Effect of fracture level on optimal Kirschner wire configuration in pediatric supracondylar humerus fractures: A finite element analysis.

Objectives: This study aims to evaluate the biomechanical stability of three pin configurations for transverse supracondylar humerus fractures at various levels using finite element analysis (FEA).

Materials and methods: Computed tomography data from a six-year-old child were used to generate a humerus bone model. Four different fracture levels (low, transolecranon, high, and ultrahigh) and three pin fixation techniques (one lateral and one medial cross-pin [1-1M], two lateral capitellar pins [1-1C], and three lateral capitellar pins [2-1C]) were designed for the study. Translational stiffness and rotational stiffness in all directions were analyzed in the mesh models. Convergence data and stiffness data were obtained in the FEA.

Results: The translational and rotational stiffness values varied across fracture levels and pin configurations. Under valgus loading, the 1-1M configuration provided the highest stability in ultrahigh fractures (3289 N/mm), while the 2-1C configuration showed superior valgus and varus stability in low and transolecranon fractures. During extension and flexion loading, the 1-1M configuration yielded the highest stiffness values for transolecranon and high fractures, while the 2-1C configuration demonstrated increased stability in low and ultrahigh fractures. For rotational loading, 1-1M produced the highest inward and outward stiffness values in low-level fractures (9175 and 11035 N·mm/degree, respectively), whereas 2-1C displayed greater rotational stiffness in ultrahigh fractures.

Conclusion: This preliminary study suggests that no single pin configuration is ideal for all fracture types, and the choice should be based on the specific fracture case.