Evaluation of internal implant failure in long bones fractures

Internal implant fixation stability is essential to promote a proper bone healing and osseointegration. Unstable internal implantation may promote complications that induced implant failure. Clinically, the fixation of the implant failure is still unexplained. Implant loosening and surrounding bone loss caused by unfavorable stress distribution and can be improved by using several parameters of the bone and implant such as screw configurations, unicortical and bicortical screws, locking, and conventional screws and long bone fracture, mechanical loadings, and bone conditions. Indeed, the investigation on the mechanical elastic interaction between screw and bone that localized at implant-bone interfaces is still unclear. Thus, this study aims to elucidate the mechanic of interactions between bone-implant interfaces subjected to various clinical internal fixation configurations. As the solution proposed, a series of biomechanical implant simulations were executed using finite element (FE) analysis. Three dimensional (3D) internal fixation models were designed based on actual clinical fixation practice to simulate the stress-strain distribution, interfragmentary strain (IFM), stress transfer parameter (STP), strain energy density transfer parameter (SEDTP), stress intensity factor (SIF) at bone-implant interfaces for different bone healing stages. Further investigation regards 3D simulation outcomes based on bone-screw interaction analysis and has considered the load directions, micro-mobility, Young modulus of surrounding bone, and bone-implant loosening. A set of computational fracture mechanic simulations were conducted to predict the stress intensity factor (SIF) based on linear elastic fracture mechanic (LEFM) and elastic-plastic fracture mechanic (EPFM) principles. Based on FEA, bone fracture found on medial side of femur and had achieved maximum value of stresses 42.396 MPa. Also, fracture angle of F = 0 , zero angle of screw orientation and stainless-steel material had minimal surrounding bone damage, 152.10 MPa of VMS obtained. The most stable screw type was Group BC (slope =1.64x10-3) and 134 configurations had absolute stability achieved (IFM < 2%). C134 had the most stable configuration based on normality test (p ≥ 0.05) and minimum constant variance value, (F=0.0059) indicate a good predictor for stability assessment. The correlation micro-mobility-based bone modulus reduced approximately 50% when ISQ increases from 60% to 70%. Interaction of geometry influenced driving stress 1 / o K K , result in amplification occurs. Constraint factor result in a greater SERR, and result in degradation of mechanical stability. Thus, the normalization of SERR, (Th,Sc,BSc) G has had a significant impact on geometry and constraints. In conclusion, the internal implantation stability index was introduced subject to various clinical fixation factors, biomechanical implant, and bone materials through many kinds of developed numerical models. For the future investigation, implant-bone infections, implant materials, and implant surface morphology, bone porosity factors should consider concerning internal implant fixation stability assessment.