Cortical parameters predict bone strength at the tibial diaphysis, but are underestimated by HR‐pQCT and μCT compared to histomorphometry

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.

Repairing a critical cranial defect using WISP1-pretreated chondrocyte scaffolds

“…Overall, in vivo data show that WISP1 pretreated chondrocyte scaffolds exhibit similar bone mass as untreated chondrocytes with improved structural parameters as trabecular thickness, periosteal surface, and perimeter and trabecular properties, previously shown to enhance bone strength. 26 – 30 Moreover, WISP1 primed chondrocytes exhibited superior MAD in defect edges and trabecular bone structures, the later which were also detected in untreated chondrocyte scaffolds. Interestingly, it was enough to introduce chondrocyte to the scaffold to detect trabecular bone formation, enhanced mineral intensity and improved anabolic activity via MAD analysis, at the defect edges.…”

“…The pretreatment of chondrocytes WISP1, appeared to further improve microstructural bone features, as judged by microCT analysis, potentially having an effect on bone strength. 26 – 30 …”

“…The pretreatment of chondrocytes WISP1, appeared to further improve microstructural bone features, as judged by microCT analysis, potentially having an effect on bone strength. [26][27][28][29][30] Histological evaluation of the defect revealed enhanced trabecular bone in chondrocyte seeded scaffolds Histological analysis monitored the distance of the unmineralized tissue within the defect (Figure 6(a) scheme), by measuring the distance between the edges and subtracting mineralized tissue islands from the total histological distance between fracture edges (Figure 6(b) images and graph). The data show WCS displayed the most statistically significant reduction in defect distance compared to BC and UCS (Figure 6(b)).…”