Jean-Christophe Maran1,2,3, Lucie Cassagnes4,5, Vincent Delmas6, Dominique Musset7, René Frydman8, Gérard Mage9, Michel Canis9, Louis Boyer4,5, Olivier Ami10,4,11,12. 1. Plateforme de recherche IMAGINAITRE, Paris, France. jc.maran@babyprogress.fr. 2. Unité de Recherche en Développement, Imagerie et Anatomie (URDIA), Université Paris Descartes, EA 4465, Paris, France. jc.maran@babyprogress.fr. 3. Institut Pascal, Image Guided Therapies (IGT), UMR UCA-CNRS 6602, Aubière, France. jc.maran@babyprogress.fr. 4. Institut Pascal, Image Guided Therapies (IGT), UMR UCA-CNRS 6602, Aubière, France. 5. CHU de Clermont Ferrand 1-Pôle de Radiologie, Clermont Ferrand, France. 6. Unité de Recherche en Développement, Imagerie et Anatomie (URDIA), Université Paris Descartes, EA 4465, Paris, France. 7. Université Paris Sud 11, Orsay, France. 8. Université Paris Descartes, Paris, France. 9. Service de gynécologie-obstétrique, CHU de Clermont Ferrand 1, Clermont Ferrand, France. 10. Plateforme de recherche IMAGINAITRE, Paris, France. 11. Service de gynécologie-obstétrique, Clinique de l'Essonne, 2 bd des Champs Elysées, F91000, Evry, France. 12. Clinique de la Muette, Ramsay Générale de Santé, Paris, France.
Abstract
PURPOSE OF THE STUDY: To describe the observable MRI changes in the urogenital sinus during the second stage of labor and delivery by comparing the changes in the positions of the anatomical structures of the maternal perineum using MRI-based vector 3-D models. MATERIALS AND METHODS: Seven pregnant women underwent 3-D MRI sequences using a Philips 1 T Panorama open MRI during the pre-labor period and during the second stage of labor. A 3-D vector reconstruction platform (BABYPROGRESS, France) enabled the transformation of volumes of 2-D images into finite element meshes. The polygonal meshes labeled with the principal components of the urogenital sinus were used as part of a biomechanical study of the pressure exerted on the perineum during fetal descent. RESULTS: The expansion of the urogenital sinus was observed in all patients. Qualitative stretching was observed toward the rear and bottom of the iliococcygeus, pubococcygeus, puborectalis and obturator internus muscles. Significant length differences were measured along the iliococcygeus and pubococcygeus muscles but not along the tendinous arch of the levator ani or the puborectalis muscle. The inversion of the levator ani muscle curvature was accompanied by the transmission of pressure generated during fetal descent to the pubic muscle insertions and the descent of the tendinous arch of the levator ani. CONCLUSION: Mechanical pressures responsible for the tensioning of the constituent muscles of the urogenital sinus were qualitatively identified during the second stage of labor. MRI-based vector 3-D models allow the quantitative assessment of levator ani muscle stretching during labor, but 2-D MRI is not sufficient for describing perineal expansion. Vector 3-D models from larger scale studies have the potential to aid in the calibration of a realistic simulation based on the consideration of the reaction of each muscular element. These models offer perspectives to enhance our knowledge regarding perineal expansion during childbirth as a risk factor for postpartum perineal defects.
PURPOSE OF THE STUDY: To describe the observable MRI changes in the urogenital sinus during the second stage of labor and delivery by comparing the changes in the positions of the anatomical structures of the maternal perineum using MRI-based vector 3-D models. MATERIALS AND METHODS: Seven pregnant women underwent 3-D MRI sequences using a Philips 1 T Panorama open MRI during the pre-labor period and during the second stage of labor. A 3-D vector reconstruction platform (BABYPROGRESS, France) enabled the transformation of volumes of 2-D images into finite element meshes. The polygonal meshes labeled with the principal components of the urogenital sinus were used as part of a biomechanical study of the pressure exerted on the perineum during fetal descent. RESULTS: The expansion of the urogenital sinus was observed in all patients. Qualitative stretching was observed toward the rear and bottom of the iliococcygeus, pubococcygeus, puborectalis and obturator internus muscles. Significant length differences were measured along the iliococcygeus and pubococcygeus muscles but not along the tendinous arch of the levator ani or the puborectalis muscle. The inversion of the levator ani muscle curvature was accompanied by the transmission of pressure generated during fetal descent to the pubic muscle insertions and the descent of the tendinous arch of the levator ani. CONCLUSION: Mechanical pressures responsible for the tensioning of the constituent muscles of the urogenital sinus were qualitatively identified during the second stage of labor. MRI-based vector 3-D models allow the quantitative assessment of levator ani muscle stretching during labor, but 2-D MRI is not sufficient for describing perineal expansion. Vector 3-D models from larger scale studies have the potential to aid in the calibration of a realistic simulation based on the consideration of the reaction of each muscular element. These models offer perspectives to enhance our knowledge regarding perineal expansion during childbirth as a risk factor for postpartum perineal defects.
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Authors: Olivier Ami; Jean Christophe Maran; Petra Gabor; Eric B Whitacre; Dominique Musset; Claude Dubray; Gérard Mage; Louis Boyer Journal: PLoS One Date: 2019-05-15 Impact factor: 3.240