Department of Obstetrics and Gynecology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
Department of Radiology, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
J Matern Fetal Neonatal Med. 2022 Dec;35(25):9736-9741. doi: 10.1080/14767058.2022.2051007. Epub 2022 Mar 14.
Intrapartum transperineal ultrasound is considered useful in judging fetal head descent; however, the inability to detect ischial spines on ultrasound images has been a drawback to its legitimacy. The current study aimed to determine the anatomical location of ischial spines, which can be directly applied to intrapartum transperineal ultrasound images.
Based on magnetic resonance imaging (MRI) of 67 pregnant women at 33 [31-34] weeks gestation (median [interquartile range: IQR]), we calculated the angle between the pubic symphysis and the midpoint of ischial spines (midline symphysis-ischial spine angle; mSIA), which is theoretically equivalent to the angle of progression at fetal head station 0 on ITU, by determining spatial coordinates of pelvic landmarks and utilizing spatial vector analysis. Furthermore, we measured symphysis-ischial spine distance (SID), defined as the distance between the vertical plane passing the lower edge of the pubic symphysis and the plane that passes the ischial spines.
As a result, mSIA was 109.6° [105.1-114.0] and SID 26.4 mm [19.8-30.7] (median, [IQR]). There was no correlation between mSIA or SID and maternal characteristics, including physique.
We established a novel method to measure the components of the pelvic anatomy by analyzing the three-dimensional coordinates of MRI data and identified the anatomical location of ischial spines which can be applied to ultrasound images. Our results provide valuable evidence to enhance the reliability of intrapartum transperineal ultrasound in assessing fetal head descent by considering the location of ischial spines.
经会阴超声在判断胎头下降方面被认为是有用的；然而，在超声图像上无法检测坐骨棘一直是其合法性的一个缺陷。本研究旨在确定坐骨棘的解剖位置，这可以直接应用于经会阴超声图像。
基于 67 名 33 周[31-34]妊娠孕妇的磁共振成像（MRI）（中位数[四分位距：IQR]），我们通过确定骨盆标志的空间坐标并利用空间向量分析，计算耻骨联合和坐骨棘中点之间的角度（耻骨联合-坐骨棘角；mSIA），该角度理论上相当于 ITU 中胎头位置 0 的进展角度。此外，我们测量了耻骨-坐骨棘距离（SID），定义为通过耻骨联合下缘的垂直平面与通过坐骨棘的平面之间的距离。
结果，mSIA 为 109.6°[105.1-114.0]，SID 为 26.4 mm[19.8-30.7]（中位数，[IQR]）。mSIA 或 SID 与产妇特征（包括体型）之间均无相关性。
我们通过分析 MRI 数据的三维坐标建立了一种新的方法来测量骨盆解剖结构的组成部分，并确定了坐骨棘的解剖位置，这可以应用于超声图像。我们的结果为通过考虑坐骨棘的位置来提高经会阴超声评估胎头下降的可靠性提供了有价值的证据。
