Biomechanical evaluation of a newly designed locking plate for opening wedge high tibial osteotomy: stress distribution and stability in the presence of lateral hinge fracture.

Background: The study aimed to evaluate whether a new OhtoFix plate reduced stress around the D-hole compared with an old OhtoFix and TomoFix plate. The study also assessed whether the new OhtoFix plate had biomechanical stability in a lateral hinge fracture (LHF).

Methods: A finite element model of the proximal tibia was developed using cross-sectional images from a 62-year-old Asian woman. The model was designed to simulate opening wedge high tibial osteotomy (OWHTO) using three types of locking plates: the newly designed locking plate (new OhtoFix plate), the prior version of the OhtoFix plate (old OhtoFix plate), and the TomoFix plate. The peak von Mises stress (PVMS) was analyzed around the D-hole and across the entire plate including the impact of different LHF types classified according to the Takeuchi classification.

Results: The new OhtoFix plate significantly reduced stress around the D-hole compared with the old OhtoFix and TomoFix plates, with peak stresses of 189.5 MPa, 251.5 MPa, and 233.3 MPa, respectively. Despite this improvement, the new OhtoFix plate did not surpass the TomoFix in terms of overall stress distribution across the entire plate. Additionally, in cases of LHF, although peak stress remained at the D-hole in both the old OhtoFix and TomoFix plates, the peak stress shifted to the C-hole in the new plate.

Conclusions: The new OhtoFix plate improved stress distribution around the D-hole (even in the presence of a LHF) compared to the old OhtoFix plate and TomoFix plates. However, although the new OhtoFix plate reduced peak stress around the D-hole, it did not demonstrate superior overall stress distribution across the entire plate compared to the TomoFix plate.