The effect of pedicle screw angle on stress distribution in lumbar spine fixation: an optimization approach based on finite element analysis.

BACKGROUND

Pedicle screw fixation is widely used for lumbar spine stabilization, and technical parameters such as screw insertion angle may influence the biomechanical behavior of the implant-bone construct.

OBJECTIVE

This study aimed to evaluate the effect of different transverse pedicle screw insertion angles (25°, 30°, 35°, and 40°) on stress distribution in the L4-L5 segment using three-dimensional finite element analysis (FEA).

METHODS

A three-dimensional finite element model of the L4-L5 lumbar segment was developed from computed tomography data of a healthy adult subject. Titanium alloy (Ti-6Al-4 V) pedicle screws (6.5 mm diameter) were modeled at four predefined insertion angles. A 400 N axial compressive load was applied to simulate physiological loading conditions. Stress distributions were analyzed using von Mises criteria within the ANSYS Workbench environment.

RESULTS

Maximum von Mises stress values varied across insertion angles. The highest stress (399.26 MPa) was observed at 25°, primarily at the screw head-rod junction and screw-bone interface. The lowest stress (297.86 MPa) was recorded at 40°. A decreasing trend in stress values was observed with increasing insertion angle.

CONCLUSION

Pedicle screw insertion angle affects stress distribution in the L4-L5 segment. Higher insertion angles were associated with lower stress values, suggesting a potentially more favorable biomechanical environment. These findings indicate that insertion angle may be an important parameter in pedicle screw fixation planning.