Reconstruction and finite element evaluation of a calcaneous implant by stereolithographic 3d printing technique

Flexible flat foot in infants can cause pain and physical limitation. Surgical treatment is preferred when pain is severe. Evans enlargement of the lateral aspect of the calcaneus has good results but has complications due to the collapse of bone grafts. Tridimensional segmentation of anatomical areas allows to obtain stereolithographic models that can be numerically analyzed. A stereolithographic model of a healthy calcaneus was obtained from a CT and virtually sectioned to simulate Evans osteotomy. A wedge-shaped implant was made and implanted as described by Evans. Both models were analyzed with a finite element software, the calcaneus model comprised cortical and cancellous bone layers (E = 20 GPa and 457 MPa respectively) The wedge-shaped was assigned PMMA properties (E = 2.4GPa). Three phases of human gait were simulated and stress obtained. The highest von Mises stress occurred at the stance phase (18.25 MPa). None of the stress exceeded the yield stress for all materials in all phases. Reconstruction of anatomic models and implants using a stereolithographic technique allow to predict stress and failure. These models could also be printed 3D to elaborate novel implants.