2.7. Blinding
All blocks were performed by a single experienced regional anesthesiologist (X.C.), together with a single assistant nurse who was otherwise not involved in the study. All other research personnel and outcome assessors were blinded to group allocations. Patient blinding was maintained as much as possible by standardizing some of the perceptible block elements, such as positioning and LA injection volumes. However, differences in ultrasound probe placement and needle insertion site still existed.