High tibial osteotomy Planned and accidental changes of tibial slope

Background High tibial osteotomy (HTO) is predominantly carried out to accomplish corrections in the frontal plane. The surgeon should be aware that this procedure may result in unplanned changes in the sagittal plane; however, simultaneous modification of the tibial slope combined with frontal plane corrections may be advantageous for the patient in certain situations. Objective Presentation of the causes of unplanned changes of tibial slope in open wedge HTO. Furthermore, the techniques of planned alterations to the tibial slope in open and closed wedge HTO are described. Material and methods An analysis of the literature and techniques developed by the author are presented. Results Open wedge valgus HTO does not automatically result in slope increase. Unplanned slope changes can be avoided if the surgeon follows the established surgical technique. Key points are release of the distal part of the medial collateral ligament, correct osteotomy of the tibia including the posterolateral area, placing the spreader at the posteromedial aspect of the tibia when opening the osteotomy and use of a stable implant which avoids loss of correction, preferably a plate fixator. Conclusion The HTO procedure should be considered a three-dimensional process and the surgeon should closely monitor slope changes as well as frontal plane correction. Tibial slope can be controlled in open wedge HTO as well as closed wedge HTO by paying careful attention to details of the surgical technique.