Cracks emanating from slipping inclusions near a bone-implant interface

It has been hypothesized that mechanical fracture at the bone-cement-implant interface is the initial causefor loosening oforthopedic implants. Previous investigators have observed cracks to emanate from methacrylate beads, apparently acting as inclusions within the cement. It is believed that the bond between these inclusions and the surrounding matrix breaks prior to emanation of radial cracks from the inclusion. An analytical model is developedfor radial cracks emanatingfrom circular inclusions that allow slip along their interface. The solution to the interaction of a single dislocation and a slipping inclusion is used as a Green’s Function to model the crack. The Mode I stress intensity factors are calculatedfor arbitrary orientations of the crack and for varying relative stiffness of the matrix and the inclusion to test feasibility of crack growth.