Incidence and Predictors of Lateral Hinge Fractures Following Medial Opening-Wedge High Tibial Osteotomy Using Locking Plate System: Better Performance of Computed Tomography Scans

Background: This study compared the rates of plain radiographs and computed tomography (CT) for detecting lateral hinge fractures and to evaluate factors affecting lateral hinge fractures in patients following medial opening-wedge high tibial osteotomy (MOWHTO). Methods: This prospective study included 59 patients (65 knees) undergoing MOWHTO for primary medial compartment osteoarthritis with a 2-year follow-up between 2013 and 2016. Clinical and radiographic evaluations were performed using Knee Society Score and Western Ontario and McMaster Universities Arthritis Index, and we calculated the hip-knee-ankle angle, weight-bearing line ratio, lateral distal femoral angle, medial proximal tibial angle, posterior tibial slope, osteotomy gap height, and osteotomy gap filling rate. Immediate plain radiographs and CT were used to detect lateral hinge fractures according to Takeuchi's method. Results: Among 65 knees, the incidence of lateral hinge fractures was 13.8% (Type I: 7, Type II: 2). Only 6 knee fractures (9.2%) were detected on postoperative plain radiographs, including 5 Type I fractures and 1 Type II fracture. An additional 3 knees (4.6%) were detected on postoperative CT scans, including 2 Type I fractures and 1 Type II fracture. Furthermore, osteotomy gap height (adjusted odds ratio = 1.831, P =.016) was the only predictor of lateral hinge fractures. Conclusion: The incidence of lateral hinge fractures after MOWHTO was 13.8%. CT (13.8%) afforded higher detection rates for lateral hinge fractures than did plain radiographs (9.2%) despite a marginal difference with uncertain significance. Osteotomy gap height was the only predictor of lateral hinge fractures. Level of Evidence: Prospective cohort study (Level II).