Stability of Three‐Dimensional Printed Custom‐Made Metaphyseal Cone for Tibial Bone Defects Reconstruction: A Finite Element Analysis and Biomechanical Study

OBJECTIVES: The reconstruction of bone defects in tibial revision knee arthroplasty is challenging. In this study, we evaluated the primary stability of a novel three‐dimensional (3D)‐printed custom‐made metaphyseal cone for Anderson Orthopedic Research Institute (AORI) IIb or III bone defect reconstruction in tibial revision knee arthroplasty using the combination of finite‐element analysis and biomechanical experiments. METHODS: In the finite‐element analysis, AORI II b and III medial tibial bone defects were designed at varying depths. A novel 3D‐printed custom‐made metaphyseal cone was designed and used to reconstruct the bone defect with or without a stem in simulated revision total knee arthroplasty (RTKA). A no‐stem group and a stem group were established (based on whether a stem was used or not). Von Mises stress and micromotion were calculated with varying depths of bone defects, ranging from 5 mm to 35 mm, and then micromotions at the bone–implant interface were calculated and compared with the critical value of 150 μm. In the biomechanical experiment, the no‐stem group was used, and the same bone defects were made in four synthetic tibias using patient‐specific instruments. Micromotions at the bone–implant interface were investigated using a non‐contact optical digital image correlation system and compared with the critical value of 150 μm. RESULTS: When the bone defect was <30 mm, micromotions at the bone–implant interface in the finite‐element analysis were all below 150 μm both in the stem groups and no‐stem groups, whereas those in the biomechanical experiment were also below 150 μm in the no‐stem group. CONCLUSIONS: The 3D‐printed custom‐made metaphyseal cone in RTKA has excellent primary stability and does not require stems in reconstructing tibial AORI type IIb or III bone defects with a depth of <30 mm.