Background: The tibial slope usually increases after open wedge high tibial osteotomy (OWHTO), and this increase could be related to incomplete osteotomy of the posterolateral cortex. If incomplete osteotomy is performed at the posterolateral side, the opening gap is dominantly increased at the anterior side, leading to an unnecessary increase in the posterior slope. For a good natural gap ratio, appropriate osteotomy of the posterior cortex is important. However, to date, the most appropriate osteotomy length or ratio of the posterior cortex has not been accurately established. Objectives: We aimed to 1) determine the length of the osteotomy and opening gap at the anterior and posterior side, 2) compare between uni- and bi-planar osteotomy, and 3) evaluate the relationship between extent of the osteotomy and change of the posterior tibial slope. The hypothesis of this study were that 1) anterior cortical osteotomy would be larger in the uni-planar osteotomy, 2) gap ratio would be larger in the bi-planar osteotomy, and 3) maintenance of the slope would be closely related to the length of posterior cortical osteotomy. …show more content…
To evaluate the length of osteotomy, osteotomy lines of the anterior and posterior cortex were analyzed in the 3D surface models. For slope measurement, the intramedullary axis of the proximal tibia (slope P), posterior cortical line of the proximal tibia (slope C), and anterior cortical line of the proximal fibula (slope F) were used. Analysis of the changes in the posterior tibial slope was performed independently using a pre- and post-operative lateral plane