Ultrasound as a tool for assessment of bone quality in the horse.

A simple non-invasive method is described for calculating the transverse apparent velocity of sound of horse bone. This was achieved, both in vivo and at post mortem examination using the metacarpal bone and its covering soft tissue. On 34 post mortem specimens (ie, 68 limbs) from horses older than one year an average measurement of 2802 +/- 37 (1sd) m/sec was obtained. There were changes noted according to age and at different sites on the shaft of the metacarpus. The highest readings were obtained in the proximal shaft where the cortex was thickest. The velocity values gradually decreased towards the distal end where the cortex was thinner, particularly in animals less than 12 months old. The soft tissue component of the velocity measurement was uniform throughout the length of the metacarpus and effectively decreased the apparent velocity of the bone alone by about 170 m/sec (6 per cent). The shortest flight path of the ultrasound beam was found to be through the midcortical region of the metacarpal shaft. A good correlation was obtained between velocity of sound measurements and bone mass. Furthermore partial demineralisation of specimens from the mid-metacarpal region caused a considerable reduction in the apparent velocity of sound. In a series of young thoroughbreds (n = 52) measured in vivo the apparent velocity of sound increased from around 2650 m/sec at six months to approximately 2880 m/sec at three years.(ABSTRACT TRUNCATED AT 250 WORDS)