The Maximum Effective Needle-to-Nerve Distance for Ultrasound-Guided Interscalene Block

Histological confirmation of needle tip position during ultrasound-guided interscalene block: a randomized comparison between the intraplexus and the periplexus approach

“…Furthermore, for the periplexus approach, our average needle tip distance was substantially closer to the brachial plexus border (0.4 mm) than the 1.6 mm shown to produce successful block in 95% of subjects. 12 Despite our close proximity to neural elements, we were unable to find any evidence of subepineurial injection following the periplexus technique. Ink was found within the middle scalene muscle and not in direct contact with the epineurium in 17/25 (68%) of our periplexus injections.…”

“…This suggests that high efficacy regional anesthesia can be achieved even by means of intramuscular needle placement without directly targeting nerves. 12 At the interscalene level of the brachial plexus, the commonly accepted intraplexus technique is to place the needle tip beyond the fascia of the middle scalene muscle between the hypoechoic roots or trunks. This space is argued to be safe based on the anatomical finding that each root is surrounded by its own investing epineurium.…”

A comparison of motor stimulation threshold in ultrasound-guided interscalene brachial plexus block for arthroscopic shoulder surgery: a randomized trial

“…The authors of a recent study sought to determine the maximal effective needle-to-nerve distance for ultrasound-guided ISBPB, and they concluded that placing the needle tip in the middle scalene muscle may be a reasonable goal to achieve a successful analgesic ISBPB. 10 Nevertheless, in our study of the eight patients who exhibited intramuscular spreading, three patients had an unsuccessful block. Intramuscular spreading was noticed only in patients in Group 0.5 and in those with a periplexus needle tip location.…”

Randomized, comparative study of the effectiveness of three different techniques of interscalene brachial plexus block using 0.5% ropivacaine for shoulder arthroscopy

“…However, not many studies have compared the efficacy of regional anesthesia with PNS vs. ultrasound-guided techniques in terms of needle placement precision [12,13]. A dual-guidance method (US-guided and PNS-confirmed) is the contemporary technique of choice; however, more studies are required on the possible complications arising from the dual-guidance method as compared to the PNS--confirmed technique [14].…”