3D full-field lacunar morphology and deformation of calcified fibrocartilage in the loaded Achilles enthesis of a mouse

Abstract Enthesis calcified fibrocartilage (CFC) is a specialized structure anchoring tendon or ligament to bone and transmitting stresses from joint motion or muscle forces. Understanding the CFC 3D microstructure–mechanics relationship is key to explaining its mechanical behaviour, failure, and regeneration after injury. Such insights can guide biomaterial design and regenerative therapies. However, current methods cannot non-invasively measure localized mechanical behaviour within this anisotropic, heterogeneous insertion. In this research, full-field micromechanical structural analysis of a murine enthesis (n = 3) was conducted to understand the mechanics underlying its structural attributes using high-resolution in-situ micro-computed tomography with deep learning reconstruction and digital volume correlation. Our findings reveal that, depending on stress angle, the central region of the CFC lacunar morphology deforms more than other regions. We also identified that CFC microstructure organization and thickness strongly correlate with strain distribution at the interface, with regions of higher lacunar density experiencing greater deformation.