Simple external rotation of the leg increases the size and accessibility of the femoral vein

Objective: To determine if external rotation of the leg increases the size and accessibility of the femoral vein compared with a neutral position.

Methods: One hundred patients presenting to a tertiary teaching hospital were prospectively recruited. The right common femoral vein of each subject was scanned with a linear probe (5-10 MHz) inferior to the inguinal ligament, with the leg in a neutral position and then in the externally rotated position. The transverse diameter of the femoral vein, the accessible diameter of the vein (lying medial to the femoral artery) and the depth of the vein were measured.

Results: The mean diameter of the femoral vein in the externally rotated leg was greater than with the leg in the neutral position (15.4 mm vs 13.8 mm); the mean difference was 1.6 mm (95% CI 1.3-1.9). The mean accessible diameter of the femoral vein was larger with the leg externally rotated (13.8 mm vs 11.7 mm, mean difference 2.1 mm, 95% CI 1.8-2.5). The depth from the skin to the femoral vein was less with the leg in external rotation (20.9 mm vs 22.6 mm, mean difference 1.7 mm, 95% CI 1.2-2.2). The mean diameter and depth were greater in patients with overweight or obese body mass index (BMI) measurements in both leg positions. The increase in femoral vein diameter and accessibility with external rotation was observed in all BMI groups.

Conclusion: The total and accessible femoral vein diameter is increased and the surface depth of the vein is decreased by placing the leg in external rotation compared with the neutral position.