MRI-based classification of lateral hinge fractures in medial opening wedge high tibial osteotomy

AIM: To investigate the variants of lateral hinge fracture and its outcome, as well as to develop a MRI based classification on the fracture line pattern. METHODS: This retrospective study analyzed 250 knees from 227 patients (169 females, 58 males) who underwent medial opening wedge high tibial osteotomy. Lateral hinge fractures were detected using MRI and classified into four types on the basis of the fracture line pattern: type A (proximal to the tibiofibular joint), type B (into the proximal tibiofibular joint), type C (distal to the tibiofibular joint), and type D (proximal into the joint). Patients were followed up with radiographs and computed tomography (CT) scans to monitor outcome. RESULTS: Type A fractures had a shorter union time (3.66 months) than type B (5.17 months), type C (6.24 months), and type D (5.75 months). Type B had a delayed union rate of 20%, higher than that of type A (2.46%). Statistical analysis confirmed that type A fractures had significantly better outcomes than types B, C, and D. Type B fractures are by definition Takeuchi type I fractures but exhibit clinical characteristics similar to type II fractures, including longer union times and a higher risk of delayed union. CONCLUSIONS: Type A fracture has union rates similar to those in non-fracture groups, whereas type B fracture has clinical similarities to Takeuchi type II fractures and therefore should be considered and managed as a subtype of Takeuchi type II fractures.