[en] The enthesis allows the insertion of tendon into bone thanks to several remarkable strategies. This complex and clinically relevant location often features a thin layer of fibrocartilage sandwiched between tendon and bone to cope with a highly heterogeneous mechanical environment. The main purpose of this study was to investigate whether mineralized fibrocartilage and bone close to the enthesis show distinctive three-dimensional microstructural features, possibly to enable load transfer from tendon to bone. As a model, the Achilles tendon-calcaneus bone system of adult rats was investigated with histology, backscattered electron imaging and micro-computed tomography. The microstructural porosity of bone and mineralized fibrocartilage in different locations including enthesis fibrocartilage, periosteal fibrocartilage and bone away from the enthesis was characterized. We showed that calcaneus bone presents a dedicated protrusion of low porosity where the tendon inserts. A spatially resolved analysis of the trabecular network suggests that such protrusion may promote force flow from the tendon to the plantar ligament, while partially relieving the trabecular bone from such a task. Focusing on the tuberosity, highly specific microstructural aspects were highlighted. Firstly, the interface between mineralized and unmineralized fibrocartilage showed the highest roughness at the tuberosity, possibly to increase failure resistance of a region carrying large stresses. Secondly, fibrochondrocyte lacunae inside mineralized fibrocartilage, in analogy with osteocyte lacunae in bone, had a predominant alignment at the enthesis and a rather random organization away from it. Finally, the network of subchondral channels inside the tuberosity was highly anisotropic when compared to contiguous regions. This dual anisotropy of subchondral channels and cell lacunae at the insertion may reflect the alignment of the underlying collagen network. Our findings suggest that the microstructure of fibrocartilage may be linked with the loading environment. Future studies should characterize those microstructural aspects in aged and or diseased conditions to elucidate the poorly understood role of bone and fibrocartilage in enthesis-related pathologies.
Disciplines :
Engineering, computing & technology: Multidisciplinary, general & others
Author, co-author :
Tits, Alexandra ; Université de Liège - ULiège > Département d'aérospatiale et mécanique > Mécanique des matériaux biologiques et bioinspirés
Plougonven, Erwan ; Université de Liège - ULiège > Department of Chemical Engineering > PEPs - Products, Environment, and Processes
Blouin, Stéphane; Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling > Ludwig Boltzmann Institute of Osteology
Hartmann, Markus A.; Hanusch Hospital of OEGK and AUVA Trauma Centre Meidling > Ludwig Boltzmann Institute of Osteology
Kaux, Jean-François ; Université de Liège - ULiège > Département des sciences de la motricité > Médecine physique, réadaptation et traumatologie du sport
Drion, Pierre ; Université de Liège - ULiège > Département des sciences biomédicales et précliniques > Méth. expér. des anim. de labo et éthique en expér. anim.
Fernandez, Justin; Auckland Bioengineering Institute - ABI > Faculty of Engineering > Musculoskeletal Modelling Group
van Lenthe, G. Harry; Katholieke Universiteit Leuven - KUL > Department of Mechanical Engineering > Biomechanics Section
Ruffoni, Davide ; Université de Liège - ULiège > Département d'aérospatiale et mécanique > Mécanique des matériaux biologiques et bioinspirés
Language :
English
Title :
Local anisotropy in mineralized fibrocartilage and subchondral bone beneath the tendon-bone interface
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