QUANTITATIVE ASSESSMENT OF EXPERIMENTAL FRACTURE REPAIR BY PERIPHERALCOMPUTED-TOMOGRAPHY

An experimental fracture model was used to assess bone mineral density at the fracture site by peripheral computed tomography and to compare the model with biomechanical, histological, and radiographic methods for the quantification of the fracture repair process. Transverse oste otomies in the mid-diaphysis of 28 tibia of sheep were externally fixe d and mineral densities, cross-sectional areas, flexural rigidities, t issue composition, and projected callus area were calculated after 9 w eeks of healing time. BMD measured by pQCT was strongly correlated wit h histologically determined percentages of mineralized tissue in the o steotomy gap (R(2) = 0.71) and in the periosteal callus (R(2) = 0.62). The percentage of mineralized tissue in the osteotomy gap was the bes t predictor of the flexural rigidity of the tibiae (R(2) = 0.74). Beca use of high correlations with the histological findings, the volumetri c BMD at the level of the osteotomy gap was also strongly correlated w ith the biomechanical findings (R(2) = 0.70). Neither the cross-sectio nal area in pQCT nor the projected callus area in plane film radiograp hy were positively correlated to the flexural rigidity of the tibiae. Quantitative computed tomography proved to be a successful estimator f or the prediction of the mechanical stability of healing bones. The no ninvasive procedure is a reliable tool for the quantification of the f racture repair process in experimental studies and may be useful for t reatment decisions in particular clinical situations.