Cortical parameters predict bone strength at the tibial diaphysis, but are underestimated by HR‐pQCT and μCT compared to histomorphometry. Issue 3 (20th October 2020)

• Record Type: Journal Article
• Authors: Schmidutz, Florian; Milz, Stefan; Schiuma, Damiano; Richards, Robert G.; Windolf, Markus; Sprecher, Christoph M.
• Is Part Of: Journal of anatomy. Volume 238:Issue 3(2021)
• Page Start: 669
• Page End: 678
• Publication Date: 2020-10-20
• Subjects: bone strength -- cortical porosity -- partial volume effect -- resolution -- thickness; Anatomy -- Periodicals; 571.3
• DOI: 10.1111/joa.13337
• Languages: English
• ISSNs: 0021-8782

Abstract

Abstract: Cortical bone and its microstructure are crucial for bone strength, especially at the long bone diaphysis. However, it is still not well‐defined how imaging procedures can be used as predictive tools for mechanical bone properties. This study evaluated the capability of several high‐resolution imaging techniques to capture cortical bone morphology and assessed the correlation with the bone's mechanical properties. The microstructural properties (cortical thickness [Ct.Th], porosity [Ct.Po], area [Ct.Ar]) of 11 female tibial diaphysis (40–90 years) were evaluated by dual‐energy X‐ray absorptiometry (DXA), high‐resolution peripheral‐quantitative‐computed‐tomography (HR‐pQCT), micro‐CT (μCT) and histomorphometry. Stiffness and maximal torque to failure were determined by mechanical testing. T ‐Scores determined by DXA ranged from 0.6 to −5.6 and a lower T ‐Score was associated with a decrease in Ct.Th ( p ≤ 0.001) while the Ct.Po ( p ≤ 0.007) increased, and this relationship was independent of the imaging method. With decreasing T ‐Score, histology showed an increase in Ct.Po from the endosteal to the periosteal side ( p = 0.001) and an exponential increase in the ratio of osteons at rest to those after remodelling. However, compared to histomorphometry, HR‐pQCT and μCT underestimated Ct.Po and Ct.Th. A lower T ‐Score was also associated with significantly reduced stiffness ( p = 0.031) and maximal torque ( p = 0.006). Improving the accuracy of Ct.Po and Ct.Th did not improve prediction of the mechanical properties, which was most closely related to geometry (Ct.Ar). The ex‐vivo evaluation of mechanical properties correlated with all imaging modalities, with Ct.Th and Ct.Po highly correlated with the T ‐Score of the tibial diaphysis. Cortical microstructural changes were underestimated with the lower resolution of HR‐pQCT and μCT compared to the histological 'gold standard'. The increased accuracy did not result in an improved prediction for local bone strength in this study, which however might be related to the limited number of specimens and thus needs to be evaluated in a larger collective. Abstract : Cortical bone loss has been identified as a main source of osteoporotic and age‐related bone substance loss and fracture risk. In this study, we evaluated the cortical microstructural properties of tibias with different imaging modalities (dual‐energy X‐ray absorptiometry [DXA], high‐resolution peripheral‐quantitative‐computed‐tomography [HR‐pQCT], micro‐CT [μCT] and histomorphometry) and directly compared them to their biomechanical properties. Notably, cortical parameters and especially Cortical Porosity (Co.Po) were underestimated with high‐resolution imaging CT compared to the 'gold standard' histology which in turn also allowed evaluation of osteonal remodeling activity. However, the improved analysis of cortical thickness and porosity did not result in an improvement in bone strength prediction. Cortical area still translated better into local bone strength indicating size and shape in a single parameter due to the simplicity of the geometry at this skeletal site.