Osteotomy Wedge Computational Study of New Implant: Interfragmentary Movement

Medial Opening Wedge Proximal Tibial Osteotomy (MOWPTO) is a surgical procedure used for treatment of medial condyle's osteoarthritis. This study aimed to analyze the interfragmentary relative movement (IFM) of a wedge after specific loading conditions were applied to the New Plate for Osteotomy (NPO), using finite element method. Three tibia distinct finite element models with an opening wedge were simulated and fixed with: (1) the NPO, (2) a straight T-plate (STP) and a (3) curved T-plate (CTP). Two postoperative loading conditions were simulated and analyzed: the first and sixth week after surgery. The maximum von Mises stress in the NPO (362.62MPa) was 57.08% higher than the STP and 23.47% higher than the CTP. The NPO displacement (1.37mm) was similar to the intact tibia. For postoperative week 1, the wedge with NPO showed a minimum axial IFM of 169.58μm and a maximum of 218.14μm, and a minimum and maximum shear IFM of 1.21μm and 0.96μm, respectively. In postoperative week 6, the minimum axial IFM was 165.20μm and a maximum of 284.01μm, and a minimum and maximum shear IFM of 47.52μm and 50.82μm, respectively. The implants showed lower stress than the yield strength of titanium alloy (Ti-6Al-4V) and allowed a displacement of the fractured tibia similar to the intact tibia displacement. The wedge showed micromotions and strain levels that allow a bone healing in both load conditions.