• Kirsten E Redborg, John G Antonakakis, Michael L Beach, Christopher D Chinn, and Brian D Sites.
• Department of Anesthesiology, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
• Reg Anesth Pain Med. 2009 May 1;34(3):256-60.

BackgroundThe tibial nerve provides the majority of sensation to the foot. Although multiple techniques have been described, there exists little evidence-based medicine evaluating different techniques for blocking the tibial nerve at the ankle. We hypothesized that an ultrasound (US)-guided tibial nerve block at the ankle would prove more successful than a conventional approach based on surface landmarks.MethodsEighteen healthy volunteers were prospectively randomized into this controlled and blinded study. Each subject was placed prone, and one ankle was randomly assigned to receive either an US-guided tibial nerve block (group US) or a traditional landmark-based tibial nerve block (group LM). The subject's other ankle then received the alternate approach. All blocks were performed with 5 mL of 3% chloroprocaine. We evaluated sensory and motor blocks. A successful block was defined as complete loss of sensation to both ice and pinprick at 5 cutaneous sites. Secondary outcome variables included performance times, number of needle passes, participant satisfaction, and presence of any complications.ResultsAt 30 mins, the block was complete in 72% of participants in group US as compared with 22% in group LM. At all times, the proportion of complete blocks was higher in group US. Ultrasound-guided blocks took longer on average to perform than traditional blocks (159 vs 79 secs; P < 0.001). There were more needle redirects in group US, with 8 subjects requiring 3 or more redirects versus none in group LM. Subjects preferred the US block 78% of the time (95% confidence interval, 52%-95%).ConclusionsIn healthy volunteers, US guidance results in a more successful tibial nerve block at the ankle than does a traditional approach using surface landmarks.

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