Effect of porous coating geometry on interfacial stress under a shear load.

Porous coated implants are loaded under both bending and shear loading. Previously, the effect of various parameters on fatigue strength under a bending load has been determined. The interfacial geometry between the porous coating and the substrate was found to increase stress concentrations leading to reduced fatigue strength. This study quantifies the effect of porous coating interfacial geometry on interfacial stress under a shear load. A two-dimensional finite element model is used to study the effect of interfacial geometry on the value of the maximum shear stress. It was found that the requirements to reduce stress concentrations are different under a shear load than under a bending load. A conventional porous coating would require a compromise to satisfy the conflicting requirements. A new geometry, however, can optimize the values of the geometric parameters to satisfy the conditions for both modes of loading.