Background: A loss of correction is one of the common complications after medial opening wedge high tibial osteotomy (MOWHTO) and can lead to deteriorate outcomes. The technique of fixation plays an important role in maintaining the correction angle until union.
Objective: The present study aims to compare the amount of correction loss between two different fixation techniques after MOWHTO.
Material and Method: Between 2005 and 2007, 67 knees from 54 patients who underwent MOWHTO were reviewed and classified into the following groups: group A, treated with T-buttress plate fixation and autologous tricortical iliac bone graft, and group B, operated upon with a locking compression medial high tibial plate without any augmentation. Preoperatively and at 1, 12 and 24 months postoperatively, medial proximal tibial angles (MPTA) were measured and the loss of correction angle was determined by measuring the decrease in MPTAs at 1 and 2 years after the operation. The differences in clinical and radiographic outcomes were analyzed using Student’s t-test and the Chi-squared test.
Results: The overall loss of correction at 2 years in group A (2.0 + 2.7 degrees) was higher than in group B (0.3 + 3.3 degree) (p = 0.026). The majority of correction loss occurred in the first year (1.6 + 2.6 and 0.4 + 2.6 degrees in groups A and B, respectively). During the second year, there was slightly more loss in group A (0.4 + 1.3 degree), while a stable angle was found in group B (-0.1 + 2.5 degree). All osteotomies were united and a 7.5% incidence of overall complications was reported.
Conclusion: Maintenance of the correction angle after MOWHTO depended on the fixation technique. The authors recommend that 2 degrees more than the planned overcorrection point is required in the non-locking plate system, with no need for such a measure in the locking plate system.

Keywords: Loss of correction, High tibial osteotomy, Locking compression plate, Medial tibial plateau angle