An automated method for defining anatomic coordinate systems in the hindfoot

Area of Science:

• Biomechanics
• Orthopedics
• Medical Imaging

Background:

• Standardized hindfoot bone coordinate systems are lacking, hindering comparison of kinematic research.
• Accurate definition of anatomical coordinate systems for the talus and calcaneus is essential for reliable gait analysis.

Purpose of the Study:

• To develop a reliable and robust procedure for defining anatomical coordinate systems for the talus and calcaneus.
• To evaluate four different methods for coordinate system definition based on consistency, repeatability, and functional axis correspondence.

Main Methods:

• Four methods were evaluated: interactively identified landmarks, principal component analysis (PCA), automatically identified landmarks, and tibial system translation.
• Systems were assessed on 40 tali and 40 calcanei.
• Functional axes of rotation were determined using dynamic biplane radiography during gait.

Main Results:

• Automated and PCA-based methods (Systems 3 and 2) demonstrated the highest repeatability and consistency due to reduced operator dependency.
• No developed coordinate system accurately reflected functional axes of rotation during gait.
• System 3 (automated landmarks) showed better clinical relevance, particularly for calcaneal angles, compared to System 2 (PCA).

Conclusions:

• An automated method for defining talus and calcaneus coordinate systems is presented, avoiding unreliable manual marker placement.
• This automated approach enhances the comparability of hindfoot kinematics research.
• The proposed method offers a more reliable alternative for establishing anatomical coordinate systems in the hindfoot.