Comparison of the mechanical performance of intramedullary nail and locking plate in tibiotalocalcaneal arthrodesis

Aims: This study uses finite element analysis (FEA) to compare intramedullary nail (IMN) and locking compression plate (LCP) in tibiotalocalcaneal arthrodesis (TTCA), examining biomechanical changes in the joints and assessing which construct better supports arthrodesis under axial loading. 

Methods: A 3D finite element model of the foot-ankle complex was constructed from CT images of a 29-year-old male’s lower limb. The model included homogeneous cortical and trabecular bones, cartilage, and 29 ligaments. Titanium alloy (Ti6Al4V) implants simulated IMN and LCP fixations. The inferior surfaces of the metatarsals and calcaneus were fixed, and axial loads of 1×, 2×, and 3× body weight (BW) were applied. Von Mises stress and joint displacement evaluated construct stability. 

Results: At 1× BW, the IMN model exhibited the highest joint surface stress (32.44 MPa, superior talus) and higher implant stresses than those of the LCP model. Under increased loading, stress rose substantially in both models, peaking at +364.38% in LCP (superior talus) and +130.98% in IMN screws. Stress in the LCP model was more widely distributed across the tibia and calcaneus, while in the IMN model it was concentrated in the talus. At 3× BW, the LCP calcaneus exhibited the largest proportion of elements within the elevated stress range (5.3%). Peak displacement was higher in LCP (376 μm at 1× BW). Although IMN showed larger relative displacement increases, absolute joint displacements remained consistently lower than LCP. Conclusion Both IMN and LCP provide sufficient mechanical support for TTCA. IMN offers greater initial stability, reflected by lower joint displacement, but generates higher implant stress, particularly under increased loading. In contrast, LCP exhibits more uniform stress distribution and smaller screw stress increases as load rises, and may offer improved mitigation of implant stress concentrations under elevated loads.