Different Positions of Weightbearing CT Images Can Influence the Hindfoot Alignment Evaluation Using 2-Dimensional...

Area of Science:

• Orthopedics
• Radiology
• Biomechanical Engineering

Background:

• Three-dimensional weightbearing CT (WBCT) is utilized for foot and ankle alignment assessment.
• Current measurement techniques often rely on 2D principles, making them susceptible to image orientation variations.
• Image positioning can substantially affect hindfoot alignment evaluations derived from WBCT.

Purpose of the Study:

• To investigate the influence of image rotation on hindfoot alignment measurements using 3D WBCT.
• To determine the reliability of Calcaneal Moment Arm (CMA) measurements under varying image orientations.
• To establish the correlation between image rotation and hindfoot alignment in WBCT analysis.

Main Methods:

• Ten healthy feet underwent WBCT scans.
• Foot images were rotated internally and externally by 5-20 degrees to simulate malposition.
• The Calcaneal Moment Arm (CMA) was measured by two independent investigators.
• Intra- and interobserver reliability was assessed using intraclass correlation coefficients (ICC).
• Linear regression analyzed the correlation between CMA and image rotation angle.

Main Results:

• Internal image rotation induced a valgus shift in hindfoot alignment, while external rotation caused a varus shift.
• A 1-degree rotation (internal or external) correlated with a 0.48 mm change in the modified WBCT-CMA value (P < .0001, R² = 0.6406).
• Measurements showed high intra- and interobserver reliability.

Conclusions:

• Despite 3D WBCT's capabilities, current alignment evaluation tools are limited by 2D principles.
• Consistent and standardized orientation of WBCT images is essential for accurate hindfoot alignment data.
• Proper image positioning is critical for reliable interpretation of foot and ankle alignment using WBCT.