Quantitative assessment of mineralization in distraction osteogenesis

Objectives: The most important decision in distraction osteogenesis is the timing of fixator removal. Various methods have been tried, such as radiographic appearance of callus and bone mineral density (BMD) assessment, but none has acquired gold standard status. The purpose of this study was to develop another objective method of assessment of callus stiffness to help clinicians in taking the most important decision of when to remove the fixator. Materials and methods: We made a retrospective study of 70 patients to compare the BMD ratio and pixel value ratio. These ratios were calculated at the time of fixator removal, and Pearson's coefficient of correlation was used to show the comparability. Inter- and intra-observer variability of the new method was also tested. Results: Good correlation was found between BMD ratio and pixel value ratio, with a Pearson's coefficient of correlation of 0.79. The interobserver variability was also low, with high intra-observer reproducibility, suggesting that this test was simple to perform. Conclusion: Pixel value ratio is a good method for assessing callus stiffness, and it can be used to judge the timing of fixator removal.