Biomechanical models of implanting prostheses into femora by means of press fit, i.e. the
mechanics of non-homogeneous layer-like composites, have been used to quantify the press-fit strength
and circumferential stress of the interface, when femora are partially replaced by different thicknesses of
bioactive ceramic coatings on a prosthesis surface during the initial implant stage. The maximum press-fit
strength appears on the interface between femora and Ti alloy prostheses with non-coating; the press-fit
strength decreases with the increased thickness of the coating. The circumferential stress displayed as the
large tensile stress at the femoral side of the interface; the compressive stress, appeared at the side of the
coating and Ti alloy prosthesis. The shearing strength, jointing between the prostheses and femora would
be bigger with the thinner bioactive ceramic coatings. Considering the biodegradability of bioactive
ceramic coatings, e.g. hydroxyapatite, HA, it is concluded that the optimum thickness of the bioactive
ceramic coatings will be about 50-60 microns.
