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

Abstract

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.