The Internal Fixation Selection and Positioning for Proximal Femoral Basicervical  Fractures: A Biomechanical Study Through Finite Element Analysis

Objectives: This study aims to determine the most suitable implant for proximal femoral basicervical fractures by comparing the biomechanical characteristics of the Dynamic Hip Screw (DHS), Proximal Femoral Nail Anti-Rotation (PFNA), and InterTAN implants through finite element analysis (FEA). Methods: Thefive fixation styles, namely DHS with a central hip screw in Anteroposterior view , PFNA with a centrally positioned helical blade (PFNA-center), PFNA with an inferiorly positioned helical blade (PFNA-inferior), InterTAN with a centrally positioned hip screw (InterTAN-center), and InterTAN with an inferiorly positioned hip screw (InterTAN-inferior), were simulated. After a three-dimension model of an intact femur was constructed and validated, three distinct basicervical fracture patterns, namely simple, intertrochanteric defect, and lateral wall defect, characterized by increasing displacement and/or bone loss with subsequent instability, were created and incorporated with the aforementioned implants. The models were subjected to FEA, and A load of 700 N was applied to simulate a 70 kg patient standing on one leg. The displacement and stress distributions on implants were analyzed for comparison between implants. Under each basicervical fracture type, we mainly compared DHS, PFNA-center, and InterTAN-center to assess the best implant performance. In addition, we compared PFNA-center and InterTAN-center with PFNA-inferior and InterTAN-inferior to assess the best hip screw position. Results: In the simple basicervical fracture, DHS, PFNA, and InterTAN exhibited similar and small results in displacement and maximum stress in implants. In the intertrochanteric defect and lateral wall defect basicervical fractures, notable differences were observed within implants. The displacement was greatest with the DHS, followed by the PFNA, then InterTAN(minimal different between PFNA and InterTAN). In contrast, the maximum stress was highest with InterTAN and was higher with PFNA than with DHS, with none of them exceeding the fatigue limit of medical titanium. Regarding the hip screw position with the cephalomedullary nails, the inferior position showed biomechanical parameters advantages compared with the central position. Conclusion: DHS, PFNA, and InterTAN are all suitable for the management of simple basicervical fractures. In the intertrochanteric defect and lateral wall defect basicervical fracture types, the cephalomedullary nail showed better mechanical stability and is preferred over DHS, with InterTAN showing slightly better stability compared to PFNA. The inferior hip screw position in cephalomedullary nails is preferable over the central hip screw position.