A novel three-dimensional proximal femoral intramedullary nail (TD-PFIN) system with better biomechanical advantages: a finite element analysis study.

Objective: The biomechanical strength of a new three-dimensional proximal femur intramedullary nail (TD-PFIN) was compared with that of the commonly used internal fixation by finite element analysis. Methods: The femur CT imaging data of a healthy volunteer were collected. Three-dimensional full-length femur was conducted by software and osteotomy was performed at the intertrochanteric crest to make AO/OTA 31-A1.1 fracture model. DHS, PFNA, InterTAN and TD-PFIN fixation systems were simultaneously made.TD-PFIN had three head nails, which were vertically and horizontally dispersed in the proximal femur. Normal physiological weight bearing was simulated by finite element analysis, and peak von Mises stress and the maximum displacement in the femur and internal fixation were recorded. Results: An axial load of 700N was applied to the femoral head to simulate normal adult weight. Among the fixation systems, the TD-PFIN had the lowest peak von-Mises stress, which was 111.79 MPa. the DHS model had the highest stress concentration, which was 231.71 MPa. In the Von-Mises stress distribution of the femur, the maximum stress was 14.696 MPa in DHS fixed model and the least was 10.162 MPa in TD-PFIN fixed model. In the displacement distribution of the internal fixations, The DHS model was 3.8991 mm, which was the most. The TD-PFIN fixed model had a minimum displacement of 3.1571m. In the displacement distribution in femur, the DHS internal fixation model was the largest (4.017 mm). The TD-PFIN fixed mod was the smallest (3.1886 mm). Conclusion: TD-PFIN designed by us had the characteristics of multi-plane fixed, with better anti-rotation ability. Its mechanical stability was better than DHS, PFNA, and InterTAN.