Biomechanical Study on the Reconstruction of Medial Tibial Bone Defects Using a Novel Spherical Block Augmentation

Background In response to the challenges of excessive bone resection, large micromotion, and shear stress associated with block augmentations, this study introduces a novel spherical augmentation design specifically tailored to the morphological characteristics of medial tibial bone defects. Methods Spherical augmentations were designed, followed by the establishment of finite element models that incorporated posterior stabilized total knee prostheses, along with spherical or block augmentations, and the tibia. The impact of these augmentations on the stability of tibial prosthesis fixation was assessed by analyzing von Mises stress in the tibia and augmentations, cement shear stress, and micromotion at the fixation interface. Additionally, the influence of augmentation thickness was examined. Results The trends in tibial stress distribution under both spherical and block augmentations were generally consistent, with stress levels in spherical augmentations being lower than those observed in block augmentations. At 72% of the gait cycle, the maximum cement shear stresses for 5, 10, and 15 mm spherical augmentations were reduced by 72.47, 73.55, and 68.57% respectively, compared to block augmentations. Furthermore, the peak micromotion at the augmentation-tibia interface for spherical augmentations was decreased by 82.38, 54.36, and 48.80% relative to block designs. Conclusion The newly designed spherical augmentation offers stable support comparable to that of block augmentations while mitigating proximal tibial stress shielding. It effectively reduces both cement shear stress and micromotion at the augmentation-tibia interface, indicating superior initial fixation stability.