Relationships between bone strength and bone quality: three-dimensional imaging analysis in ovariectomized mice

Abstract

Objectives

Low-energy trauma resulting in fractures of the distal femur is often observed in elderly patients with osteoporosis; such fractures are often associated with treatment difficulties and poor prognosis. The purpose of this study was to clarify the factors that affect the bone strength of the distal femur.

Methods

We used ovariectomized mice to demonstrate bone quality factors associated with deterioration of the strength of the distal femur. Ten-week old ICR-strain mice were ovariectomized or sham-ovariectomized. Total bone mineral density (BMD), total bone area, cortical BMD, cortical thickness, and trabecular BMD were measured by peripheral quantitative computed tomography in the distal metaphyseal region of the femora. As three-dimensional architectural parameters, the trabecular number, trabecular thickness (Tb.Th), trabecular separation, and connectivity density were measured in the same region by microcomputed tomography. The maximum load measured by compression testing of the distal metaphyseal region was regarded as the bone strength of each sample.

Results

No significant differences in total bone area or in cortical BMD were found between the groups. Bone strength showed the closest relationship with total BMD (r = 0.834). Multiple regression analysis demonstrated that total BMD greatly depended on cortical thickness. The addition of Tb.Th to trabecular BMD markedly reflected bone strength (R = 0.857), suggesting that Tb.Th affected bone strength more significantly than trabecular BMD.

Conclusions

These findings suggested that deterioration of bone strength of the distal femur (metaphysis) was not caused by a reduction in cortical BMD, but was related to reduced cortical thickness, which reduced total BMD, and to trabecular BMD and architecture, in particular to reduced Tb.Th.