Comparison of Perineural Catheter Depth for the Continuous Popliteal Nerve Block Using Ultrasound Guidance and Dermabond

Traditionally for the lower extremity, peripheral nerve catheters have been threaded greater than or equal to 5 centimeters past the tip of the Tuohy needle. The major rational for this practice is to reduce dislodgement. However, the greater the distance that a catheter is advanced, the greater the risk of contacting undesired structures, kinking, looping and knotting. For the continuous popliteal nerve block, the catheter is threaded perpendicular to the course of the nerve. This could result in the tip of the catheter being a significant distance from the targeted nerve which may lead to a decrease in the success rate or efficacy of the block. Greater efficacy may be seen if the needle is closer to its target. This may be quantified by documenting a faster onset of motor and sensory changes and/or a lower catheter infusion rate required to maintain pain control. The study will investigate the difference in success rate between popliteal peripheral nerve catheters placed at 1 centimeter compared to 5 centimeters past the tip of a Tuohy needle.