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This study was performed to determine whether metal block augmentation is suitable for large uncontained bone defect via evaluations of differences in biomechanical characteristics among the configurations of metal block augmentations for medium or large uncontained bone defects in revision total knee arthroplasty (TKA). Three-dimensional finite element (FE) models of the proximal tibia with revision TKA were developed and analyzed considering the configurations of the metal block augmentations for medium and large uncontained bone defects. To identify differences in biomechanical characteristics according to the configurations of metal block augmentations, the stress transfer, strain distribution, and peak von Mises stresses (PVMSs) were assessed. Large and medium uncontained bone defects had similar ranges of strain below the critical bone-damage strain for the metal block augmentations, but the strain distribution characteristics differed in response to the metal block-augmentation configurations. PVMSs exceeding the yield strength of the bone cement for the single metal block-augmentation configurations were, on average, 1.4 times higher than those for double metal block-augmentation configurations for both medium and large uncontained bone defects. These findings suggest that metal block augmentation may be suitable for large uncontained bone defects (≤20 mm), compared with the results obtained for metal block augmentation used in medium uncontained bone defects (≤10 mm). If possible, double metal block augmentation is recommended for both medium and large uncontained bone defects rather than single metal block augmentation. It is also recommended that the metal block augmentation should be customized to meet the contact characteristics with the cortical bone, thereby ensuring better stress transfer and reducing the risk of the bone resorption due to stress shielding and bone-cement failure. [ABSTRACT FROM AUTHOR]