Prediction of strength of cortical bone in vitro by microcomputed tomography

Objective. The aim of this study was to evaluate the predictive value of bo ne mineral density and intracortical porosity measured by micorcomputed tom ography for the strength of cortical bone biopsies. Design. Experimental study comparing the predictive value of bone mineral d ensity and of intracortical porosity determined in vitro by microcomputed t omography for the mechanical properties of cortical bone cylinders. Background. The assessment of cortical bone strength might be relevant for the prediction of fracture risk or the choice of suitable therapy strategie s in orthopaedic surgery. The predictive value of cortical density for the mechanical properties is discussed controversially. The relevance of intrac ortical porosity measured by histomorphometry has been established, but the predictive value of porosity determined by microcomputed tomography remain s to be explored. Methods. Femoral cortical bone specimens from the mid diaphysis of 24 patie nts were harvested during total hip replacement procedure at the location, where a diaphyseal hole (circle divide4.5 mm) was drilled in order to reduc e the intramedullary pressure. In vitro intracortical porosity and bone min eral density measurements by microcomputed tomography were compared with st rength and elastic modulus assessed by a compression test transverse to the Haversian systems of the same specimens. Results. Significant negative correlations were found between porosity meas ured by microcomputed tomography scans and yield stress, stiffness and elas tic modulus (P < 0.001), however, the positive correlations between bone mi neral density and mechanical parameters were stronger (P < 0.0001). The mec hanical parameter best predicted by mineral density as well as by porosity was yield stress (r = 0.72, P < 0.0001; r = -0.64, P < 0.001), Conclusions. Bone mineral density determined by microcomputed tomography im aging in vitro may be a potent method to predict mechanical properties of c ortical bone non-destructively. The application in vivo remains to be explo red.