Antegrade versus retrograde elastic stable intramedullary nail in treating different types of distal femoral fracture: A finite element study.

Introduction: Titanium elastic nails (TEN) was the optimal treatment for diaphyseal fractures of femoral in children. However, achieving similar stability in distal femur was more challenging. The optimal needle insertion method is still controversial. The purpose of the study was to compare the stability of antegrade and retrograde TEN for the treatment of distal femoral metaphyseal-diaphyseal junction (MDJ) fracture in children.

Hypothesis: We hypothesized that retrograde approach will provide greater stability in both fracture models.

Material and methods: The computed tomography (CT) data of the femur of a 10-year-old boy were imported into the computer software to create transverse and oblique MDJ fractures. The finite element method was used to calculate the axial, rotational and bending stability of the two fracture models with different TEN insertion methods.

Results: In transverse fractures, the rotational, axial, and bending stability with retrograde approach was better than antegrade approach. In oblique fractures, the rotation and axial stiffness of retrograde approach were greater than anterograde approach. However, the bending stiffness of anterograde approach was greater than retrograde approach. The rotation stiffness of oblique fracture was greater than transverse fracture in two fixation methods.

Discussion: Retrograde approach can provide better stability in the transverse fracture. Antegrade approach has better bending stiffness in the fixation of oblique fractures. The mechanical testing results suggest that retrograde nailing is suitable for transverse fractures, while antegrade nailing is better for oblique fractures.

Level of evidence: II; Comparative biomechanical study.