In these individuals, their higher fracture risk BMS 354825 and decreased hip strength have been attributed to significant deficits in the cortical shell ,  and . Thus, protecting and improving the cortical compartment may be paramount to observe fracture reduction in the elderly population. Supporting this observation is the report that denosumab significantly
reduced the risk of hip fractures in subjects aged ≥ 75 years by 62% (95% CI, 22%, 82%). This observed hip fracture incidence in the denosumab-treated older subjects was similar to that of untreated subjects < 75 years in whom hip fractures are a less frequent event . The data reported here therefore provide more accurate insight on the effects of denosumab on trabecular, subcortical, and cortical bone compartments, and the possible relationships to fracture reductions. In FREEDOM, improvements in total hip aBMD observed with denosumab treatment accounted for approximately 80% of the nonvertebral fracture risk reduction , and this robust relationship suggested CHIR-99021 supplier that the gains in mass with denosumab treatment were achieved across all compartments, a hypothesis now documented in this study. This study also highlights the value of evaluating absolute change, in addition to percentage
change, when documenting changes over time with QCT. Indeed, previous reporting of percentage change rather than absolute change may have obscured our understanding of the impact of therapies on different bone compartments and their possible contributions to fracture risk reductions. Percentage changes in both vBMD and BMC in the denosumab-treated subjects were larger in the trabecular compartment than in the cortical compartment, but assessment of absolute changes enough revealed that larger gains in vBMD and BMC were observed in the cortical compartment. The absolute increases in vBMD and BMC were also noteworthy in the subcortical compartment, particularly
because those increases occurred in a significantly smaller subcortical volume compared with the trabecular and cortical volumes. The apparent discrepancy between percentage and absolute changes is explained by the fact that vBMD in the trabecular compartment is lower because of the large inter-trabecular spaces and the low density of the surrounding fatty bone marrow. While it is informative to differentiate percentage and absolute changes, as well as vBMD and BMC changes, it remains to be determined, which has the greatest influence on biomechanical strength. Nevertheless, this study supports the use of techniques other than DXA in the evaluation of changes in response to therapy to better understand their impact on fracture risk reductions.