Ultrasound-guided sciatic nerve block: a comparison between four different infragluteal probe and needle alignment approaches.

Purpose: Our aim was compare onset time of sciatic nerve blockade (SNB) performed distal to the subgluteal fold using four different ultrasound (US)-guided approaches in patients undergoing foot or ankle surgery.

Methods: Patients were assigned to one of four groups: SI patients received SNB using short-axis (SA) view of the SN and in-plane (IP) placement of block needle (SA-IP approach); LI patients received SNB using long-axis (LA) view of the SN and IP needle placement (LA-IP approach); SO patients received the block using SA view of the SN and out-of-plane (OP) needle placement (SA-OP approach); LO patients received SNB using LA view of the SN and OP needle placement (LA-OP). Primary outcome included onset time of sensory and motor SNB. Patient satisfaction concerning the postoperative analgesia was noted.

Results: The LI group had significantly faster onset of sensory blockade on the distribution of tibial nerve (16.0 ± 5.6 vs. 23.5 ± 3.6) and common peroneal nerve (12.5 ± 4.3 vs. 19.1 ± 5.4 min) in comparison with the LO group. The LI group had significantly faster onset of motor blockade on the distribution of tibial nerve (21.1 ± 6.2 vs. 26 ± 3.1) and common peroneal nerve (17.7 ± 4.8 vs. 23.7 ± 5.8 min.) in comparison with the LO group. The LI group had the highest rate of patient satisfaction for postoperative analgesia and the LO group had the lowest.

Conclusion: The LA-IP approach resulted in a rapid onset of SNB and was associated with the best satisfaction for postoperative analgesia in comparison with LA-OP, SA-IP, and SA-OP approaches for patients undergoing foot and ankle surgery.