Biomechanical comparison of four different internal fixation constructs applied to stabilise Letenneur type I Hoffa fractures: a finite element analysis.

OBJECTIVE

To simulate and compare the biomechanical characteristics of different internal fixation constructs for treating Letenneur type I Hoffa fractures via finite element analysis to establish a theoretical foundation for selecting a fixation method in clinical practice.

METHODS

On the basis of computed tomography (CT) data acquired from a healthy adult male volunteer, a finite element model of Letenneur type I Hoffa fracture—characterized by a fracture line oriented parallel to the posterior femoral cortex—was developed. Four different internal fixation constructs were constructed: anteroposterior cannulated screw fixation (AP group), posteroanterior cannulated screw fixation (PA group), posteroanterior cannulated screws with a posterior plate (PA + P-plate group), and posteroanterior cannulated screws with a lateral plate (PA + L-plate group). Under a vertical load of 2100 N, the displacement distribution, stress distribution, and peak values of the internal fixation and femur were analyzed.

RESULTS

Under a 2100 N axial load, the AP and PA groups presented the highest and comparable peak displacement values in the femur and internal fixation (3.80 mm, 3.46 mm, and 3.84 mm, 3.41 mm, respectively). The PA + P-plate group presented the lowest peak displacement value (1.85 mm and 1.58 mm), followed by the PA + L-plate group (2.25 mm and 2.19 mm). Similarly, the AP and PA groups presented the highest peak stresses in the internal fixation (535.65 and 574.39 MPa, respectively), whereas the PA + P-plate group presented the lowest peak stress (287.21 MPa). The stress distribution patterns in the femur were similar across all groups, with concentrations primarily on both sides of the fracture line, the posterolateral region, and the anterior aspect.

CONCLUSIONS

The mechanical stability of Anteroposterior (AP) and posteroanterior (PA) screws is comparable. While the addition of a plate significantly enhanced fixation stability, the posterior plate demonstrated superior biomechanical performance compared with the lateral plate.