Higher fibular head is a risk for lateral hinge fracture in medial open wedge high tibial osteotomy

Abstract Purpose To examine the association between the hinge position, fibular head position, and type III lateral hinge fracture (LHF) in patients with knee osteoarthritis (OA) who underwent medial open wedge high tibial osteotomy (MOWHTO). Methods This retrospective study examined patients who underwent MOWHTO. Radiographically, the Kellgren–Lawrence (K/L) classification, distance between the articular surface and the tip of the fibular head (fibular head position), hinge point (hinge position), type of LHF, and safe zone (within the proximal tibiofibular joint) outlier were evaluated. To determine the cut‐off value of the hinge position and fibular head position associated with type III LHF, a receiver operating characteristic (ROC) curve analysis was performed. The odds ratio (OR) was calculated from the obtained cut‐off values using logistic regression, which was adjusted by age, gender, body mass index, and opening distance. Results Among 132 knees in 120 patients, the radiographic severity of knee OA was 19 (14%), 73 (55%), and 40 (30%) of K/L grades 2, 3, and 4, respectively. LHF was observed in 40 knees (30%), including types I, II, and III fractures in 21 (16%), 5 (4%), and 14 (11%) knees, respectively. Hinge and fibular head positions were 16 and 10 mm, respectively, with significant correlation. Safe zone outlier was observed in 38 knees (29%). The hinge and fibular head positions with type III LHF were significantly higher (more cranial) than those with no fracture or other LHF subtypes. The ROC curve revealed that the cut‐off value for the hinge and fibular head positions was 13.3 and 8.6 mm, respectively. The OR of the hinge and fibular head positions was 22.42 and 13.86, respectively. Conclusions A higher hinge position was a risk factor for type III LHF and was associated with a higher fibular head in patients with knee OA who underwent MOWHTO. The hinge position should be placed at a certain distance from the articular surface to avoid type III LHF, especially in participants with higher fibular head position, even if the hinge position is located in the safe zone. Level of evidence Retrospective cohort study, Level III.