Abstract
<title>Abstract</title> <p> <bold>Background:</bold> The present study aimed to evaluate the changes in rotational alignment of the lower extremity under weight-bearing conditions before and after open-wedge distal tibial tuberosity osteotomy (OWDTO) using the EOS imaging system. <bold>Methods:</bold> 63 knees from 63 subjects who underwent OWDTO were included in the present study. Rotational alignment, including femorotibial rotation angle (FTRA) and tibial torsion angle (TTA), and coronal alignment were evaluated by EOS imaging both preoperatively and 6 months postoperatively. Additionally, the correction angle, the tibial osteotomy angle, and the presence of hinge fracture were evaluated by CT scanning 1 week postoperatively. Clinical outcomes were assessed using the Knee injury and Osteoarthritis Outcome Score (KOOS) preoperatively and 6 months postoperatively. The changes in rotational alignment and the association between rotational alignment and other parameters were analyzed. <bold>Results:</bold> There was no significant difference between preoperative and postoperative FTRA (preoperative: 0.6 ± 4.0°, postoperative: -0.3 ± 3.6°, <italic>p</italic> = 0.215), but TTA significantly increased (21.1 ± 6.7°, 23.5 ± 6.7°, <italic>p</italic> = 0.012). The change in TTA was not associated with changes in coronal alignment or other radiological parameters. TTA increased significantly in the group without hinge fractures (ΔTTA: 3.4 ± 3.2°, <italic>p</italic> < 0.001), but not in the group with hinge fractures (ΔTTA: -0.2 ± 2.9°, <italic>p</italic> = 0.491). Multivariable linear regression analysis demonstrated that hinge fracture remained significantly associated with ΔTTA. Although ΔTTA was positively associated with improvement in the KOOS Symptoms subscale at 6 months postoperatively, no significant associations were observed for the other KOOS subscales. <bold>Conclusions:</bold> A significant external rotation of the distal tibia was observed after OWDTO but not in the group with hinge fractures. This result suggests that the structural integrity of the hinge may play an important role in determining distal tibial rotational change. Although postoperative distal tibial external rotation did not appear to adversely affect short-term patient-reported outcomes, its long-term clinical implications remain unclear. </p>