Prediction of breaking strength in osteoporotic avian bone using digitizedfluoroscopy, a low cost radiographic technique

Bone fragility in caged laying hens is a severe welfare problem, with fract ure incidences in commercial flocks of up to 30% of all hens during their l ife. This fragility has been attributed to osteoporosis, the etiology of wh ich is multifactorial in birds, as in humans, with genetic, environmental, and nutritional components. Greater under standing of the development of th e disorder in hens could be obtained from the same kind of in vivo assessme nts available in human studies of osteoporosis. These high technology techn iques for evaluation of bone mineral density (BMD), such as single or dual energy X-ray absorptiometry (SXA or DXA), quantitative computerized tomogra phy (QCT), or attenuation by ultrasound (US), are so far not widely availab le to nonclinical researchers. We have modi fled an older X-ray film techni que, radiographic absorptiometry (RA) by digitization of the analog video s ignal from a Philips BV-25 image intensifier, in single pulse fluoroscopy m ode, and subsequent computer analysis with the public domain software packa ge, NIH-Image 1.60. Compared with conventional RA, which uses standard X-ra y film, our modified technique reduces X-ray exposure and allows the operat or to digitize, store, and analyze many more images in a shorter time. We h ave called this modified technique "digitized fluoroscopy" (DF). In a longi tudinal study of humeral radiographic density in a flock of 165 laying hens , significant relationships (P < 0.001) were observed between assessments m ade as early as 25 weeks, utilizing this DF technique in the humerus, and b reaking strengths land other postmortem indicators of osteoporosis) measure d at 70 weeks. We conclude that DF can predict some eventual parameters of bone mass measured at 70 weeks from 25 to 40 weeks onward in bones from the same site in laying hens. The relationship between DF measurements made in the humerus and postmortem measurements of radiographic density and breaki ng strength made at another site (tibia) are less strong but still signific ant from 40 weeks onward.