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. 2022 May 9;10(5):23259671221094346.
doi: 10.1177/23259671221094346. eCollection 2022 May.

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

Claire D Eliasberg  1 , Kyle N Kunze  1 , Erica Swartwout  1 , Atul F Kamath  2 , Hugo Robichaud  3 , Anil S Ranawat  1
Affiliations

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

Claire D Eliasberg et al. Orthop J Sports Med. .

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.

Keywords: ACL; knee; ligament; osteotomy.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: K.N.K. has received education payments from Arthrex; consulting fees from Arthrex, Biom’Up, Bodycad, Corin, Heraeus Medical, Intellijoint Surgical, LinkBio, Medical Device Business Services, Ortho Development, United Orthopedic, and Zimmer Biomet; speaking fees from Arthrex, Ortho Development, and Pacira Pharmaceuticals; and hospitality payments from Biocomposites, OrthoSensor, and Stryker. A.S.R. has received education payments from Gotham Surgical; consulting fees from Anika Therapeutics, Arthrex, Bodycad, Flexion Therapeutics, Heron Therapeutics, Smith & Nephew, and Stryker; speaking fees from Smith & Nephew; and royalties from ConforMIS. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
(A) Axial view of a 3-dimensional computed tomography (3D CT)–reconstructed tibia demonstrating the posterior condylar axis (green line), the hinge axis position (yellow line), and the angle between the 2 lines (dashed red line). (B) Coronal view of a 3D CT–reconstructed tibia showing an example of medial opening wedge high tibial osteotomy. (C) Sagittal view of a 3D CT–reconstructed tibia demonstrating the medial aspect of the osteotomy site and measuring of the gap at the position of the maximum opening (millimeter).
Figure 2.
Figure 2.
(A) Axial view of a 3-dimensional computed tomography–reconstructed tibia demonstrating the posterior condylar axis (black line) and the hinge axis position (gray line). The angle between these 2 lines was calculated to be a mean of 102.6° ± 8.3° for the hinge axis position at which medial opening wedge high tibial osteotomy could be performed without affecting the posterior tibial slope (PTS). (B) For 3.0° of PTS correction, the hinge axis position for 5.0° of mechanical tibiofemoral angle (mTFA) correction (green), 7.5° of mTFA correction (blue), 10.0° of mTFA correction (yellow), 12.5° of mTFA correction (red), and 15.0° of mTFA correction (pink) was more internally rotated for smaller degrees of mTFA correction. (C) Hinge axis positions for 6.0° of PTS correction. (D) Hinge axis positions for 9.0° of PTS correction. (E) Hinge axis positions to create neutral-slope osteotomy (9.5° of PTS correction).
Figure 3.
Figure 3.
The hinge axis positions for 0.0° of posterior tibial slope (PTS) correction (gray line), 3.0° of PTS correction (green line), 6.0° of PTS correction (blue line), 9.0° of PTS correction (orange line), and slope-neutral osteotomy (red line) are shown for (A) 5.0°, (B) 7.5°, (C) 10.0°, (D) 12.5°, and (E) 15.0° of mechanical tibiofemoral angle correction. The black line represents the posterior condylar axis.
Figure 4.
Figure 4.
Hinge axis position angle required for posterior tibial slope correction of 0.0°, 3.0°, 6.0°, 9.0°, and 9.5°. mTFA, mechanical tibiofemoral angle.
Figure 5.
Figure 5.
Amount of maximum opening required for posterior tibial slope correction of 0.0°, 3.0°, 6.0°, 9.0°, and 9.5°. mTFA, mechanical tibiofemoral angle.
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