Tissue level microstructure and mechanical properties of the femoral head in the proximal femur of fracture patients

This study aims to investigate the regional variations of trabecular morphological parameters and mechanical parameters of the femoral head,as well as to determine the relationship between trabecular morphological and mechanical parameters.Seven femoral heads from patients with fractured proximal femur were scanned using a micro-CT system.Each femoral head was divided into 12 sub-regions according to the trabecular orientation.One 125 mm^3 trabecular cubic model was reconstructed from each sub-region.A total of 81 trabecular models were reconstructed,except three destroyed sub-regions from two femoral heads during the surgery.Trabecular morphological parameters,i.e.trabecular separation（Tb.Sp）,trabecular thickness（Tb.Th）,specific bone surface（BS/B V）,bone volume fraction（BV/TV）,structural model index（SMI）,and degree of anisotropy（DA） were measured.Micro-finite element analyses were performed for each cube to obtain the apparent Young＇s modulus and tissue level von Mises stress distribution under 1%compressive strain along three orthogonal directions,respectively.Results revealed significant regional variations in the morphological parameters（P〈0.05）.Young＇s moduli along the trabecular orientation were significantly higher than those along the other two directions.In general,trabecular mechanical properties in the medial region were lower than those in the lateral region.Trabecular mechanical parameters along the trabecular orientation were significantly correlated with BS/BV,BV/TV,Tb.Th,and DA.In this study,regional variations of microstructural features and mechanical properties in the femoral head of patients with proximal femur fracture were thoroughly investigated at the tissue level.The results of this study will help to elucidate the mechanism of femoral head fracture for reducing fracture risk and developing treatment strategies for the elderly.