Quantitative backscattered electron imaging of bone in proximal femur fragility fracture and medical illness

Abstract

Bone quality consists of a number of factors including the amount of bone, bone architecture and the degree of bone mineralization. Quantitative backscattered electron imaging is a technique that allows the degree of mineralization of trabeculae to be assessed and in this study is applied to inter-trochanteric bone biopsies of the proximal femur. Biopsy cores from 22 controls, nine individuals with acute and chronic medical conditions and 22 fragility fracture individuals undergoing total hip replacement were processed into methyl methacrylate, polished and analysed in a Philips XL20 scanning electron microscope. A mean and distribution of weight percent calcium were determined for each individual, and for the control, medically ill and fragility fracture groups. All individuals and groups of individuals showed normal distributions of percent calcium with both the ill and fragility fracture groups being under mineralized relative to the control group. The shape and position of the mineralization distributions suggest that the fragility group resulted from increased bone turnover with a slow progression to under mineralization. In contrast, the ill group appears to have had a more rapid change in the mineralization dynamic. Clear distinctions between the control, fragility fracture and medically ill groups could be seen when the mineralization data were plotted as a scatter graph against age. Graphing the data in this way showed an age-related increase in the degree of mineralization in control individuals with the under-mineralized, fragility fracture group scattered below this normal trend. The medically ill group was similarly less mineralized which highlighted the degree to which medical conditions and treatments can alter bone matrix mineralization.