Fractures Around the Lateral Cortical Hinge After a Medial Opening-Wedge High Tibial Osteotomy: A New Classification of Lateral Hinge Fracture

Purpose: The purpose of this study was to determine the frequency of lateral hinge fractures after opening-wedge high tibial osteotomy and investigate the patterns of fracture and their clinical outcome. Methods: We analyzed 104 knees in 93 patients with a mean age of 68 +/- 7 years. Of the knees, 74 were diagnosed as having primary osteoarthritis and 30 with osteonecrosis. The mean follow-up period was 41 months. Lateral hinge fractures were classified as follows: type I, the fracture reaches just proximal to or within the tibiofibular joint; type II, the fracture reaches the distal portion of the proximal tibiofibular joint; and type III, a lateral plateau fracture. A standard postoperative rehabilitation protocol was used for type I fractures, 3 of 5 patients with type II fractures were treated with non-weight bearing, and type III fractures were treated with non-weight bearing until visible callus formation. Results: The Knee Society scores for the knee and for function showed improvement from 49 +/- 11 to 91 +/- 7.7 points and from 62 +/- 13 to 95 +/- 8.2 points, respectively. Lateral cortex fractures were observed in 26 knees (25%): 19 type I, 5 type II, and 2 type III. In the type II fracture group, 2 of 5 patients were judged to have a delayed bone union. There were 2 cases of infection (2%) and 1 case of traumatic neuroma (1%) but no instances of implant failure, nonunion, or deep vein thrombosis among our patient cohort. Conclusions: High tibial osteotomy patients treated with a combination of TomoFix (Synthes, Bettlach, Switzerland) and bone substitute were able to walk with full weight bearing 2 weeks after surgery. No complications were seen in 19 patients with type I fractures. Of 5 patients with type II fractures, 2 had delayed unions with a correction loss of 3 and 7, respectively. Level of Evidence: Level IV, therapeutic case series.