Effect of table tilt on ligamentum flavum length measured using ultrasonography in pregnant women*.

The purpose of this study was to assess whether applying dorsal table tilt to a seated parturient positioned for neuraxial anaesthesia (i.e. facing laterally with her legs over the side of the table) increased the size of the target area for the neuraxial needle. We performed lumbar ultrasonography on 20 pregnant women with the table level (0°) and tilted 8° and 15° dorsally. For each position, the size of the 'target area', defined as the visible length of the ligamentum flavum in the longitudinal paramedian view, and the interlaminar distance, were measured at the L3-4 interspace. There were significant increases in the mean (SD) size of the target area with increasing table tilt (10.7 (1.3) mm at 0°, 11.5 (1.3) mm at 8° and 12.2 (1.7) mm at 15°; p < 0.0001). Interlaminar distances were not significantly increased. These data show that using dorsal table tilt in obstetric patients increases the target area for neuraxial needles. Additional research is required to assess whether this eases the placement of neuraxial needles in clinical practice. Anaesthesia