ISAKOS: 2023 Congress in Boston, MA USA

2023 ISAKOS Biennial Congress ePoster

 

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

Erica Swartwout, BA, New York, NY UNITED STATES
Hugo Robichaud, Quebec City, Québec CANADA
Anil S. Ranawat, MD, New York, NY UNITED STATES
Atul F. Kamath, MD, Rochester, MN UNITED STATES

Hospital for Special Surgery, New York, New York, UNITED STATES

FDA Status Not Applicable

Summary

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.

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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 ¼ .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.