Intercristal line as palpation landmarks to identifying the vertebral level is frequently inaccurate.To find more safe and reliable body surface markers and convenient methods to be solved in clinical work.The investigators performed a two-stage study to evaluated the accuracy of intercristal line and the The Posterior Superior Iliac Spine (PSIS) line to identify the lumbar interspinous spaces for spinal anesthesia using ultrasonography in pregnant woman which will provide a second option.
After obtaining written informed consents,pregnant women at 37-42 weeks of gestation
BMI ≥ 40 kg/m² (to minimize palpation variability), History of lumbar surgery/deformity (scoliosis, spondylolisthesis or osteoporotic vertebral collapse), Inability to maintain the flexed lateral decubitus position, Participant withdrawal, Unforeseen anatomical anomalies discovered during screening.
We enrolled parturients aged 22-45 years at 37-42 weeks of gestation scheduled for epidural or combined spinal-epidural anesthesia (for labor or cesarean section)
Case-control
Prospective
Not listed
The distance between the PSIS line and each mid-interspinous space
PSIS line was defined as an intercristal line drawn between the the final posterior superior iliac spine point.Use a ruler to measure the distance between the PSIS line and each midddle- interspinous space （L1/2 through L5/S1）and record. The mean of distances and 95% confidence interval are calculated.
The accuracy of the anatomic landmarks to determine the L3/4 interspinous space
The L3-L4 intervertebral space was detected using intercristal line and the PSIS line in a random order by 2 experienced anesthesiologists. After determining the L3-L4 intervertebral space using each method alternately, horizontal skin marks were created with an erasable pen. Then, another experienced anesthesiologist for ultrasonographic examination assessed the intervertebral spaces.After identifying the sacrum, the investigator moved the probe in a cephalad direction, counted the intervertebral spaces and assessed the actual intervertebral spaces of the 2 skin marks.
The distance between the palpated intercristal line and PSIS line
palpated intercristal line line was identified and marked by bilateral palpation of the iliac crest summits. Subsequently, two reference points were defined: "point PSIS" (intersection of the PSIS line with the spinal midline) and "point PI" (intersection of the PI line with the spinal midline). We then calculated the following three distances: the "L3/4 distance" (from the L3/4 interspinous space midpoint to point PSIS), the "PI distance" (from point PI to point PSIS) The experienced anesthesiologist for ultrasonographic examination assessed the actual interspinous space of the intercristal line.
baseline data
The age
baseline data
body mass index (BMI)
Maternal height
Maternal height
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