Bone Strength: The Whole Is Greater Than the Sum of Its Parts

ObjectiveTo summarize the current knowledge regarding the various determinants of bone strength.MethodsRelevant English-language articles acquired from Medline from 1966 up to January 2005 were reviewed. Searches included the keywords bone AND 1 of the following: strength, remodeling, microcrack, structur*, mineralization, collagen, organic, crystallinity, osteocyte, porosity, diameter, anisotropy, stress risers, or connectivity. Abstracts from applicable conference proceedings were also reviewed for pertinent information.ResultsBone strength is determined from both its material and its structural properties. Material properties such as its degree of mineralization, crystallinity, collagen characteristics, and osteocyte viability have substantial impacts on bone strength. Structural properties such as the diameter and thickness of the cortices, the porosity of the cortical shell, the connectivity and anisotropy of the trabecular network, the thickness of trabeculae, and the presence of trabecular stress risers and microcracks impact bone strength in diverse manners. Remodeling activity either directly or indirectly impacts all of these processes.ConclusionsBone strength is dependent on numerous, interrelated factors. Remodeling activity has a direct impact on almost all of the components of bone strength and requires further investigation as to its impact on these factors in isolation and in unison.