Biomechanical evaluation of asymmetric metaphyseal cone applications for lateral tibial plateau fractures : a finite element study.

Abstract

<h4>Aims</h4>Tibial plateau fractures (TPFs) commonly occur in older osteoporotic individuals and pose significant challenges during acute total knee arthroplasty (TKA). This study aimed to evaluate the biomechanical performance of asymmetric metaphyseal cones in managing lateral TPFs during acute TKA.<h4>Methods</h4>A finite element model was developed using a generic size 5 tibia geometry with an integrated asymmetric metaphyseal cone system. Various lateral TPF patterns were systematically simulated through 12 uncontained defect configurations, quantified by the unsupported surface area ratios of the cone (<i>R_u</i>). Four physiological loading conditions (standing up, walking, knee bending, and stair descending) were analyzed under standardized boundary constraints. Bone-implant interface micromotions were assessed against an osseointegration threshold (150 μm), while cancellous bone strains were evaluated against yield criteria (greater than 0.5% for tension and less than -0.7% for compression).<h4>Results</h4>The implant system demonstrated stable biomechanical performance across all loading conditions when <i>R_u</i> ≤ 44%, with micromotions remaining below 50 μm. Maximum interface micromotions of 82 µm occurred during stair descending at <i>R_u</i> = 56%, remaining substantially below the osseointegration threshold. Significant increases in micromotions and in the volume of bone exceeding the strain criteria occurred for <i>R_u</i> > 44%. The posterolateral region exhibited the highest micromotion and strain concentrations, indicating a critical zone for biomechanical stability.<h4>Conclusion</h4>Asymmetric metaphyseal cones provide effective stabilization for lateral uncontained defects, managing micromotions and bone strains within clinically safe limits. The recommended maximum defect size for cone treatment is an unsupported area ratio <i>R_u</i> = 44%. These findings suggest that asymmetric metaphyseal cones present a promising option for addressing severe lateral TPFs during acute TKA.