High-resolution peripheral quantitative computed tomography can assess microstructural and mechanical properties of human distal tibial bone

Abstract

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a newly developed in vivo clinical imaging modality. It can assess the 3D microstructure of cortical and trabecular bone at the distal radius and tibia and is suitable as an input for microstructural finite element (microFE) analysis to evaluate bone's mechanical competence. In order for microstructural and image-based microFE analyses to become standard clinical tools, validation with a current gold standard, namely, high-resolution micro-computed tomography (microCT), is required. Microstructural measurements of 19 human cadaveric distal tibiae were performed for the registered HR-pQCT and microCT images, respectively. Next, whole bone stiffness, trabecular bone stiffness, and elastic moduli of cubic subvolumes of trabecular bone in both HR-pQCT and microCT images were determined by microFE analysis. The standard HR-pQCT patient protocol measurements, derived bone volume fraction (BV/TV(d)), trabecular number (Tb.N*), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), and cortical thickness (Ct.Th), as well as the voxel-based direct measurements, BV/TV, Tb.N*, Tb.Th*, Tb.Sp*, Ct.Th, bone surface-to-volume ratio (BS/BV), structure model index (SMI), and connectivity density (Conn.D), correlated well with their respective gold standards, and both contributed to microFE-predicted mechanical properties in either single or multiple linear regressions. The mechanical measurements, although overestimated by HR-pQCT, correlated highly with their gold standards. Moreover, elastic moduli of cubic subvolumes of trabecular bone predicted whole bone or trabecular bone stiffness in distal tibia. We conclude that microstructural measurements and mechanical parameters of distal tibia can be efficiently derived from HR-pQCT images and provide additional information regarding bone fragility.

Fig. 1

The registered 2D gray-scale image (A, B), 3D thresholded image (C, D), and 3D cubic subvolume (E, F) of HR-pQCT and µCT images of human distal tibia. The first row shows the high-resolution µCT images, and the second row shows the corresponding HR-pQCT images.

Fig. 2

Correlations between microstructural measurements of HR-pQCT by patient and direct analysis and their respective µCT gold standards.

Fig. 3

Correlation between (A) whole bone stiffness, (B) trabecular bone stiffness, (C) elastic moduli, and (D) shear moduli of registered subvolumes of HR-pQCT and gold standard µCT images.