Comparison of 2D and 3D bone microarchitecture evaluation at the femoral neck, among postmenopausal women with hip fracture or hip osteoarthritis

Abstract

Objectives: High resolution peripheral quantitative tomography (HR-pQCT) is used more widely to assess microarchitecture, but we are lacking comparisons between HR-pQCT and histomorphometry, which is considered the gold standard. They have only been assessed on different anatomical regions. The purpose of our study was to assess the microarchitecture and the relative contribution of cortical and trabecular bone in hip fracture with this 3D imaging technique, compared with the 2D histomorphometry.

Material and methods: We compared the distribution of cortical and trabecular bone in the ultradistal femoral neck samples (~3mm thick) obtained after total hip replacement in 21 hip osteoarthritis (HOA, 66±8yrs) and 20 hip fracture (HF, 79±8yrs) menopausal women by a direct 3D evaluation method (HR-pQCT: XtremeCT, Scanco Medical AG) and by histomorphometry, performed and averaged on three 10μm-thick sections 800μm apart.

Results: Significant correlations were found between both techniques for trabecular bone volume, number, thickness, separation and cortical thickness (0.51<r'<0.81, p<0.01). The connectivity was also significantly correlated (r'=0.58, p<0.001) between both techniques, as well as the trabecular bone pattern factor measured in 2D with the structural model index (SMI) measured in 3D (r'=0.62, p<0.001). However HR-pQCT overestimated the absolute value of most parameters, with higher values being even more overestimated. The agreement between the two techniques was weak for cortical porosity. With the 3D measurements we found that trabecular bone volume was 43% lower in HF than HOA (p<0.01), associated with loss of trabecular connectivity (-50%, p<0.01) and a more rod-like structure (SMI, 22%, p<0.01), mainly at the inferior (34%, p<0.01) and posterior (22%, p<0.05) quadrants. Cortical thickness was found to be lower in the posterior quadrants (-22%, p<0.05) and tended to be lower in HF than in HOA at the inferior quadrant (-14%, p=0.08), but it was still the highest at the inferior quadrant in both groups. In conclusion, 3D methods confirmed the alteration of trabecular and cortical bone found by histomorphometry in HF compared with HOA and the frequency of the rod-like structure in HF.