|| Checking for direct PDF access through Ovid
An experiment was designed to determine whether the material properties of fracture callus can be predicted by the measurement of mineral density. Rat tibiae that had a closed fracture were used to obtain uniform specimens of fracture callus at sequential stages of healing. An in vitro indentation test was done and tissue was biopsied, using a trephine, to determine the hardness and calcium content of a standardized area of callus tissue. The hardness of the callus was correlated with the mineral density of the local tissue, which initially had been measured non-invasively with single-photon-based micro-bone densitometry. The progress of differentiation and remodeling of callus was determined by comparative planimetric and microradiographic analyses of tissue. Determinations of density showed a linear correlation with concentrations of a hydroxyapatite equivalent solution (r = 0.997, p less than 0.001), with the ash weight of control specimens of cortical-trabecular bone (r = 0.998, p less than 0.001), and with the calcium content (micrograms per cubic millimeter) of the fracture callus (r = 0.854, p less than 0.001). The hardness of the callus had a non-linear relationship (r = 0.959, p less than 0.005) with the mineral density per volume of tissue, as measured by micro-bone densitometry. Clinical Relevance: The appearance of fracture callus on conventional radiographs is an important clinical finding in the assessment of fracture-healing. It is, however, an unreliable predictor of the strength of the union of the fracture. Three-dimensional imaging and quantification of bone mineral provide additional data about the quality and geometry of fracture callus. Our study showed that mineral content per unit of volume is a good index of hardness of the fracture callus. Thus, quantitative imaging may be useful clinically for monitoring fracture-healing.