Relationship Between Toluidine Blue-stained Calcification Fronts and Tetracycline-labeled Surfaces in Normal Human Iliac Crest Biopsies

The relationship between toluidine blue-stained calcification fronts and tetracycline labeling was examined in iliac crest biopsies from 56 normal subjects aged 19-80 years, all of whom had received double tetracycline labeling. Sections were quantitated using an eye-piece graticule and all values were expressed as a percentage of osteoid surface. Values for double plus single tetracycline-labeled surfaces were lower than those obtained for toluidine blue-stained calcification fronts in 66% of subjects, although the difference between the two measurements was not statistically significant. Values obtained for calcification fronts demonstrated by toluidine blue staining were significantly greater than those obtained for single, double, and double plus half single tetracycline-labeled surfaces. No significant correlation could be demonstrated between toluidine blue-stained calcification and tetracycline-labeled surfaces. In conclusion, the fraction of osteoid bearing a tetracycline label differed from that showing a toluidine blue-stained calcification front and no correlation could be demonstrated between the two measurements. These differences may arise from methodological problems associated with their demonstration and identification; alternatively their lack of similarity might reflect uptake of stain and tetracycline at different sites within the calcification front. Which of the two parameters most accurately represents the active mineralizing surface is unknown.