An Analysis of Pectoralis Major Muscle Morphology and Topography During the Fetal Period Clinical Aspects

Transkrypt

1 original papers Adv Clin Exp Med,, 6, ISSN -X Copyright by Wroclaw Medical University Alicja Kędzia, Michał Tkaczyszyn, Jowita Woźniak, Arkadiusz Szkutnik, Krzysztof Dudek An Analysis of Pectoralis Major Muscle Morphology and Topography During the Fetal Period Clinical Aspects Analiza morfologii i topografii mięśnia piersiowego większego w okresie prenatalnym w aspekcie klinicznym Department of Anatomy, Wrocław Medical University, Wrocław, Poland Institute of Machine Design and Operation, Wrocław Technical University, Wrocław, Poland Abstract Background. Recognition of pectoralis major muscle morphology and variation is of major clinical importance both for mammography readings and for plastic surgery. Objectives. The goal of the study was to describe pectoralis major muscle (PMM) morphology and topography in the fetal period. Material and Methods. The observations were carried on 98 fetuses aged 66 weeks of fetal life, from the collection of Wroclaw Medical University s Department of Anatomy. The study was based on anthropological methods, preparation, computer image acquisition, computer image processing using the ImageJ measurement tool and statistical methods. Topographic parameters were designated and symmetry, sexual dimorphism and growth rates were noted. Results. No sexual dimorphism was found. Pectoral major muscle size symmetry was observed on the left and right sides. The muscle linear dimensions showed high interindividual variability. Two cases of sternal muscle presence were noted (Adv Clin Exp Med,, 6, 69979). Key words: pectoralis major muscle, sternal muscle, fetal period, anatomy, morphometry. Streszczenie Wprowadzenie. Poznanie morfologii i odmian m. piersiowego większego ma duże znaczenie kliniczne w badaniach mammograficznych i chirurgii plastycznej. Cel pracy. Ocena morfologii i topografii m. piersiowego większego w okresie prenatalnym. Materiał i metody. Zbadano 98 płodów, w tym płci żeńskiej, w wieku 66 tygodni życia płodowego, w przedziale CRL: mm. Materiał pochodził ze zbiorów Katedry i Zakładu Anatomii Prawidłowej Akademii Medycznej we Wrocławiu. W pracy posługiwano się metodami: antropologicznymi, preparacyjnymi, cyfrową akwizycją obrazu, komputerowym systemem przetwarzania obrazu z wykorzystaniem opcji pomiarowej Image J oraz metodami statystycznymi. Wyniki. Dla każdego mięśnia piersiowego większego określono punkty pomiarowe: A punkt przyczepu części obojczykowej PMM do bocznej części obojczyka, B punkt przyczepu włókien części obojczykowej do przyśrodkowej części obojczyka, C punkt przyczepu części mostkowo-obojczykowej do dolnej części mostka, E punkt wyjścia wiązek mięśnia z przyczepu na kości ramiennej. Zmierzono odległości między nimi: AA, BB, CC, oraz długości poszczególnych odcinków: AE, AB, BC, AC oraz pole powierzchni mięśnia i wymiary kątowe: α kąt między odcinkami AE i AB i kąt β kąt między obojczykowym a mostkowym przyczepem mięśnia. Parametry topograficzne oznaczono w systemie O/. Zbadano symetrię, dymorfizm płciowy i tempo wzrostu. Wnioski. Stwierdzono brak dymorfizmu płciowego. Obserwowano symetrię po stronie prawej i lewej. Wymiary liniowe mięśnia cechowała duża zmienność międzyosobnicza, do opisu ich wzrastania użyto modeli regresyjnych liniowych. Wzrastanie pola powierzchni mięśnia opisano za pomocą modelu wielomianowego. Nie zaobserwowano różnic w częstości występowania analizowanych cech topograficznych u płodów żeńskich i męskich. Opisano dwa przypadki występowania mięśnia mostkowego (Adv Clin Exp Med,, 6, 69979). Słowa kluczowe: mięsień piersiowy większy, mięsień mostkowy, okres prenatalny, anatomia, morfometria.

