A Comparison of the Ultrasound Measured Posterior Longitudinal Ligament Length in Parturients in the Standard Sitting and Crossed Leg Positions: an Observational Study

This is a prospective observational study involving a total of 30 healthy term gestation pregnant patients with singleton fetuses.Patients will be randomly allocated to sit crossed leg or in standard position first. Using ultrasonography, the acoustic window for lumbar spinal anesthesia at L3-4 will be evaluated in both traditional sitting and crossed leg positions. Ultrasonography will be performed sequentially to measure the best visualized length of posterior longitudinal ligament,ligamentum flavum and interlaminar distance in the paramedian view.The scanned image will be saved to be remeasured by a third observer. Patients will be asked to score their comfort level while sitting in both positions.