Cracks emanating from circular voids or elastic inclusions in PMMA near a bone-implant interface.

Mechanical fracture is believed to be a primary reason for loss of fixation at the bone-cement-implant interface. In addition to the expected cracks at the bone-cement interface, cracks are also observed to be formed at voids and inclusions within the cement. An analytical solution is presented for cracks emanating from circular voids or elastic inclusions under uniaxial tension using the solution for a single dislocation as a Green's function. Stress intensity factors are calculated for arbitrary orientations of the cracks, and for varying relative stiffnesses of the inclusion and the matrix, to determine the most favorable combination of parameters for crack growth.