Calculated stress-shielding in the distal femur after total knee replacement corresponds to the reported location of bone loss

This study sought to determine the similarities between features of calculated stress-shielding and observed bone loss in the distal femur after total knee replacement. Stress-shielding was determined by comparing the magnitudes and distributions of strain energy density, calculated using three-dimensional finite element models oft. the intact bone, the bone after total knee replacement with bonding assumed at all prosthesis-bone interfaces, and the bone after total knee replacement with bonding assumed only at the distal interface. The loading condition simulated static lifting with the knee flexed at 45 degrees, producing tibiofemoral and patellofemoral joint reactions of 900 and 450 N, respectively. The maximum magnitudes of strain energy density calculated using the total knee replacement models wire less than 15% of the corresponding magnitudes from the intact hone model. The greatest difference was found to occur at the anterior distal corner of the femur, suggesting this location as the cine most vulnerable to stress-shielding. Clinically observed bone loss after total knee replacement frequently occurs at this location. At the anterior distal corner, the calculated magnitudes for the two total knee replacement models were similar, suggesting that stress-shielding at this location was not reduced by limiting fixation only to the distal interface. Although the study corresponded to one leading condition and one geometry of th total knee replacement femoral component with the inherent limitations of model calculations, the result suggest a possible scenario for stress-shielding.