2 7 The pectoralis major muscle (PMM) consists of three parts: the clavicular part begins on the proximal part of clavicle; the sternocostal part begins on the anterior surface of the sternum and the first six costal cartilages; the small ventral part originates from the tendinous sheath of rectus abdominis muscle. In the humerus attachment area there is a bistratal tendon []. Pectoral muscle variations are not rare. Numerous anomalies of the PMM have been described in the literature. During routine post mortem dissections of two adult males, Yamasaki observed the absence of the clavicular head and traces of a sternocostal head []. In 7 females, Mosconi and Kamath found nosternal part of the PMM sternocostal head and a total absence of the muscle on the other side []. Cases of an extra muscle head also appear in the literature []. The PMM is not indispensable for the proper functioning of the shoulder girdle []. Lee et al. discussed the case of a -year-old male with congenital unilateral absence of the PMM, which did not significantly influence his normal functioning [6]. Mysnyk and Johnson stated that congenital deficiency of the sternocostal head in major and minor pectoral muscles did not prevent two males from becoming college wrestling champions [7]. In accessory investigations carried out on these subjects, their muscle adductory force was found to be % to % less in the vertical plane than in normal subjects [7]. Recognizing muscle anomalies, variants and topography are especially useful in radiology (mammography) [8] and in plastic surgery, where this muscle flap is commonly used in head or neck reconstructions [9]. The goal of this study was to investigate PMM metrology and topography in the fetal period. Material and Methods A. Kędzia et al. The material consisted of pectoralis major muscles dissected from 98 fetuses ( females) aged from 6 to 6 weeks of fetal life (crown to rump length [CRL] from to mm) from the collection of the Department of Anatomy at Wroclaw Medical University, Wrocław, Poland. The fetuses were preserved in formalin solution for similar time intervals. The following methods were incorporated in the study: preparation with microsurgical instruments, anthropological methods, digital image acquisition, computer image processing using the ImageJ. measurement system and statistical methods (the Statistica software package). The anthropological methods involved determining the biological age of the fetuses using CRL in conjunction with the Scammon-Calkins formula []. Digital image acquisition enabled repeated and thorough measurements and prevented excessive damage of unique fetal material. The ImageJ program can convert pixels to millimeters and ensures measurement accuracy to within. mm. For every PMM, the following measurement points were determined (Fig. ): A the attachment of the pars clavicularis of the pectoralis major muscle to the lateral part of the clavicle, B the attachment of the pars clavicularis fibers to the median part of the clavicle, C the attachment of the pars sternocostalis to the inferior part of the sternum, E the divergence of the muscle bundles from the humerus attachment; angle α the angle between sections AE and AB, and angle β the angle between the muscle s clavicular and sternal attachments. Fig.. The scheme of notations used in pectoralis major muscle measurements and an example of PMM dissection from a six-month female fetus. : pars clavicularis, : pars sternocostalis, : pars abdominalis, Cla: clavicle, S: sternum Ryc.. Schemat oznaczeń stosowanych w pomiarach mięśnia piersiowego większego oraz przykładowy preparat mięśnia trójgłowego ramienia u płodu płci żeńskiej w 6. miesiącu życia płodowego: część obojczykowa, część mostkowo-żebrowa, część brzuszna, Cla obojczyk, S mostek

