Abstract ID: A17
Abstract Title: Vascular relationships of the femoral nerve at the inguinal region.
Poster Type: Poster
ABSTRACT BODY
Introduction: Femoral nerve blockade is widely utilized for management of acute postoperative pain after knee surgery (1). Intravascular injection of local anesthetic must be carefully avoided due to the proximity of the nerve to major vessels. Palpation of the arterial pulsation allows one to avoid the femoral artery, but smaller vessels exist in this region(2), which will not be readily palpable. This investigation characterizes the relationships of the femoral nerve and vascular strutures in the femoral triange. In particular, the presence of the lateral circumflex artery (LCA) and its proximity to the nerve at the inguinal crease was evaluated, as this may present a particular risk of intravascular injection.
Materials and Methods: After approval of the proposal by the University of Pittsburgh Committee on Research Involving the Dead, 40 femoral triangle dissections were conducted on preserved cadavers. The skin, fascia lata and fascia iliacus were sharply dissected and the femoral nerve (FN) exposed. The vascular sheath was entered and blunt dissection utilized to expose the femoral artery (FA) and vein and their branches including the LCA. The relationships between nerves and vessels, and the depth from skin surfact to these structures, was noted and measured.
Results: in 20 out of the 40 dissections (50%), the LCA was located at or within 1 cm of the inguinal crease. Other relationships include:
Interval Measured Mean Distance in cm (std dev)
FA to FN at inguinal ligament 1.2 (0.4)
Skin to FN at inguinal ligament 2.2 (0.5)
FA to FN at inguinal crease 1.4 (0.3)
Skin to FN at inguinal crease 1.1 (0.5)
Inguinal ligament to inguinal crease 5.1 (1.0)
Ingiunal ligament to LCA 5.7 (1.2)
Skin to LCA (depth) 1.7 (0.8)
Discussion: The FN lay deeper at the inguinal ligament than at the inguinal crease, consistent with the findings of other investigators (3). Considerable variability was found in the relations of the FN and vessels in the femoral triangle. Other studies have not characterized the positions of LCA and its accompanying vein, which course laterally from the FA and FV in the femoral triangle. These are not detectable by palpation ,and may pose a hazard of intravascular injection despite needle insertion at a safe distance from the FA. In one study of femoral nerve blockade, the authors encountered vascular puncture lateral to the FA in 6% of patients (4). Thus, appreciation of these anatomic relationships may prove useful to the regional anesthesiologist.
References:
1. Gligorijevic S. Techniques Reg Anesth Pain Manag 2000;4:3036.
2. Moore KL and Dalley AF. Clinically Oriented Anatomy (4th edition). Lippincott, William and Wilkins, 1999, pp. 543-5.
3. Vloka JD, Hadzic A, Drobnik L, et al. Anesth Analg 1999;89:1467-72
4. Vloka JD, Hadzic A, Drobnik L, et al. Anesthesiology 1998;89:3A,A861.
ATTACHED FILES
Reg Anesth Pain Med 2004; 29(2):A17