No abstract

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)

No abstract

Summary The current methods for non‐invasive measurement of bone quality are reviewed. In the horse this has traditionally involved the use of radiography, but there are now two other modalities available for the critical evaluation of cortical bone quality and strength. These utilise single photon absorptiometry and ultrasound velocity. Photon absorptiometry gives a direct measurement of bone mineral content, by using a monoenergetic radionuclide source, and transverse ultrasound velocity in bone gives a measure of bone stiffness or elasticity. They can both be used conveniently on the metacarpus of the conscious horse. Both ultrasound velocity and bone mineral content can be used as accurate indicators of skeletal maturity. In addition, the effects of disuse on bone and certain types of lameness can be monitored accurately. Preliminary data show an association with exercise in young and mature horses. There also appears to be considerable scope for in vivo research of bone changes in horses produced by immobilisation, weightlessness, exercise and nutrition.

A safe, non-invasive method for the accurate measurement of bone mineral content in the third metacarpal bone of the horse is described. The technique involves scanning the bone with a single photon beam from an Americium-241 source. Data were obtained from the excised metacarpal bones from both forelimbs of 50 normal and seven lame horses. Measurements were made in vivo on eight normal and seven lame horses and on one experimental horse with osteopenia induced by partial weightlessness in a flotation tank. In the normal horses bone mineral content altered with age, particularly in the first six months of life. There were also differences according to the site of scanning on the metacarpus. The contribution of the splint bones to the total bone mineral content was less than 2 per cent distal to the mid-point of the metacarpus, but in the proximal shaft it increased to 12 per cent. No significant differences were noted either between right and left limbs, or between male and female animals. A reduction in bone mineral content was demonstrated in the affected leg of horses with chronic lameness and with osteopenia induced by weightlessness. The bone mineral content (g/cm) correlated well with the ash content (mg/100 mg dry bone weight), the specific gravity and the apparent transverse velocity of ultrasound (m/sec) through the bone. A measure of bone mineral density (g/cm3) was calculated from the bone mineral content and cross sectional area of the bone to overcome the individual differences in size of the metacarpus.