The Role of Matrix Composition in the Mechanical Behavior of Bone
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Purpose of Review
While thinning of the cortices or trabeculae weakens bone, age-related changes in matrix composition also lower fracture resistance. This review summarizes how the organic matrix, mineral phase, and water compartments influence the mechanical behavior of bone, thereby identifying characteristics important to fracture risk.
In the synthesis of the organic matrix, tropocollagen experiences various post-translational modifications that facilitate a highly organized fibril of collagen I with a preferred orientation giving bone extensibility and several toughening mechanisms. Being a ceramic, mineral is brittle but increases the strength of bone as its content within the organic matrix increases. With time, hydroxyapatite-like crystals experience carbonate substitutions, the consequence of which remains to be understood. Water participates in hydrogen bonding with organic matrix and in electrostatic attractions with mineral phase, thereby providing stability to collagen-mineral interface and ductility to bone.
Clinical tools sensitive to age- and disease-related changes in matrix composition that the affect mechanical behavior of bone could potentially improve fracture risk assessment.
KeywordsMineral Type 1 collagen Bone quality Advanced glycation end-product Post-translation modifications Water
We thank Dr. Mathilde Granke for developing the hierarchical figure of toughening mechanisms. Part of this material was supported by National Institute of Arthritis and Musculoskeletal and Skin Diseases (AR067871). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or other funding agencies.
Compliance with Ethical Standards
Conflict of Interest
Jeffry Nyman reports grants for the following: NIH/NIAMS AR063157, NIH/NIAMS AR067871, VA BLR&D BX001018, and NSF 1068988, during the conduct of the study; non-financial support from ActiveLife Scientific, Inc.; and holds a patent, US Patent 8,923,948 System, pertaining to the measurement of bound water and pore water as an indicator of fracture risk (not licensed and no royalties received).
Amy Creecy reports grants from NIH/NIAMS and NIH/NIDDK, during the conduct of the study.
Mustafa Unal reports no conflict of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
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