Tiffany Tavernier

 L4-S3 spinal nerve roots  Largest nerve trunk in the human body  Distribution = hamstrings, long head of biceps femoris, adductor magnus; part of hip and knee joint  Blocks skin of posterior aspect of thigh and entire leg below knee exception of skin of medial aspect of lower leg

 Classical Posterior Approach › Pt lies in lateral decubitus position › Landmarks: greater throchanter and posterior-superior iliac spine › Needle is inserted 4-5 cm distal to midpoint btw the two landmarks perpendicular to skin in all planes  Parasacral Approach › Pt lies in lateral decubitis position › Landmarks: posterior superior iliac spine and ischial tuberosity › Needle is inserted 6cm caudal to line btw the 2 in sagittal plane

 Lithotomy › Pt is supine with hip flexed and upper leg perpendicular to torso › Landmarks: greater trochanter of femur and ischial tuberosity › Needle is inserted 4 cm in claudal direction midway between the 2 › Needle is advanced parallel to horizontal plane  Anterior approach › Pt is supine with legs extended › Landmarks: femoral crease and femoral arterial pulse › Needle inserted 405 cm distal from pulse of femoral artery and perpendicular to line of femoral crease

 100 pts undergoing minor knee surgery  Randomly divided by envelope to receive anterior or posterior approaches combined with femoral and lateral femoral cutaneous nerve blocks using US  1% mepivacaine with short 1100m, 21 gauge  Block: 20mL of 1.5% mepivacaine with 1:400,000 epinephrine Anterior Approach  Nerve stimulator was 2Hz to elicit foot plantar- or dorsiflexion Posterior Approach  Same as anterior, but without nerve stimulator.

 both then placed in supine position with legs extended and femoral and lateral femoral cutaneous blocks were performed  Measurements of depth and size of sciatic nerve, needle depth, block execution time for sciatic nerve block, block execution time for all 3 blocks, time required for onset of sensory and motor blocks of sciatic nerve and duration of blockade of sciatic nerve were measured

 Sciatic nerve was located deeper in anterior approach  Both had similar block execution time for sciatic nerve block, but anterior approach took less time to complete all 3 blocks  Onset of sensory block for superficial peroneal, sural and tibial nerves was similar  Sensory block of posterior femoral cutaneous nerve was achieved less often with the anterior approach - less block of posterior area of thigh  Onset of motor block was similar with both approaches

 Although posterior femoral cutaneous nerve was rarely blocked with anterior approach, can still be used in knee surgery where thigh tourniquet is used  pts who required fentanyl was similar btw groups  tourniquet pain is not affected by presence of posterior femoral cutaneous nerve block