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.

Introduction. Several ongoing studies aim to improve the survival rate following total knee arthroplasty (TKA), which is an effective orthopedic surgical approach for patients with severely painful knee joint diseases. Among the studied strategies, baseplate rotational arrangement techniques for TKA components have been suggested but have been the subject of only simple reliability evaluations. Therefore, this study sought to evaluate comparatively three different baseplate rotational arrangement techniques that are commonly used in a clinical context. Materials and Methods. Three-dimensional (3D) finite element (FE) models of the proximal tibia with TKA were developed and analyzed considering three baseplate rotational arrangement techniques (anterior cortex line, tibial tuberosity one-third line, and tibial tuberosity end line) for six activities of daily life (ADLs) among patients undergoing TKA. Mechanical tests based on the ASTM F1800 standard to validate the FE models were then performed using a universal testing machine. To evaluate differences in biomechanical characteristics according to baseplate rotational arrangement technique, the strain and peak von Mises stresses (PVMSs) were assessed. Results. The accuracy of the FE models used in this study was high (94.7 ± 5.6%). For the tibial tuberosity one-third line rotational arrangement technique, strains ≤ 50 µstrain (the critical bone damage strain, which may affect bone remodeling) accounted for approximately 2.2%–11.3% and PVMSs within the bone cement ranged from 19.4 to 29.2 MPa, in ADLs with high loading conditions. For the tibial tuberosity end line rotational arrangement, strains ≤ 50 µstrain accounted for approximately 2.3%–13.3% and PVMSs within the bone cement ranged from 13.5 to 26.7 MPa. For anterior cortex line rotational arrangement techniques, strains ≤50 µstrain accounted for approximately 10.6%–16.6% and PVMSs within the bone cement ranged from 11.6 to 21.7 MPa. Conclusion. The results show that the most recently developed frontal cortex line rotational alignment technique is the same or better than the other two rotational alignment techniques in terms of biomechanics. This finding can be, however, dependent on the contact characteristics between the baseplate and the proximal tibia. That is, it is indicated that the optimum baseplate rotational arrangement technique in terms of reducing the incidence of TKA mechanical failure can be achieved by adjusting the characteristics of contact between the baseplate and the proximal tibia.

Computer modeling and simulation (CM&S) technology is widely used in the medical device industry due to its advantages such as reducing testing time and costs. However, the developer’s parameter settings during the modeling and simulation process can have a significant impact on the results. This study developed a test model for the rotational shear strength of dental implants and the constraint force of total knee replacements based on CM&S technology and proposes ideal parameters to ensure reliability. For dental implants, the load area and sliding contact conditions were considered, and for total knee replacements, the friction coefficient, medial–lateral displacement, valgus–varus rotation, and elastic modulus were considered. By comparing the simulation results and mechanical tests, boundary conditions with an error rate of less than 1.5% were selected. When a jig (gripper and collector) was applied with the same boundary conditions, an error rate of 48~22% occurred; otherwise, it was confirmed that the error rate was within 10~0.2%. The FE model was verified with an error of 2.49 to 3% compared to the mechanical test. The friction coefficient variable had the greatest influence on the results, accounting for 10 to 13%, and it was confirmed that valgus–varus rotation had a greater influence on the results than medial–lateral displacement. Relatively, the elastic modulus of the insert had the least effect on the results. These research results are expected to make CM&S techniques useful as a medical device digital development tool (M3DT) in the development of total knee replacements and dental implants.

Park SC, et al. Clin Orthop Surg. 2023 Mar;15:e19. https://doi.org/10.4055/cios22360