The effect of tibial rotational deformity on ankle joint loadings: A finite element analysis.

BACKGROUND: Tibial shaft fractures are common, and malrotation is a frequent complication after intramedullary nailing. This study evaluated the effect of tibial malrotation on ankle joint loading using finite element analysis. METHODS: Finite element models were created from Visible Human Project CT data. A distal one-third transverse tibial shaft fracture was fixed with an intramedullary nail. Seven models were analyzed: neutral, 5°, 15°, and 25° internal rotation (IR), and 5°, 15°, and 25° external rotation (ER). A 2500 N axial load was applied, and tibiotalar cartilage and implant stresses were assessed. RESULTS: Tibiotalar cartilage loading increased with malrotation, peaking in the 25° IR model. Internal rotation consistently produced greater stresses than equivalent external rotation. CONCLUSION: Tibial malrotation increases ankle cartilage loading after intramedullary nailing. Internal rotation causes greater biomechanical changes than external rotation and may increase the risk of ankle arthrosis.