Stress fluoroscopic evaluation of dynamic knee stability after medial open-wedge high tibial osteotomy: preoperative instability predicts postoperative stabilization

Medial open-wedge high tibial osteotomy (OWHTO) is widely performed for medial compartment pathology associated with varus malalignment. Although OWHTO corrects static alignment, its influence on dynamic knee stability remains unclear. This study aimed to evaluate changes in coronal and sagittal dynamic stability after OWHTO using intraoperative stress fluoroscopic assessment.

Thirty-eight knees in 35 patients undergoing OWHTO were retrospectively reviewed. Coronal stability was assessed using dynamic joint line convergence angle (dJLCA) and dynamic femorotibial angle (dFTA), and sagittal stability was evaluated using anterior tibial translation relative to Blumensaat's line (ATB). Alignment parameters included femorotibial angle (FTA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS). Clinical outcomes were assessed using Lysholm, IKDC, and KOOS scores up to 12 months postoperatively. Pre- and postoperative differences were analyzed using the Wilcoxon signed-rank test, and correlations were evaluated using Spearman's rank correlation.

All alignment and stability parameters significantly improved postoperatively (p < 0.001). dJLCA and ATB showed marked reductions, indicating decreased stress-induced coronal and sagittal instability. Clinical scores significantly improved at 12 months (p < 0.001). Greater preoperative instability was strongly correlated with greater postoperative stabilization (dJLCA ρ = 0.794; dFTA ρ = 0.765; ATB ρ = -0.765; PTS ρ = 0.530).

OWHTO improves coronal and sagittal dynamic stability under stress conditions. These findings suggest that dynamic instability in varus knees is largely caused by malalignment and can be improved by osteotomy. Stress fluoroscopic assessment may aid in identifying correctable instability and guiding surgical planning.

IV.