The femur is the longest bone in the human body, extending from the hip to the knee. In obstetric ultrasound, measuring the femur length is one of the four standard biometric measurements used to estimate gestational age and fetal weight. The femur is measured from the greater trochanter to the distal metaphysis, excluding the femoral epiphysis. A femur length that is significantly shorter than expected for gestational age can suggest skeletal dysplasia, chromosomal abnormalities like Down syndrome, or fetal growth restriction. In postnatal musculoskeletal ultrasound, the femur and its surrounding soft tissues are evaluated for fractures, muscle tears, and other injuries.
Sonography Term