Determination of Vertebral Structure using Ultrasound Examination at Manually Identified Midpoint of Intercristal Line in Pregnant Women at Term: A Cross-sectional Study

Abstract

Introduction: Manual palpation has traditionally been used to locate the intercristal line and corresponding vertebral level for administering subarachnoid blocks. However, ultrasound examination provides an alternative approach for accurate vertebral identification. Aim: To determine the vertebral structure using ultrasound at the manually marked midpoint of the intercristal line in pregnant women at term. Materials and Methods: A cross-sectional study was conducted at Government Dharmapuri Medical College Hospital (GDMCH) in Dharmapuri, Tamil Nadu, India from March 20, 2023 to April 18, 2023. It involved 100 pregnant women at term. Two independent observers estimated the vertebral space at the intercristal line – one using manual palpation and the other using ultrasound guidance. The primary outcome assessed was the determination of the vertebral structure using ultrasound examination at the manually marked midpoint of the intercristal line in pregnant women at term. The secondary outcome assessed included evaluating the accuracy of manual palpation in identifying vertebral levels compared to ultrasound examination and assessing factors such as Body Mass Index (BMI) that may influence the accuracy of vertebral level identification. One-way Analysis of Variance (ANOVA) was used to compare the mean±SD of continuous variables among more than two groups. A p-value <0.05 was considered statistically significant. Results: The study included 100 pregnant women with a mean age of 22.91±3.74 years and a mean BMI of 25.87±3.98 kg/m2. The ultrasonographic assessment revealed that the manually palpated intercristal line corresponded to the L4 vertebra level in 50% of cases, the L3-L4 intervertebral space level in 30%, the intended L4-L5 intervertebral space level in 15%, the L5 vertebra level in 3%, and the L3 vertebra level in 2%. Notably, the ultrasound examination showed that the manually palpated intercristal line was higher than the L4 vertebra or L4-L5 intervertebral space in 32% of the pregnant women. Conclusion: The study indicates that ultrasound examination may offer a more accurate method for identifying vertebral structures in pregnant women at term compared to traditional manual palpation.