Comparison of sagittal and frontal plane alignment after open- and closed-wedge osteotomy: a matched-pair analysis.

High tibial osteotomy (HTO) is a procedure for treating medial compartment osteoarthritis (OA) of the varus deformed knee. Frontal and sagittal alignment after closed- and open-wedge HTO were compared radiologically in a matched-pair study. The mean intra-operative frontal plane correction (FT axis) was +7.5 degrees for closed-wedge HTO and +8 degrees for open-wedge HTO; it increased by +0.5 degrees in closed-wedge HTO and decreased by -0.5 degrees in open-wedge HTO at last follow-up. Post-operatively, tibial slope had decreased by -0.5 degrees in closed-wedge HTO and increased significantly by +3 degrees in open-wedge HTO. Both techniques effectively and safely corrected varus deformity. A high degree of stability of the frontal plane correction was noted, however a significant change in the tibial slope after open-wedge HTO was observed post-operatively. As no loss of correction was shown, it may be related to the surgical technique rather than to the implant used.