Randomization
Patients were randomly assigned to either the preprocedural handheld ultrasound-assisted technique group (ultrasound group) or the conventional palpation-guided technique group (palpation group) using computer-generated random numbers secured in sealed, opaque envelopes. The CSE procedures were performed by one of the three anesthesiologists (S-KP, JB, and YK); each anesthesiologist had performed over 50 neuraxial ultrasound scans prior to this study. Block randomization was conducted to balance the allocation of the anesthesiologists to each group.