Assessment of osteonal and interstitial bone quality using a novel custom-made microscope-indenter assembly

INTRODUCTION: Prediction of bone fracture goes beyond bone mineral density measurement. The quality of bone matrix is instrumental in providing fracture resistance to bone. Thus assessment of bone quality is critical to understanding bone fracture. Reference point indentation (RPI) purports to measure bone matrix quality in vivo and has been shown to separate fracture and non-fracture groups with over-lapping BMD [1]. Here, we compare the material properties of osteonal and adjacent interstitial bone using RPI and evaluate its ability to distinguish bone with different tissue age. It is known that interstitial bone is more mineralized and contains post-translationally modified collagen. Consequently, it is likely to accumulate damage as linear microcracks while osteons are predisposed to accumulating diffuse damage [2, 3] a bone toughening mechanism. The accumulation of diffuse damage has been associated with higher fracture toughness [3].