Sagittal Plate Position and Posterior Tibial Slope Changes After Medial Open-Wedge High Tibial Osteotomy

Medial open-wedge high tibial osteotomy (HTO) is a well-established joint-preserving procedure for medial compartment osteoarthritis with varus malalignment. However, unintended changes in posterior tibial slope (PTS) may occur and affect knee biomechanics and cruciate ligament loading. This retrospective cohort study included 60 patients who underwent medial open-wedge HTO between 2018 and 2024. We investigated whether sagittal plate position on postoperative lateral radiographs (anterior vs posterior) influenced postoperative PTS change and its association with coronal alignment and short-term functional outcomes. Radiographic assessments included PTS, tibiofemoral angle, hip-knee-ankle angle, and mechanical axis deviation. Clinical outcomes were evaluated using the Hospital for Special Surgery (HSS) Knee Score and the Tegner Activity Scale. Multivariable linear regression was used to determine whether plate position independently predicted ΔPTS. The posterior plate group demonstrated a significantly greater increase in PTS than the anterior group (ΔPTS 4.3° ± 1.6° vs 0.9° ± 1.2°, p < 0.001), and postoperative PTS ≥12° was more frequent in the posterior group (67% vs 10%, p < 0.001). Coronal alignment parameters and functional scores were comparable between groups (all p > 0.05). Sagittal plate position was independently associated with postoperative PTS change after medial open-wedge HTO. Posterior placement resulted in greater slope increase, whereas anterior positioning better preserved sagittal alignment without compromising coronal correction or short-term clinical outcomes.