A New Design for Maximum Conformity of Total Knee Prosthesis to Femur and Tibia.

Total knee arthroplasty (TKA) is a common procedure for treating patients with excessively arthritic knees. Nonetheless, early failure of TKA may occur in the first 5 yr, and up to 20% of TKA procedures can fail after 20 yr. In this study, a new anatomic prosthesis was designed to provide maximum conformity to knee bones and produce less stress and strain, in an effort to avoid possible failure of the prosthesis. Anatomical and conventional knee models were compared on the basis of both geometric conformity and stress and strain results obtained from finite element analysis. To compare geometric conformity, anatomic prosthesis components were manufactured by laser melting, and conventional prosthesis components were fixed to sawbone knee models. The anatomical model yielded up to 50% less contact pressure at the insert, which may indicate potential for reduced wear between insert and femur components. This model also resulted in less principal strain value at the tibial component, considered to be an important parameter to indicate loosening. The anatomical model with a new femur component in the anterior cortex design also yielded less stress at the femoral cortex, when compared to the conventional model. The findings in this study suggest that the anatomic prosthesis model may be a better design alternative to conventional knee prostheses in terms of wear, aseptic loosening, and normal joint biomechanics.