Ultrasound Description of the Sciatic Nerve

• The primary objective is to describe the appearance of the sciatic nerve and its location in relation to adjacent anatomic structures using ultrasound from the lateral mid-thigh position. [ Time Frame: 10 minutes ] [ Designated as safety issue: No ]
  

• A secondary objective is to describe correlations between any of the measured variables and the patient's mid-thigh circumference or weight. [ Time Frame: 10 minutes ] [ Designated as safety issue: No ]
  

The sciatic nerve block is frequently used for anesthesia or analgesia for surgery of the lower extremities. Ultrasound-guided sciatic nerve blocks performed at the lateral mid-femoral level have been successfully described with subjects in the supine position and the lower limb elevated in order to accommodate the ultrasound probe against the posterior aspect of the thigh. In the pediatric setting in which nerve blocks are commonly performed with the patient anesthetized rather than awake, we find this technique to be unwieldy as a single-operator technique. Using a more ergonomic approach that has not been previously described, we plan to identify and describe the sciatic nerve with the ultrasound positioned against the lateral aspect of the thigh. We hope to describe the appearance of the sciatic nerve and its location in relation to adjacent anatomic structures using this modified approach.

This a prospective cross-sectional study of 40 pediatric subjects 11-17 years of age. Three ultrasound images of the sciatic nerve will be obtained via the lateral mid-thigh approach in 40 pediatric patients scheduled to undergo sciatic nerve block - the first image prior to placement of the block, the second after the nerve is located by the stimulating needle and the third after the injection of local anesthetic.