Effect of the Osteotomy Inclination Angle in the Sagittal Plane on the Posterior Tibial Slope of the Tibiofemoral Joint in Medial Open-Wedge High Tibial Osteotomy: Three-Dimensional Computed Tomography Analysis

Abstract

The posterior tibial slope of the tibiofemoral joint changes after medial open wedge high tibial osteotomy (MOWHTO), but little is known about the effect of the sagittal osteotomy inclination angle on the change in the posterior tibial slope of the tibiofemoral joint. The purpose of this study was to investigate the effect of the osteotomy inclination angle in the sagittal plane on changes in the posterior tibial slope after MOWHTO by comparing how anterior and posterior inclination affect the posterior tibial slope of the tibiofemoral joint. The correlation between the osteotomy inclination angle and the postoperative posterior tibial slope angle was also assessed. Between May 2011 and November 2017, 80 patients with medial compartment osteoarthritis who underwent MOWHTO were included. The patients were divided into two groups according to the sagittal osteotomy inclination angle on the 3D reconstructed model. Patients with an osteotomy line inclined anteriorly to the medial tibial plateau line were classified into group A (58 patients). Patients with posteriorly inclined osteotomy line were classified as group P (22 patients). In the 3D reconstructed model, the preoperative and postoperative posterior tibial slope, osteotomy inclination angle relative to medial tibial plateau line in sagittal plane, and gap distance and ratio of the anterior and posterior osteotomy openings were measured. The preoperative and postoperative hip-knee-ankle angle, weight-bearing line ratio, and posterior tibial slope were also measured using plain radiographs. In the 3D reconstructed model, the postoperative posterior tibial slope significantly increased in group A (preoperative value = 9.7 ± 2.9°, postoperative value = 10.7 ± 3.0°, p < 0.001) and decreased in group P (preoperative value = 8.7 ± 2.7°, postoperative value = 7.7 ± 2.7°, p < 0.001). The postoperative posterior tibial slope (group A = 10.7 ± 3.0°, group P = 7.7 ± 2.7°, p < 0.001) and posterior tibial slope change before and after surgery (group A = 1.0 ± 0.8°, group P = −0.9 ± 0.8°, p < 0.001) also differed significantly between the groups. The Pearson correlation coefficient was 0.875 (p < 0.001) for the osteotomy inclination angle, and multivariate regression analysis showed that the only significant factor among the variables was the sagittal osteotomy inclination angle (β coefficient = 0.216, p < 0.001). The posterior tibial slope changed according to the osteotomy inclination angle in the sagittal plane after MOWHTO. The postoperative posterior tibial slope tended to increase when the osteotomy line was inclined anteriorly with respect to the medial tibial plateau line but decreased when the osteotomy line was inclined posteriorly. To avoid inadvertent change of posterior tibial slope, close attention needs to be paid to maintaining the sagittal osteotomy line parallel to the medial joint line during MOWHTO.

Effect of the sagittal osteotomy inclination angle on the posterior tibial slope change in high tibial osteotomy: three-dimensional simulation study

“…However, the present study demonstrated that even if the osteotomy opening gap ratio is adjusted to an appropriate value of 2/3 during MOWHTO 21 , the postoperative posterior tibial slope can change depending on the osteotomy inclination angle in the sagittal plane. These results are consistent with those of previous clinical studies 22,23 . In addition, some previous studies have also argued that the posterior tibial slope did not change when an osteotomy line was created parallel to the joint line 32,33 .…”

“…The changes in the posterior tibial slope were observed after MOWHTO when there was an osteotomy inclination angle with an absolute value of 10° or more between the osteotomy line and the medial tibial plateau line in the sagittal plane. Multiple factors need to be appraised during MOWHTO to prevent unwanted changes in the posterior tibial slope [20][21][22][23] . The most common factor to influence the change in the posterior tibial slope is the opening gap ratio, which is derived based on the difference between anterior and posterior osteotomy opening gaps 20,21 .…”

“…measured on the 3D tibial model. In a true lateral position 28 , the image of the 3D tibial model was captured and measurement of the posterior tibial slope was conducted as presented in a previous study 23 . The posterior tibial www.nature.com/scientificreports/ slope was defined as the angle formed by the medial tibial plateau line and the line perpendicular to the line bisecting the tibial shaft (Fig.…”

“…The postoperative posterior tibial slope increased when the anterior part of the osteotomy line was inclined distally with respect to the line parallel to the medial tibial plateau line in the sagittal plane, and decreased when the anterior part of the osteotomy line was inclined proximally. The results of these studies 22,23 suggest that the posterior tibial slope may increase or decrease depending on whether the osteotomy line is inclined anteriorly or posteriorly in the sagittal plane. However, the above-mentioned studies did not provide sufficient conclusions for quantitative analysis of the extent to which the change in the osteotomy inclination angle in the sagittal plane affects the change in the posterior tibial slope.…”

“…Increase in the posterior tibial slope can cause the tibia to shift anteriorly in relation to the femur and overload the anterior cruciate ligament and the patellofemoral joint 15,17,18 . The posterior tibial slope has been reported to change after MOWHTO 19 , and this change can be affected by various factors [20][21][22][23] . The most common cause of change in the posterior tibial slope is an improper value of osteotomy opening gap ratio according to the difference between anterior and posterior osteotomy opening gaps 20,21 .…”