Extreme Hinge Axis Positions Are Necessary to Achieve Posterior Tibial Slope Reduction With Small Coronal-Plane Corrections in Medial Opening Wedge High Tibial Osteotomy

Abstract

Background: Both coronal- and sagittal-plane knee malalignment can increase the risk of ligamentous injuries and the progression of degenerative joint disease. High tibial osteotomy can achieve multiplanar correction, but determining the precise hinge axis position for osteotomy is technically challenging. Purpose: To create computed tomography (CT)–based patient-specific models to identify the ideal hinge axis position angle and the amount of maximum opening in medial opening wedge high tibial osteotomy (MOWHTO) required to achieve the desired multiplanar correction. Study Design: Descriptive laboratory study. Methods: A total of 10 patients with lower extremity CT scans were included. Baseline measurements including the mechanical tibiofemoral angle (mTFA) and the posterior tibial slope (PTS) were calculated. Virtual osteotomy was performed to achieve (1) a specified degree of PTS correction and (2) a planned degree of mTFA correction. The mean hinge axis position angle for MOWHTO to maintain an anatomic PTS (no slope correction) was 102.6° ± 8.3° relative to the posterior condylar axis (PCA). Using this as the baseline correction, the resultant hinge axis position and maximum opening were then calculated for each subsequent osteotomy procedure. Results: For 5.0° of mTFA correction, the hinge axis position was decreased by 6.8°, and the maximum opening was increased by 0.49 mm for every 1° of PTS correction. For 10.0° of mTFA correction, the hinge axis position was decreased by 5.2°, and the maximum opening was increased by 0.37 mm for every 1° of PTS correction. There was a significant difference in the trend-line slopes for hinge axis position versus PTS correction ( P = .013) and a significant difference in the trend-line intercepts for maximum opening versus PTS correction ( P < .0001). Conclusion: The mean hinge axis position for slope-neutral osteotomy was 102.6° ± 8.3° relative to the PCA. For smaller corrections in the coronal plane, more extreme hinge axis positions were necessary to achieve higher magnitudes of PTS reduction. Clinical Relevance: Extreme hinge axis positions are technically challenging and can lead to unstable osteotomy. Patient-specific instrumentation may allow for precise correction to be more readily achieved.

Influence of variable hinge positioning on coronal and sagittal alignment in uniplanar medial open‐wedge high tibial osteotomy

“…At the same time, according to the findings of this study, changes of hinge rotation between 20° and 90° had little influence on the MPTA, which was mainly influenced by the opening height of the osteotomy gap. These findings were also observed by Eliasberg et al [ 8 ]. Based on the results of this study, we proposed a formula (PTS = 19.39 + 0.97 × hinge rotation + 0.61 × gap height ) to predict the aspired changes in the coronal and sagittal plane, with regard to the factors opening height and hinge rotation.…”

“…Although not clinically visible, this posterior hinge malrotation was associated with a significant increase of the PTS by an average of 3.3° [ 15 ]. In a computational simulation model, Eliasberg et al picked up on these findings and proposed a hinge axis rotation of 102.6° relative to the posterior condylar axis, in order to achieve a PTS‐neutral coronal correction during mowHTO [ 8 ]. This observation may be explained by a compensational effect, with regard to the tibial anatomy.…”

“…This observation may be explained by a compensational effect, with regard to the tibial anatomy. On the other hand, the definition of the ‘hinge axis’ is not uniform throughout literature, which could be a source of bias in this context [ 8 ]. Yet, hinge rotation was consistently identified to be a controllable influence factor for intentional changes of the PTS [ 8 ].…”

“…Against this background, increased attention has been brought to the influence of the hinge position on the sagittal alignment, in the course of uniplanar HTO. A recent simulation study has proposed an anterolateral hinge placement for a PTS‐neutral correction during mowHTO [ 8 ]. In another study, successful simultaneous slope reduction during mowHTO was achieved by a medial soft‐tissue release, which was combined with a release of ‘the posterolateral aspect, close to the lateral hinge’, thus creating an intentional asymmetric hinge [ 26 ].…”

Three-Dimensional Hinge Axis Orientation Contributes to Simultaneous Alignment Correction in All Three Anatomical Planes in Opening-Wedge High Tibial Osteotomy

“…The results show a clear (and expected) coupling between the orientation of the HA in 3D space and its effect on alignment parameter values in all 3 anatomical reference planes. Although similar effects of HA orientation on alignment in 2 of the 3 anatomical reference planes as the ones reported in the present study have been reported before, 18 , 19 , 20 , 22 , 23 , 37 Jörgens et al. 31 investigated the effects of HA rotation and HA tilt on alignment angles in all 3 anatomical reference planes.…”