Preferred Orientation in Bone

Abstract

Anisotropy in bone has long been recognised. In mammalian bone it may be observed at two distinct levels of organisation, the first being the arrangement of the osteons within the whole bone, and the second the ultrastructure of the osteons themselves. The preferred orientation of material within a single lamella of an osteon, (and in the whole bone of fish), has previously been explained in terms of the alignment of arrays of needle-like mineral crystallites within the collagen fibrils which are themselves arranged in parallel. Based on observations of bone from a variety of sources, this paper proposes an alternative hypothesis, in which the preferred orientation and ultimately the anisotropy have their origins in the existence of columns of mineral, the orientations of which are related to those of the collagen fibres. These columns are linked together to form a continuous mineral phase interpenetrated by a second continuous network of collagen fibres.