3 Pectoralis Major Muscle Morphology and Topography 7 For every fetus, the following measurements were taken: crown-to-rump length (CRL), vertexto-plantare length (V-PL), the distance between points A on the left and right sides (AA distance), the distance between points B on the left and right sides (BB distance), the distance between points C on the left and right sides (CC distance), the distance between points A and E (AE distance), the distance between points A and B (AB distance), the distance between points B and C (BC distance), the distance between points A and C (AC distance), the area of the PMM (Area), Angle α and Angle β. Figure presents example preparation and measurement points. Symmetry, sexual dimorphism and growth rate were examined. Topographic parameters were described using a Yes/No system for the following features: Pars abdominalis absent, Pars sternocostalis absent, connection with m. deltoideus absent, trigonum deltoidopectorale clear and sulcus interpectoralis clear. The pars clavicularis, pars sternocostalis and pars abdominalis were each described as symmetrical, larger on the left or larger on the right. Results The basic statistics describing the somatic features of the examined fetuses are presented in Table. The examined features were symmetrical in both genders with regard to pectoralis major shape; the only statistically significant difference was observed in BC length (Table ). The exam- Table. Characteristics of the examined fetuses (mean ± SD) Tabela. Charakterystyka badanych płodów (mean ± SD) Week (Tydzień) N (Liczba) CRL mm (Długość CRL mm) V-PL mm (Długość v-pl mm) Mass g (Masa ciała g) F M female male female male female male ± 9 ± 7 ± 8 ± 9 7 ± ± 9 ± ± 9 ± 7 7 ± 8 ± 9 ± 69 6 ± 7 ± ± 8 6 ± 76 6 ± 8 8 ± ± 8 ± 8 ± 8 ± 6 8 ± 8 ± ± 6 ± 8 ± ± ± 9 ± 66 ± 69 ± 7 ± 7 8 ± 88 ± Table. Comparison of basic statistics (mean ± SD) of the muscle measurements on the right and left sides, with t-student test results for related features Tabela. Porównanie podstawowych statystyk (mean ± SD) badanych wymiarów mięśnia po stronie prawej i lewej oraz wyniki testów t-studenta dla cech powiązanych Dimensions (Wymiary) Right (Prawa) n = 98 Left (Lewa) n = 98 t p AE distance mm (Odległość AE mm) AB distance mm (Odległość AB mm) BC distance mm (Odległość BC mm) AC distance mm (Odległość AC mm) Area mm (Pole powierzchni mm ) Angle α (Kąt α ) Angle β (Kąt β ). ±.9. ±. 8.9 ±. 6. ± 6. 7 ± 89 7 ± 9 ±. ±.. ±. 9. ±.9 6. ± 6. ± 8 8 ± 9 ±

4 7 A. Kędzia et al. ined fetuses were homogenous in terms of age, somatic features, pectoralis major muscle size, shape and location; the only statistically significant differences noted were in the V-PL and AA distance (Table ). In terms of qualitative features, no statistically significant differences were observed between male and female fetuses (Table ). The statistical analysis revealed that the differences between the topographic features of male and female fetuses were statistically insignificant (p <.). Due to the homogeneity of pectoral muscle size and the lack of sexual dimorphism, all measurements from all 98 fetuses were used in the further analysis. Table presents the results of the different mathematical models for the parameters assessed and the relationship between PMM length and morphological age (in weeks). To describe the growth rate, four widely used formula types were applied (Table ):. linear L(t) = a + b c. logistic L(t) = A/( + c exp(k t)). Gompertz s (t) = A exp(c exp(k t)). von Bertalanffy s L(t) = A exp ( c exp(k t)) Mean absolute error was used as a measure of the degree to which the theoretical models matched the results obtained. A comparison of the models for the dimensions analyzed is presented in Figs. 8. Due to the relatively high interindividual variability of pectoralis major muscle linear dimensions, linear regression models seem suitable for describing their growth in weeks 6 to 6 of fetal life (Table 6). The highest growth rates were observed in AC distance (. mm/week), AA distance (.9 mm/ week) and BC distance (.9 mm/week). In the observed period of fetal life, α and β angle values did not change significantly (p <.). The polynominal model: x = b + b * t + b * t provides a good approximation of the muscle area increase; with the parameters b = mm, b = mm/week and b =.86 mm/week, it explains almost % of the variations (Fig. 9). In the material examined, two cases of anomalies in the form of sternal muscles were observed (Fig. ). Table. Comparison of basic statistics (mean ± SD) of features of male and female fetuses, with t-student test results Tabela. Porównanie podstawowych statystyk (mean ± SD) badanych cech u płodów żeńskich i męskich oraz wyniki testów t-studenta Variables (Zmienne) Female (Płeć żeńska) n = Male (Płeć męska) n = 76 t p Morphological age week (Wiek morfologiczny tydzień) CRL mm (Długość ciała CRL mm) V-PL mm (Długość ciała V-PL mm) Mass g (Masa ciała g). ±. 69 ± 7 ± 8 ±.8 ±. 9 ± ± 7 ± AA distance mm (Odległość AA mm) BB distance mm (Odległość BB mm) CC distance mm (Odległość CC mm) AE distance mm (Odległość AE mm) AB distance mm (Odległość AB mm) BC distance mm (Odległość BC mm) AC distance mm (Odległość AC mm) 8. ± 9..6 ±.6. ±.. ±.9. ±. 9.6 ± ± 6.. ± 7..8 ±.. ±.. ±.9. ±. 8.7 ±..6 ± Area mm (Pole powierzchni mm ) Angle α (Kąt α ) Angle β (Kąt β ) 76 ± 6 ± ± 6 6 ± 8 9 ± 9 9 ±

