[Precision in the planning of open wedge HTO]

The high tibial osteotomy (HTO) is regarded as an established method for varus deformity. To quantify the varus deformity, the anatomic and the mechanical leg axis can be determined. The success of HTO depends on the correct assessment of the preoperative axis deviation and the exact as planned correction. The aim of the retrospective study was to verify the accuracy (± 1.5° of mechanical tibiofemoral angle tolerance compared to the planning) with the preoperative planning compared to the postoperative result after correction using the TomoFix™ plate in open wedge HTO.

A retrospective study of patients was carried out after open wedge HTO with the TomoFix™ plate. A full-weight bearing, long-standing anteroposterior radiograph of the whole lower extremity was performed before and after correction. The mechanical angles in the frontal plane were determined and compared with the plan as drawn.

The preoperative mechanical tibiofemoral angle (mTFA) was -5.33 ± 3.29° (varus) and at follow-up -0.3 ± 3.0° (varus). The mean correction was 4.9 ± 2.9°. The planned mTFA was 2.2 ± 1.6°(valgus). The corrected lower extremity showed a mean difference of -2.5 ± 3.4° in angle correction of the varus deformity as preoperatively assumed to be the optimal correction compared to the planning. The planning goal was not achieved in 73 % of the cases.

The results are comparable to those of other publications. However, taking into account the required accuracy of the drawn plan combined with the surgical precedure, it is not possible to achieve results within the desired tolerance.