Ultrasonographic measurement of the ligamentum flavum at different angles in the lateral tilt position

The aim of this study was to take ultrasonographic measurements of the length of the ligamentum flavum (LF), the LF–skin distance and the interspinous distance, which are critical for the application of neuraxial anaesthesia, with volunteers in the sitting position and with lateral tilt of the operating table at different angles to evaluate whether the target structures in neuraxial anaesthesia can be better visualised with the lateral tilt position and to determine whether or not these measurements change at different angles. The study included 29 volunteers. For the measurements, the operation table was first set into the neutral position and the length of the LF, the skin–LF distance and the interlaminar distance were measured at between L1–S1 spaces with a paramedian oblique sagittal approach with a linear ultrasound probe. Then the table was moved into 5°, 10° and 15° lateral tilt positions and the LF, LF–skin distance and the interlaminar distance were measured at the L1–S1 interspaces and recorded. At L2–3, L3–4, L4–5 and L5–S1 intervertebral interspaces, as the lateral tilt angle increased, so the measured LF length and interlaminar distance was determined to increase, this increase was statistically significant. In the ultrasonographic measurements of the skin–LF distance, at L3–4 and L4–5 intervertebral interspaces, there was a statistically significant increase. With lateral tilt applied to the table, there was determined to be an increase in ultrasonographic measurements of the LF length in the lumbar intervertebral interspaces. Therefore, for neuraxial blocks applied in the sitting position, the procedure may be facilitated with lateral tilt of the operating table.