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

original papers Adv Clin Exp Med 2011, 20, 6, 699–709 ISSN 1230-025X © Copyright by Wroclaw Medical University Alicja Kędzia1, Michał Tkaczyszyn1, J...
Author: Marian Adamczyk
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original papers Adv Clin Exp Med 2011, 20, 6, 699–709 ISSN 1230-025X

© Copyright by Wroclaw Medical University

Alicja Kędzia1, Michał Tkaczyszyn1, Jowita Woźniak1, Arkadiusz Szkutnik1, Krzysztof Dudek2

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 1 2

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 16–26 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 2011, 20, 6, 699–709). 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 22 płci żeńskiej, w wieku 16–26 tygodni życia płodowego, w przedziale CRL: 104–215  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/1”. 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 2011, 20, 6, 699–709). Słowa kluczowe: mięsień piersiowy większy, mięsień mostkowy, okres prenatalny, anatomia, morfometria.

700 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 [1]. 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  [2]. In 72 females, Mosconi and Kamath found nosternal part of the PMM sternocostal head and a total absence of the muscle on the other side [3]. Cases of an extra muscle head also appear in the literature [4]. The PMM is not indispensable for the proper functioning of the shoulder girdle [5]. Lee et al. discussed the case of a 22-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 20% to 30% 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.

A. Kędzia et al.

Material and Methods The material consisted of pectoralis major muscles dissected from 98 fetuses (22 females) aged from 16 to 26 weeks of fetal life (crown to rump length [CRL] from 104 to 215 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  1.41 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 [10]. 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 0.01 mm. For every PMM, the following measurement points were determined (Fig. 1): 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. 1. The scheme of notations used in pectoralis major muscle measurements and an example of PMM dissection from a six-month female fetus. 1: pars clavicularis, 2: pars sternocostalis, 3: pars abdominalis, Cla: clavicle, S: sternum Ryc. 1. Schemat oznaczeń stosowanych w pomiarach mięśnia piersiowego większego oraz przykładowy preparat mięśnia trójgłowego ramienia u płodu płci żeńskiej w 6. miesiącu życia płodowego: 1 – część obojczykowa, 2 – część mostkowo-żebrowa, 3 – część brzuszna, Cla – obojczyk, S – mostek

701

Pectoralis Major Muscle Morphology and Topography

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 1  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 1. 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 2). The exam-

Table 1. Characteristics of the examined fetuses (mean ± SD) Tabela 1. Charakterystyka badanych płodów (mean ± SD) Week (Tydzień)

16 17 18 19 20 21 22 23 24 25 26

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

0 1 0 3 1 4 7 4 1 0 1

 1  9  6  3  3 16 22 14  2  0  0

– 118 – 154 ± 21 155 159 ± 2 172 ± 4 184 ± 2 190 – 215

104 117 ± 4 130 ± 3 139 ± 3 153 ± 3 159 ± 7 173 ± 3 180 ± 15 194 ± 2 – –

– 169 – 261 ± 53 170 221 ± 5 255 ± 18 263 ± 11 276 – 310

144 161 ± 8 182 ± 3 200 ± 11 218 ± 8 222 ± 32 248 ± 16 258 ± 24 283 ± 16 – –

–   78 – 348 ± 150 350 246 ± 28 313 ± 72 374 64 415 – 590

  63 100 ± 30 140 ± 12 194 ± 66 223 ± 45 269 ± 40 327 ± 74 358 ± 88 510 ± 0 – –

Table 2. 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 2. 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 – mm2 (Pole powierzchni – mm2) Angle α – ° (Kąt α – °) Angle β – ° (Kąt β – °)

14.0 ± 3.9

14.3 ± 4.3

–0.805

0.423

10.5 ± 4.0

10.5 ± 4.3

–0.268

0.790

18.9 ± 4.4

19.4 ± 4.9

–2.161

0.033

26.1 ± 6.3

26.1 ± 6.3

0.034

0.973

437 ± 189

432 ± 182

0.763

0.447

127 ± 21

128 ± 23

–0.326

0.745

119 ± 14

119 ± 12

–0.145

0.885

702

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 3). In terms of qualitative features, no statistically significant differences were observed between male and female fetuses (Table 4). The statistical analysis revealed that the differences between the topographic features of male and female fetuses were statistically insignificant (p 

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