The evaluation of cortical bone remodeling with a new ultrasonic technique

Three complementary techniques were used to study the local adaptive remodeling of bone due to hip prosthesis implantation. A graphics package was used to obtain second geometrical information, an ultrasonic wave propagation technique to determine elastic properties, and a scanning acoustic microscope (SAM) to map the acoustic impedance profile of each section. The effects of the implantation of two different types of hip prostheses were investigated. The two types were an uncemented bipolar prosthesis with an Austin-Moore-type stem and a cemented Charnley prosthesis. Prosthesis implantation resulted in an increase in cortical area and medio-lateral diameter and a decrease in anterio-posterior diameter. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.