Age-related regional deterioration patterns and changes in nanoscale characterizations of trabeculae in the femoral head

• Age-related regional deteriorations of the femoral head at nano-level were investigated.
• Deteriorations of bone materials with aging followed different patterns among regions.
• Trabecular properties deteriorated more quickly along the longitudinal direction.
• The results contribute to an understanding of the age-related fracture mechanism.

This study aimed to investigate the mechanical properties and features of bone materials at the nanoscale level in different regions of the femoral head in elderly patients with femoral neck fracture. Ten femoral heads from female patients with femoral neck fractures were extracted during surgery (five for the Aged group, aged 65–66 years; five for the Advanced aged group, aged 85–95 years). The femoral head was divided into three equal layers (anterior, central, and posterior) in the coronal view, and each layer was segmented into five regions (superior, central, inferior, medial, and lateral). Nanoindentation testing and atomic force microscopy imaging were used to study the mechanical properties and surface morphology of the specimens. No statistical differences in grain size were found between age groups, which suggested that the nanostructure of trabeculae in the femoral heads of postmenopausal women cannot be used to predict age-related bone loss and fracture risk. Mechanical properties in the longitudinal direction deteriorated more quickly than those in the transverse direction for the whole femoral head. Comparisons between layers showed a higher deterioration rate with aging in the anterior layer than in other layers. In different regions, mechanical properties of the medial and lateral regions deteriorated more quickly than those in the three other regions, and deterioration in the longitudinal direction was more serious than that in the transverse direction. The regional deterioration patterns and material properties with aging observed in this study contribute to an understanding of the age-related fracture mechanism and provide a basis for predicting age-related fracture risk and decreasing early fixation failure in the proximal femur.