Correlations between orthogonal mechanical properties and density of trabecular bone: use of different densitometric measures.

To compare the numerous modulus-density and strength-density relations that have been found for human trabecular bone from the proximal tibia, correlations between various measures of density were sought. Hydrated and dry apparent density, ash density, and density from quantitative computed tomography (QCT) were determined for cubic trabecular specimens taken from the proximal portion of human tibiae, and correlations between these measures were found (r > 0.99, P < .001). Orthogonal moduli and strengths of the specimens were measured mechanically, and were significantly correlated with ash density according to power relations (r > or = 0.85, P < .001). The strong correlation between density from QCT and ash density indicates that these measures can be used with nearly equal precision in estimating modulus and strength of tibial trabecular bone. Equations between mechanical properties and density reported in previous studies were converted to use a common density measure and, after considering the effects of specimen size, were in general agreement with results of the present study.