Background: The corner pocket (CP) approach for supraclavicular block (SCB) prevents ulnar nerve (UN) sparing due to needle proximity of lower trunk. Improved ultrasound resolution has suggested that the intertruncal (IT) approach is a suitable alternative method. However, the comparative efficiency of these two approaches on UN block has not been evaluated.Methods: Sixty patients were randomized to undergo SCB using the ultrasound-guided CP or IT approach. For lower trunk blockade, 10 mL of local anesthetic agents (1:1 mixture of 0.75% ropivacaine and 1% lidocaine) were injected in the CP (CP approach) or between the lower and middle trunk (IT approach). Additional 15mL was injected identically to block the middle and upper trunks in both groups. Sensory and motor blockade was evaluated after intervention. Results: Complete sensory blockade (75.9% [22/29] vs 43.3% [13/30], P = 0.023) and complete motor blockade (82.8% [24/29] vs 50.0% [15/30], P = 0.017) of the UN at 15 min after SCB were significantly more frequent in the IT than in the CP group. Sensory block onset time of UN was significantly shorter in the IT compared to the CP group (15.0 [10.0; 15.0] min vs 20.0 [15.0; 20.0] min; P = 0.011). Conclusions:The IT approach provided a more rapid onset of sensory and motor block of the UN than the CP approach. These results suggest that the IT approach is a suitable alternative to the CP approach and can provide faster surgical readiness.