A noncontacting electromagnetic device for the determination of in vivo properties of bone.

A noncontacting, electromagnetic device to monitor stress waves in bone has been developed. Since bone exhibits piezoelectric-like behavior, a propagating stress wave in bone generates both electric and magnetic fields. The present device detects the magnetic field and thus provides a measure of the stress-wave amplitude in the bone. Excised dry and wet human femora, as well as a model system consisting of a bar of strongly piezoelectric ceramic, were examined using the device. Magnetic signals associated with elastic waves were also recorded in the long bones of human volunteers. Since the observed signals are not perturbed by the mechanical quality of the soft tissue over the bone, the device may be used to quantitatively assess the mechanical properties of bone in vivo.