Measurement of the velocity of ultrasound in the human femur in vivo.

A pulse-echo technique for measuring the velocity of ultrasound in the cortex of the femur in vivo is presented. The average result for 27 asymptomatic volunteers is 3250 +/- 190 m/s. The results show no significant differences between proximal and distal femoral sites, right and left femora, males and females. There is also no significant difference between the velocity of sound in the femur and in the radius in normal volunteers. The reproducibility of the time of flight measurement for three volunteers is found to be about 2%, and the total uncertainty of the femoral velocity of ultrasound measurement is determined to be 4% for proximal sites and 7% for distal sites. As the femur is a load-bearing bone, the site of frequent fracture both in the elderly and in the osteoporotic, the measurement of the velocity of sound at this new site may be of great value in investigating these conditions and may ultimately be helpful in assessing "quality" of the femoral cortex in those patients undergoing total hip or knee replacement.