Mechanical Properties of Four Human Longbones

摘要

The four human long bones (femur, tibia, humerus, and fibula) were fractured under bending loading conditions, torsion loading conditions, and combinations of bending and torsion. Forty-eight fresh bones, 12 of each type (left and right sides of 6 cadavers), were loaded until fracture occurred. Forty-six bones of all types were loaded quasi-statically while two humeri were fractured at a more rapid rate. End slopes, mid-diaphyseal deflections, and twist angles of the deforming bones were recorded during all tests. Forty-three of the bones, including all of the types, were strain gaged with axial and rosette resistance strain gages. Interaction boundaries are presented which allow the prediction of fracture loads from various combinations of bending and torsion loadings given the bone type and the geometry at a particular location along the bone diaphysis. With the fracture loads known, graphs depicting end slopes, mid-diaphyseal deflections, and twist angles as functions of load, which are also presented, may be used to estimate fracture displacements. Fracture patterns expected from each of the three types of loadings are discussed and illustrated. The states of strain and stress at specific locations along the disphyses of the different bone types are described. An osteometry study compares the bones tested with the general population. A brittle lacquer test describes the areas of highest strain for a femur subjected to pure torsion. A scanning electron microscope study presents fracture appearances of tension as well as suspected shear surfaces and illustrates graphically the difficulty involved with modeling bone microstructure, mathematically, in terms of its constituents.