2025 ISAKOS Biennial Congress ePoster
Changes In Coronal Tibial Alignment In Anterior Tibial Closing Wedge Osteotomy Are Caused By Axial Rotation Of The Hinge
Julius Watrinet, MD, Dr. med. GERMANY
Philipp Blum, MD, Murnau GERMANY
Julian Mehl, MD, Munich, Bavaria GERMANY
Sebastian Siebenlist, MD, MHBA, Prof., Munich, Bavaria GERMANY
Julian Fürmetz, PD MD, Murnau GERMANY
BG Trauma Center Murnau, Murnau, Bavaria, GERMANY
FDA Status Cleared
Summary
Unintended decrease of the MPTA during ATCWO can be explained by axial hinge axis rotation, while a neutral hinge can be defined in ACTWO that only affects the sagittal alignment.
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Abstract
Background
Clinical evidence indicates that an unintended increase in the medial proximal tibial angle (MPTA) can occur during slope-reducing tibial osteotomies, which is most relevant in ACL deficient knees. Therefore, this study aims to assess how adjustments to the axial and coronal hinge axes in anterior tibial closing wedge osteotomies (ATCWO) affect alignment parameters. It was hypothesized that that a neutral hinge axis in ATCWO can be identified, which does not cause changes in coronal and axial alignment.
Methods
A 3D surgical simulation was used to perform ATCWO with a stepwise increment of one-degree (1°-5°) rotation around different hinge axis. Surface models were created from CT scans of 21 individuals with pathological PTS (>12°) and 28 lower limbs with neutral PTS (7°-12°). Thirteen distinct hinge axes were established, comprising one neutral hinge axis and twelve others with varying orientations. These included six hinge axes with rotations in the axial plane (±10°, ±20°, and ±30° relative to the neutral axis) and six hinge axes with rotations in the coronal plane (±10°, ±20°, and ±30° relative to the neutral axis). While some of these orientations were impractical, they were intentionally included to assess the potential effects of hinge axis rotation, resulting in a total of 3185 simulations. Anatomical landmarks were determined for each simulation to measure the posterior tibial slope (PTS), MPTA, hip-knee-ankle angle (HKA), and tibial torsion (TT). Axial and sagittal rotation of the hinge axis were tested for their effects on PTS, MPTA and TT.
Results
A neutral hinge axis not changing the coronal or axial alignment was defined oriented parallel to the posterior tibial plateau 1cm underneath the articular surface. Clinically relevant hinge axis rotation in the coronal or axial plane below 20° did not significantly influence PTS correction (p > 0.05). In contrast, rotation of the axial hinge axis exceeding 10° led to significant MPTA changes compared to the neutral hinge (p<0.001). The initial MPTA had no influence on MPTA changes (p > 0.05).
Conclusion
In conclusion, unintended decrease of the MPTA during ATCWO can be explained by axial hinge axis rotation. In virtual simulation, a neutral hinge can be defined in ACTWO that only affects the sagittal alignment. By understanding the geometrical principles underlying PTS correction, postoperative alignment can be improved in the management of complex knee pathologies.