Clinical outcomes after medial open-wedge high tibial osteotomy are not affected by joint space in extension and flexion on standing radiographs

This study aimed to evaluate the surgical outcomes of MOWHTO in patients categorized based on joint space width (JSW) patterns observed in extension and flexion positions and to identify factors associated with these outcomes. This retrospective study involved 172 patients who underwent MOWHTO between 2016 and 2021. Patients were classified into four groups based on the median values of preoperative medial JSW in extension and flexion positions, measured on standing AP and Rosenberg views, respectively: the extension osteoarthritis (OA) group, the flexion OA group, the minimal JSN group, and the severe JSN group. Perioperative parameters, including demographic data, meniscal status, cartilage grade (International Cartilage Repair Society grading system), knee alignment, and posterior tibial slope (PTS), were analyzed. Clinical outcomes were assessed between groups using the Lysholm score, recorded preoperatively and during follow-ups. Among all enrolled patients, the mean follow-up duration was 3.54 years; the Lysholm score significantly improved from 48.31 preoperatively to 89.32 at 2 years postoperatively. No significant differences in Lysholm scores(P = .795) were observed between the groups postoperatively. PTS showed a negative correlation with extension JSW(R = -.315, P < .001) and a positive correlation with preoperative varus deformity(R = .258, P = .004), as measured with the hip-knee-ankle angle. Additionally, preoperative PTS values differed significantly among the groups, with the flexion OA group exhibiting higher PTS(p < .001). MOWHTO is an effective surgical procedure regardless of knee JSW in extension or flexion positions. PTS was identified as a distinguishing factor for flexion JSN. : Level IV, retrospective therapeutic case series.