Purpose: We conducted this prospective, observational study using ultrasound to describe the neuro-vascular relationships at the femoral crease. In particular, we sought to identify and describe the incidence of vascular structures lying lateral to the femoral artery at this level, and the frequency with which needle insertion would require adjustment to avoid contact with these vessels during femoral nerve blockade (FNB).
Methods: Twenty-five patients undergoing surgery on the knee for femoral nerve block were scanned with ultrasound in the femoral triangle region to evaluate the anatomy of the vessels in this region. Specifically, the position and course of the profunda femoral and lateral circumflex arteries, and their relationship to the site of typical FNB, were described. Depth and dimensions of the vessels and nerves were recorded. The patients' body mass indices and the depth of the femoral nerve were evaluated for correlation.
Results: In 52% of the cases, the profunda femoral artery coursed lateral to the femoral artery, while in the others, it remained deep to the femoral artery. The profunda femoral artery emerged from the femoral artery above the femoral crease in 12% of the cases, and below it in the remainder, while the lateral circumflex femoral artery emerged above the crease in 8% of the patients. The site of needle insertion for FNB was adjusted to avoid vessels lateral to the femoral artery in 12% of the cases.
Conclusion: Ultrasound scanning at the femoral crease in preparation for FNB reveals branches lying lateral to the main femoral artery in a significant proportion of patients, presenting a significant risk of needle contact with one of these vessels. The use of ultrasound likely reduces the risk of vascular trauma in this setting.