Comparative 3D finite element analysis of intramedullary fixation versus locking plate fixation in calcaneal...

Calcaneal fracture fixation remains a challenging procedure in orthopedics, with computational tools increasingly aiding in the optimization of preoperative planning. To compare the biomechanical stability of intramedullary fixation and locking plate fixation for Sanders II and III calcaneal fractures by three-dimensional (3D) finite element analysis and to provide a theoretical basis for clinical application.

The Computed Tomography (CT) images were segmented using Mimics software (Materialise NV, Belgium) to identify the region of interest based on threshold segmentation. The 3D morphology was reconstructed using Mimics 10.01 software. Subsequently, Geomagic2012 software (3D Systems, USA) was employed to remove noise points, sharp corners, and scattered points, achieving a smooth surface map. This map was saved in Initial Graphics Exchange Specification (IGES) format and imported into Solidworks (Dassault Systèmes, France) for model assembly and volume model construction. A three-dimensional finite element model of Sanders II/III, calcaneal fractures with intramedullary fixation and locking plate fixation, was established and analyzed by linear finite element analysis. The forced displacement, stiffness, and stress distribution of the two fixation methods were calculated. In addition, the three-dimensional model was tested using a compression mechanical experiment.

Comparing fixation methods for Sander II and III fractures, the force-displacement curve of the intramedullary nail group aligned more closely with standards. Under axial compression, bone stress was highest with the Sanders II locking plate and lowest with the intramedullary nail. Across models, the intramedullary nail consistently exhibited slightly higher stress than the locking plate. The intramedullary nailing group model of the overall stiffness was slightly greater than the locking plate. By comparing the compressive mechanical test performance of the two fixation methods, it was found that the plate fixation group had an abnormal load until 7092.895 N, which was 1.5 times more than the load of the intramedullary nail.

Both intramedullary fixation and locking plate fixation for Sanders II and III calcaneal fractures have certain biomechanical stability, and locking plate fixation has potential application value in clinical practice.