New Fixation Method for Pauwels Type III Femoral Neck Fracture: a Finite Element Analysis of Sliding Hip Screw, L-shaped, and L-shaped with Medial Plate

In this study, we aimed to evaluate the biomechanical behavior of three fixations for Pauwels type III fractures (sliding hip screw (SHS), L-shaped, and L-shaped with medial plate), by finite element analysis (FEM). Three internal fixators were developed to treat Pauwels type III fracture by finite elements: SHS; L-shaped; and L-shaped with medial plate. Under the same conditions, localized and total vertical fracture displacement, maximum and minimum principal and von Mises stresses were evaluated. The localized and total vertical displacement evaluated for the SHS, L-shaped, and L-shaped with medial plate were 0.15 mm, 0.17 mm, and 0.07 mm (localized), and 4.52 mm, 6.97 mm, and 6.83 mm (total), respectively. The maximum values obtained in the upper region of the femoral neck for the internal fixations were 1.43 MPa, 1.29 MPa, and 1.24 MPa, and the minimum values obtained in the lower region of the femoral neck were  − 0.73 MPa,  − 1.09 MPa, and  − 1.03 MPa, respectively. The maximum Von Mises peak stress values were 6.35 MPa, 10.7 MPa, and 16.2 MPa for the fixation models using the SHS, L-shaped, and L-shaped with medial plate, respectively. The present FEM analysis showed that SHS yields better results in terms of total vertical displacements, maximum distribution, and Von Mises peak stresses reduction. On the other hand, the L-shaped construction plus a medial plate decreases localized vertical displacements and maximum principal distribution when compared to the SHS and L-shaped constructions. These results demonstrate that both constructions, SHS and L-shaped plus a medial plate, are biomechanically efficient for the fixation of Pauwels type III femoral neck fractures.