Impact of the angle used in 2D Ultrasonography on the foetal femur diaphysis measurement

Objective: The purpose of this pilot study is to compare the 2D scanning measurement of the foetal femoral
diaphysis using anterior or lateral/external incidence at ultrasound.
Methods: In August 2016, 30 consecutive patients underwent a second trimester morphology ultrasound between
21 and 24 weeks of gestation by a senior sonographist. In each case, the femur length was measured either with an
anterior angle, estimating the straight aspect of the diaphysis or with a lateral angle, assessing its curved aspect.
The two measures were collected prospectively. The difference between paired measurements was calculated and
expressed in percentage (mm) and in percentile.
Results: The median difference between the two ultrasound angles in terms of femur length was 3,55% and in terms
of percentile variation was 17,16.
Conclusion: An anterior angle of measurement of the femur length seems to allow an optimal measure of the
straight and longest aspect of the diaphysis. According to our results, this angle should be considered when scoring
the quality of a morphological ultrasound, but further and larger studies should be done to confirm our hypothesis.