5 Pectoralis Major Muscle Morphology and Topography 7 Table. Comparison of the numerousness (fraction) of pectoralis major muscles of male and female fetuses, divided into subgroups according to topography, with chi-square test results Tabela. Porównanie liczności (frakcji) mięśni piersiowych większych płodów żeńskich i męskich w podgrupach różniących się topografią oraz wyniki testów chi-kwadrat Topography (Topografia) PMMs from females (Płeć żeńska) n = PMMs from males (Płeć męska) n = χ p Pars clavicularis absent (Część obojczykowa nieobecna) (.%) (.%).8.9 Pars sternocostalis absent (Część mostkowo-żebrowa nieobecna) (.%) (.%) Pars abdominalis absent (Część brzuszna nieobecna) (.%) 88 (7.9%).8.99 Connected with m. deltoideus (Połączenie z mięśniem naramiennym) (6.8%) (6.6%).8.77 Clear trigonum deltoideopectorale (Czysty trójkąt naramienno-piersiowy) (7.%) (7.%)..99 Topography (Topografia) Female (Płeć żeńska) n = Male (Płeć męska) n = 76 χ p Clear sulcus interpectoralis (Czysta bruzda między mięśniami piersiowymi większymi) 8 (8.8%) 6 (8.6%)..8 Superimpose of muscles (Nakładanie się mięśni) (8.%) (8.%).8.77 Pars clavicularis: (Część obojczykowa) symmetrical larger on the left larger on the right 7 (77.%) (.%) (.7%) 6 (7.7%) (.%) 9 (.8%) Pars sternocostalis: (Część mostkowo-żebrowa) symmetrical larger on the left larger on the right 9 (86.%) (.%) (9.%) 69 (9.8%) (.%) 6 (7.9%).99.6 Pars abdominalis: (Część brzuszna) symmetrical larger on the left larger on the right (9.%) (.%) (.%) 7 (96.%) (.%) (.6%)..8

6 7 A. Kędzia et al. Table. PMM size increases over time (t) [weeks] Tabela. Modele wzrastania wymiarów m. pectoralis maior z czasem t [tydzień] Distance L(t) (Odległość L(t)) Models (Modele). linear. logistic. Gompertz. von Bertalanffy AE mm a = 8.7 b =.7 R =.97 A =. c = K =. R =.9 A =.97 c =. K =. R =.9 A =.86 c =.7 K =.6 R =.9 AB mm a = 7.68 b =.89 R =.98 A =.79 c = 9 K =.6 R =.8 A =. c =.89 K =.9 R =.8 A =.7 c =.8 K =. R =.8 BC mm a = 9.67 b =.7 R =.6776 A =.79 c = 79 K =. R =.69 A =.7 c = 9. K =. R =.6898 A =.6 c = 9.7 K =. R =.6896 AC mm a =.7 b =.8 R =.66 A =. c = 97 K =.8 R =.678 A =.66 c =. K =. R =.67 A =.8 c = 7.9 K =. R =.67 AA mm a =. b =. R =.6 A =. c = K =. R =. A =.6 c =. K =.8 R =.9 A =. c = 6. K =.7 R =. BB mm a = 8.6 b =. R =.9 A =. c = K = R =.96 A =.6 c =. K =.8 R =.96 A =. c =.6 K =. R =.96 CC mm a =.6 b =.7 R =.6 A = 6. c =.8 K =.8 R =.7 A =. c = 9.8 K =.9 R =.8 A =.9 c = 9. K =. R =. t: morphological age (in weeks), R: coefficient of determination AE [mm] Fig.. Comparison of models for AE distance Ryc.. Porównanie modeli dla analizowanej odległości AE morphological age weeks wiek morfologiczny tygodnie

7 7 Pectoralis Major Muscle Morphology and Topography Fig.. Comparison of models for AB distance AB [mm] Ryc.. Porównanie modeli dla analizowanej odległości AB morphological age weeks wiek morfologiczny tygodnie 8 Fig.. Comparison of models for BC distance BC [mm] Ryc.. Porównanie modeli dla analizowanej odległości BC morphological age weeks wiek morfologiczny tygodnie 8 Fig.. Comparison of models for AC distance AC [mm] Ryc.. Porównanie modeli dla analizowanej odległości AC morphological age weeks wiek morfologiczny tygodnie 8

