Primary stability of various implants in tibial opening wedge osteotomy: a biomechanical study.

High tibial osteotomy (HTO) is an established method for treating varus gonarthrosis. The opening wedge HTO has some advantages over the lateral closed wedge technique. In this biomechanical study various systems of internal fixation of medial HTO were compared using an animal cadaver model (lower leg specimens from 1-year-old female domestic pigs). The first osteotomy (10 degrees ) was carried out and stabilized with a C-plate, an Arthrex spacer plate, or an AO tibial plate with or without bone graft. The resistance to axial stress was tested in a mechanical testing machine. Under lower axial stress (25, 50, 75, 100 N) the axial displacement between the various specimens did not show any significant differences. Under maximal axial force, the specimen fixed with the C-plate ( Fmax 2042 N) showed significantly better stability than the Arthrex plate ( Fmax 1687 N); P < 0.05. The AO plate ( Fmax 1612 N without bone graft and Fmax 1583 N with bone graft) showed the lowest axial exposure to stress. Moreover, the influence of the osteotomy angle (7.5 degrees, 10 degrees, 12.5 degrees, 15 degrees ) on axial stress resistance ( Fmax 2548, 2090, 1975, and 1740, respectively) was evaluated, and a direct correlation was found ( R = 0.794, P < 0.05).