Accuracy of an image matching technique for assessing knee alignment during the stance phase of gait using single-plane anteroposterior radiography.

The article focuses on the development and validation of an image matching technique to measure three-dimensional (3D) knee alignment using single-plane anteroposterior (AP) radiography during the stance phase of gait. Using artificial femoral and tibial bone models fixed on a 3D goniometer stage, the study compared the 3D positions estimated by the image matching method to ground truth measurements obtained via a 3D coordinate measuring machine. Results showed translation errors within approximately ±2.1 mm and rotation errors within ±0.9° for both bones, indicating the method's suitability for evaluating 3D knee alignment from single-plane radiographs. The technique offers a practical alternative to existing methods by enabling dynamic assessment during treadmill walking without requiring specialized equipment or large radiation-shielded spaces, though further validation in clinical settings is needed.