8 76 A. Kędzia et al. Fig. 6. Comparison of models for AA distance AA [mm] Ryc. 6. Porównanie modeli dla analizowanej odległości AA morphological age weeks wiek morfologiczny tygodnie 8 Fig. 7. Comparison of models for BB distance AA [mm] 8 Ryc. 7. Porównanie modeli dla analizowanej odległości BB morphological age weeks wiek morfologiczny tygodnie 8 Fig. 8. Comparison of models for CC distance CC [mm] 7 6 Ryc. 8. Porównanie modeli dla analizowanej odległości CC morphological age weeks wiek morfologiczny tygodnie 8

9 Pectoralis Major Muscle Morphology and Topography 77 Table 6. Regression models of PMM size increases over time t [weeks]: x = b + b t Tabela 6. Modele regresyjne wzrastania wymiarów m. pectoralis maior z czasem t [tydzień]: x = b + b t Dimensions x (Wymiary x) r x,t b b AE mm AB mm BC mm AC mm Area F mm (Pole powierzchni F mm ) Angle α (Kąt α ) Angle β (Kąt β ) AA Distance (Odległość między punktami A) BB Distance (Odległość między punktami B) CC Distance (Odległość między punktami C) (7 ) 7 ( ) 9 (7 ).68 (.6.7). (.7.).9 (.89.9). (..8). (..).9 (..7).6 (..9). (.9.) F [mm ] t Fig. 9. Model of increases in muscle area (F) with age (t), with the measurement results in the background Ryc. 9. Model wzrastania powierzchni mięśnia (F) z wiekiem (t) na tle wyników pomiaru Fig.. A case of sternal muscle (SM) in the prenatal period Ryc.. Przypadek m. sternalis (SM) w okresie prenatalnym

10 78 Discussion A. Kędzia et al. The available literature provides mainly descriptions of pectoralis major muscles of adult corpses. The paper by Pande and Singh is one of the few publications based on fetal material []. Those authors examined ten fetuses of CRL ranging from 9 to 9 mm. The prepared them, weighed them and measured the symmetry of the following muscles: the pectoralis major, deltoid, coracobiachialis, triceps, superficial flexors of the forearm and extensors of the forearm; they also examined bones: the humerus, radius and ulna. The total mass of the dissected structures was bigger on the right (dominant) side in nine out of the ten examined fetuses (p <.), but the average pectoralis major muscle mass in was 7 mg larger on the left side. The authors were not able to explain why their results regarding the PMM differed from others. Chhibber and Singh, in turn, observed that the PMM increased in mass on the dominant side []. Other descriptions of PMM morphometry were not found. The analysis of the material in the current study (two pectoral muscles per fetus) revealed the following features: In two cases (.%) there was no clavicular part of the pectoralis major muscle. The sternoclavicular part was found in all fetuses. In cases (7.%) the ventral part of the muscle was absent. In cases (6.6%), the muscle fiber junction with the delta muscle was detected. Muscle absence within the trigonium deltoidepoctoralis was found in 7 cases (7%). In 8 cases (.%), muscle fibers overlapped on the sternum. No significant asymmetry was found in the dimensions of particular parts of the muscle. The influence of individual variations on PMM linear dimensions is so large that a simple linear model is sufficient to describe the size increases in the period from week 6 to week 6. For the same reason, a second degree polynomial can be adopted as a model of muscle area growth. In two cases in the current study sternal muscles were observed on the left side with fibers running parallel to the sternum (Figure ). The available literature provides descriptions of numerous morphological variations of sternal muscles [, ]. Pojchamarnwiputh et al. observed that the frequency of rare anatomical variations can be estimated as about 8% in both sexes []. Harper dissected sternal muscles in three out of six fetuses with anencephaly, and in one fetus, sternal muscle was found bilaterally [6]. O Neill et al. stated that sternal muscle presence in the anterior wall of the thoracic cavity can accompany PMM anomalies [7]. Kabay et al. examined the clinical significance of sternal muscles in mastectomies, and concluded that pre-operational identification of sternal muscles and a topographic description of them can help in making decisions about their potential resection during mastectomies [8]. Bradley et al. showed the presence of four sternal muscles in the mammographs of, women, and noted that the superficial location of the muscle favors sporadic mammogram visualization in the form of asymmetric condensation in the median part of the mammary gland [8]. Accessory muscles can be also a source of diagnostic mistakes. In such cases, Bradley et al. suggested CT or MR imaging in order to differentiate muscle from hyperplastic lesions of the mammary gland [8]. Sarıkçıoğlu et al. [9] described a case report of three sternal muscles co-existing in a 6-year-old male corpse, two on the left and one on the right side. The authors stated that PMM anomalies required diagnostic procedures so much indispensable in pectoral region surgery. The authors concluded that pectoralis major muscle size symmetry was observed on the left and right side. No sexual dimorphism was observed. The linear dimensions of the muscle in the examined period (weeks 6 to 6 of fetal life) showed high interpersonal variability, so a linear regression model was used to describe their growth. The area increase was described using a binominal model. No differences were observed between male and female fetuses in terms of the topographic features analyzed. References [] Connell DA, Potter HG, Sherman MF et al.: Injuries of the pectoralis major muscle: evaluation with MR imaging. Radiology 999,, [] Yamasaki M: Anatomical study on cases of the congenital partial defect of pectoralis major and minor muscles. Anat Anz 989, 68,. [] Mosconi T, Kamath S: Bilateral asymmetric deficiency of the pectoralis major muscle. Clin Anat, 6, 6 9. [] Marmor L, Bechtol CO, Hall CB: Pectoralis Major Muscle: Function of Sternal Portion and Mechanism of Rupture of Normal Muscle: Case Reports. J Bone Joint Surg Am 96,, 887. [] Loukas M, South G, Louis RG et al.: A case of an anomalous pectoralis major muscle. Folia Morphol 6, 6(),. [6] Lee YH, Chun SI: Congenital absence of pectoralis major: a case report and isokinetic analysis of shoulder motion. Yonsei Med J 99,, 879.

