Quantification of fracture healing with three-dimensional computed tomography

Quantitative methods are necessary for an objective evaluation of fracture healing. Three-dimensional computed tomography (CT) for the measurement of callus volume and density could be such a method and was investigated in an animal model. In 23 goats a closed tibial fracture was created and stabilized with a cast. The animals were killed at 2, 4 and 6 weeks for radiographical, CT and biomechanical analysis. From the CT scans a three-dimensional reconstruction of the callus was made to measure its volume and mean density. At 2 weeks the callus volume had already reached its maximum. In contrast, callus density, torsional strength and torsional stiffness increased over time (P < 0.0001, analysis of variance, ANOVA). Multiple regression analysis showed that the callus volume was not related to the torsional properties. However, callus density was a significant explanatory variable for both torsional strength (R-2 = 0.72, P < 0.0001) and torsional stiffness (R-2 = 0.82, P < 0.0001). Therefore, callus density as measured by three-dimensional CT is a predictor of the extent of fracture consolidation. CT with three-dimensional reconstruction of the callus seems a valid technique for the quantification of fracture healing.