Anatomical landmarks for femoral nerve block: A comparison of four needle insertion sites

The site for needle insertion in femoral nerve block varies significantly a mong various descriptions of the technique. To determine the site with the highest likelihood of needle-femoral nerve contact, femoral nerve block was simulated in a human cadaver model (17 femoral triangles from 9 adult cada vers). Four 20-gauge 50-mm-long styletted catheters were inserted at four f requently suggested insertion sites for femoral nerve block. At the levels of inguinal ligament and the inguinal crease, the catheters were inserted a djacent to the lateral border of the femoral artery and 2 cm lateral to the femoral artery. During anatomical dissection, we studied the number of cat heter-nerve contacts for each of the four insertion sites, and relationship s between the femoral nerve and other anatomical structures of relevance to femoral nerve block. Insertion of the needle at the level of the inguinal crease, next to the lateral border of the femoral artery resulted in the hi ghest frequency of needle-femoral nerve contacts (71%). Of note, the femora l nerve was significantly wider (14.0 vs 9.8 mm) and closer to the fascia l ata (6.8 vs 26.4 mm) at the inguinal crease than at the inguinal ligament l evel. We conclude that needle insertion at the inguinal crease level immedi ately adjacent to the femoral artery produced the highest rate of needle-fe moral nerve contacts. The main factors influencing this result include the greater width of the femoral nerve and the more predictable femoral artery- femoral nerve relationship at the inguinal crease level, compared with the inguinal ligament level. Implications: Insertion of a needle at the inguina l crease level and immediately adjacent to the lateral border of the femora l artery results in a high rate of needle-femoral nerve contact.