Effect of riders sitting position on the lumbar spine in patients undergoing neuroaxial anesthesia

In this study we will use an ultrasound procedure to define the lumbar ultrasonoraphic distances of patients undergoing neuroaxial anesthesia. The ultrasound will be applied by anesthesist who is certified to use ultrasound. Initially, the patients will be informed to sit in a Classic Sitting Position (CSP), then to sit in a Hamstring Stretching Position (HSP) and the last to sit in a Driver Sitting Position (DSP). In CSP, the knees were in 90 degrees flexion, hip adduction, and feet were on a stool support. In HSP the knees were supported by the bed in extension. In DSP, the patients will swinging freely their knees with the knees flexed, and the hip abducted on the operating table. In all three positions, the 2-5 mHz convex ultrasonography (US) probe was placed in the longitudinal paramedian position in the sacral region to see the spinal canal 2-3 cm laterally from the midline. After the sacrum was identified as a continuous hyperechoic line, the US probe was shifted towards the gutter and the intervertebral spaces (acoustic window) and spinous processes (acoustic shadows) of the lumbar vertebrae will be visualized as a sawtooth view. Ultrasonography will be performed by the same anesthesiologist with at least 50 patients' experience in ultrasonography in neuroaxial blocks and images will be recorded. All USG images will then be evaluated by a different anesthesiologist who does not know which position the measurements have been made and the distance between the L3-L4 spinous processes (SPAM) and the distance between the skin and the ligamentum flavum (DLFM) will be measured in this intervertebral space.