Stochastically simulated assessment of anabolic treatment following varying degrees of cancellous bone resorption

The aim of this study was to investigate the recovery in cancellous bone stiffness resulting from anabolic treatment following varying degrees of resorption, using a stochastic simulation applied to a simplistic structure consisting of five vertical and five horizontal trabeculae. The structure was initially resorbed, and “bone” elements were stochastically removed until nominal resorptions of 10%, 15%, 20%, 25%, and 30% were achieved. A stochastic simulation of anabolic treatment was then applied where bone elements were added, continuing until the original stiffness had been regained, for example, simulating treatment of a patient with an anabolic agent after a period of postmenopausal resorption. The resorption and anabolic simulations were repeated three times for each of the nominal resorptions. The stiffness of the bone structure decreased linearly with resorption, with a slope of approximately −2 and an R 2 of 97.0%; hence, the stiffness fell at approximately twice the rate of the reduction in density. When the various structures regained their original density, the resultant stiffness also had a linear relationship with the original resorption, with a slope of −1 and a lower R 2 of 86.1%. This implies that the reduction in stiffness, when original density was regained, fell proportionately with the degree of initial resorption and, therefore, after a resorption of 30%, when original density was regained, the stiffness of the resultant structure was approximately 30% less than that of the original structure. The density required for the original stiffness to be regained increased linearly with the degree of initial resorption, with a slope of approximately 0.5 and an R 2 of 65.2%, lower than that observed for the previous relationships. This indicates a greater spread of data and suggests greater variability in the formation phase beyond the point of regained original density. Because irreversible connectivity reduction is widely considered to be one of the earliest manifestations of estrogen loss, these findings, although obtained on a simulation of a simplistic cancellous bone structure, support the concept of early intervention to prevent potentially irreversible deterioration of trabecular architecture after menopause.