Arcuate Linea or stretched out tissue? A concept to be revised in the understanding of anterolateral abdominal wall
Authors: Barros Mirna Duarte , Mendes Carlos José Lazzarini 
Published: April 2020

IntroductionSince James Douglas (1675–1742), a Scottish anatomist physician, researchers have been studying the existence of the arched line (AL). The understanding of the mechanisms by which this anatomical repair occurs is still little understood. According to Rizk (1991), the adult AL might be poorly defined. Mekonen et al. (2015) proposed an embryological model of the abdominal wall (AW), related to the craniocaudal growth of the embryo. According to the “classic” descriptions, the anterior displacement of the aponeuroses of the abdominal muscles forming the rectus sheat determine the formation of the AL. How this phenomenon occurs is not clear. The objective of this study was to discuss the existence of the AL, as per the anatomical findings in the dissection of the abdominal wall in human fetuses.MethodThree fetuses conserved in a modified Larsen solution were dissected, focusing on the posterior laminae of rectus sheath (PLRS), in the umbilical and hypogastric regional topography. The specimen ages were: Fetus 1, term stillbirth; Fetus 2, 14 weeks, and; Fetus 3, 32‐week preterm, as per Figures
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and 3.ResultsIn the three fetuses, the PLRS were whole, without discontinuities or signs of rupturing, throughout the entire hypogastric region.Discussion and ConclusionRizk (1991) concluded that the AL is very variable, poorly defined and absent in 70% of the cases. Monkhouse et al. (1986) concluded that the position of the AL is variable in up to millimeters of the pubic symphysis. McArdle (1997), studying the inguinal hernia etiology, also demonstrated the AL in varied positions. Cunningham et al. (2004) concluded that the AL is located further above the anterior superior iliac spine (ASIS) in the obese (3.1 ± 3.4 cm) than in the lean (1.3 ± 1.3 cm). Loukas (2008) detected that in 65% of the cases the PLRS fibers disappeared gradually. Mwachaka (2010) observed that the AL occurs in only 63.9% of the female cases. Mekonem (2015) highlighted the importance of the fetal curvature in the origin and insertion of the AW muscles. Lamboune et al. (2019) highlighted the importance of the AL in the TAR (transversus abdominal release) for the hernia correction. The studies above demonstrate that the AL is an inconstant anatomical repair, having gender‐ and biotype‐dependent characteristics. The absence of the AL in the three dissected fetuses supports the hypothesis that the persistence of the anterior curvature of the trunk in this developmental phase should maintain the PLRS intact. Furthermore, with the growth and pélvis ptosis, the aponeuroses should fray, causing the inferior margin of the PLRS to “rise”, with definitive positioning distancing from the pelvis. We propose that further studies be made and that there be a revision in the concept that the broad muscles aponeuroses under the anterior superior iliac spine, passing in front of the abdominal straight muscle, are the cause of the formation of the AL.FETUS 1. S: superior, I: inferior; L: lateral;*: umbilical scar. A. 1: skin; B.2: subcutaneous tissue; C. 3: external oblique muscle aponeurosis; D. 4: rectus sheat anterior wall folded laterally); D. 5: rectus abdominis muscle; E. 6: intact PLRS.Figure 1FETUS 2. A2. 1. umbilical cord; B2 blue light line: rectus abdominis muscle lateral edge; B2, C2. 2: rectus abdominis muscles diastais, 3: anterior laminae of rectus sheat, 4: external oblique muscle; C. 5: intact PLRS. FETO 3. A3. 1: umbilical cord; B3. 1: subcutaneous tissue, 2: anterior laminae of rectus sheat; C3. 3: anterior laminae of rectus sheat folded laterally, 4: rectus abdominis muscle; D3. 5: intact PLRS, 6: rectus abdominis muscle.Figure 2