Editorial Commentary: Tibial Slope Should Be Naturally Maintained by Proper Posterior Cortical Osteotomy and Gap Distraction in Open-Wedge High Tibial Osteotomy

The tibial slope usually increases after open-wedge high tibial osteotomy (OWHTO) because of several factors. The anteromedial cortex of the proximal tibia is angulated 45 degrees relative to the posterior cortex, whereas the lateral cortex is nearly perpendicular. Therefore, an OWHTO with equal anterior and posterior gaps will increase the tibial slope. In addition, an anteromedial approach to the proximal tibia because of concern about neurovascular injury results in the failure to perform a proper osteotomy of the posterolateral cortex. Slope-optimization methods include a sagittally oriented hinge, posterior bone grafting, posterior plating, and forcefully extending the knee to compress the anterior gap sagittally oriented hinge, posterior positioning of the wedged plate, and knee extension during fixation. However, if the tibial slope is easily controlled using knee extension, this may indicate fracture of the lateral hinge, whereas a preserved lateral hinge is a prerequisite for a successful OWHTO. Most of all, a proper posterior cortical osteotomy is the key step to preventing increased tibial slope in OWHTO. Again, if an incomplete osteotomy is performed posterolaterally, the opening gap is increased anteriorly, leading to an unnecessary increase in posterior tibial slope; for biplanar osteotomy, retrotubercular osteotomy should be performed close to the patellar tendon and not be advanced to the posterolateral side of the hinge.