Pre-procedural Ultrasound Techniques Versus Conventional Landmark Technique of Spinal Anesthesia in Elderly Patients

The site of needle insertion will be determined via manual palpation. A line joining the superior aspect of the iliac crests posteriorly (Tuffier's line') will be used as a surface landmark for the L4 vertebral body. The midline will be established by palpation of the tips of the spinous processes, and the site of needle insertion will be marked on the patient's skin. The interspace that appears widest, based on manual palpation, will be chosen for the first attempt. If the first attempt is unsuccessful, further attempts can be made at the same interspace or another interspace.

The transducer will be applied in the parasagittal plane and the intervertebral levels will be identified by counting upwards from the sacrum (continuous hyperechoic line). The probe will then be angled obliquely to obtain a PSO view. The locations of the interlaminar spaces will be identified by visualizing the ligamentum flavum-dura mater complex and the posterior aspect of the vertebral body. The angulation at which the ligamentum flavum-dura mater complex and posterior vertebral body are best visualized will be considered the optimal angle for needle insertion and clearly communicated to the operator. The interlaminar space will be centered on the ultrasound screen and a skin marker will be used to make a mark on the patient's back at the middle of the ultrasound probe.

The transducer will be applied in the parasagittal plane, and after identification of the intervertebral levels, the probe will be rotated 90 degree to obtain the TM view. The transducer is moved in a cephalad-caudad direction between the spinous processes of L2 and L5 vertebra. The probe will be tilted slightly up and down to ensure a sufficient echogenic window at the selected intervertebral space. A skin marker will be used to make a mark on the patient's back at the middle of the ultrasound probe. The angle at which the ligamentum flavum-dura mater complex and the posterior aspect of the vertebral body are best visualized will be noted