Radiographic videodensitometry for quantitative monitoring of experimental bone healing

A method for non-invasive assessment of experimental bone healing in animals is described. Optimized radiographs were analysed by digital processing using a computer-based image analysis system. Values of the total mass were expressed as the equivalent mass of a simultaneously exposed aluminium roentgen-density reference. In order to assess the potential of the method, measurements were initially performed on phantoms and bone specimens. The systematic error was negligible. An excellent correlation (r = 0.999) was found between the densitometric weight (mu) and the corresponding dry weight (m) of the analysed bone samples and a calibration factor mu/m = 1.38 was established. The total random error was low, the coefficient of variation (CV) amounting to less than 5% or, if duplicate analyses were performed, less than 3%. The accuracy was not impaired when radiography was carried out with addition of water to mimic overlying soft tissue in the model. The method was applied to the assessment of callus mass longitudinally in vivo in the healing of a bone defect in the rabbit radius, yielding reproducible values (CV less than 5%) and a quantitative analysis of the healing sequence.