Greater tissue mineralization heterogeneity in femoral neck cortex from hip-fractured females than controls. A microradiographic study.

In addition to bone quantity, bone quality affects bone strength. Bone quality depends in part on the degree of mineralization of bone tissue (DMB). The relationship between the DMB distribution and the risk of osteoporotic hip fractures remains incompletely investigated. Here, our aim was to compare DMB distribution in femoral neck cortex specimens from 23 women with hip fractures (age, 65-96 years) and 14 control women (age, 75-103 years). Mineralization was determined using quantitative microradiography. We evaluated the following parameters of DMB frequency histograms, for both osteons and interstitial tissue: mode (oDMB(Al)mode and intDMB(Al)mode, respectively); 25th (oDMB(Al)q25, intDMB(Al)q25), 50th (oDMB(Al)q50, intDMB(Al)q50), and 75th (oDMB(Al)q75, intDMB(Al)q75) percentiles; and interquartile range (oDMB(Al)iqr, intDMB(Al)iqr). For each specimen, we also calculated the variance of pixel mineral content for osteons and interstitial tissue (oDMB(Al)var and intDMB(Al)var). We used nonparametric tests to compare frequency histogram parameters between hip-fractured women and controls and Fisher's test to compare variances between groups. All frequency histogram parameters for osteons and interstitial tissue except the 25th percentile, and the variances of pixel mineral content in osteons and interstitial tissue, were significantly different between hip-fractured women and controls, indicating greater heterogeneity of mineralization in the hip-fracture patients than in the controls. These cross-sectional data suggest that bone fragility may be related to greater DMB heterogeneity in osteons and interstitial tissue.