Tibiotalocalcaneal Arthrodesis: A Biomechanical Comparision of Multiplanar External Fixation with Intramedullary Fixation

Background: Methods of achieving tibiotalocalcaneal arthrodesis include intramedullary nailing, crossed lag screws, blade plates, and external fixation. While reports in the orthopaedic literature have compared the biomechanical properties of some of these fixation techniques, to our knowledge none has evaluated multiplanar external fixation. The purpose of this study was to compare the biomechanical properties of intramedullary nail fixation and external ring fixation for tibiotalocalcaneal arthrodesis. Materials and Methods: Tibiotalocalcaneal arthrodesis was performed on ten matched pairs of fresh-frozen human cadaveric legs. A ring fixator stabilized the arthrodesis in one leg from each pair and a 10 mm × 150 mm nail inserted retrograde across the subtalar and ankle joint stabilized the arthrodesis in the contralateral leg. The bending stiffness of the resulting constructs was quantified in plantarflexion, dorsiflexion, inversion, and eversion, and torsional stiffness was measured in internal and external rotation. Results: No difference in bending stiffness between the two constructs was identifiable in any of the four bending directions (p > 0.05). Torsional stiffness was approximately two-fold greater in both internal and external rotation in specimens with the ring fixator arthrodesis than in those with the intramedullary nail (p = 0.002). Conclusion: The ring fixator provides a stiffer construct than a 10 mm × 150 mm intramedullary nail in torsion, but no difference in bending stiffness was demonstrable. Both techniques can provide satisfactory fixation; however, the ring fixator may better minimize rotational joint motion. Clinical Relevance: This study provides a basis for selecting an arthrodesis method that offers optimized fixation.