[Changes in the Femoral Vein Diameter due to Lower Limb Flexion]

The purpose of this study was to in- vestigate the changes in the femoral vein (FV) diam- eter and the positional relationship during lower limb flexion using ultrasonography.

Twenty five male healthy volunteers were positioned in the supine and the hip joint was flexed to the target angles, followed by external rota- tion and abduction of the hip joint (hemi-frog-leg posi- tion). The flexion angle of the hip joint was mea- sured: before flexion (control), and at 30', 450, 60*, 75* flexion. The ultrasonograph transducer was held over the line which was 2 cm distal and parallel to the inguinal ligament Results: Compared with controls, the distance from the skin to the anterior wall of the FV was signifi- cantly shorter at 30 (15.1 mm vs 13.3 mm, P<0.01) and longer at 75" (15.1 mm vs 16.4 mm, P<0.03). The exposed width of the FV (length not overlapped by the femoral artery) was longest at 300(9.9 mm vs 12.1 mm, P<0.01).

This study demonstrated that the hemi-frog-leg position was associated with significant increases in the diameter and exposed width of the FV. In particular, the most effective angle of the hip joint flexion was about 30*.