Relationships between material properties and CT scan data of cortical bone with and without metastatic lesions

Breast, prostate, lung, and other cancers can metastasize to bone and lead to pathological fracture. To lay the groundwork for new clinical techniques for assessing the risk of pathological fracture, we identified relationships between density measured using quantitative computed tomography (ρQCT), longitudinal mechanical properties, and ash density (ρAsh) of cortical bone from femoral diaphyses with and without metastatic lesions from breast, prostate, and lung cancer (bone with metastases from six donors; bone without metastases from one donor with cancer and two donors without cancer). Moderately strong linear relationships between ρQCT and elastic modulus, strength, and ρAsh were found for bone with metastases (0.73<r<0.93, P<0.05). After accounting for differences in ρQCT, the elastic modulus, compressive strength, tensile yield strain, and ρAsh of bone with metastatic lesions differed from those of bone from donors without cancer (P<0.01). However, differences in tensile strength or compressive yield strain, after controlling for ρQCT, were not found. Thus, these cancers degrade the elastic modulus and compressive strength, but not the tensile strength, of cortical bone beyond the amount that would be expected from decreased density alone. The ρQCT-mechanical property relationships reported may be useful for evaluating bone integrity and assessing the risk of fracture of bone with metastases.