Department of Ultrasound, Shengjing Hospital of China Medical University, Shenyang, China.
Department of Ultrasound, Affiliated Maternity Hospital of Dalian Medical University, Dalian, China.
J Ultrasound Med. 2019 Apr;38(4):929-934. doi: 10.1002/jum.14771. Epub 2018 Oct 7.
This study explored the use of 2-dimensional (2D) ultrasound scans for the quantitative assessment of the fetal conus medullaris (CM) position and its correlation with gestational age (GA).
This was a prospective study. We identified the first sacral vertebra (S1) by intersection of 2 lines in 2D scans, then counted upward from S1 to determine the CM level and recorded the number of ossified sacral vertebral bodies. A quantitative assessment of the CM position was performed by measuring the distance between the CM and the midpoint of the S1 (CM-S1). The correlation between the CM-S1 distance and GA was evaluated.
We determined the CM level by identifying S1 first in 521 fetuses (GA, 20-38 weeks). The CM position in 70% of cases was at the L2 and L2-3 level, and at the L2 level or above after 37 weeks. The number of ossified sacral veterbral bodies was not consistent. CM-S1 measurements were easy to perform. A significant positive correlation between CM-S1 distance and GA was observed (R = .89, P < .05). The best-fit formula was: CM-S1 distance = 1.57 × GA - 16.43. The normal reference range was established and the fifth percentile was calculated for each GA.
S1 was easily identified, and the CM position relative to S1 was useful. There was a substantial correlation between CM-S1 and GA. Below the fifth percentile it was suggested that tethered cord may exist.
本研究探讨了二维（2D）超声扫描在定量评估胎儿终丝（CM）位置及其与胎龄（GA）的相关性中的应用。
这是一项前瞻性研究。我们通过 2D 扫描中的两条线相交确定第一骶椎（S1），然后从 S1 向上计数以确定 CM 水平，并记录骨化骶椎的数量。通过测量 CM 与 S1 中点（CM-S1）之间的距离来对 CM 位置进行定量评估。评估了 CM-S1 距离与 GA 的相关性。
我们在 521 例胎儿（GA，20-38 周）中首先确定 S1 的 CM 水平。70%的病例中 CM 位置在 L2 和 L2-3 水平，37 周后在 L2 或以上水平。骨化骶椎的数量不一致。CM-S1 测量易于进行。CM-S1 距离与 GA 之间存在显著正相关（R =.89，P <.05）。最佳拟合公式为：CM-S1 距离= 1.57×GA - 16.43。建立了正常参考范围，并计算了每个 GA 的第五百分位数。
S1 易于识别，CM 相对于 S1 的位置很有用。CM-S1 与 GA 之间存在很强的相关性。低于第五百分位数时，建议存在拴系脊髓。
