[Early effectiveness analysis of lateral hinge fracture during medial opening-wedge high tibial osteotomy]

To compare the clinical and radiologic effectiveness in patients with versus without lateral hinge fracture during medial opening-wedge high tibial osteotomy (MOWHTO) to evaluate the effect of lateral hinge fracture on short-term effectiveness.

The clinical data of 84 patients (97 knees) with medial compartment osteoarthritis who treated with MOWHTO between September 2015 and July 2018 was retrospectively analyzed. There were 10 males (10 knees) and 74 females (87 knees). The age ranged from 45 to 65 years with an average of 57.7 years. Lateral hinge fracture was recognized by the intraoperative fluoroscopy or immediate postoperative X-ray film. Fractures were classified into types Ⅰ, Ⅱ, and Ⅲ according to the Takeuchi classification. The healing of osteotomy was observed by radiographs during follow-up; the femur tibia angle (FTA), medialproximal tibial angle (MPTA), and hip-knee-ankle angle (HKA) were also calculated. The knee joint function was evaluated by Hospital for Special Surgery (HSS) score and knee society score (KSS).

The incision healed by first intention. All patients were followed up 15-48 months with an average of 24.8 months. No hinge fracture occurred in 78 knees (80.41%, group A), and lateral hinge fractures were observed in 19 knees (19.59%, group B) and were divided into the type Ⅰ (13 knees, 13.40%) and type Ⅲ (6 knees, 6.19%) groups. Type Ⅰ fractures were not additionally treated, type Ⅲ fractures were anatomic reduced fixed with additional lag screws. X-ray film and CT examination showed that all patients had bone healing at 3 months after operation without delayed healing or nonunion. During follow-up, there was no loosening or fracture of internal fixation plates and screws. HKA, FTA, and MPTA of patients in group A and group B (type Ⅰ and Ⅲ) were significantly improved at each time point after operation compared with preoperative values ( P<0.05); there was no significant difference between groups at each time point before and after operation ( P>0.05). After operation, the pain of knee joint was alleviated and the function of joint was improved. At last follow-up, KSS score and HSS score of groups A and B were significantly improved compared with those before operation ( P<0.05), but there was no significant difference between the two groups ( P>0.05).

The lateral hinge fracture may occur during MOWHTO. As long as the treatment and rehabilitation were guided according to the fracture classification of the hinge, the effectiveness can be similar to those without the hinge fracture.