Experimental and numerical analysis of the influence of intramedullary nail position on the cut-out phenomenon

• Published in: Computer methods and programs in biomedicine 2023-10, Vol.240, p.107734-107734, Article 107734
• Main Authors: Arias-Blanco, A., Marco, M., Giner, E., Larraínzar-Garijo, R., Miguélez, M.H.
• Format: Article
• Language: English
• Subjects: Cut-out; Digital image correlation; Extracapsular fracture; Finite element method; Hip fracture; Intramedullary nail
• ISSN: 0169-2607; 1872-7565
• DOI: 10.1016/j.cmpb.2023.107734

•Cut-out numerical model has been developed and validated against experimental tests.•Different positions of the intramedullary nail have been tested by means of the numerical model, comparing torque, damage….•Variables such as torque or stresses around the nail are very difficult to measure experimentally.•Damage on trabecular bone has been implemented in the model, to evaluate the cut-out risk.•The centred position of the nail leads to the minimum risk for cut-out problem with intramedullary nail. Proximal femur fractures, colloquially known as hip fractures, are a common pathology with increasing incidence in the last years due to the enhanced ageing population. Regarding the extracapsular fracture, the treatment for this pathology consists of a fixation of the fragments using an osteosynthesis device, mainly the intramedullary nail. This repairing method implies several complications, which may include the failure of the fixation device, frequently occurring due to the “cut-out” mechanism. The present work focuses on the study of how the position of the cephalic screw, which should be fixed during surgery, affects the cut-out risk. Through experimental tests and numerical models some variables that can be critical for the cut-out phenomenon are analysed. This study has been carried out through a numerical model based on the finite element method and experimental tests. The digital image correlation technique has been used in experimental tests to measure displacements on the femoral surface with the objective of numerical model validation. Some basic daily activities with different intramedullary nail positions have been analysed through the numerical model, considering variables that can induce the cut-out complication. The results show how the intramedullary nail position clearly influences the cut-out risk, showing that displacements in the upper, anterior and posterior direction increase the cut-out risk, while displacement in the lower direction endangers the intramedullary nail itself. Thus, the centred position is the one which reduces the cut-out risk. This work supposes an improvement in the knowledge of the cut-out phenomenon thanks to the combination of experimental testing and validated numerical models. The effects of different intramedullary nail positions in the femoral head are studied, including a novelty variable as torque, which is critical for the structural integrity of the fixation. The main conclusion of the work is the determina