Effects of Schanz screw location on reduction efficiency in distal femur fractures: A finite element analysis.

OBJECTIVES

The aim of this study was to evaluate the biomechanical efficiency of different Schanz screw positions for indirect reduction of distal femur fractures using finite element analysis.

MATERIALS AND

METHODS

A three-dimensional finite element model of a comminuted distal femur fracture was constructed, incorporating relevant anatomical structures including ligaments, menisci, and the gastrocnemius muscle. A 30 N posterior force simulated gastrocnemius-induced deformity, followed by a 15 N horizontal traction force applied through Schanz screws inserted at six positions (hole 1 to 6) on a standard distal femur locking plate. Residual displacement and reduction ratios were measured to assess reduction efficiency.

RESULTS

The model successfully replicated the characteristic posterior displacement (~15 mm) caused by gastrocnemius contraction. Among the six pin positions, hole 6 (most anterior and distal position) achieved the greatest reduction (12.90 mm) with an 86.83% correction ratio, while hole 4 (most posterior and distal position) performed the worst (26.88%). More anterior and distal pin locations provided superior reduction outcomes due to improved mechanical advantage and alignment with the deforming force vector.

CONCLUSION

Schanz screw placement significantly influences the effectiveness of traction-assisted reduction in distal femur fractures. Hole position 6 yielded the most optimal biomechanical performance and may serve as a practical reference for optimizing intraoperative pin placement, potentially improving surgical efficiency and outcomes.