Intercristal line determined by palpation in parturients in the sitting and the lateral decubitus positions: a...

We aimed to investigate intersected vertebral level changes in the palpated intercristal line (PI-line) when shifting from a sitting to a lateral decubitus position in parturients.

We consecutively enrolled parturients with a gestational age of ≥36 weeks. The attending anesthesiologists palpated the superior aspects of the posterior iliac crests bilaterally in a sitting position and then in a lateral decubitus position. The blinded investigators performed the ultrasound and recorded the intersected segment level of the PI-line. The distance between any two consecutive vertebral interspaces was divided into 3 segments, and comparisons were made with 15 segments of five vertebral interspaces above the sacrum. The primary outcome was the concordance rate of intersected segment level of the PI-line between the two positions. We also examined the intersected segment level of the PI-line of the two positions and the magnitude of these changes.

Thirty-nine parturients were analyzed. The concordance rate of intersected segment levels of the PI-line between the two positions was 21% (8/39). In 56% (22/39) of the parturients, the intersected segment level of the PI-line in the sitting position was more cephalad and 23% (9/39) were more caudal. Fifteen percent (6/39) of parturients had three or more segment differences between the two positions.

The intersected segment level of the PI-line, measured with trisected segments in each vertebral interspace, was different between the sitting and the lateral decubitus positions in approximately 80% of the parturients. Notably, 15% (6/39) of the parturients had at least one vertebral interspace deviation.