Tibial Slope Can Be Maintained During Medial Opening-Wedge Proximal Tibial Osteotomy With Sagittally Oriented Hinge, Posterior Plate Position, and Knee Hyperextension: A Cadaveric Study.

Abstract Purpose The purpose of this study is (1) to determine if, when optimizing modern techniques, medial opening-wedge osteotomies can effectively maintain tibial slope and (2) to determine how different magnitude coronal plane corrections affect tibial slope. Methods Proximal tibial osteotomies (PTOs) were performed on 10 fresh frozen cadaveric knees leaving a consistent lateral hinge, using either a 5mm or a 10mm trapezoidal wedged osteotomy plate. Techniques including posterior plate placement, a trapezoidal, sloped plate, and knee hyperextension were used during plate fixation to help close the anterior osteotomy gap. Medial coronal proximal tibia angle and posterior tibial slope were measured pre-osteotomy, after a 5mm implant, and after a 10mm implant using true anteroposterior and lateral fluoroscopic images. Three independent observers performed all radiographic measurements and intraclass correlation coefficients were calculated. Results The 5mm and 10mm osteotomy plates increased the coronal medial proximal tibia angle by a mean of 3.4° (range, 3.0° to 3.7°) and 7.3° (range, 6.7° to 7.7°), respectively. The 5mm and 10mm trapezoidal wedged osteotomy plates decreased the posterior tibial slope by a mean of 0.9° (range, 0.5° to 1.2°) and 0.3° (range, 0° to 0.6°), respectively. Intraobserver reliability was found to be high for both the coronal medial proximal tibia angle (ICC = 0.897, [0.821-0.946]) and the tibial slope measurements (ICC = 0.761, [0.672-0.826]). Conclusions When optimizing the medial opening-wedge proximal tibial osteotomy, including utilization of a sagittally-oriented hinge, placement of a trapezoidal plate posteriorly, and fixation with knee hyperextension, posterior tibial slope can be maintained regardless of the degree of coronal correction. Clinical Relevance Tibial slope has a significant effect on cruciate ligament stress and a better understanding of coronal plane correction and its effect on tibial slope is critical when performing proximal tibia osteotomies.