High tibial osteotomy (HTO) has been appreciated as a valid and highly effective treatment modality for young and active patients with medial compartment osteoarthritis of knee joint. The rationale behind this surgery is shifting of axis of load transfer from the damaged medial compartment to the intact lateral one via correcting the varus deformity in the frontal plane . Open wedge high tibial osteotomy (OWHTO) has gained wider popularity especially after introduction of rigid fixation devices aiding in the protection of modified alignment. Main advantages of the technique are preservation of the tibial bone stock and avoidance of fibular osteotomy. The amount of angular correction can be adjusted intraoperatively . It is possible to combine OWHTO with ligament reconstruction procedures. Another advantage is that performing a total knee arthroplasty over OWHTO is relatively simpler when compared to the procedures over closed wedge or dome type HTOs. This is mostly related to the fact that proximal tibial geometry is less distorted with OWHTOs . Apart from the intended alignment changes in the frontal plane, HTO is also associated with untoward changes in the sagittal plane which presents itself as posterior tibial slope (PTS) alterations. Studies focusing on the influence of HTO over PTS have led to general conclusions that both closed wedge (CWHTO) and dome type HTOs caused decreases in PTS, however OWHTO was associated with increased PTS . Several methods were suggested to prevent the unintended slope increase in OWHTO including insertion of a tricortical iliac bone graft into the posterior part of the osteotomy gap, using mathematical formulations to predict the height of the gap preoperatively, posterior plating, and intraoperative assistance of an external fixator . It was reported that it was possible to control the PTS change in OWHTO if certain surgical details were taken into consideration. Besides the changes in PTS, HTOs were also shown to be associated with changes in patellar height. In a meta-analysis, it was reported that patellar height was decreased following OWHTO and unchanged after CWHTO . This is important because patellar height . changes can cause patellofemoral problems. In addition, in case of a failed osteotomy, the altered patellar height could cause technical difficulties when performing total knee arthroplasty.
In the study of Kaya et al, 2020 a modification in OWHTO was utilized; the proximal tibia was osteotomized in a direction from posteromedial to anterolateral lying posterior to medial collateral ligament (MCL) and sufficient valgization was achieved with a posteromedial distraction. The primary aim of this study was to evaluate the influence of the surgical modification on PTS and patellar height in OWHTO. The secondary aim was to evaluate the influence of preoperative mechanical axis deviations on PTS. The hypothesis of this study was with a modification in the surgical technique, PTS changes could be prevented.
Patients were positioned supine on the operating table. An arthroscopic examination was performed to assess the cartilage status of the three compartments and adress another pathologies. An eight cm long longitudinal skin incision was made midway between tibial tubercle and posteromedial part of tibia. Following the incision of sartorial fascia, posterior border of MCL was longitudinally cut. MCL was gently released proximal to distal keeping its insertion mostly intact. Insertion of the popliteus muscle was released posteriorly and Hohman retractor was inserted to protect neurovascular structures. Under fluoroscopic guidance, two parallel Kirschner wires were introduced above the level of pes anserinus tendons from the posteromedial tibia. These wires were directed proximally towards anterolateral part targeting the midpoint of proximal tibiofibular joint to provide additional stability to the lateral hinge. A uniplanar proximal tibial osteotomy was performed in a posteromedial – anterolateral direction. Anterior cortex was cut with osteotomes at the level of tibial tubercle. By inserting osteotomes sequentially, the gap was made ready for distraction. Subsequently, the distractor was inserted posteromedially and with distraction mechanical axis deviations were corrected as planned preoperatively. Usually a 3° overcorrection was aimed. Cable test was always used to verify the amount of correction. Fixation of the osteotomy was achieved utilizing TomoFix plate (Synthes, Bettlach, Switzerland). The osteotomy gap was routinely filled with autologous bone grafts harvested from anterior iliac crest utilizing mosaicplasty chisels . In this graft harvesting technique, the insertions of support. Radiographic Analysis gluteal muscles were preserved. Graft was harvested from the tabula interna aiming to avoid donor site problems. The tubular grafts were tightly packed to fill the void and facilitate bony union. However, unlike tricortical grafts, these did not have the potential to provide mechanical support.
