Topology Optimization of a Hip Implant for Additive Manufacturing

Abstract Large acetabular defects in revision total hip arthroplasty (THA) revision surgery pose a major challenge in achieving stable fixation and restoring physiological load transfer. In such cases, patient-specific implants are currently used to ensure secure anchoring through customized fit. These implants can be additively manufactured to ensure price competitiveness with standard implants. A major disadvantage of metallic implants is the difference in compliance compared to human bone, which leads to stress shielding, one of the main reasons for revision surgeries. To address this challenge, this work analyzes different optimization approaches for the inner design of additively manufactured implants for large-volume defects. These approaches include the use of contact force constraints, regional strain energy constraints, or manufacturing constraints. A biomechanical finite element model of the hip with a Paprosky type 3A defect was created. The optimized implants were evaluated regarding the contact forces, the regional strain energy, and the von Mises stresses across different load cases. The results showed that the implant optimized concerning contact force and manufacturing constraints provided the most native regional strain energy and low contact forces. These parameters lead to improved implant durability and a more favorable outcome for the patient, suggesting it as a promising candidate for clinical application. Additionally, initial experimental tests were conducted. Tensile tests were performed to validate the material parameters of the model, while dynamic tests were used to evaluate the initial implant design.