11 Pectoralis Major Muscle Morphology and Topography 79 [7] Mysnyk MC, Johnson DE: Congenital absence of the pectoralis muscles in two collegiate wrestling champions. Clin Orthop Relat Res 99, 6, 886. [8] Bradley FM, Hoover HC Jr, Hulka C et al.: The sternalis muscle: an unusual normal finding seen on mammography. Am J Roentgenol 996, 66, 6. [9] Kovacević P, Ugrenović S, Kovacević T: Vascularisation of pectoralis maior myocutaneous flap: anatomical study in human fetuses and cadavers. Bosn J Basic Med Sci 8, 8, 887. [] Carlson BM: Human embryology and developmental biology. Mosby, St Louis 999,. [] Pande BS, Singh I: One-sided dominance in the upper limbs of human fetuses as evidenced by asymmetry in muscle and bone weight. J Anat 97, 9(), 79. [] Chhibber SR, Singh I: Asymmetry in muscle weight in the human upper limbs. Acta Anat 97, 8(), 66. [] Demirpolat G, Oktay A, Bilgen I et al.: Mammographic features of the sternalis muscle. Diagn Interv Radiol, 6, [] Loukas M, Bowers M, Hullett J: Sternalis muscle: a mystery still. Folia Morphol, 6, 79. [] Pojchamarnwiputh S, Muttarak M, Na-Chiangmai W et al.: Benign breast lesions mimicking carcinoma at mammography. Singapore Med J 7, 8, [6] Harper WF: The Sternalis Muscle in the Anencephalous Foetus. J Anat 96, 7, 7. [7] O Neill MN, Folan-Curran J: Case report: bilateral sternalis muscles with a bilateral pectoralis major anomaly. J Anat 998, 9, 899. [8] Kabay B, Akdogan I, Ozdemir B et al.: The left sternalis muscle variation detected during mastectomy. Folia Morphol, 6, 8. [9] Sarıkçıoğlu L, Demirel DM, Oğuz N, Uçar Y: Three sternalis muscles associated with abnormal attachments of the pectoralis major muscle. Anatomy 8,, 677. Address for correspondence: Alicja Kędzia Department of Anatomy Wroclaw Medical University ul. Chałubińskiego 6a -68 Wrocław Poland Tel.: jowita_wozniak@yahoo.com Conflict of interest: None declared Received:.6. Revised:.7. Accepted: 7..