Quantitative morphometry of the vertebrae and femur of the beagle as a function of age and sex/

New methodology was developed to study bone microradiographs on a television image analyzing system, The optimum exposure time for producing microradiographs of 100 micron ground bone sections with sufficient contrast for the quantitative television microscope was determined. The microradiographs were standardized by using a step wedge made from aluminum foil. The microradiographs produced from a bone section (cross-section of lumbar vertebra) ground in several steps from 120 to 70 microns were found to give the same morphometric measurements. With the use of the image editor light pen of the image analyzer (QTM-720) to separate cortical and trabecular bone, complete information of the bone was obtained from the serial cross-sections. The variations of the measurements were detected from one end of the bone to the other leading to the reconstruction of the bone and to a determination of the accuracy of selecting samples for a specific morphometric study. The first lumbar vertebra and the proximal femur from each of 14 beagles were chosen to study changes in morphometric parameters as a function of age and sex. In the cross-sections of the ventral vertebra the maxima of trabecular bone area, percent bone and surface area per volume of tissue were detected at the end potions; these values decreased gradually and had a minimum at the middle part of the main vertebral body. The specific bone surface was more or less uniform within the main vertebral body but dropped abruptly as it reached the end portions where the epiphysis was located. In contrast there were no significant changes in the measurements among sections in the dorsal vertebra; greater trabecular width and higher percent bone were characteristics of this portion. In the cross-sections of the proximal femur the head region had greater trabecular width and higher percent bone than the non-head portion; percent bone was nearly uniform within the head portion but decreased gradually from the proximal end of the non-head portion down into the shaft. The morphometric parameters and dimensions of the bones were presumed to be a function in response to stresses; the variations were observed in beagles of the same age and sex and to a higher degree in the proximal femur than in the vertebra. Bone is rapidly developing in the three month old beagles and could not be compared with the adults. No specific differences in measurements were detected in beagles from 17 months to 11 years, male and female. There was no indication of osteoporosis. Cross-sections of the vertebra and proximal femur showed isotropic orientation of the trabeculae while in the longitudinal sections anisotropic trabeculae were detected in all portions of the vertebra and the non-head portion of the proximal femur. The isotropic structures were preferred for study since the three dimensional measurements could be calculated from a universal k value of 4 over pi whereas in anisotropic structures the k value could not be given directly, since the anisotropy varied from section to section and within different regions of the same section.