Digital radiography - A predictor of regenerate bone stiffness in distraction osteogenesis

The newly formed regenerate bone during limb lengthening usually is assesse d by observing standard plain radiographs. However, no objective data corre late the radiographic appearance with the quantitative strength of the newl y formed bone. A noninvasive method was developed to assess the regenerate bone using digital radiography, The investigations were performed in a micr opig animal model. The right tibia was distracted for 10 days at 2 mm per d ay, Digital radiography was performed after the distraction during a 10-day consolidation period, For quantitative analysis, an aluminum step wedge wa s placed on all images, and a region of interest was outlined in the regene rate bone, A calibration curve was calculated by measuring the correspondin g gray values of the aluminum phantom, The calibration equation was used fo r determining the mean density in the region of interest. This method was s ensitive in assessing day to day healing progress, The measurements taken t he day before sacrifice were compared with torsional mechanical data using a material testing machine. The high correlation between the densimetric ev aluations and the biomechanical data suggests this method is a useful tool for in vivo assessment of the regenerate bone during the consolidation peri od in distraction osteogenesis.