Effects of K-wire diameter and insertion angle on femoral bone medial closing-wedge osteotomies: a finite element study

Medial closing-wedge surgery for distal femoral osteotomy is employed to correct genu valgum by correcting coronal plane malalignment. This procedure involves pre-surgery planning, creating a wedge incision, performing the osteotomy, and stabilizing with plates and screws. However, hinge fractures during wedge closure present significant challenges, often necessitating revisions. Contemporary solutions have explored the use of k-wires, and this study investigates their biomechanical implications. The interplay between k-wire insertion angle and diameter, often overlooked in existing literature, is a critical determinant of their efficacy in achieving successful osteotomies, highlighting gaps in our understanding of these key parameters. We hypothesize that k-wire mechanics vary with insertion angle and diameter. This study examines the introduction of k-wires at different angles (30°, 45°, and 60°) and diameters (1.6, 1.8, and 2 mm) using computed tomography-based finite element models to assess structural integrity during femoral medial closing-wedge osteotomy. Results reveal angle-dependent stress variations, with 60° configurations exhibiting favorable patterns that reduce tensile and compressive loads and plastic deformation-crucial in preventing hinge fractures. Diameter variations show no significant differences in stresses or system stiffness. It was also found that while angle significantly affects stresses, lower diameters appear optimal only in combination with higher angles. Comparative analysis of k-wire systems with a naïve model demonstrates that k-wires at a 60° angle reduce tensile and compressive loadings and plastically deformed volume fractions, thus lowering fracture risk. This study underscores the importance of optimizing k-wire placement and configuration, particularly highlighting the significance of the insertion angle. Future research should expand the range of angles and diameters tested and examine different femoral geometries and osteotomy angles to provide a more comprehensive understanding and enhanced clinical application.