were not contacted
because their telephone numbers were no longer valid. This may have influenced our
results. This method is proposed for comparison of psychological characteristics before
versus after procedures due to the high demand of this procedure, and we focused on
social reinsertion22.
This study does not present itself as a pioneer in terms of technique description,
but it proved to be more extensive with a greater number of cases and additional data
than the study by Friedrich in 201323.
CONCLUSION
The results obtained in this study showed that the proposed technique is both feasible
and effective with low complication rates and high satisfaction levels. Therefore,
it provides another option in the surgeon's technical arsenal that can restore the
physical integrity of women and proposes new studies for the presentation of an operative
technique. In addition to reconstructing an integral part of the breast, it produces
aesthetic benefits in the donor area.
The proposed technique does not suffer interference, in terms of evolution, to any
of the specific types of breast reconstruction and can be applied in any situation
before surgical decision attributed by the professional.
Finally, this study concluded that, regardless of the theoretical division between
aesthetic and reconstructive plastic surgeries, given the existence of scientific
journals and specific international societies, these distances are dwindling. We note
that in this technique, cosmetic and reparative principles were used to achieve better
results.
COLLABORATIONS
CAJ
|
Analysis and/or data interpretation, Conception and design study, Final manuscript
approval, Realization of operations and/or trials, Writing - Review & Editing
|
JPF
|
Analysis and/or data interpretation, Conception and design study, Data Curation, Final
manuscript approval, Formal Analysis, Realization of operations and/or trials, Writing
- Original Draft Preparation
|
WM
|
Analysis and/or data interpretation, Formal Analysis, Software, Writing - Review &
Editing
|
JPV
|
Conception and design study, Final manuscript approval, Supervision, Writing - Review
& Editing
|
REFERENCES
1. Jaimovich CA. Mamilo hipertrófico - Contribuição ao estudo de sua reparação cirúrgica.
A técnica em "W". Rev Bras Cir Plást. 1982;72(2):123-130.
2. Ribeiro RC, Saltz R. Cirurgia da mama, estética e reconstrutora. 2ª ed. São Paulo:
Thieme Revinter; 2012.
3. Ministério da Saúde (BR). Instituto Nacional de Câncer José Alencar Gomes da Silva
(INCA). Estimativa 2016: incidência de câncer no Brasil [Internet]. Rio de Janeiro
(RJ): INCA; 2015. Disponível em: http://www2.inca.gov.br/wps/wcm/connect/tiposdecancer/site/home/mama
4. Silva LC. Câncer de mama e sofrimento psicológico: aspectos relacionados ao feminino.
Psicol Estud. 2008 Abr/Jun;13(2):239-237.
5. Cosac O, Camara Filho JPP, Barros APGSH, Borgatto MS, Esteves BP, Curado DMC, et al.
Reconstruções mamárias: estudo retrospectivo de 10 anos. Rev Bras Cir Plást. 2013
Mar;28(1):59-64.
6. Hartrampf CR, Scheflan M, Black PW. Breast reconstruction with a transverse abdominal
island flap. Plast Reconstr Surgery. 1982 Feb;69(2):216-25.
7. Tanzini I. Spora il mio nuova processo di amputazione della mammella. Riforma Medica.
1906;22:757.
8. Radovan C. Breast reconstruction after mastectomy using the temporary expander. Plast
Reconstr Surg. 1982 Feb;69(2):195-208.
9. Cunha RJC Jaimovich CA, Nogueira AJS, Lins DSMR, Nogueira CF. Reduced mastoplasty:
modified Silveira Neto's tactical maneuver for ascension of the nippleareola complex.
Arq Bras Med Nav. 1990 Sep/Dec;52(3):65-83.
10. Hahn S, Holds JB, Couch SM. Upper lid blepharoplasty. Facial Plast Surg Clin North
Am. 2016 May;24(2):119-27.
11. Ishizuka CK. Autoestima em pacientes submetidas a blefaroplastia. Rev Bras Cir Plást.
2012 Mar;27(1):31-36.
12. Saito FL, Gemperli R, Hiraki PY, Ferreira MC. Cirurgia de ptose palpebral: análise
de dois tipos de procedimentos cirúrgicos. Rev Bras Cir Plást. 2010;25(1):11-17.
13. Zanella PSM, Castro CC, Boechat CEJ, Aboudib JH. Tratamento de rugas glabelares por
abordagem transpalpebral dos músculos corrugadores do supercílio. Rev Bras Cir Plást.
2006;21(2):97-101.
14. Lessa S, Sebastiá R, Nanci M, Flores E, Sforza M. A síndrome do blefarocalásio e sua
diferenciação com dermocalásio. Rev Bras Cir Plást. 2007;22(2):89-96.
15. Sand JP, Zhu BZ, Desai SC. Surgical anatomy of the eyelid. Facial Plast Surg Clin
North Am. 2016 May;24(2):89-95.
16. Standring S. Gray's Anatomia: A base anatômica da prática clínica. 40a ed. Rio de
Janeiro: Elsevier Ltda.; 2008.
17. Rosique MJF, Arantes HL. Reconstrução do Complexo Areolopapilar e refinamentos técnicos.
In: Mélega JM, Viterbo F, Mendes FH, organizadores. Cirurgia Plástica - os princípios
e a atualidade. Rio de Janeiro: Guanabara Koogan; 2011. p. 762-66.
18. Mélega JM, Viterbo F, Mendes FH. Cirurgia Plástica - os princípios e a atualidade.
Rio de Janeiro: Guanabara Koogan; 2011.
19. Glavas IP. The diagnosis and management of blepharoplasty complications. Otolaryngol
Clin North Am. 2005 Oct;38(5):1009-21.
20. Beier JP, Breuel C, Leffler M, Bani B, Beckmann MW, Horch RE, et al. Rekonstruktion
des Mamillen-Areola-Komplexes durch lokale Lappenplastik oder "Nipple-sharing" in
Kombination mit Vollhauttransplantation aus den Oberlidern. Senologie. 2009;6(2).
21. Kruavit A. Asian blepharoplasty: an 18-year experience in 6215 patients. Aesthet Surg
J. 2009 Jul/Aug;29(4):272-83.
22. Raaf CAL, Derks EAJ, Torensma B, Honig A, Vrounenraets BC. Breast reconstruction after
mastectomy: does it decrease depression at a long-term?. Gland Surg. 2016 Aug;5(4):377-84.
23. Friedrich OL, Heil J, Golatta M, Domschke C, Sohn C, Blumestein M. Upper blepharoplasty
for areola reconstruction. Gerburshilfe Frauenheilkd. 2013 Jul;73(7):720-23.
1. Santa Casa da Misericórdia, Rio de Janeiro, Rio de Janeiro, Brazil.
2. Universidad Cientifica del Sur, Lima, Lima, Peru.
Corresponding author: João Paulo Figueiredo Avenida das Américas, 8585, Grupo 411, Barra da Tijuca, Rio de Janeiro, RJ, Brazil.
Zip code: 22793-081. E-mail: jpofigueiredo@gmail.com
Article received: May 2, 2019.
Article accepted: October 21, 2019.
Conflicts of interest: none.