HTO and peripheral instability
High tibial osteotomy (HTO) is a surgical procedure used to change the mechanical weight-bearing axis of the lower limb. Traditionally knee instabilities were considered as a contraindication to this surgery. Recently it has been emphasized that an HTO procedure can change not only the coronal but also the sagittal plane of the knee. The sagittal plane modifications have generally been ignored in HTO literature, but they have a significant impact on biomechanics and joint stability. It has been demonstrated that decreased posterior tibial slope causes posterior tibial translation and helps the anterior cruciate ligament (ACL). On the other hand, increased tibial slope causes anterior tibial translation and helps the posterior cruciate ligament (PCL). Furthermore, chronic instabilities can be associated with initial malalignment, like in the “triple varus” knee. For these reasons, an HTO can be useful to treat a PCL-/posterolateral corner (PLC)-deficient knee associated with a varus malalignment, combined with or without ACL deficiency. In this chapter we analyze the role of HTO in peripheral instability, focusing on alignment, rationale in using an osteotomy to correct an unstable knee, preoperative planning, and surgical technique and outcomes.
