Influence of Tibial Torsion on Measurement of Proximal Alignment on Frontal Plane

Introduction: Tibial frontal plane deformities are common in dogs and are usually evaluated from a caudo-cranial radiographic view. This study aims to determine the influence of torsion on the measurement of mechanical medial proximal tibial angle (mMPTA) and to assess the inter-observer reliability.

Materials and Methods: Ten tibiae were retrieved from cadavers, 10-degree increments of External Tibial Torsion (ETT) and Internal Tibial Torsion (ITT) were created and radiographs in caudo-cranial view were performed. The mMPTA were blindly measured by four observers. A linear regression model was calculated to assess how the torsion influences the mMPTA. The interclass correlation coefficient (ICC) was employed to quantify the agreement and consistency of measurements between observers.

Results: The ICC was high considering both single (0.9084) and average (0.9802) measures. The linear regression analysis revealed a statistically significant relationship between torsion and the change in mMPTA. The coefficient of determination (R ²) was 0.98 indicating that 98% of the variance in the change in mMPTA could be explained by ETT; in the case of ITT the R ² was 0.96. The scatterplot of the data points revealed a linear trend, suggesting a positive or negative linear association between ETT or ITT, respectively, and the change in mMPTA.

Discussion/Conclusion:  Torsion adversely affects the radiographic measurement. As ETT increases, mMPTA increases, creating an artifactual valgus. As ITT increases, mMPTA decreases, creating an artifactual varus. The high inter-observer agreement proved the accuracy of mMPTA measurements and the consistency of artifactual frontal plane deformity caused by torsion.

Acknowledgment

None.

 

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Publication History

Article published online:
15 July 2025