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

Purpose: To investigate the simultaneous effect of 3-dimensional (3D) hinge axis (HA) orientation on alignment parameters in all 3 anatomical planes in high tibial osteotomy. Methods: A computed tomography-based 3D model of a human tibia/fibula was used to establish a 3D tibial coordinate system based on the tibial mechanical axis. In here, an HA was positioned and an opening-wedge high tibial osteotomy with a rotation angle of 10° over the HA was simulated. HA rotation in the axial plane ranged from 0° to 90° and HA tilt relative to the axial plane ranged from -20° to +20°. The study quantified the simultaneous effect of HA orientation on change of alignment parameters in all anatomical reference planes. Results: HA rotation within the tibial axial plane between orientations perpendicular to the coronal and sagittal planes primarily affected both coronal and sagittal plane alignment, with an inverse relationship between these planes (range: 0°-9.7°); the effect of HA rotation on the change in axial plane alignment was maximally 0.9°. In contrast, HA tilt relative to the tibial axial plane primarily affected axial alignment (maximum change: 6.9°); the effect on change in both coronal and sagittal plane alignment was maximally 0.6°. Conclusions: HA rotation in the tibial axial plane primarily affects sagittal and coronal plane alignment, and HA tilt relative to the tibial axial plane primarily affects axial plane alignment. Clinical Relevance: Integrating 3D HA orientation in malalignment planning and correction offers the potential to minimize unintended corrections in nontargeted planes in uniplanar correction osteotomies and to facilitate intentional multiplanar correction with a single osteotomy.