Finite element analysis of different internal fixation methods for the treatment of Pauwels type III femoral neck fracture.

OBJECTIVE

To compare the bifomechanical advantages and disadvantages of different internal fixation methods for the treatment of Pauwels type III femoral neck fractures.

METHODS

4 internal fixations were developed to treat Pauwels type III femoral neck fracture finite element models: a: the "F" shaped cannulated screw model, b: the traditional cannulated screw model, c: the "F" shaped cannulated screw coupled with medial plate model, d: the traditional cannulated screw coupled with medial plate. Under the same conditions, the 4 internal fixations and femur of von Mises stress and displacement distribution were studied.

RESULTS

The most significant displacement of all models occurred at the femoral head. The maximum displacement of the femoral heads included: a: 1.53 mm, b: 1.73 mm, c: 1.18 mm and d: 1.34 mm. The von Mises peak stresses of the femoral calcar area in different models were: a: 115.2 MPa, b: 143.5 MPa, c: 107.8 MPa and d: 120.5 MPa. The peak stresses of the four internal fixation models included: a: 318.0 MPa, b: 360.9 MPa, c: 468.8 MPa and d: 771.5 MPa.

CONCLUSION

The "F" shaped cannulated screw technique is capable of eliminating the torsional stress and shear stress while maintaining the axial compressive stress at the fracture end. Besides, the medial support plate can effectively resist the shearing force of the Pauwels III femoral neck fracture and create an excellent mechanical environment for fracture healing. Thus, for the Pauwels III femoral neck fracture, the use of "F" shaped cannulated screws combined with medial plate internal fixation are recommended.