Non-invasive measurement of long bone cross-sectional moment of inertia by photon absorptiometry.

The use of the Norland-Cameron Bone Mineral Analyzer (BMA) to measure the cross-sectional moment of inertia of the mineral in a long bone is described and data regarding the usefulness and precision of the method are presented. The correlation coefficients between BMA-measured CSMI and that obtained from cross-sectional geometry were 0.99 both for a series of aluminum tubes and five bones of different sizes. The BMA-measured CSMI was linearly correlated with the CSMI digitized from cross-sections of a series of human ulnas at the r = 0.92 and 0.95 level in the AP and ML directions, respectively. The BMA-measured CSMI also correlated well with the torsional and bending behavior of ulnar specimens. Finally, a method for estimation the CSMI of a long bone section from BMA readings of mineral content and bone width is described. A linear correlation of r = 0.98 with the CSMI digitized from sections of human radii is demonstrated.