A Parametric Study on the Geometrical Design of Augmented Cones for Revision Total Knee Arthroplasty

The purpose of this research was to address the design of augmented cones used in revision knee arthroplasty surgeries to fill the large bone defects in metaphyseal regions. A parametric finite element study was performed to investigate the effect of the geometrical design variables of the cone on its biomechanical performance. The model included a nonhomogeneous voxel-based representation for bone, a parametric model of the cone, a standard femoral component of the revision knee arthroplasty, and a cement layer between the cone and implant. Sixteen designs of the cone were analyzed by changing its upper and lower radii, which resulted in different cone angles and cone thicknesses. The modeling results were investigated for the mechanical strength of the cone and cement layer, the micromotion at the bone-implant interface, as an indicative of osseointegration potential, and the micromotion at the cone-cement interface, as an indicative of the wear risk. Considering the cone angles ranging from 3.43 to ${1 0. 2}$ degrees and the cone thickness varying from 1.18 mm to 2.68 mm, the maximum stress in the cone was found to change in the range of 33.69 MPa to 45.28 MPa, and that of the cement layer in the range of 10.33 MPa to ${1 5. 6 8} \mathrm{MPa}$. Moreover, micromotion at the cone-cement interface varied from 0.0026 mm to 0.0085 mm, and that of the bone-cone interface was less than 50 micrometers. The results suggest that the cone’s mechanical strength decreases with an increase in cone angle and increases with an increase in cone thickness, while the cement’s mechanical strength decreases by increasing both cone angle and cone thickness. Also, wear decreases with the cone angle enlargement while osteointegration is always in the safe range (micromotion < 50 micrometers).