Biomechanical properties of four internal fixations for femoral neck fracture: a finite element comparison / 中华创伤骨科杂志

ABSTRACT

Objective:To compare the biomechanical properties of dynamic hip screw (DHS), traditional cannulated compression screw (CCS) configuration, traditional CCS configuration+medial locking plate and compression buttress screw (CBS) in the treatment of femoral neck fracture by finite element analyses.Methods:A simulation model of Pauwels type Ⅲ femoral neck fracture with discontinuous medial cortex was established by the finite element method. The maximum displacement, maximum principal stress, normal form equivalent stress, hip varus angle and fracture end stress were compared between DHS (group A), traditional CCS configuration (group B), traditional CCS configuration+medial locking plate (group C) and CBS (group D) in the simulation model.Results:In the internal fixation model in groups A, B, C and D, respectively, the maximum displacement of the femur was 0.41 mm, 2.04 mm, 0.94 mm and 0.30 mm; the maximum displacement of internal fixation 0.34 mm, 1.18 mm, 0.84 mm and 0.22 mm; the peak normal form stress of internal fixation 83.6 MPa, 231.4 MPa, 259.8 MPa and 194.8 MPa; the maximum principal stress of internal fixation 52.3 MPa, 216.3 MPa, 151.7 MPa and 74.6 MPa; the maximum normal form stress of the femur 101.1 MPa, 282.3 MPa, 100.5 MPa and 181.2 MPa; the maximum principal stress 99.7 MPa, 201.0 MPa, 60.9 MPa and 56.1 MPa; the axis angle of the femoral neck after loading 179.55°, 176.97°, 179.66° and 179.64°; the normal form equivalent stress at the fracture end ranged from 42.0 to 50.0 MPa, from 258.7 to 282.3 MPa, from 50.8 to 58.1 MPa, and from 45.3 to 60.4 MPa.Conclusion:Considering stability, stress distribution and prevention of hip varus and femoral neck shortening, CBS may be a choice treatment for femoral neck fracture because it is comparable to DHS in mechanical stability.