Finite element analysis applied in design of orthopedic implants for repairing tibial bone defects in revision total knee arthroplasty

Abstract

Objective To discuss application of finite element (FE) analysis in design of orthopedic implants for repairing bone defects in revision total knee arthroplasty (RTKA).Methods A healthy 25 year-old male volunteer,170 cm in height and 62 kg in weight,was enrolled in the present study.First 3D FE models of the knee joint were reconstructed on the basis of the spiral CT scans of the male volunteer.Five FE models were constructed of the wedge-shaped bone defects in the medial tibia plateau (5.0,7.5,10.0,12.5and 15.0 mm in height respectively).In simulated repair of the bone defects in FE models,cement (in group 1),cement with reinforcement screws (in group 2) and metal augmentation (in group 3) were used.Loading and boundary conditions were set to reflect the real situations.The displacement between the bone-cement interfaces and the maximum shear stress in the cement between the bone-cement interfaces were investigated and compared.Results When the defects were 12.5 mm and 15.0 mm,the displacement exceeded the threshold of loosening in groups 1 and 2,higher than 150 μm.When the defects were 7.5 mm and 10.0 mm,the displacements were higher than 150 μm in group 1,but lower than 150 μm in group 2.When the defect was 5.0 mm,the displacement was at the threshold of loosening in all groups.In all groups,the cement maximum shear stress increased as the defects became larger.The maximum shear stresses in group 2 were lower by 21％,16％,11％,9％,and 7％ than those in group 1 as the defect sizes decreased accordingly.Group 3 showed the lowest maximum shear stress.Conclusion In the FE models of repairing bone defects in RTKA,cement with reinforcement screws can be used to repair wedge-shaped bone defects no larger than 10.0 mm and result in fine biomechanical stability because higher displacement and interface shear stress imply a high incidence of loosening. Key words: Knee joint; Arthroplasty; Finite element analysis