THE EFFECT OF FRACTURE AND FRACTURE FIXATION ON ULTRASONIC VELOCITY AND ATTENUATION

Measurement of the velocity of propagation and atttenuation of ultraso und (200 kHz) is believed to be a useful non-invasive technique for as sessing the mechanical properties of bone. A new method for the determ ination of ultrasound velocity and attenuation of longitudinal waves i n cortical bone was used in vivo and in situ on intact and fractured h uman tibiae. The measured ultrasound attenuation and velocity were fou nd to be unaffected by the soft tissue between transducers and bone. T he ultrasound velocity in vivo on control tibiae was 3614 +/- 32 m s(- 1) and the attenuation was 5.52 +/- 0.43 dB MHz(-1) cm(-1). The ultras ound velocity in fractured tibiae was considerably lower 1 week after fracture (2375 +/- 82 m s(-1)), but had significantly increased after 3 weeks (to 2882 +/- 90 m s(-1)). A higher attenuation was measured 1 week after fracture (17.81 +/- 3.91 dB MHz(-1) cm(-1)), but it had dec reased again 3 weeks after fracture (10.42 +/- 3.56 dB MHz(-1) cm(-1)) . In situ studies under well-defined conditions confirmed the in vivo results. The effects of internal plate fixation and gradually cutting through the cortex on the ultrasound velocity and attenuation were stu died in situ. These results demonstrate the clinical potential of this technique for the non-invasive assessment of bone fracture healing.